State of Arizona Exceptional Event Documentation 

for the Event of June 16, 2012, for the 

Phoenix PM10 Nonattainment Area 

Produced by: 

Sierra Research, Inc. 

Arizona Department of Environmental Quality 

Maricopa County Air Quality Department 

Maricopa Association of Governments 

 Final Report 

February 13, 2013 
EXECUTIVE SUMMARY 

In 2005, Congress identified a need to account for events that result in exceedances of the National 

Ambient Air Quality Standards (NAAQS) that are exceptional in nature1 (e.g., not expected to reoccur or 

caused by acts of nature beyond man-made controls). In response, EPA promulgated the Exceptional 

Events Rule (EER) to address exceptional events in 40 CFR Parts 50 and 51 on March 22, 2007 (72 FR 

13560). On May 2, 2011, in an attempt to clarify this rule, EPA released draft guidance documents on the 

implementation of the EER to State, tribal and local air agencies for review. Based on numerous 

comments EPA received on the May 2011 draft, EPA issued a revised draft guidance document in June 

2012. The EER allows for states and tribes to “flag” air quality monitoring data as an exceptional event 

and exclude those data from use in determinations with respect to exceedances or violations of the 

NAAQS, if EPA concurs with the demonstration submitted by the flagging agency. 

Due to the arid nature of the state, Arizona is highly susceptible to windblown dust events. These events 

are often captured by various air quality monitoring equipment throughout the state, sometimes resulting 

in exceedances or violations of the PM10 NAAQS. In the past, the Arizona Department of 

Environmental Quality (ADEQ) has submitted exceptional event documentation for these events. Due in 

part to issues within the EER, obtaining concurrence on these events has been a difficult task. The ADEQ 

is now taking a new approach and focusing exceptional event documentation on events that are believed 

to be clear-cut exceptional events that are not controllable by human intervention, such as the dust events 

that frequently occurred during the monsoon season of 2011. This new approach was used for the 

exceptional event demonstration submitted in March 2012 by ADEQ for several PM10 events that 

occurred from July 2 – July 8, 2011, in the Phoenix region. In September 2012, EPA concurred that the 

July 2–8, 2011 events were indeed exceptional. As a result, this document is designed to follow the 

format used in the July 2–8, 2011 events submission. 

This demonstration contains detailed information about the windblown dust event that affected the 

Phoenix PM10 nonattainment area on June 16, 2012. On that day, seven exceedances of the PM10 

NAAQS occurred within the nonattainment area. Additional exceedances occurred outside of the Phoenix 

PM10 nonattainment area on this date, and additional documentation may be submitted as a separate 

package at a later time. ADEQ contends that the exceedances that were measured on June 16, 2012, 

within the Phoenix PM10 nonattainment area were the result of natural events that were not reasonably 

controllable or preventable. This assessment report of the June 16, 2012, dust event was a collaborative 

effort involving staff from Sierra Research, Inc., the Arizona Department of Environmental Quality, 

Maricopa Association of Governments, Maricopa County Air Quality Department, and Pinal County Air 

Quality Control District. 

 

Section I of this assessment provides a summary of the exceptional event rules and requirements and lays 

out how those rules are met within this specific assessment. 

Section II of this assessment introduces the conceptual model of the thunderstorms and the subsequent 

dust storm that transpired on June 16, 2012, providing a background narrative of the exceptional event. 

Section III of this assessment provides data summaries and time series graphs that help illustrate that the 

event of June 16, 2012, produced PM10 concentrations in excess of normal historical fluctuations. 

 

1

 Section 319 of the Clear Air Act (CAA), as amended by section 6013 of the Safe Accountable Flexible EfficientTransportation Equity Act: A Legacy for Users (SAFE-TEA-LU of 2005), required EPA to propose the Federal Exceptional 

Events Rule (EER) no later than March 1, 2006. 
Section IV of this assessment details the existing area control measures and demonstrates that despite the 

presence and enforcement of these controls, the event on June 16, 2012, was not reasonably controllable 

or preventable. 

Section V of this assessment establishes a clear causal connection between the natural events of June 16, 

2012, and the exceedances of the 24-hour PM10 standard at the monitoring stations. The evidence in this 

section (and the previous section on historical fluctuations) also confirms that the event in question both 

affected air quality and was the result of natural events. 

Section VI of this assessment builds upon the demonstration showing a clear causal connection between 

the natural events and the exceedances and concludes there would have been no exceedances on June 16, 

2012, but for the presence of the natural events. 

Section VII contains conclusions that summarize the exceptional event that occurred on June 16, 2012, 

and relates the requirements in the EER to the information within this document. 

-ii-
Table of Contents 

I. EXCEPTIONAL EVENT RULE (EER) REQUIREMENTS........................ 1

Procedural Requirements.................................................................................................... 1

Public notification that event was occurring (40 CFR 50.14(c)(1(i)) ................................ 1

Place informational flag on data in AQS (40 CFR 50.14(c)(2)(ii)).................................... 1

Notify EPA of intent to flag through submission of initial event description by July 1 of 

calendar year following event (40 CFR 50.14(c)(2)(iii)).................................................... 1

Document that the public comment process was followed for event documentation (40 CFR 

50.14(c)(3)(iv)).................................................................................................................... 2

Submit demonstration supporting exceptional event flag (40 CFR 50.14(a)(1-2))............ 2

Documentation Requirements ............................................................................................ 2

II. CONCEPTUAL MODEL................................................................................. 4

Geographic Setting and Climate......................................................................................... 4

Geographic Setting of Monitors.......................................................................................... 4

Climate ................................................................................................................................ 7

Monsoon Season Description and Event Summary .......................................................... 8

Conclusions......................................................................................................................... 10

III. HISTORICAL FLUCTUATIONS............................................................... 14

Conclusions......................................................................................................................... 17

Regulatory Measures and Control Programs.................................................................. 18

PM10 Rule Effectiveness................................................................................................... 21

Compliance and Enforcement Activities.......................................................................... 22

Conclusions......................................................................................................................... 23

V. CLEAR CAUSAL RELATIONSHIP............................................................ 25

Introduction........................................................................................................................ 25

Event – June 16, 2012 ........................................................................................................ 25

Visibility Cameras.............................................................................................................. 34

Conclusion........................................................................................................................... 34

VI. “BUT FOR” ANALYSIS .............................................................................. 35

VII. CONCLUSIONS .......................................................................................... 36

Affects Air Quality ............................................................................................................. 36

Natural Event ..................................................................................................................... 36

Summary............................................................................................................................. 37

-iii-
 List of Figures 

Figure 2-1. Phoenix Geographic Setting and PM10 Monitor Locations (source: EPA AQS 

DataMart, NASA MODIS Satellite, Google Earth). PM10 monitor locations are indicated by 

the white markers. ..................................................................................................................................5

Figure 2-2. Drainage System of Phoenix, Arizona. ......................................................................................6

Figure 2-3. Phoenix Monthly Precipitation (top) and Maximum Temperature (bottom) 

Climatology (source: National Weather Service) ..................................................................................7

Figure 2-4. Cross-section of a thunderstorm creating an outflow boundary and haboob (Source: 

Desert Meteorology. Thomas T. Warner. 2004.)...................................................................................9

Figure 2-5. U.S. Drought Monitor analysis released during the time period of the exceedances 

described in this report. ........................................................................................................................11

Figure 2-6. Timeline of PM10 concentrations at monitors in the Phoenix area before, during and 

after the June 16, 2012, event...............................................................................................................12

Figure 3-1. Plot of daily maximum hourly average PM10 concentrations (January 1, 2007 – 

September 30, 2012) at the West Phoenix monitoring site..................................................................14

Figure 3-2. Plot of 24-hour average PM10 concentrations (January 1, 2007 – September 30, 2012) 

at the West Phoenix monitoring site. ...................................................................................................15

Figure 3-3. Plot of daily maximum hourly average PM10 concentrations (January 1, 2007 – 

September 30, 2012) at the Higley monitoring site. ............................................................................16

Figure 3-4. Plot of 24-hour average PM10 concentrations (January 1, 2007 – September 30, 2012) 

at the Higley monitoring site................................................................................................................17

Figure 4-1. Timeline of Maricopa County Fugitive Dust Rules and Ordinances. ......................................22

Figure 5-1. Satellite imagery showing strong storms developing and dissipating over southeastern 

Arizona. These storms are believed to have been responsible for the thunderstorm outflow 

boundary that caused PM10 exceedances in Maricopa and Pinal counties on June 16, 2012.............26

Figure 5-2. Phoenix nonattainment area PM10 monitor readings, Sky Harbor wind speed and 

visibility, and Williams Gateway wind speed for June 16, 2012.........................................................27

Figure 5-3. Pinal County PM10 monitor readings and Casa Grande wind speed and visibility for 

June 16, 2012 .......................................................................................................................................28

-iv-
List of Tables 

Table 2-1. Summary of Statewide PM10 Measurements for June 16, 2012...............................................13

Table 4-1. Rules and Ordinances Regulating Particulate Matter Emissions in Maricopa County .............19

Table 4-2. Pinal County Rules Regulating Existing and New Non-point Sources in Pinal County............20

Table 4-3. Pinal County Rules Regulating Fugitive Dust in Pinal County Portion of Maricopa 

County PM10 Nonattainment Area......................................................................................................21

-v-
-viList of Appendices 

Appendix A – 5-year Historical Fluctuation Graphs for the Phoenix Nonattainment Area PM10 Sites 

Appendix B – ADEQ Forecast Products for Phoenix, Maricopa County, and Pinal County 

Appendix C – Notice of Public Comment Period 

Appendix D – National Weather Service Forecasts, Warnings, and Alerts 

Appendix E – Additional National Weather Service Meteorological Data Tables for Maricopa County 

Airports 
I. EXCEPTIONAL EVENT RULE (EER) REQUIREMENTS 

In addition to the technical requirements that are contained within the EER, procedural requirements must 

be met in order for EPA to concur with the flagged air quality monitoring data. This section of the report 

lays out the requirements of the EER and associated guidance, and discusses how the Arizona Department 

of Environmental Quality (ADEQ) addressed those requirements. 

Procedural Requirements 

This section presents a review of the procedural requirements of the EER as required by 40 CFR 50.14 

(Treatment of Air Quality Monitoring Data Influenced by Exceptional Events) and explains how ADEQ 

fulfills them. The Federal EER requirements include notifying the public that an event was occurring, 

placing informational flags on data in EPA’s Air Quality System (AQS), notifying EPA of the intent to 

flag through submission of initial event description, documenting that the public comment process was 

followed, and submitting a demonstration supporting the exceptional events flag. ADEQ has addressed 

all of these procedural and documentation requirements. 

Public notification that event was occurring (40 CFR 50.14(c)(1(i)) 

ADEQ issued a Dust Control Action Forecast and an Ensemble Forecast for the Greater Phoenix area on 

June 16, 2012, advising citizens of the general potential for blowing dust due to very dry conditions. 

More information on ADEQ’s forecasting program can be found in Section IV. The forecast products 

that were issued for June 16, 2012, are included in Appendix B. 

Place informational flag on data in AQS (40 CFR 50.14(c)(2)(ii)) 

ADEQ and other operating agencies in Arizona submit data into EPA’s AQS. Data from both filter-based 

and continuous monitors operated in Arizona are submitted to AQS. 

When ADEQ and/or another agency operating monitors in Arizona suspects that data may be influenced 

by an exceptional event, ADEQ and/or the other operating agency expedites analysis of the filters 

collected from the potentially affected filter-based air monitoring instruments, quality assures the results, 

and submits the data into AQS. ADEQ and/or other operating agencies also submit data from continuous 

monitors into AQS after quality assurance is complete. 

If ADEQ and/or the operating agency have determined a potential exists that the monitor reading has been 

influenced by an exceptional event, a preliminary flag is submitted for the measurement in the AQS. The 

data are not official until they undergo more thorough quality assurance and quality control, leading to 

certification by May 1 of the year following the calendar year in which the data were collected 

(40 CFR 58.15(a)(2)). The presence of the flag can be confirmed in AQS. 

Notify EPA of intent to flag through submission of initial event description by July 1 of calendar year 

following event (40 CFR 50.14(c)(2)(iii)) 

ADEQ submitted notice to EPA on August 29, 2012 listing all days from calendar year 2012 that ADEQ 

intends to analyze under the Exceptional Events Rule and notifying the EPA of which PM10 data were 

flagged in AQS. Exceedances that occurred on June 16, 2012, within the Phoenix PM10 nonattainment 

area were included on that list. This report serves as the demonstration supporting the flagging of these 

data. 

-1-
On June 16, 2012, seven monitoring sites within the boundaries of the Phoenix PM10 nonattainment area 

exceeded the 24-hour PM10 standard during the high wind event that occurred during the late 

afternoon/evening hours. The PM10 monitors impacted were the Buckeye, Durango Complex, Dysart, 

Higley, South Phoenix, West 43rd, and West Phoenix monitors operated by Maricopa County Air Quality 

Department (MCAQD). 

Document that the public comment process was followed for event documentation (40 CFR 

50.14(c)(3)(iv)) 

ADEQ posted this assessment report on the ADEQ webpage and placed a hardcopy of the report in the 

ADEQ Records Management Center for public review. ADEQ will open a 30-day public comment period 

on January 14, 2013. A copy of the public notice certification, along with any comments received, will be 

submitted to EPA, consistent with the requirements of 40 CFR 50.14(c)(3)(iv). See Appendix D for a 

copy of the affidavit of public notice. 

Submit demonstration supporting exceptional event flag (40 CFR 50.14(a)(1-2)) 

At the close of the comment period, and after ADEQ has had the opportunity to consider any comments 

submitted on this document, ADEQ will submit this document, the comments received, and ADEQ’s 

responses to those comments to EPA Region IX headquarters in San Francisco, California. The deadline 

for the submittal of this demonstration package is September 30, 2014. 

Documentation Requirements 

Section 50.14(c)(3)(iii) of the EER states that in order to justify excluding air quality monitoring data, 

evidence must be provided for the following elements: 

a. The event satisfies the criteria set forth in 40 CFR 501(j) that: 

(1) the event affected air quality, 

(2) the event was not reasonably controllable or preventable, and 

(3) the event was caused by human activity unlikely to recur in a particular location or was a 

natural event; 

b. There is a clear causal relationship between the measurement under consideration and the event; 

c. The event is associated with a measured concentration in excess of normal historical fluctuations; 

and 

d. There would have been no exceedance or violation but for the event. 

Section II of this assessment introduces the conceptual model of the high wind event that transpired on 

June 16, 2012, providing a background narrative of the exceptional events and an overall explanation on 

how “the event affected air quality.” Further evidence that “the event affected air quality” is provided in 

Section V. Sections II and V also provide evidence that the event was a natural event. 

Section III of this assessment provides data summaries and time series graphs that help illustrate that the 

event on June 16, 2012, produced PM10 concentrations in excess of normal historical fluctuations. 

Section IV of this assessment details the existing area control measures and demonstrates that despite the 

presence and enforcement of these controls, the event on June 16, 2012, was not reasonably controllable 

or preventable. 

-2-
Section V of this assessment establishes a clear causal connection between the natural events of June 16, 

2012, and the exceedances of the 24-hour PM10 standard at the monitoring stations. The evidence in this 

section (and the previous section on historical fluctuations) also confirms that the event in question both 

affected air quality and were the result of natural events. 

Section VI of this assessment builds upon the demonstration showing a clear causal connection between 

the natural events and the exceedances and concludes there would have been no exceedances on June 16, 

2012, but for the presence of the natural events. 

Section VII contains conclusions that summarize the exceptional event that occurred on June 16, 2012, 

and relates the requirements in the EER to the information within this document. 

-3-
II. CONCEPTUAL MODEL 

Geographic Setting and Climate

 

This section describes the geographic and climatic setting of the monitors. 

Geographic Setting of Monitors 

Phoenix is located in the Salt River Valley in south-central Arizona. It lies at a mean elevation of 1,090 

feet above mean sea level (msl) in the northeastern part of the Sonoran Desert. Other than the mountains 

in and around the city, the topography of Phoenix is generally flat. The Phoenix area is surrounded by the 

McDowell Mountains (~4,200 ft msl) to the northeast, the foothills of the Bradshaw (~7,900 ft msl) and 

Mazataal (~7,900 ft msl) ranges to the north, the White Tank Mountains (~4,500 ft msl) to the west, the 

Sierra Estrella (~4,450 ft msl) to the southwest, and the Superstition Mountains (~5,000 ft msl) far to the 

east. Within the City are the Phoenix Mountains (~2,600 ft msl) and South Mountain (~2,600 ft msl). 

Current development is pushing north, west, and south into Pinal County. The Phoenix metropolitan area 

contains a fairly dense network of PM10 monitors throughout the area, with a much less dense network of 

monitors located throughout the rest of the state. Figure 2-1 shows the general geographic setting of 

Phoenix, as well as the locations of PM10 monitors throughout the state. It should be noted that some of 

the monitors shown in Figure 2-1 are filter-based monitors; therefore, monitoring data from all locations 

may be available only for select days (i.e., 1-in-6 run days). 

-4-
Figure 2-1. Phoenix Geographic Setting and PM10 Monitor Locations (source: EPA AQS DataMart, 

NASA MODIS Satellite, Google Earth). PM10 monitor locations are indicated by the white markers.

Figure 2-2 depicts the drainage systems or watersheds for the State of Arizona. Many of the rivers that 

form Arizona’s drainage system are dry for most of the year and, consequently, are sources of silt and fine 

soils that become suspended and add to regional PM10 loadings during high wind events. Much of this 

alluvial matter and fine soil is deposited in the low lying areas of central and southern Arizona, with 

larger depositional areas focused in and around the confluences of dry river channels. 

-5-
Figure 2-2. Drainage System of Phoenix, Arizona. 

-6-
Climate 

Phoenix has an arid climate, with very hot summers and temperate winters. The average summer high 

temperature is among the hottest of any populated area in the United States. The temperature reaches or 

exceeds 100oF an average of 110 days during the year and highs top 110oF an average of 18 days during 

the year. Phoenix receives an average of 7.66 inches of rain per year. 

As shown in Figure 2-3, precipitation is sparse during the first part of the summer, but the influx of 

monsoonal moisture, which generally begins in early July and lasts until mid-September, raises humidity 

levels and can cause heavy localized precipitation and flooding. Although thunderstorms are possible at 

any time of the year, they are most common during the monsoon season from July to mid-September as 

humid air is advected from the Gulf of California, Gulf of Mexico, and large thunderstorm complexes that 

form over the Sierra Madre Occidental Mountains in Mexico. This influx of moisture, combined with 

intense solar heating, often creates a very unstable environment that is ripe for thunderstorm development. 

These thunderstorms can bring strong winds and blowing dust, large hail, and heavy rain. Dust storms 

associated with these thunderstorms typically occur in the early part of the monsoon season 

(June/July/August) before soaking rains help keep soil particles bound to one another. However, 

depending on the amount of precipitation received during the monsoon season, extremely hot 

temperatures act to dry out the surface quickly, and dust storms can occur at any time. During the 

December through March period, winter storms moving inland from the Pacific Ocean can produce 

significant rains throughout Arizona. This December–March time period and the July–August time 

period are typically the wettest parts of the year. Meanwhile, a distinct dry season occurs from April 

through June for the Phoenix area and the rest of Arizona. While these weather patterns describe the 

general climatology for the Phoenix area over a long period of time, Phoenix and the entire state of 

Arizona are also prone to a high degree of variability in these weather patterns from year to year. 

Figure 2-3. Phoenix Monthly Precipitation (top) and Maximum Temperature (bottom) Climatology 

(source: National Weather Service)

-7-
Monsoon Season Description and Event Summary

A multi-day period, including the event day of June 16, 2012, was characterized by monsoonal 

thunderstorm activity over southeast Arizona and New Mexico. The North American Monsoon is a shift 

in wind patterns in the summer that occurs as Mexico and the southwest U.S. warm under intense solar 

heating. As this happens, low level moisture is transported primarily from the Gulf of California and 

eastern Pacific Ocean into the southwestern U.S. The Gulf of California, a narrow body of water 

surrounded by mountains, is particularly important for low-level moisture transport into Arizona and 

Sonora. Mid- and upper-level moisture is also transported into the region, mainly from the Gulf of 

Mexico by easterly winds aloft. This combination causes a distinct rainy season over large portions of 

western North America, which develops rather quickly and sometimes dramatically. Rainfall during the 

monsoon is not continuous and varies considerably, depending on a variety of factors. There are usually 

distinct “burst” periods of heavy rain during the monsoon, and “break” periods with little or no rain. 

Even during active monsoon periods, some areas can go without receiving any significant precipitation 

while other nearby areas experience heavy rains and flooding.

The thunderstorm activity in Arizona on June 16, 2012, was active in and around the desert areas of 

southeastern Arizona. These thunderstorms did not result in any precipitation for the Phoenix area, but 

the storms were severe in nature and caused a dust-carrying outflow boundary which propagated into the 

Phoenix area in the evening. Downdrafts associated with heavy precipitation from thunderstorms or from 

collapsing thunderstorms can end up producing what are called downbursts, or sometimes more 

concentrated and severe microbursts, which are rapidly descending bursts of air that come through the 

thunderstorms. These downward bursts of air hit the ground and then disperse away from the storms as 

areas of outflow. These outflow boundaries from the thunderstorms can kick up large areas of dust, 

sometimes called haboobs, and transport that dust for long distances from the initiating thunderstorms 

(see Figure 2-4). 

The active monsoon occurring on June 16th led to numerous thunderstorms and a large thunderstorm 

outflow that produced blowing dust throughout southeastern and central Arizona, including the Phoenix 

Metropolitan area. The windblown dust event produced seven PM10 exceedances in the Phoenix PM10 

nonattainment area on June 16, 2012. The event was primarily driven by strong outflow winds from 

severe thunderstorms producing wind gusts from one prominent direction. The June16th event was a 

widespread dust event with mostly south-southeasterly winds transporting dust from the desert areas of 

Pima and Pinal Counties into all areas of the Phoenix region. Further details on the event can be found in 

Section V. 

-8-
Figure 2-4. Cross-section of a thunderstorm creating an outflow boundary and haboob (Source: Desert 

Meteorology. Thomas T. Warner. 2004.)

The nature of these monsoonal dust events is such that specific source areas are difficult to determine, as 

outflows from thunderstorms can carry dust over vast distances encompassing many source areas. 

Because of this, it is more appropriate to speak of general source regions for these monsoonal dust storms, 

which typically are identified based upon the locations of the thunderstorms that are believed to have 

created the dust generating and carrying outflow winds. The majority of the PM10 impacting the Phoenix 

area from thunderstorm-driven high winds on June 16, 2012, originated outside of the Phoenix PM10 

nonattainment area. The contributing source regions to the dust event were somewhat widespread, but a 

large portion of the PM that was transported into Maricopa County likely came from areas within Pinal 

County to the south and southeast of Maricopa County. Other potential source contributors to the PM10 

events were areas in northern Pima County and southeastern Maricopa County. The exact origin of the 

PM sources is often difficult to determine due to the less dense monitoring networks in the general source 

area. 

Another important factor that led to these significant dust storms was the on-going drought across the 

region. The most recent U.S. Drought Monitor placed the area between Tucson and Phoenix, the primary 

dust source region for winds out of the southeast, in D2 (Severe) to D3 (Extreme) drought (see Figure 2-

5). Rainfall in Phoenix since October 1, 2011, had been 45% of normal, and only 11% of normal since 

January 1, 2012 (see the Daily Climate Report for June 16 in Appendix D). For additional general 

information pertaining to the monsoon season in Arizona, see the news media web links provided below. 

2011 Monsoon Season Summary and Review  http://bcove.me/krh3qk29

This video contains information about the 2011 monsoon season and the general formation 

of dust storms in Arizona, which is relevant each year. 

-9-
-10-

2011 Monsoon Season Review 2  http://bcove.me/tc6otk0h

This video contains information about the 2011 monsoon season, focusing on the large 

number of dust storms that occurred, and a discussion of why there were so many dust 

storms in 2011. Since similar meteorological factors were in place in 2012, dust storms 

formed this year for many of the same reasons as they did in 2011. 

The abnormally dry conditions that were in place during the early part of the monsoon season (which 

persisted throughout the duration of the monsoon season) resulted in a large fetch of soils that were 

vulnerable to particulate suspension. The thunderstorm outflow boundaries that affected Maricopa and 

Pinal counties on June 16, 2012, resulted in very little rainfall throughout south-central Arizona, but the 

high winds associated with the outflow boundary did transport moderate to very high levels of particulate 

concentrations into the Phoenix area. A timeline summarizing the June 16 event can be seen in Figure 2-

6. This figure shows hourly PM10 concentrations for a three-day period around, and including, the event 

day. During the 24 hours prior to the event, there were low PM10 concentrations across the Phoenix 

region throughout the entire day. On the event day, the figure shows low PM10 concentrations during the 

day and then very high PM10 concentrations during the evening hours when the thunderstorm outflow 

boundary traveled through the Phoenix area. Lastly, the figure shows that PM10 concentrations gradually 

dropped back down to low levels during the 24 hours after the event, indicating that without the impacts 

of the thunderstorm outflow boundary, PM10 concentrations at all sites in the Phoenix PM10 

nonattainment area on June 16, 2012, would have been below the 24-hour average PM10 exceedance 

threshold of 150 μg/m3

. 

Following Figure 2-6, Table 2-1 details the PM10 24-hour average concentrations, the daily maximum 

hourly concentrations and the time at which they occurred, and the flag given to the data in EPA’s AQS 

for all PM10 monitoring sites in Arizona for the event day. The table shows exceedances of the national 

24-hour PM10 standard at several sites in Maricopa and Pinal Counties on June 16, 2012, and the timing 

of the 1-hour maximum values across those sites indicates that PM10 was increasing sequentially from 

the southeast to the northwest across central Arizona during the evening hours. This timing coincides 

with a thunderstorm outflow boundary with sustained southeasterly winds over 30 miles per hour (mph) 

that blew through Pinal County and into Maricopa County between 5 p.m. and 7 p.m. on June 16th. 

Conclusions

This Conceptual Model was created to provide a basic description of the general climate and weather 

patterns that led to the active thunderstorm period on June 16, 2012, and produced the dust storm and 

seven PM10 exceedances in the Phoenix PM10 nonattainment area during the one-day episode. A more 

detailed analysis of the windblown dust event is included in Section V, where a demonstration of the clear 

causal connection between the uncontrollable natural events and PM10 exceedances is presented. 
Figure 2-5. U.S. Drought Monitor analysis released during the time period of the exceedances described in this r

-11-
Figure 2-6. Timeline of PM10 concentrations at monitors in the Phoenix area before, during and after the June 1

-12-
June 16, 2012 

Table 2-1. Summary of Statewide PM10 Measurements for June 16, 2012. 

Monitor 

Monitor 

Type Operator AQS Monitor ID 

24-hr Avg 

PM10 

(μg/m3) 

1-hr Max 

PM10 

(μg/m3) 

Max 

Time 

AQS 

Qualifier 

Flag 

Apache County 

 N/A TEOM WMAT 04-001-1003-81102-1 24 148 1800 

Cochise County 

 Paul Spur Chemical Lime Plant TEOM ADEQ 04-003-0011-81102-3 34 58 1500 

Coconino County 

 N/A TEOM NN 04-005-1237-81102-1 N/A N/A N/A 

Gila County 

 Hayden Old Jail TEOM ADEQ 04-007-1001-81102-3 83 581 1600 IJ 

Maricopa County 

 Buckeye TEOM MC 04-013-4011-81102-1 202 1965 1900 RJ 

 Central Phoenix TEOM MC 04-013-3002-81102-4 97 990 1800 

 Durango Complex TEOM MC 04-013-9812-81102-1 186 2096 1800 RJ 

 Dysart TEOM MC 04-013-4010-81102-1 167 1269 1900 RJ 

 Fort McDowell/Yuma Frank TEOM FMIR 04-013-5100-81102-3 55 N/A N/A 

 Glendale TEOM MC 04-013-2001-81102-1 136 723 2000 

 Greenwood TEOM MC 04-013-3010-81102-1 145 1482 1800 

 Higley TEOM MC 04-013-4006-81102-1 194 2018 1800 RJ 

 JLG Supersite BAM ADEQ 04-013-9997-81102-3 118 1084 1800 IJ 

 JLG Supersite TEOM ADEQ 04-013-9997-81102-4 97 708 1800 IJ 

 North Phoenix BAM MC 04-013-1004-81102-1 74 596 1800 

 South Phoenix TEOM MC 04-013-4003-81102-1 165 1864 1800 RJ 

 Tempe TEOM MC 04-013-4005-81102-1 95 1018 1800 

 West Chandler TEOM MC 04-013-4004-81102-1 104 669 1700 

 West Forty Third TEOM MC 04-013-4009-81102-1 211 2299 1800 RJ 

 West Phoenix BAM MC 04-013-0019-81102-1 189 1945 1800 RJ 

 Zuni Hills TEOM MC 04-013-4016-81102-1 147 733 2100 

Navajo County 

 N/A TEOM WMAT 04-017-1002-81102-1 N/A N/A N/A 

Pima County 

 Ajo TEOM ADEQ 04-019-0001-81102-3 39 176 0500 

 Geronimo BAM PCDEQ 04-019-1113-81102-1 43 119 1500 

 Green Valley BAM PCDEQ 04-019-1030-81102-1 42 102 1400 

 Orange Grove FRM PCDEQ 04-019-0011-81102-2 38 N/A N/A 

 Rillito TEOM ADEQ 04-019-0020-81102-3 45 110 0100 

 South Tucson FRM PCDEQ 04-019-1001-81102-1 44 N/A N/A 

Pinal County 

 Apache Junction Fire Stn. TEOM PCAQCD 04-021-3002-81102-3 66 655 1800 

 Casa Grande Downtown TEOM PCAQCD 04-021-0001-81102-3 235 2006 1700 RJ 

 Combs School TEOM PCAQCD 04-021-3009-81102-3 177 2683 1800 RJ 

 Cowtown TEOM PCAQCD 04-021-3013-81102-3 698 12276 1800 RJ 

 Maricopa TEOM PCAQCD 04-021-3010-81102-3 256 2405 1800 RJ 

 Pinal County Housing TEOM PCAQCD 04-021-3011-81102-3 541 6838 1700 RJ 

 Stanfield TEOM PCAQCD 04-021-3008-81102-3 339 5102 1800 RJ 

Santa Cruz County 

 Nogales Post Office BAM ADEQ 04-023-0004-81102-3 55 125 1500 

Yuma County 

 Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 29 79 2300 

Operator Abbreviations: MC – Maricopa County Air Quality Department 

 PCAQCD – Pinal County Air Quality Control District 

 ADEQ – Arizona Department of Environmental Quality 

 FMIR – Fort McDowell Indian Reservation 

 NN – Navajo Nation, AZ, NM, UT 

 PCDEQ – Pima County Department of Environmental Quality 

 SRP-MIC – Salt River Pima-Maricopa Indian Community of Salt River Reservation, AZ 

 WMAT – White Mountain Apache Tribe of Fort Apache Reservation, AZ 

-13-
III. HISTORICAL FLUCTUATIONS 

The PM10 concentrations measured across much of Maricopa County on June 16, 2012, were some of the 

highest hourly and 24-hour averages measured over the last five-plus years. Time series plots of the 24-

hour PM10 concentrations for the period January 1, 2007, through September 30, 2012, were created for 

all PM10 monitors in the Phoenix PM10 nonattainment area. Additionally, time series plots of the daily 

maximum hourly average PM10 concentrations were created for two monitors in Maricopa County. 

These two additional plots were created to provide a deeper understanding of the magnitude of short-term 

particulate concentrations and their contribution to PM10 exceedances in the Phoenix PM10 

nonattainment area. Time series plots for two monitoring sites (West Phoenix and Higley) are included 

within this section, while the remaining 24-hour average plots are available in Appendix A. The West 

Phoenix monitor was selected because of its central location in relation to all monitors in Maricopa 

County and it was severely impacted site during the June 16 windblown dust event. The Higley monitor 

was selected because it is representative of eastern Maricopa County, an area of the region frequently 

impacted by dust storms caused by thunderstorm outflow events. The graphs below and in Appendix A 

show that the June 16th event was in the top five most extreme events of the last five-plus years for 

multiple sites. 

Figure 3-1. Plot of daily maximum hourly average PM10 concentrations (January 1, 2007 – September 

30, 2012) at the West Phoenix monitoring site. 

-14-
Figure 3-1 shows the daily maximum hourly averages from the West Phoenix PM10 monitor. The plot 

shows that the June 16th hourly average of 1,945 μg/m3

 was the second highest hourly PM10 

concentration recorded in the last five-plus years. The plot also shows that the maximum hourly average 

PM10 concentration on June 16 was only second to that observed during the July 5, 2011, haboob event 

which recently received EPA concurrence. The hourly average concentrations from this event surpassed 

most of the dust storms that occurred during the 2011 monsoon season, which was one of the worst dust 

storm seasons on record. It is also clear that the most significant hourly average PM10 concentrations at 

the West Phoenix monitor typically occur during the June through September time frame, a period during 

which the monsoon season is most active and the Phoenix region is frequently impacted by haboob 

events. 

Figure 3-2 shows the daily 24-hour averages from the West Phoenix PM10 monitor and indicates that the 

June 16th event produced the seventh highest 24-hour average PM10 concentration measured in the last 

five-plus years. Similar to haboob events that occurred in 2009 and during several months in 2011, the 

June 16th event experienced PM10 concentrations that were well above the 24-hour exceedance threshold. 

Figure 3-2. Plot of 24-hour average PM10 concentrations (January 1, 2007 – September 30, 2012) at the 

West Phoenix monitoring site. 

Figures 3-3 and 3-4 provide an historical look at the daily maximum hourly averages and daily 24-hour 

averaged PM10 concentrations from the Higley monitor. The plots also show that the maximum hourly 

concentration and exceedance measured at the Higley monitor on June 16 was among the 12 highest 

PM10 concentrations measured over the last five-plus years. As was the case for the West Phoenix 

-15-
monitor, the most significant hourly average PM10 concentrations at the Higley monitor typically occur 

during the June through September time frame, a period during which the monsoon season is most active 

and the Phoenix region is frequently impacted by haboob events. 

Figure 3-3. Plot of daily maximum hourly average PM10 concentrations (January 1, 2007 – September 

30, 2012) at the Higley monitoring site. 

-16-
Figure 3-4. Plot of 24-hour average PM10 concentrations (January 1, 2007 – September 30, 2012) at the 

Higley monitoring site. 

Conclusions

The plots within this section provide an historical perspective of PM10 concentrations since 2007. These 

plots, along with those in Appendix A, show that the haboob event that occurred on June 16, 2012, 

resulted in one of the top 12 highest 24-hour average PM10 concentrations seen in the last five-plus years 

at multiple sites. This equates to PM10 concentrations in the 99.9th percentile when compared to historic 

data. In the case of the West Phoenix and Dysart monitoring sites, the 24-hour averaged PM10 

concentrations measured on June 16 were in the top seven highest concentrations observed during the last 

five-plus years. While the PM10 concentrations that were measured on June 16th were extreme in many 

cases, the plots also show that similar events are not uncommon during the monsoon season. As 

documented in several published journals and academic text books, haboobs generated from thunderstorm 

outflow boundaries are a phenomenon that Arizona deals with every year, some years more so than 

others, namely in 2007, 2009, and 2011. 

-17-
IV. NOT REASONABLY CONTROLLABLE OR PREVENTABLE

Section 50.1(j) of Title 40 CFR Part 50 requires that an event must be “not reasonably controllable or 

preventable” in order to be defined as an exceptional event. This requirement is met by demonstrating 

that despite reasonable control measures in place within Maricopa County and the Phoenix PM10 

nonattainment area, high wind conditions overwhelmed all reasonably available controls. The event 

occurring on June 16, 2012, was directly related to strong and gusty winds generated by a thunderstorm 

outflow boundary. The strong winds overwhelmed all reasonably available controls, and were also 

responsible for transporting PM into the Phoenix PM10 nonattainment area from areas outside of the 

nonattainment area. As explained in the conceptual model, downdrafts from collapsing thunderstorms 

produce outflow boundaries that contain gusty, turbulent wakes that raise dust from the desert surfaces 

that can be as wide as 100 miles in severe cases. As shown in Section V, the source region for all of the 

dominant thunderstorm outflows and associated transported dust on June 16, 2012, generally came from 

areas outside of the Phoenix PM10 nonattainment area—primarily from the deserts of Pinal, Pima, and 

southern Maricopa counties. While it is likely that some dust was generated within the PM10

nonattainment area as gusts from the thunderstorm outflows passed through the area, the amount of dust 

generated locally was easily overwhelmed by, and largely unnoticeable as compared to, the dust 

transported in from the source regions of the thunderstorm outflows. Strict controls on local sources of 

fugitive dust were in place and enforced on June 16, 2012, but were not capable of controlling transported 

dust and PM10 raised by the gusty and turbulent thunderstorm outflows on this date. 

The following sections describe the BACM- and MSM-level PM10 control measures in place June 16, 

2012, and the robustness of the programs designed to enforce these measures. Pro-active response and 

analysis of each event as it is occurring verify the uncontrollable nature of each event, while inspections 

of local sources performed before, during, and after the June 16, 2012, event confirmed that no unusual 

anthropogenic PM10-producing activities occurred in Maricopa County, the Phoenix PM10 

nonattainment area, or the local areas surrounding the exceeding monitors. 

Regulatory Measures and Control Programs

ADEQ and MCAQD are responsible for implementing regulatory measures to control emissions from 

agricultural sources, stationary sources, fugitive dust sources, and open burning within Maricopa County. 

Three major programs provide or contribute to air pollution control measures for the Greater Phoenix 

area: 

1. ADEQ’s Agricultural Best Management Program (AgBMP); 

2. Maricopa County’s Inspection and Compliance Program; and 

3. ADEQ’s Air Quality Forecasting Program. 

Specifically, ADEQ is responsible for compliance assistance and enforcement of Agricultural Best 

Management Practices developed by the Governor’s Agricultural Best Management Practices Committee, 

while MCAQD is responsible for compliance assurance for all other significant sources of PM10 

emissions. In addition to routine inspections and inspections driven by complaints, inspections are often 

increased when (1) ADEQ forecasters issue a High Risk for the Maricopa County Dust Control Forecast, 

(2) ADEQ forecasters issue a High Pollution Advisory, or (3) near-real-time monitoring data indicate 

unique activity via high PM concentrations. The forecasting program and inspection/compliance 

programs work together so that resources can be best utilized during days that are of greatest risk for 

elevated PM emissions. 

-18-
On July 25, 2002, EPA took initial action to finalize approval of the Best Available Control Measure 

(BACM) and the Most Stringent Measure (MSM) demonstrations in the Serious Area PM10 plan for the 

Maricopa County portion of the metropolitan Phoenix PM10 nonattainment area (67 FR 48718). These 

BACM and MSM demonstrations were again approved by EPA on July 14, 2006 (71 FR 43979). The 

Agricultural Best Management Practices General Permit rule and related definitions have been approved 

into the Arizona Administrative Code as R18-2-610 and R18-2-611 pursuant to Arizona Revised Statutes 

§ 49-457.2 Maricopa County regulations of PM10 emissions are listed in Table 4-1. 

Table 4-1. Rules and Ordinances Regulating Particulate Matter Emissions in Maricopa County 

Rule/Ordinance Number 

& Title Description 

Rule 300: Visible 

Emissions 

Establishes standards for visible emissions and opacity. 

Rule 310: Fugitive Dust 

from Dust-Generating 

Operations 

Establishes limits for the emissions of particulate matter into the 

ambient air from any property, operations, or activity that may 

serve as a fugitive dust source 

Rule 310.01: Fugitive Dust 

from Non-Traditional 

Sources of Fugitive Dust 

Establishes limits for the emissions of particulate matter into the 

ambient air from open areas, vacant lots, unpaved parking lots, 

and unpaved roadways that are not regulated by Rule 310 and 

that are not required to have either a permit or a dust control 

plan 

Rule 311: Particulate 

Matter from Process 

Industries 

Establishes emission rates based on process weight applicable to 

any affected operations not subject to Rule 316. 

Rule 312: Abrasive 

Blasting 

Establishes limits for particulate emissions from abrasive 

blasting operations 

Rule 314: Open Outdoor 

Fires and Indoor Fireplaces 

at Commercial and 

Institutional Establishments

Establishes limits for the emissions of air contaminants 

produced from open burning 

Rule 316: Nonmetallic 

Mineral Processing 

Establishes limits for the emissions of particulate matter into the 

ambient air from any nonmetallic mining operation or rock 

product processing plant 

Rule 317:

Hospital/Medical/ 

Infectious Waste 

Incinerators 

Establishes limits for the emissions of air pollutants from 

medical waste incinerators 

Rule 322: Power Plant 

Operations 

Establishes limits for the emissions of nitrogen oxides, sulfur 

oxides, carbon monoxide and particulate matter from existing 

power plants and cogeneration plants 

Rule 323: Fuel Burning 

Equipment from 

Industrial/Commercial/ 

Institutional (ICI) Sources 

Establishes limits for the emissions of nitrogen oxides, sulfur 

oxides, carbon monoxide and particulate matter from ICI 

sources 

 

2

 Updates to the AgBMP program in December, 2011, clarified BMPs for crop and added BMPs for animal operations. 

Effective 12/29/2011, R18-2-611 was renumbered to R18-2-610.01 Agricultural PM10 General Permit for Crop 

Operations and R18-2-611.01 Animal Operations PM10 General Permit was added. Definitions for Crop Operations were 

revised at R18-2-610, and new definitions for Animal Operations were added at R18-2-611. 

-19-
Rule/Ordinance Number Description & Title 

Rule 324: Stationary 

Internal Combustion (IC) 

Engines 

Establishes limits for the emissions of carbon monoxide, 

nitrogen oxides, sulfur oxides, volatile organic compounds, and 

particulate matter from stationary internal combustion engines, 

including stationary IC engines used in cogeneration 

Rule 325: Brick and 

Structural Clay Products 

(BSCP) Manufacturing 

Establishes limits for particulate matter emissions from the use 

of tunnel kilns for curing in the brick and structural clay product 

(BSCP) manufacturing processes 

Ordinance P-25: Leaf 

Blower Restriction 

Establishes restrictions for leaf blowers in incorporated and 

unincorporated sections of Area A in Maricopa County 

Ordinance P-26:

Residential Woodburning 

Restriction 

Establishes restrictions for residential woodburning 

Ordinance P-27: Vehicle 

Parking and Use on 

Unstabilized Vacant Lots 

Establishes restrictions for vehicle parking and use on 

unstabilized vacant lots in unincorporated sections of Area A in 

Maricopa County 

Ordinance P-28: OffRoad Vehicle Use in 

Unincorporated Areas of 

Maricopa County 

Establishes restrictions for operating vehicles on unpaved 

property in unincorporated areas of Maricopa County 

Arizona Administrative 

Code R18-2-611 & 610: 

Agricultural PM10 General 

permit 

Establishes a requirement for commercial farmers to implement 

best management practices and maintain a record demonstrating 

compliance 

In addition to the rules and regulations listed in Table 4-1, other PM10 reducing control measures (e.g., 

paving of unpaved roads, PM10 certified street sweepers, controlling unpaved parking lots, etc.) have 

been committed to, and implemented by, local jurisdictions throughout the PM10 nonattainment area, and 

incorporated into the Arizona SIP through PM10 plans such as the Revised MAG 1999 Serious Area 

Particulate Plan for PM10 for the Maricopa County Nonattainment Area. The Pinal County Air Quality 

Control District (PCAQCD) also implements regulatory control measures on emissions from existing and 

new non-point sources within Pinal County (see Table 4-2). Additionally, the PCAQCD implements 

specific nonattainment rules for that part of the Phoenix PM10 nonattainment area that resides in Pinal 

County (see Table 4-3). 

Table 4-2. Pinal County Rules Regulating Existing and New Non-point Sources in Pinal County 

Article Number & Title Description 

Chapter 4, Article 2: Fugitive 

Dust 

Provides a mechanism to reasonably regulate operations which 

periodically may cause fugitive dust emissions into the 

atmosphere 

Chapter 4, Article 3: 

Construction Sites – Fugitive Dust 

Improves the control of excessive fugitive dust emissions that 

have been traditionally associated with construction, earthwork, 

and land development, and thereby minimize nuisance impacts 

-20-
Table 4-3. Pinal County Rules Regulating Fugitive Dust in Pinal County Portion of Maricopa 

County PM10 Nonattainment Area 

Article Number & Title Description 

Chapter 4, Article 4: 

Nonattainment Area Rules; 

Dustproofing for Commercial 

Parking, Drives and Yards 

Establishes rules to avoid violations of the prevailing PM10 

standard and additionally minimize nuisance impacts by 

improving control of excessive fugitive dust emissions from 

unpaved parking lots 

Chapter 4, Article 5: 

Nonattainment Area Rules; 

Stabilization for Residential 

Parking and Drives 

Establishes rules for stabilizing residential properties 

Chapter 4, Article 6: Restrictions 

on Vehicle Parking and Use on 

Vacant Lots

Establishes rules for unpaved or unstabilized vacant lots (valid 

in Pinal County portion of Area A) 

Chapter 4, Article 7: 

Construction Sites in 

Nonattainment Areas – Fugitive 

Dust

Establishes rules to avoid violations of the prevailing PM10 

standard and additionally minimize nuisance impacts by 

improving control of excessive fugitive dust emissions from 

activities associated with construction, earthwork, or land 

development 

Chapter 4, Article 8: 

Nonattainment Area Rules, 

Requirement for Stabilization of 

Disturbed Areas at Vacant Lots

Establishes rules for stabilizing disturbed areas at vacant lots 

PM10 Rule Effectiveness

MCAQD analyzed the effectiveness of its fugitive dust rules (Rules 310, 310.01 and 316) in terms of 

permit compliance rates. This rule effectiveness (RE) study was designed to assess how many sources 

regulated by MCAQD during the subject time period received no PM10 emissions-related violations. As 

a basis for comparison, the percentage of permitted sources in compliance during calendar year 2007 was 

76% for sources subject to Rule 310, 85% for Rule 310.01 sources, and 40% for Rule 316 sources. In 

early 2008, Rules 310, 310.01, and 316 were strengthened, and new ordinances (covering additional 

source categories such as leaf blowers, vacant lots, and off-road vehicles) were adopted. These 

enhancements resulted from MCAQD department’s obligations under such agreements as the 2005 

Revised PM10 State Implementation Plan for the Salt River Area and the Maricopa Association of 

Governments (MAG) 2007 Five Percent Plan for PM10 for the Maricopa County Nonattainment Area to 

reduce PM10 emissions throughout the county. Three major areas that contributed to increased 

compliance were an increase in departmental staffing (especially inspectors), a robust training program, 

and regulatory changes that broadened and strengthened control measures under Rules 310, 310.01, and 

316. 

Source compliance rates were re-assessed for FY 2009 (July 2008–June 2009), a period that allowed time 

for the new and revised regulations to take effect. The results showed significant increases in compliance 

compared with the earlier period: to 90% (from 76%) for Rule 310 sources, to 95% compliance (from 

85%) for Rule 310.01 sources, and to 65% (from 40%) for Rule 316 sources. These improvements 

continued into calendar year 2010 with compliance rates of 94% for Rule 310 sources, 96% for Rule 

310.01, and 73% for Rule 316 sources. The timeline provided in Figure 4-1 illustrates the improvements 

-21-
in RE over the last several years, and also points out significant revisions to previous rules, as well as 

newly adopted rules and ordinances. 

01/27/2010

Rules 310 & 310.01

Revised

01/12/2011

Ordinances

P‐27 & P‐28 Revised

06/01/2005

06/08/2005

Rule 316 Revised

04/07/2004

Rule 310 Revised

02/17/2005

Rule 310.01 Revised

03/26/2008

Rules 310 & 310.01

Revised

March 2008

September 2006

02/20/2008

Ordinances P‐25, P‐27

& P‐28  Adopted

03/12/2008

Rule 316 Revised

Figure 4-1. Timeline of Maricopa County Fugitive Dust Rules and Ordinances. 

Compliance and Enforcement Activities

MCAQD is prepared to proactively respond to high wind events and to protect human health and wellbeing. MCAQD’s approach consists of two primary components: routine proactive inspections, as well 

as surveillance inspections, conducted both during and after significant events. MCAQD routinely 

inspects dust control-permitted sites and increases the frequency of inspections for permits covering areas 

of 10 acres or more. Rule 316 sources are also regularly inspected multiple times every year. Maricopa 

County also responds to the majority of complaints within 24 hours. 

Maricopa County monitors the ADEQ Five-Day Dust Control Forecast to identify the potential for 

elevated PM10 pollution levels due to high winds or stagnant conditions. When a High Pollution 

Advisory (HPA) is issued for Maricopa County, MCAQD conducts additional surveillance before, during, 

and after the forecast event(s). MCAQD also conducts event surveillance and post-event activities during 

exceedance days that had not been forecast (i.e., those instances in which an HPA had not been issued). 

Pre-event surveillance consists of surveying high-risk areas for any dust-generating activities, educating 

sources of the impending HPA event, and issuing violations for failure to comply with local, state, or 

federal regulations. During the event, MCAQD inspectors survey high-risk areas to confirm that control 

measures are in place, document any violations, and contact other regulatory agencies if necessary. Postevent activities include continued surveys of high-risk areas, re-inspecting sources that had received 

violations within two business days, and an internal MCAQD debriefing of event activities. 

During 2011 and 2012, a total of 17 MCAQD air monitoring sites were upgraded with new equipment to 

allow the monitoring sites to automatically report monitored readings at five-minute intervals. 

Previously, hourly readings were only available. The real-time data reporting system includes a 

mechanism to alert MCAQD field staff when PM concentrations are elevated. The system allows 

MCAQD responders to review concentrations at the monitor and to consult the National Weather Service 

website to check for weather event activity. This capability allows the MCAQD responder to identify 

-22-
regional events and monitor specific issues. If necessary, the MCAQD responders can inform nearby 

stakeholders and local governments of the elevated PM10 concentrations. 

For June 16, 2012, a Maricopa County Dust Control Forecast was issued by ADEQ indicating a low-risk 

level for unhealthy PM10. The Dust Control Forecast stated mostly light winds were expected. 

An evaluation of all inspection reports, air quality complaints, compliance reports, and other 

documentation indicate no evidence of unusual anthropogenic-based PM10 emissions. During the time 

period of June 13 through June 19, 2012, MCAQD inspectors conducted a total of 200 inspections of 

permitted facilities, of which 97 were at fugitive dust sources. Additionally, MCAQD conducted 10 

inspections on vacant lots and unpaved parking lots during this period. 

During this 7-day period, a total of 13 violations were issued county-wide for PM10 and non-PM10-related 

violations. No violations were issued for PM10 emissions within a 4-mile radius of an exceeding monitor. 

MCAQD was prepared for any complaints received due to the high wind event. During the 7-day period 

from June 13 through June 19, 2012, MCAQD received 31 complaints, of which 23 were windblown 

dust-related. Each complaint was assigned to and investigated by a MCAQD inspector. A review of all 

pertinent records from this period indicates that MCAQD inspectors did not observe any PM10 emission 

violations of local, state, or federal regulations within a 4-mile radius of an exceeding monitor. 

In addition to MCAQD’s efforts in pre-event surveillance and proactive inspections, ADEQ’s 

Agricultural Best Management Practice Program (Ag BMP) inspector monitors the ADEQ Five-Day Dust 

Control Forecast and the MCAQD air monitoring sites that include real-time data. The ADEQ Ag BMP 

inspector uses specific knowledge of seasonal activities and associations with the local growers and 

dairymen to communicate the importance of limiting dust-generating activities, especially during highwind events. Additional outreach is conducted with facility representatives prior to forecasted high-wind 

alert days. Should the PM10 readings at a MCAQD air monitoring site show notable increases, the 

ADEQ Ag BMP inspector is dispatched to contact the owners and operators of agriculture fields in the 

area to discern if their activities are causing negative impacts. The Ag BMP inspector is prepared to 

respond to most agriculture complaints within 24 hours. 

Based on a review of the inspection reports and site visit documentation, there is no evidence to suggest 

that agricultural activities produced unusual PM10 emissions. On June 15, 2012, the ADEQ Ag BMP 

inspector observed activity in the Higley area and noted no harvesting or tilling activities. The inspector 

also noted a straw cuttings fire in the area of 27th Avenue and South Mountain road was extinguished by 

local fire agency. No complaints were received in the 2 days prior to the event. 

Conclusions

The thunderstorm outflow event of June 16, 2012, first described in Section II and discussed in more 

detail in Section V, produced strong gusts and turbulent wakes that transported dust and PM10 into the 

Phoenix PM10 nonattainment area. The source region of the outflows that caused the exceedances was 

largely located in areas outside the Phoenix PM10 nonattainment area, primarily the deserts of Pinal, 

Pima, and southern Maricopa County. The Phoenix area is designated as a serious nonattainment area for 

PM10 and is required to have BACM for all significant sources of PM10. BACM-approved control 

measures on significant anthropogenic sources were in place and enforced during the events, and proactive tracking and response to the events by regulatory agencies and local governments confirmed the 

uncontrollable nature of the dust emissions; therefore, these pre-existing/prior approved required controls 

-23-
are adequate for meeting the requirements of an exceptional event and should be considered “reasonable” 

for these purposes. 

Despite the deployment of comprehensive control measures and sophisticated response programs and a 

few localized, low-impact violations of the dust control rules, high wind conditions associated with 

thunderstorms and thunderstorm outflows brought high concentrations of PM10 emissions into, and also 

overwhelmed controls within, the Phoenix PM10 nonattainment area. Strong thunderstorm outflows with 

sustained winds ranging from 20-30 mph, and even greater speeds nearest the source regions, described in 

Section V, were enough to overwhelm all available efforts to limit PM10 concentrations from the event. 

The fact that these were natural events involving strong thunderstorm outflow winds that transported 

PM10 emissions into Maricopa County, with a majority of the PM10 emissions recorded by Maricopa 

County area monitors coming from sources outside of the Phoenix PM10 nonattainment area, provides 

strong evidence that the events and exceedances of June 16, 2012, recorded within the Phoenix PM10 

nonattainment area, were not reasonably controllable or preventable. 

-24-
V. CLEAR CAUSAL RELATIONSHIP 

Introduction

A demonstration of the clear causal connection between uncontrollable natural events or uncontrollable 

emissions associated with thunderstorm outflows and PM10 exceedances on June 16, 2012, is presented 

in the following time series graphs, infrared satellite imagery, and National Weather Service (NWS) data 

tables for selected, representative airports. These various pieces of information contain data on sustained 

wind speed, wind speed gusts, PM10 concentrations, visibility, weather observations, and thunderstorm 

development areas and provide the causal connection between the uncontrollable emissions associated 

with thunderstorm outflows and elevated PM10 concentrations. For reference, Appendix D provides 

additional NWS text products issued preceding and on June 16 containing forecasts and warnings of 

blowing dust due to thunderstorms outflows. A summary of the event day is provided below. 

Event – June 16, 2012

On June 16, 2012, the Phoenix region experienced typical summertime weather conditions with a 

maximum temperature of 106°F, relative humidity of 10-20%, winds <6 miles per hour (mph) from 

various directions for much of the day, and visibility at 10 miles all day, as reported at the Phoenix Sky 

Harbor Airport. Broad high pressure over the southwestern U.S. limited thunderstorm development and 

kept winds light on the June 15th, causing PM10 concentrations to be generally low (20-80 μg/m3

 range) 

on the day preceding the dust event and through the early afternoon on June 16th, despite prevalent dry 

conditions due to very little rain over the previous few months. Between 3 p.m. Mountain Standard Time 

(MST) and 5 p.m. MST on June 16, severe thunderstorms developed over a limited portion of Arizona to 

the southeast of the Phoenix region (as shown in Figure 5-1) and by 6 p.m., outflows from the 

thunderstorms entrained dust from desert areas of Pinal County and generated a “haboob” that progressed 

northwestward into Maricopa County, transporting large amounts of PM10. As shown in Figure 5-2, the 

“haboob” had the following impacts in the Phoenix area: southeasterly winds increased to 21-25 mph, 

with gusts up to 32 mph; visibility dropped from 10 miles to 0.75 miles; weather conditions were reported 

as “blowing dust”; and hourly PM10 concentrations increased to nearly 2,300 μg/m3 at the West 43rd

monitoring site and exceeded 1400 μg/m3

 at six sites. Once the winds subsided during the 7 p.m. hour, 

PM10 concentrations remained high for several hours, resulting in 24-hour average concentrations above 

180 μg/m3

 at five monitoring sites on June 16. In total, seven monitoring sites in the region exceeded the 

PM10 NAAQS and, as was mentioned in the Historical Fluctuation section, most of those seven PM10 

monitoring sites saw one of their 12 highest 24-hour average PM10 concentrations measured in the past 

five years. Without the existence of the emissions generated by the thunderstorm outflows, there would 

not have been any exceedances of the 24-hour PM10 standard in the Phoenix PM10 nonattainment area. 

-25-
11:00 a.m. 2:00 p.m. 4:00 p.m. 6:00 p.m. 

1800z Jun 16 2100z Jun 16 2300z Jun 16 0100z Jun 17 

8:00 p.m. 10:00 p.m. 12:00 a.m. 2:00 a.m. 

0300z Jun 17 0500z Jun 17 0700z Jun 17 0900z Jun 17 

Figure 5-1. Satellite imagery showing strong storms developing and dissipating over southeastern 

Arizona. These storms are believed to have been responsible for the thunderstorm outflow boundary that 

caused PM10 exceedances in Maricopa and Pinal counties on June 16, 2012. 

Figure 5-2 depicts the dust event that occurred in Maricopa County impacting the Phoenix area on June 

16, 2012. Hourly averaged PM10 concentrations at monitors throughout Maricopa County are shown 

along with visibility readings (blue diamonds) and wind speeds reported at the Phoenix Sky Harbor 

Airport. Measurements at Sky Harbor were used due to its central location amongst most of the monitors 

that experienced exceedances on June 16. Wind speeds for the Mesa Williams Gateway Airport on the 

eastern-side of the Phoenix region were also included on the graph. As can be seen in the graph, visibility 

was reduced down to 0.75 miles at the Sky Harbor Airport during the windblown dust event, and this 

visibility reduction coincided with rapidly increasing PM10 concentrations and sustained wind speeds up 

to 25 mph in the Phoenix area. The NWS data tables after Figure 5-3 also show reports of blowing dust 

during the 6 p.m. hour, when PM10 concentrations were the highest. Additionally, the NWS issued dust 

storm warnings (see Appendix D) for many areas in Pinal and Maricopa Counties due to the large haboob 

that was moving across southeastern and central Arizona for upwards of 100 miles. The daily 

climatology report June 16th also listed under “Weather Conditions” for the day: “Sandstorm”, providing 

another clear indication of an exceptional natural event. 

-26-
Figure 5-2. Phoenix nonattainment area PM10 monitor readings, Sky Harbor wind speed and visibility, 

and Williams Gateway wind speed for June 16, 2012.

As shown in Figure 5-3, several monitoring sites in the upwind, dust source region of Pinal County 

measured 24-hour average PM10 exceedances, with the peak site (Cowtown) having a 24-hour average of 

698 μg/m3 and an extremely high maximum 1-hour average during the 5 p.m. hour of 12,276 μg/m3, 

when the southeasterly winds were strongest and the visibility was lowest at the Casa Grande Airport (see 

the NWS data tables below). Two other monitoring sites also measured hourly concentrations over 5,000 

μg/m3

. These spikes at the Pinal County monitors preceded the PM10 concentration spikes at the 

monitoring sites in Maricopa by one to two hours, which is consistent with wind speeds and directions 

observed at the Phoenix Sky Harbor Airport in Maricopa County and the Casa Grande Airport in Pinal 

County for the propagation of the haboob across the region. Only monitoring sites in Maricopa and Pinal 

counties exceeded the NAAQS due to thunderstorm outflows on this day, but the broad range of sites and 

the extreme hourly- and daily-averaged PM10 concentrations reflect the magnitude of the haboob. 

Additionally, the NWS airport meteorological data tables for the Phoenix Sky Harbor and Casa Grande 

airports show that the strongest winds associated with the haboob were out of the southeast. These winds, 

combined with the high PM10 concentrations in Pinal County, indicate that PM10 was already entrained 

in the atmosphere outside of the Phoenix PM10 nonattainment area and then transported into the region 

by the strong winds. 

-27-
Figure 5-3. Pinal County PM10 monitor readings and Casa Grande wind speed and visibility for June 16, 

2012

A visualization of this dust event was created using Phoenix visibility camera images that can be viewed 

as an animation here: 

Looking south toward Phoenix, with South Mountain in the distance: 

www.phoenixvis.net/videos/mpeg4/SOMT_06162012.mp4

The video clearly shows the wall of dust blowing across the Phoenix region in the early evening of June 

16, 2012. The snapshot on the cover of this report was taken from the 6:10 p.m. mark of the video and 

coincides with the PM10 concentration spikes seen in the 5-minute data from the PM10 monitoring sites 

in the central Phoenix area. Videos showing other views across the Valley on this date are also available 

(see Visibility Cameras section).

-28-
-29-

U.S. Department of Commerce National Oceanic & Atmospheric Administration QUALITY CONTROLLED LOCAL CLIMATOLOGICAL DATA 

(final) 

HOURLY OBSERVATIONS TABLE 

PHOENIX SKY HARBOR INTL AIRPORT (23183) 

PHOENIX, AZ 

(06/2012) 

Elevation: 1107 ft. above sea level Latitude: 33.427 Longitude: -112.003 Data Version: VER3

Dry 

Bulb 

Temp

Wet 

Bulb 

Temp

Dew

Point

Temp Date Time (LST) Station Type Sky Conditions Visibility (SM) Weather Type

(F) (C) (F) (C) (F) (C)

Rel

Humd 

%

Wind 

Speed (MPH)

Wind

Dir

Wind

Gusts

(MPH)

Station

Pressure

(in. hg)

Press

Tend

Ne

3-h

Ch

(m

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 

16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

0051 0151 0251 0351 0451 0551 0651 0751 0851 0951 1051 1151 1251 1351 1451 1551 1651 1751 1807 1811 1815 1819 1828 1835 1851 1951 2051 2151 2251 2351

11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11

CLR CLR CLR CLR CLR FEW180 SCT250 FEW180 SCT250 FEW200 SCT250 FEW200 SCT250 FEW200 SCT250 SCT200 SCT250 SCT200 SCT250 FEW200 SCT250 FEW120 SCT200 SCT250 FEW120 SCT200 SCT250 FEW120 SCT200 SCT250 FEW120 SCT200 SCT250 FEW120 SCT200 SCT250 FEW018 SCT120 SCT200 BKN018 BKN020 BKN022 BKN025 BKN120 BKN200 SCT030 SCT120 SCT200 FEW035 SCT120 SCT200 SCT120 SCT200 SCT250 SCT120 SCT200 SCT250 FEW120 SCT200 SCT250 FEW120 SCT200 SCT250 FEW120 SCT200 SCT250

10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 1.00 1.00 0.75 1.00 2.50 3.00 8.00 10.00 10.00 10.00 10.00 10.00

BLDU BLDU BLDU 

878584838078828590939698101102103103106104102100100999999979695959391

30.629.428.928.326.725.627.829.432.233.935.636.738.338.939.439.441.140.039.038.038.037.037.037.036.135.635.035.033.932.8

605858575656575859616263656666666665676767676767666665656465

15.414.614.214.013.413.314.014.115.015.816.717.418.218.618.618.619.018.419.319.319.319.419.419.419.018.618.518.317.918.2

373534343436353231323436383938383736434545464646464545444447

2.81.71.11.11.12.21.70.0-0.60.01.12.23.33.93.33.32.82.26.07.07.08.08.08.07.87.27.26.76.78.3

17 17 17 17 19 22 18 15 12 11 11 11 11 11 11 11 9 9 13 15 15 16 16 16 17 17 18 17 18 22

8 7 9 6 5 0 3 3 6 0 5 5 5 3 5 0 13 15 18 24 21 21 22 22 21 14 3 0 3 5

270290310310220000240200VR 000310VR VR VR 010000140160170170160160130140150140260000160090

30 32 32 31 31 31 29 

28.58 28.59 28.61 28.62 28.64 28.66 28.66 28.69 28.68 28.68 28.68 28.66 28.64 28.62 28.60 28.56 28.57 28.58 28.59 28.60 28.60 28.60 28.60 28.61 28.62 28.62 28.64 28.66 28.68 28.66

3 3 3 6 8 5 1 3

013018014003018019019017

Dynamically generated Wed Dec 26 21:52:51 EST 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD
-30-

U.S. Department of Commerce National Oceanic & Atmospheric Administration QUALITY CONTROLLED LOCAL CLIMATOLOGICAL DATA 

(final) 

HOURLY OBSERVATIONS TABLE 

WILLIAMS GATEWAY AIRPORT (23104) 

PHOENIX, AZ 

(06/2012) 

Elevation: 1382 ft. above sea level Latitude: 33.3 Longitude: -111.666 Data Version: VER2

Dry 

Bulb 

Temp

Wet 

Bulb 

Temp

Dew

Point

Temp Date Time (LST) Station Type Sky Conditions Visibility (SM) Weather Type

(F) (C) (F) (C) (F) (C)

Rel

Humd

%

Wind 

Speed 

(MPH)

Wind

Dir

Wind

Gusts

(MPH)

Station

Pressure

(in. hg)

Press

Tend

Net

3-hr

Chg

(mb)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 

16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 

0015 0035 0055 0115 0135 0155 0215 0235 0255 0315 0335 0355 0415 0435 0455 0515 0547 0747 0847 0947 1047 1147 1347 1447 1547 1720 1747 1825 1847 1947 1955 

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR SCT120 SCT200 SCT120 SCT200 SCT120 BKN200 FEW100 SCT200 FEW100 SCT200 FEW100 SCT200 SCT120 SCT120 SCT120 SCT012 SCT120 SCT120 SCT120 BKN200 BKN SCT100 

10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 35.00 35.00 35.00 35.00 35.00 35.00 35.00 30.00 30.00 0.50s 1.00 3.00 10.00 20.00 10.00 

DSs BLDU BLDU 

8282818179797777777777777777777573848893971021021061061049997979795

28.028.027.027.026.026.025.025.025.025.025.025.025.025.025.024.023.029.031.034.036.039.039.041.041.040.037.036.036.036.035.0

5958606056565656555555555555565554606162636565676767676666M66

14.714.315.315.313.513.113.313.312.712.712.712.712.712.713.112.812.415.515.916.517.318.218.219.219.219.619.319.019.0M 18.6

39374343363437373434343434343637374139373737373939434646464846

4.03.06.06.02.01.03.03.01.01.01.01.01.01.02.03.03.05.04.03.03.03.03.04.04.06.08.08.08.09.08.0

22 20 26 26 21 20 24 24 21 21 21 21 21 21 23 25 27 22 18 14 12 11 11 10 10 13 16 17 17 M 19 

5 5 7 5 5 7 7 6 6 7 6 7 6 5 0 5 5 0 0 3 6 6 5 9 3 17 23 29 23 9 8 

200 

170 110 100 100 090 130 100 090 100 100 110 090 090 000 120 090 000 000 VR 310 350 VR 310 VR 180 160 130 130 120 140 

30 39 34 

28.33 28.34 28.34 28.34 28.34 28.35 28.36 28.36 28.37 28.37 28.37 28.38 28.38 28.39 28.39 28.40 28.41 28.43 28.43 28.43 28.42 28.41 28.40 28.34 28.32 28.36 28.37 28.37 28.37 M 28.38 
-31-

16 16 16 16 16 16 16 16 16 16 16 16 16

2015 2035 2047 2055 2115 2135 2155 2215 2235 2255 2315 2335 2355

0 0 0 0 0 0 0 0 0 0 0 0 0

CLR CLR BKN CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR

10.00 10.00 20.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00

93959393939193939190909088

34.035.034.034.034.033.034.034.033.032.032.032.031.0

6566M65656464646363646463

18.318.6M 18.118.117.717.717.717.317.117.517.517.2

46464645454543434343454545

8.08.08.07.07.07.06.06.06.06.07.07.07.0

20 19 M 19 19 20 18 18 19 19 21 21 22

8 8 7 7 5 6 0 0 5 5 0 3 3

120 140 140 160 140 170 000 000 240 270 000 360 330

28.38 28.37 M 28.38 28.39 28.40 28.42 28.42 28.42 28.43 28.42 28.43 28.43

Dynamically generated Wed Dec 26 22:18:53 EST 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD
-32-

U.S. Department of Commerce National Oceanic & Atmospheric Administration QUALITY CONTROLLED LOCAL CLIMATOLOGICAL DATA 

(final) 

HOURLY OBSERVATIONS TABLE 

CASA GRANDE MUNICIPAL ARPT (03914) 

CASA GRANDE, AZ 

(06/2012) 

Elevation: 1462 ft. above sea level Latitude: 32.95 Longitude: -111.766 Data Version: VER2

Dry 

Bulb 

Temp

Wet 

Bulb 

Temp

Dew

Point

Temp Date Time (LST) Station Type Sky Conditions Visibility (SM) Weather Type

(F) (C) (F) (C) (F) (C)

Rel 

Humd

%

Wind

Speed (MPH)

Wind 

Dir

Wind

Gusts

(MPH)

Station 

Pressure

(in. hg)

Press

Tend

Net

3-hr

Chg

(mb)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 

16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 

0015 0035 0055 0115 0135 0155 0215 0235 0255 0315 0335 0355 0415 0435 0455 0515 0535 0555 0615 0635 0655 0715 0735 0755 0815 0835 0855 0915 0935 0955 1015 

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR 

10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 

81 79 75 75 77 75 73 73 72 70 72 72 72 72 72 72 73 70 72 73 75 77 79 81 82 86 88 90 90 91 91 

27.0

26.024.024.025.024.023.023.022.021.022.022.022.022.022.022.023.021.022.023.024.025.026.027.028.030.031.032.032.033.033.0

57575555565554545452545454545454545254545657575759606161616262

14.113.712.812.613.212.612.212.211.911.111.911.911.911.911.911.912.211.112.112.413.213.714.114.114.715.515.916.316.316.516.5

37373736373636363634363636363636363437373939393739393939393939

3.03.03.02.03.02.02.02.02.01.02.02.02.02.02.02.02.01.03.03.04.04.04.03.04.04.04.04.04.04.04.0

21 22 25 24 24 24 26 26 27 27 27 27 27 27 27 27 26 27 28 27 27 26 24 21 22 19 18 17 17 16 16 

0 7 6 0 0 0 0 0 5 3 0 3 6 5 0 0 0 5 3 0 0 0 3 0 0 0 0 6 0 5 5 

000 

220 200 000 000 000 000 000 030 040 000 030 010 020 000 000 000 040 040 000 000 000 220 000 000 000 000 320 000 250 170 

28.25 28.24 28.25 28.25 28.27 28.27 28.27 28.27 28.27 28.27 28.28 28.28 28.28 28.29 28.29 28.30 28.31 28.31 28.32 28.32 28.33 28.34 28.34 28.34 28.34 28.34 28.34 28.34 28.34 28.34 28.34 

2 2 2 

010 010 017 

M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M 
-33-

16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

1035 1055 1115 1135 1155 1215 1235 1255 1315 1335 1355 1415 1435 1455 1515 1535 1555 1615 1635 1655 1715 1735 1755 1815 1835 1855 1915 1935 1955 2015 2035 2055 2115 2135 2155 2215 2235 2255 2315 2335 2355

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR OVC010 BKN010 CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR CLR

10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 9.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 0.25 1.75 3.00 2.00 3.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00

91 93 93 95 97 97 99 99 10010010010010210010210210210210210299 97 95 93 91 91 91 91 91 91 91 91 90 90 88 88 86 84 84 81 81

33.034.034.035.036.036.037.037.038.038.038.038.039.038.039.039.039.039.039.039.037.036.035.034.033.033.033.033.033.033.033.033.032.032.031.031.030.029.029.027.027.0

6262626364646666676766676767676767676767666666656464646464646464646463636362636161

16.516.916.917.318.018.018.718.719.319.318.919.319.619.319.619.619.619.619.619.619.119.018.618.317.917.917.917.917.917.917.917.717.517.717.417.417.016.617.116.016.0

3939393941414343454543454545454545454545454646464646464646464645454646464646484646

4.04.04.04.05.05.06.06.07.07.06.07.07.07.07.07.07.07.07.07.07.08.08.08.08.08.08.08.08.08.08.07.07.08.08.08.08.08.09.08.08.0

16 15 15 14 14 14 15 15 15 15 14 15 14 15 14 14 14 14 14 14 16 17 19 20 21 21 21 21 21 21 21 20 21 22 23 23 25 27 29 29 29

0 6 7 5 3 3 5 7 5 6 0 9 7 8 13 11 13 0 7 7 32s 28 22 24 20 16 13 8 7 5 5 7 8 7 6 0 3 5 0 3 5

000 360 360 250 250 260 260 250 200 260 000 020 290 290 280 280 270 000 200 160 110 120 120 110 110 090 090 100 160 140 130 120 130 150 130 000 160 090 000 020 040

20 20 16 17 46 38 34 36 28 28 

28.34 28.34 28.34 28.33 28.32 28.32 28.31 28.30 28.30 28.29 28.28 28.27 28.27 28.25 28.25 28.24 28.24 28.25 28.25 28.25 28.27 28.27 28.27 28.28 28.28 28.29 28.29 28.29 28.29 28.29 28.30 28.30 28.31 28.32 28.32 28.32 28.33 28.33 28.34 28.33 28.34

4 7 7 2 

000 020 010 014 

M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M

Dynamically generated Wed Dec 26 21:48:16 EST 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD

A description of the fields and data codes/abbreviations used in these tables can be found here: http://cdo.ncdc.noaa.gov/qclcd/qclcddocumentation.pdf
Visibility Cameras

Visibility camera images were compiled into time lapse photography videos in order to visually show the 

dust impacts on portions of Maricopa County on June 16. The animations are available online for each 

event and for each of the visibility camera sites in Maricopa County. These views can be accessed using 

the camera site codes SOMT (South Mountain), CAME (Camelback Mountains), SUPM (Superstition 

Mountains), ESMO (Estrella Mountains), and WHTM (White Tank Mountains). It should be noted that 

these time lapse photography videos may require the installation of a mp4 viewer. 

 

The video files can be accessed as follows: 

 

http://www.phoenixvis.net/videos/mpeg4/xxxx_mmddyyyy.mp4

 

xxxx = 4-character site code (ie. SOMT) 

mm = 2-character month (ie. 06) 

dd = 2-character day (ie. 16) 

yyyy = 4-character year (ie. 2012) 

Conclusion

The information presented within this section has adequately demonstrated a clear causal relationship 

between the emissions generated by uncontrollable natural events and the exceedances measured at the 

monitors. The satellite images, time series graphs, and meteorological data tables provided in this section 

show the temporal progression of the dust events from the development of the thunderstorms, to the 

increase in wind speeds, and to the rise in PM10 concentrations. The combination of the PM10 and wind 

data from Maricopa and Pinal counties shows the transport of particulate matter from the south through 

Pinal County and into the Phoenix PM10 nonattainment area. This information supports the conclusion 

that the events were primarily caused by windblown dust from emission sources outside of Maricopa 

County and the transport of PM10 into the Phoenix PM10 nonattainment area. 

-34-
VI. “BUT FOR” ANALYSIS 

Section 50.14(c)(3)(iv)(D) in 40 CFR part 50 requires that an exceptional event demonstration must 

satisfy that “[t]here would have been no exceedance or violation but for the event.” The prior sections of 

this submittal have provided detailed information that the exceedances on June 16, 2012, were not 

reasonably controllable or preventable and there is a clear causal relationship between transported PM10 

from thunderstorm outflows originating in the desert areas outside of the Phoenix PM10 nonattainment 

area and the measured exceedances within the nonattainment area. The weight of evidence in these 

sections demonstrates that but for the existence of emissions generated by these thunderstorm outflows 

and associated transported PM10, there would have been no exceedances of the 24-hour PM10 standard. 

As detailed in Section IV, all reasonable control measures were in place and actively enforced before, 

during, and after the exceedances of June 16, 2012. Inspection and compliance data of local fugitive dust 

sources during this time period revealed that PM10 from anthropogenic activities was well controlled and 

constant. Local regulatory agencies, industry, and the general public were alerted to the possibility of 

dust storms due to thunderstorm activity through daily forecasts and media reports. Heightened, real-time 

surveillance of PM10 monitoring stations during the events established a clear link between rapidly rising 

PM10 concentrations and the arrival of the thunderstorm outflows. On-the-ground observations recorded 

during the events consistently identify transported or re-entrained PM10 as the cause of the elevated 

concentrations near the exceeding monitors. 

As shown in Section V, detailed, time series data establish a clear causal relationship between the arrival 

of emissions generated by thunderstorm outflows and elevated PM10 concentrations at the monitors. 

Multiple, independent measurements of wind speed, wind direction, and visibility all point to the presence 

of thunderstorm outflows as the delivery vehicle for transported PM10 into the nonattainment area. Any 

local PM10 emissions generated during the arrival of the thunderstorm outflows are linked to the 

turbulent and gusty outflow front of the storm and pale in comparison to the amount of transported PM10 

originating outside the nonattainment area. The source region for the primary thunderstorm outflow 

boundary and transported PM10 are clearly identified as the desert areas to the southeast of the Phoenix 

PM10 nonattainment area. 

The body of evidence presented in this submittal provides no alternative that could tie the exceedances of 

June 16, 2012, to any other causal source but transported and re-entrained PM10 generated from 

thunderstorm outflows, confirming that there would have been no exceedances but for the presence of 

these uncontrollable natural events. 

-35-
VII. CONCLUSIONS 

The exceedances that occurred on June 16, 2012, satisfy the following criteria of 40 CFR 50.1(j) and meet 

the definition of an exceptional event: 

 The event affects air quality; 

 The event is not reasonably controllable or preventable; and 

 The event is unlikely to reoccur at a particular location or [is] a natural event. 

Affects Air Quality

As stated in the preamble to the Exceptional Events Rule, the event in question is considered to have 

affected air quality if it can be shown that there is a clear causal relationship between the monitored 

exceedance and the event, and that the event is associated with a measured concentration in excess of 

normal historical fluctuations. Given the information presented in Sections II, III, IV, and V, we can 

reasonably conclude that the event in question affected air quality. 

Not Reasonably Controllable or Preventable

Section 50.1(j) of Title 40 CFR Part 50 requires that an event must be “not reasonably controllable or 

preventable” in order to be defined as an exceptional event. This requirement is met by demonstrating 

that, despite reasonable control measures in place within Maricopa County and the Phoenix PM10 

nonattainment area, high wind conditions overwhelmed all reasonably available controls. Despite the 

deployment of comprehensive control measures and sophisticated response programs, high wind 

conditions associated with thunderstorms and thunderstorm outflows brought high concentrations of 

PM10 emissions into, and also overwhelmed controls within, the Phoenix PM10 nonattainment area. The 

event discussed in this document that caused the exceedances in this request (see Sections II and V) were 

caused by thunderstorm-driven outflow winds that transported dust into Maricopa County from areas 

largely outside of the Phoenix PM10 nonattainment area. The fact that these were natural events 

involving strong thunderstorm outflow winds that transported PM10 emissions into Maricopa County, 

with a majority of the PM10 emissions recorded by Maricopa County area monitors coming from sources 

outside of the Phoenix PM10 nonattainment area, provides strong evidence that the event and 

exceedances of June 16, 2012, recorded within the nonattainment area were not reasonably controllable or 

preventable. 

Natural Event

As discussed above, the events shown to cause these exceedances were emissions of PM10 driven by high 

winds caused by thunderstorm activity and related outflow boundary on June 16, 2012. The events 

therefore qualify as natural events. 

-36-
-37-

Summary

In summary, the exceedances of the federal 24-hour PM10 standard on June 16, 2012, would not have 

occurred but for the monsoonal thunderstorm-driven high winds and windblown dust transport from areas 

largely outside the Phoenix PM10 nonattainment area, based on the weight of evidence summarized 

below. 

 Graphs of PM10 at various Phoenix area monitors in Section V and the tables containing 

meteorological data for representative NWS airport sites show that the timing of elevated PM10

events was consistent with decreased visibility and high winds at the NWS sites. 

 Visibility camera imagery discussed in Section V indicates that large quantities of PM10 were 

transported into the Phoenix Metro area during the June 16th event. The timing of the dust storms 

depicted in the visibility camera imagery is consistent with the PM10 concentration 

measurements, elevated winds, and reduced visibility reported during the event. 

 Historical Fluctuation analyses and graphs in Section III and Appendix A showing five years of 

24-hour average data for each of the Phoenix PM10 nonattainment area monitors depict numerous 

atypically high PM10 concentrations on June 16, 2012. The sudden increase in the frequency of 

elevated PM10 concentrations during this time period was exceptional from an historical 

perspective. 

 Each of the exceedances of the PM10 standard recorded on June 16 is tied to thunderstorm activity 

and thunderstorm generated outflow winds, as can be seen in data and analyses in Section V. 

 Figures and tables in Section V show that the timing of the thunderstorm-generated outflow 

boundary passage, and increases in wind speeds at the monitoring locations and National Weather 

Service stations during this event, is consistent with the timing of elevated PM10 concentrations 

recorded at the monitoring locations in the Phoenix PM10 nonattainment area. 

 Wind directions, thunderstorm-generated outflow boundary propagation, and concentration 

patterns showing elevated levels of PM10 in Pinal County prior to levels increasing in Maricopa 

County, all depicted in Section V, help show that the majority of the dust which impacted Phoenix 

PM10 nonattainment area monitors originated in Pinal County and other areas located generally to 

the south of the Phoenix PM10 nonattainment area. 

 Section IV discusses rules that are in place in the Phoenix PM10 nonattainment area as well as 

inspections that were conducted in the area to verify compliance with those rules in order to show 

that the events are not reasonably controllable or preventable. Additionally, the visibility webcam 

time lapse photography videos referenced in Section V help illustrate the magnitude and scale of 

these events, which supports the claim that the exceedances recorded during this period were not 

reasonably controllable or preventable. 
APPENDIX A

5-YEAR HISTORICAL FLUCTUATION GRAPHS FOR 

THE PHOENIX PM10 NONATTAINMENT AREA MONITORING SITES
0

50

100

150

200

250

300

350

400

450

500

PM10 Concentration (μg/m3

)

Date

Buckeye 5-Year Historical Fluctuation - 24 Hour Averages
0

50

100

150

200

250

300

350

400

450

500

PM10 Concentration (μg/m3

)

Date

West Phoenix 5-Year Historical Fluctuation - 24 Hour Averages
0

50

100

150

200

250

300

350

400

450

500

PM10 Concentration (μg/m3

)

Date

West 43rd 5-Year Historical Fluctuation - 24 Hour Averages
0

50

100

150

200

250

300

350

400

450

500

PM10 Concentration (μg/m3

)

Date

South Phoenix 5-Year Historical Fluctuation - 24 Hour Averages
0

50

100

150

200

250

300

350

400

450

500

PM10 Concentration (μg/m3

)

Date

Durango 5-Year Historical Fluctuation - 24 Hour Averages
0

50

100

150

200

250

300

350

400

450

500

PM10 Concentration (μg/m3

)

Date

Higley 5-Year Historical Fluctuation - 24 Hour Averages
0

50

100

150

200

250

300

350

400

450

500

PM10 Concentration (μg/m3

)

Date

Dysart 5-Year Historical Fluctuation - 24 Hour Averages
APPENDIX B

ADEQ FORECAST PRODUCTS FOR PHOENIX, 

MARICOPA COUNTY, AND PINAL COUNTY
MARICOPA COUNTY DUST CONTROL FORECAST 

ISSUED FRIDAY, JUNE 15, 2012

Three-day weather outlook:

Mostly light winds are expected through the weekend and into next week, as high pressure begins to build over the 

region from the south. Daytime temperatures will soar above 110°F by Sunday. Moisture will increase next Thursday 

and Friday, a precursor our thunderstorms/dust storm season. With desert soil getting very dry, distant thunderstorms 

present an increased risk of blowing dust here in the Valley. It’s just a matter of time. For now, the risk of exceeding 

the 24-hr PM10 health standard in Phoenix is forecast to be Low through Wednesday of next week. 

RISK FACTORS

WINDS STAGNATION UNHEALTHY PM-10 

RISK LEVEL

Day 1: Sat 06/16/2012 Mostly light winds are 

expected. + 

Rather stagnant 

conditions are likely 

early, improving late. 

= LOW

Day 2: Sun 06/17/2012 Mostly light winds are 

expected. + 

Rather stagnant 

conditions are likely 

early, improving late. 

= LOW

Day 3: Mon 06/18/2012

West winds between 

5 and 15 mph are 

expected, gusting 

near 20 mph at times. 

+ 

Slightly stagnant 

conditions are likely 

early, improving late. 

= LOW

EXTENDED OUTLOOK 

Day 4: Tue 06/19/2012 Mostly light winds are 

likely. + 

Rather stagnant 

conditions are likely 

early, improving late. 

= LOW

Day 5: Wed 06/20/2012 Mostly light winds are 

likely. + 

Rather stagnant 

conditions are likely 

early, improving late. 

= LOW

The Maricopa County Dust Control Action Forecast is issued to assist in the planning of work 

activities to help reduce dust pollution. A recorded message of this forecast can be accessed at 

602-771-2368. To review the complete air quality forecast for the Phoenix metropolitan area, 

as well as the health impacts and reduction methods for different air pollutants, call 602-771-

2367 for recorded forecast information or click on ADEQ's Air Quality Forecast at 

http://www.azdeq.gov/environ/air/ozone/ensemble.pdf. 

JRP 04/28/2011
VERY UNHEALTHY (201-300) 

UNHEALTHY (151-200)

UNHEALTHY FOR SENSITIVE GROUPS (101-150) 

MODERATE (51-100)

GOOD (0-50) 

 For more information visit: 

http://www.airnow.gov/index.cfm?action=aqibasics.aqi

 

*LINK TO 2011 AIR POLLUTION EXCEEDANCE GRAPH*

AIR QUALITY FORECAST FOR SATURDAY, JUNE 16, 2012

This report is updated by 1:00 p.m. Sunday thru Friday and is valid 

for areas within and bordering Maricopa County in Arizona

 

* O3 = Ozone CO = Carbon Monoxide PM-10 = Particles 10 microns & smaller PM-2.5 = Particles smaller than 2.5 microns

*“Ozone Health Watch” means that the highest concentration of OZONE may approach the federal health standard. 

“PM-10 or PM-2.5 Health Watch” means that the highest concentration of PM-10 or PM-2.5 may approach the federal health standard. 

“High Pollution Advisory” means that the highest concentration of OZONE, PM-10, or PM-2.5 may exceed the federal health standard. 

“DUST” means that short periods of high PM-10 concentrations caused by outflow from thunderstorms are possible.

FORECAST 

DATE

NOTICES 

(*SEE BELOW 

FOR DETAILS) 

AIR POLLUTANT

YESTERDAY 

THU 06/14/2012

Highest AQI Reading/Site 

(*Preliminary data only*) 

TODAY 

FRI 06/15/2012

TOMORROW 

SAT 06/16/2012

EXTENDED 

SUN 06/17/2012

O3* 42 

CAVE CREEK 

64 

MODERATE

48 

GOOD

51 

MODERATE

CO* 5 

GREENWOOD 

8 

GOOD

6 

GOOD

6 

GOOD

PM-10* 54 

SOUTH PHOENIX 

46 

GOOD 

45 

GOOD 

44 

GOOD 

PM-2.5* 28 

WEST PHOENIX 

34 

GOOD 

31 

GOOD 

30 

GOOD 
Health Statements 

Friday, 06/15/12 Unusually sensitive people should consider limiting prolonged or heavy 

exertion outdoors. 

Saturday, 06/16/12 No health impacts are expected. 

SYNOPSIS AND DISCUSSION

 

 

MONITORING SITE MAPS 

STATIC MAP http://www.azdeq.gov/environ/air/monitoring/images/map.jpg

http://aqwww.maricopa.gov/AirMonitoring/SitePollutionMap.aspx

INTERACTIVE MAPS http://156.42.96.39/alert/Google/air.html

http://www.airnow.gov/

POLLUTION MONITOR READINGS FOR THURSDAY, JUNE 14, 2012

O3 (OZONE) 

Info on current 8-hour ozone standard: http://www.epa.gov/air/ozonepollution/pdfs/2008_03_aqi_changes.pdf

For archived AQI maps go to: http://www.airnow.gov/index.cfm?action=airnow.maps

SITE NAME MAX 8-HR VALUE (PPB) MAX AQI AQI COLOR CODE

Alamo Lake 44 37 

Apache Junction 40 34 

Blue Point 43 36 

Buckeye 38 32 

Casa Grande 36 31 

Cave Creek 50 42 

Central Phoenix 38 32 

Dysart 42 36 

Falcon Field 37 31 

Fountain Hills 41 35 

Glendale 43 36 

Humboldt Mountain 40 34 

North Phoenix 44 37 

Phoenix Supersite 44 37 

Pinal Air Park 38 32 

Queen Valley 45 38 

Rio Verde 44 37 

South Phoenix 40 34 

South Scottsdale 42 36 

Tempe 39 33 

Tonto Nat’l Mon. 45 38 

Air quality levels will remain pretty good through the weekend. It’s the heat that will be the 

biggest concern. Daytime highs will soar above 110°F Sunday through early next week as high 

pressure builds over the region from the south. Winds will continue to be relatively light. Ozone 

may rebound early next week as winds shift back out of the southwest. 

PM10 levels have slipped into the lower Moderate range while winds remain very light. This 

is an indication that the desert soil is very dry now, with the top layer ready for liftoff. By next 

Thursday and Friday, we’ll start to feel moisture levels increase as high pressure finds its way 

near the Four Corners. This gets us one step closer to our thunderstorm season. It also raises 

the likelihood of large dust storms impacting local PM10 levels. We are now on notice. 

Check back on Sunday for a look ahead at next week’s weather and air quality. Until then, 

have a great weekend! -J.Paul 
West Chandler 37 31 

West Phoenix 42 36 

Yuma 46 39 

CO (CARBON MONOXIDE)

SITE NAME MAX 8-HR VALUE (PPM) MAX AQI AQI COLOR CODE

Central Phoenix 0.2 2 

Greenwood 0.4 5 

West Phoenix 0.3 3 

PM-10 (PARTICLES)

SITE NAME MAX 24-HR VALUE (μg/m3) MAX AQI AQI COLOR CODE

Apache Junction 37.5 35 

Buckeye 48.2 44 

Central Phoenix 41.2 38 

Combs School (Pinal County) 72.6 60 

Durango 49.1 45 

Dysart 31.9 29 

Glendale 29.7 27 

Greenwood 45.4 41 

Higley 43.2 39 

Maricopa (Pinal County) 64.7 56 

North Phoenix 32.8 30 

Phoenix Supersite 31.1 28 

South Phoenix 61.8 54 HIGHEST LOCALLY 

Tempe 35.8 33 

West Chandler 43.2 39 

West Forty Third 59.1 53 

West Phoenix 41.2 38 

Zuni Hills 27.0 25 

PM-2.5 (PARTICLES) 

 (Some data derived from light-scattering equipment)

For maps go to: http://www.airnow.gov/

SITE NAME MAX 24-HR VALUE (μg/m3) MAX AQI AQI COLOR CODE

Durango 7.0 23 

Dysart 5.2 17 

Estrella Mountain Park 4.5 15 

Glendale 5.5 18 

Phoenix Supersite 3.6 12 

North Phoenix 8.6 28 

South Phoenix 5.4 18 

Tempe 6.0 19 

Vehicle Emissions Lab 4.0 13 

West Phoenix 8.5 28 

LOCAL AIR POLLUTANTS IN DETAIL 

O3 (OZONE): 
Description – 

This is a secondary pollutant that is formed by the reaction of other primary pollutants (precursors) 

such as VOCs (volatile organic compounds) and NOx (Nitrogen Oxides) in the presence of heat 

and sunlight. 

Sources – VOCs are emitted from motor vehicles, chemical plants, refineries, factories, and 

other industrial sources. NOx is emitted from motor vehicles, power plants, and other sources of 

combustion. 

Potential health impacts – Exposure to ozone can make people more susceptible to respiratory 

infection, result in lung inflammation, and aggravate pre-existing respiratory diseases such as 

asthma. Other effects include decrease in lung function, chest pain, and cough. 

Unit of measurement – Parts per billion (ppb). 

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight)

Reduction tips – Curtail daytime driving, refuel cars and use gasoline-powered equipment as late in 

the day as possible. 

CO (CARBON MONOXIDE): 

Description – A colorless, odorless, poisonous gas formed when carbon in fuels is not burned 

completely. 

Sources – In cities, as much as 95 percent of all CO emissions emanate from automobile exhaust. 

Other sources include industrial processes, non-transportation fuel combustion, and natural 

sources such as wildfires. Peak concentrations occur in colder winter months. 

Potential health impacts – Reduces oxygen delivery to the body’s organs and tissues. The health 

threat is most serious for those who suffer from cardiovascular disease. 

Unit of measurement – Parts per million (ppm). 

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight)

Reduction tips – Keep motor vehicle tuned properly and minimize nighttime driving. 

PM-10 & PM-2.5 (PARTICLES): 

 Description – The term “particulate matter” (PM) includes both solid particles and liquid droplets 

found in air. Many manmade and natural sources emit PM directly or emit other pollutants that 

react in the atmosphere to form PM. Particles less than 10 micrometers in diameter tend to pose 

the greatest health concern because they can be inhaled into and accumulate in the respiratory 

system. Particles less than 2.5 micrometers in diameter are referred to as “fine” particles and are 

responsible for many visibility degradations such as the “Valley Brown Cloud” (see 

http://www.phoenixvis.net/). Particles with diameters between 2.5 and 10 micrometers are referred 

to as “coarse”. 

Sources – Fine = All types of combustion (motor vehicles, power plants, wood burning, etc.) and 

some industrial processes. Coarse = crushing or grinding operations and dust from paved or 

unpaved roads. 

Potential health impacts – PM can increase susceptibility to respiratory infections and can 

aggravate existing respiratory diseases, such as asthma and chronic bronchitis. 

Units of measurement – Micrograms per cubic meter (ug/m3) 

Averaging interval – 24 hours (midnight to midnight). 

Reduction tips – Stabilize loose soils, slow down on dirt roads, carpool, and use public transit. 

{Updated 12/19/2011} 
APPENDIX C

NOTICE OF PUBLIC COMMENT PERIOD
APPENDIX D

NATIONAL WEATHER SERVICE FORECASTS, 

WARNINGS, AND ALERTS
149 

CDUS45 KPSR 170821

CLIPHX

CLIMATE REPORT

NATIONAL WEATHER SERVICE PHOENIX AZ

121 AM MST SUN JUN 17 2012

...................................

...THE PHOENIX AZ CLIMATE SUMMARY FOR JUNE 16 2012...

CLIMATE NORMAL PERIOD 1981 TO 2010

CLIMATE RECORD PERIOD 1895 TO 2012

WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST

 VALUE (LST) VALUE VALUE FROM YEAR

 NORMAL

..................................................................

TEMPERATURE (F)

YESTERDAY

 MAXIMUM 106 451 PM 115 1974 104 2 105

 1896

 MINIMUM 78 552 AM 54 1907 78 0 78

 1897

 AVERAGE 92 91 1 92

PRECIPITATION (IN)

 YESTERDAY 0.00 0.01 1930 0.00 0.00 0.00

 MONTH TO DATE 0.00 0.00 0.00 0.00

 SINCE OCT 1 2.38 5.32 -2.94 2.78

 SINCE JAN 1 0.36 3.21 -2.85 1.04

SNOWFALL (IN)

 YESTERDAY 0.0

 MONTH TO DATE 0.0

 SINCE JAN 1 0.0

 SINCE JUL 1 0.0

 SNOW DEPTH 0

DEGREE DAYS

HEATING

 YESTERDAY 0 0 0 0

 MONTH TO DATE 0 0 0 0

 SINCE JUN 1 0 0 0 0

 SINCE JUL 1 837 935 -98 893

COOLING

 YESTERDAY 27 26 1 27

 MONTH TO DATE 415 384 31 349

 SINCE JUN 1 415 384 31 349

 SINCE JAN 1 1467 1270 197 1213

..................................................................
WIND (MPH)

 HIGHEST WIND SPEED 28 HIGHEST WIND DIRECTION SE (140)

 HIGHEST GUST SPEED 33 HIGHEST GUST DIRECTION SE (140)

 AVERAGE WIND SPEED 5.9

SKY COVER

 AVERAGE SKY COVER 0.3

WEATHER CONDITIONS

THE FOLLOWING WEATHER WAS RECORDED YESTERDAY.

 HAZE

 SANDSTORM

RELATIVE HUMIDITY (PERCENT)

HIGHEST 21 600 AM

LOWEST 9 600 PM

AVERAGE 15

..........................................................

THE PHOENIX AZ CLIMATE NORMALS FOR TODAY

 NORMAL RECORD YEAR

MAXIMUM TEMPERATURE (F) 105 114 1896

MINIMUM TEMPERATURE (F) 78 54 1965

 1944

1923

SUNRISE AND SUNSET

JUNE 17 2012..........SUNRISE 518 AM MST SUNSET 740 PM MST

JUNE 18 2012..........SUNRISE 518 AM MST SUNSET 740 PM MST

- INDICATES NEGATIVE NUMBERS.

R INDICATES RECORD WAS SET OR TIED.

MM INDICATES DATA IS MISSING.

T INDICATES TRACE AMOUNT.

&&

.....................................................................

DEW POINT

 HIGHEST DEW POINT 47

 LOWEST DEW POINT 31

 AVERAGE DEW POINT 38

.....................................................................

$$

995 

FXUS65 KPSR 161033

AFDPSR
AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE PHOENIX AZ

330 AM MST SAT JUN 16 2012

.SYNOPSIS...

PRIMARILY HOT AND DRY WEATHER WILL CONTINUE ACROSS MUCH OF THE 

REGION THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. A FEW THUNDERSTORMS 

WILL BE POSSIBLE LATE THIS AFTERNOON AND EVENING ACROSS FAR 

SOUTHEAST ARIZONA...HOWEVER A LACK OF MOISTURE MAY LIMIT ANY FURTHER 

MOVEMENT TO THE NORTH AND WEST. TEMPERATURES WILL BEGIN CLIMBING 

AGAIN TODAY...REACHING NEAR OR ABOVE 110 DEGREES ON SUNDAY AND 

MONDAY FOR LOW DESERT LOCATIONS. THE ABNORMALLY HOT WEATHER WILL 

CONTINUE THROUGH MOST OF NEXT WEEK. 

&&

.DISCUSSION...

THE WELL ADVERTISED CUTOFF LOW FEATURE WILL CONTINUE TO RETROGRADE 

TO THE SOUTHWEST OFF THE BAJA COAST...INTO THE PACIFIC FOR THE NEXT 

SEVERAL DAYS AS STRONGER RIDGING STEADILY INTENSIFIES OVER THE 

DESERT SOUTHWEST AND FOUR CORNERS REGION. IN THE INTERIM...SATELLITE 

IMAGERY INDICATES A SUBTLE VORTICITY CENTER CROSSING INTO THE GULF 

OF CALIFORNIA WITH BACKING SOUTHERLY FLOW IN THE H8-H5 LAYER. WATER 

VAPOR LOOPS SHOW SOME INCREASE IN ATMOSPHERIC MOISTURE CONTENT 

PULLING NORTH AHEAD OF THIS VORT CENTER...THOUGH THE BEST DEEP 

MOISTURE REMAINS RELEGATED TO THE CONTINENTAL DIVIDE AND POINTS 

EAST. CONVECTIVE REMNANTS AND MESOSCALE OUTFLOW INITIATED LAST 

EVENING IN THE EL PASO VICINITY HAS PUSHED SOMEWHAT BETTER LOW LEVEL 

MOISTURE WESTWARD THROUGH FAR SOUTHWEST NEW MEXICO WHERE DEWPOINTS 

HAVE INCREASED INTO THE MIDDLE/UPPER 40S...THOUGH JUST ENTERING FAR 

SOUTHEAST ARIZONA WHERE KDUG REMAINS WITH LOWER 30 DEWPOINTS. 

BOTH OPERATIONAL AND HIGH RESOLUTION DIRECT CONVECTIVE ALLOWING 

MODELS HAVE VARYING SOLUTIONS REGARDING CONVECTIVE EVOLUTION THIS 

AFTERNOON AND EVENING. GIVEN THE SYNOPTIC ENVIRONMENT WITH DEEP 

SOUTHERLY FLOW...CONCEPTUALLY WOULD EXPECT ELEVATED HIGH TERRAIN 

CONVECTION TO BLOSSOM ACROSS SOUTHEAST ARIZONA THIS AFTERNOON...AND 

HAVE DISCOUNTED MODELS WITH LACK OF CONVECTIVE RESPONSE (I.E. LOCAL 

6KM NMM CORE). AT THE OTHER END OF THE SPECTRUM...A DRIER WESTERLY 

FETCH IN THE LOW TERRAIN REGIONS OF CENTRAL ARIZONA SHOULD LIMIT THE 

EXTENT OF ORGANIZED CONVECTIVE PROPAGATION TO THE NORTHWEST...AND 

HAVE ELIMINATED MODELS SHOWING PRECIPITATION IN THIS AREA (I.E. GFS 

CORES). HAVE MOSTLY UTILIZED SREF PROBABILISTIC OUTPUT ALONG WITH 

THE OPERATIONAL NAM AND THE NCEP 4KM WRF-NMM HIGH RESOLUTION MODEL 

TARGETING FAR SOUTHEAST ARIZONA THROUGH WEST CENTRAL NEW MEXICO WITH 

THE STRONGEST SIGNALS FOR PERSISTENT CONVECTION. 

THESE AREAS JUST OUTSIDE THE SOUTHERN AND EASTERN PERIPHERY OF THE 

FORECAST AREA SHOULD BE CHARACTERIZED BY MUCAPES EXCEEDING 500 

J/KG...DEEPLY MIXED BOUNDARY LAYERS WITH MIXING RATIOS NEAR 6 

G/KG...AND CLASSIC INVERTED-V SOUNDINGS WITH CLOUD BASES AROUND 

600MB. SREF PROBABILITIES FOR CONVECTIVE 0.01 PRECIP TOTALS 

JUXTAPOSED WITH MIDLEVEL UVV AND THUNDERSTORM GUIDANCE ARE 

UNQUESTIONABLY HIGH...YIELDING BETTER CONFIDENCE IN THESE AREAS FOR 

AT LEAST SOME ORGANIZED THUNDERSTORMS. MEAN FLOW VECTORS FROM THE 

S/SW IN THE MAJORITY OF THE CLOUD BEARING LAYER SHOULD ALLOW 
ELEVATED CONVECTIVE ELEMENTS TO PROPAGATE TOWARDS GILA 

COUNTY...THOUGH ECHOES MAY REMAIN PRIMARILY VIRGA...AND HAVE KEPT 

JUST A MEAGER MENTION OF POPS AT THE HIGHEST ELEVATIONS. GIVEN THE 

HIGH CLOUD BASES AND LARGE DCAPE VALUES ON THE WESTERN EDGE OF THE 

THETA-E GRADIENT...STILL CANNOT RULE OUT THAT OUTFLOW GENERATION 

COULD STIR UP BLOWING DUST INTO PINAL AND NORTHEAST MARICOPA 

COUNTIES. HOWEVER...CONFIDENCE IN THIS SCENARIO IS STILL TOO LOW TO 

INTRODUCE INTO THE GRIDDED DATABASE. 

BY SUNDAY...THE INFLUENCE OF THE CUTOFF SYSTEM WILL LARGELY HAVE 

DRIFTED WESTWARD...WITH MUCH STRONGER SUBSIDENCE ALOFT AND A 

PREVAILING WESTERLY FETCH SHUNTING ANY DIURNAL CONVECTION WELL TO 

THE EAST. H5 HEIGHTS WILL RAPIDLY INCREASE AOA 588DM WITH H7 

TEMPERATURES IN A +12C TO +15C RANGE...YIELDING HIGHS MUCH ABOVE 

AVERAGE. HAVE KEPT THE FORECAST FOR LOWER ELEVATIONS IN A 105F-115F 

RANGE...WITH THE MAJOR METROPOLITAN AREAS STILL JUST SHORT OF 

EXCESSIVE HEAT CRITERIA. NEVERTHELESS...THE PERSISTENCE AND 

MAGNITUDE OF THE HEAT SHOULD NOT BE TAKEN LIGHTLY...AND WILL 

MAINTAIN MENTIONS IN THE HAZARDOUS WEATHER OUTLOOK AND WEBPAGE.

HEIGHTS AND TEMPERATURES ALOFT WILL BE DAMPENED SLIGHTLY ON TUESDAY 

AS A WAVE PASSES THROUGH THE NRN/CNTRL ROCKIES...HOWEVER THIS WILL 

ONLY BE A TEMPORARY REPRIEVE...AS STRONG RIDGING BUILDS RAPIDLY OVER 

THE FOUR CORNERS REGION WITH H5 HEIGHTS EXCEEDING 590DM BY 

WEDNESDAY. HAVE STAYED SOMEWHAT CONSERVATIVE FORECASTING HIGHS 

EITHER SIDE OF 110F FOR THE LAST SEVERAL DAYS OF THE WEEK...AGAIN 

STILL JUST SHORT OF EXCESSIVE HEAT CRITERIA. IF THE RIDGE CENTER 

BECOME SITUATED CLOSER TO THE FORECAST AREA AND COMPRESSIONAL 

EFFECTS MORE PRONOUNCED...THEN THE FORECAST HIGHS MAY NEED TO BE 

INCREASED CLOSER TO WARNING THRESHOLDS.

&&

.AVIATION...

SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL...

THROUGH 20Z SAT...CLEAR SKIES LIGHT WIND UNDER 10 KNOTS. 

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

THROUGH 20Z SAT...CLEAR SKIES AND LIGHT WIND UNDER 10 KNOTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

MONDAY THROUGH FRIDAY...

A STRONG UPPER RIDGE WILL BUILD ACROSS THE AREA AND REMAIN IN PLACE 

THROUGH THE MIDDLE OF NEXT WEEK. THIS WILL KEEP CONDITIONS HOT AND 

DRY...WITH HUMIDITY VALUES DROPPING INTO THE SINGLE DIGITS EACH 

AFTERNOON FOLLOWED BY GENERALLY POOR OVERNIGHT RECOVERY. 

OVERALL...WINDS WILL BE LIGHT IN THE EARLY MORNING HOURS...WITH 

UPSLOPE FLOW BECOMING GUSTY EACH AFTERNOON TO AROUND 25 MPH DUE TO 

STRONG SURFACE HEATING. AFTERNOON WEST WINDS WILL BE STRONGEST 

MONDAY AS AN AREA OF LOW PRESSURE AND JET STREAM ENERGY PASSES 

THROUGH THE GREAT BASIN AND CENTRAL ROCKIES. 
&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...MO

AVIATION...VASQUEZ

FIRE WEATHER...MEYERS/MO

212 

FXUS65 KPSR 161701

AFDPSR

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE PHOENIX AZ

1000 AM MST SAT JUN 16 2012

.SYNOPSIS...

PRIMARILY HOT AND DRY WEATHER WILL CONTINUE ACROSS MUCH OF THE 

REGION THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. A FEW THUNDERSTORMS 

WILL BE POSSIBLE LATE THIS AFTERNOON AND EVENING ACROSS FAR 

SOUTHEAST ARIZONA...HOWEVER A LACK OF MOISTURE MAY LIMIT ANY FURTHER 

MOVEMENT TO THE NORTH AND WEST. TEMPERATURES WILL BEGIN CLIMBING 

AGAIN TODAY...REACHING NEAR OR ABOVE 110 DEGREES ON SUNDAY AND 

MONDAY FOR LOW DESERT LOCATIONS. THE ABNORMALLY HOT WEATHER WILL 

CONTINUE THROUGH MOST OF NEXT WEEK. 

&&

.DISCUSSION...

WATER VAPOR IMAGERY SHOWS THE UPPER LOW CENTERED JUST WEST OF 

NORTHERN BAJA WITH A VORT LOBE MOVING ACROSS NORTHERN BAJA AND THE 

NORTHERN SEA OF CORTEZ INTO FAR SOUTHWEST ARIZONA. TO THE EAST IS 

UPPER HIGH/ANTICYCLONE CENTERED OVER TEXAS WITH SOUTHERLY FLOW OVER 

MUCH OF ARIZONA AND NEW MEXICO. PRECIPITABLE WATER HAS INCREASED 

OVER MUCH OF SOUTHERN ARIZONA AND CUMULUS HAS ALREADY DEVELOPED IN 

THIS AREA. OBSERVED AND MODEL FORECAST SOUNDINGS INDICATE THAT CAPE 

OVER OUR FORECAST AREA WILL BE QUITE MODEST AND LIMITED TO OUR 

EASTERN AREAS. SOUTHEAST ARIZONA SHOULD BE MORE ACTIVE BUT THOSE 

STORMS WILL STRUGGLE TO PRODUCE MEANINGFUL PRECIP BUT WILL HAVE THE 

POTENTIAL TO PRODUCE STRONG WINDS. WILL EXPAND THE SLIGHT CHANCE OF 

THUNDERSTORMS FOR TODAY TO COVER A LITTLE BIT MORE OF ZONE 24 AND 

WILL ADD MENTION OF BLOWING DUST TO A COUPLE OF OUR SOUTH-CENTRAL AZ 

DESERT ZONES. WILL ALSO INCREASE CLOUD COVER OVERNIGHT TO REFLECT 
REMNANT DEBRIS CLOUDS. MORE LATER.

PREVIOUS DISCUSSION...

THE WELL ADVERTISED CUTOFF LOW FEATURE WILL CONTINUE TO RETROGRADE 

TO THE SOUTHWEST OFF THE BAJA COAST...INTO THE PACIFIC FOR THE NEXT 

SEVERAL DAYS AS STRONGER RIDGING STEADILY INTENSIFIES OVER THE 

DESERT SOUTHWEST AND FOUR CORNERS REGION. IN THE INTERIM...SATELLITE 

IMAGERY INDICATES A SUBTLE VORTICITY CENTER CROSSING INTO THE GULF 

OF CALIFORNIA WITH BACKING SOUTHERLY FLOW IN THE H8-H5 LAYER. WATER 

VAPOR LOOPS SHOW SOME INCREASE IN ATMOSPHERIC MOISTURE CONTENT 

PULLING NORTH AHEAD OF THIS VORT CENTER...THOUGH THE BEST DEEP 

MOISTURE REMAINS RELEGATED TO THE CONTINENTAL DIVIDE AND POINTS 

EAST. CONVECTIVE REMNANTS AND MESOSCALE OUTFLOW INITIATED LAST 

EVENING IN THE EL PASO VICINITY HAS PUSHED SOMEWHAT BETTER LOW LEVEL 

MOISTURE WESTWARD THROUGH FAR SOUTHWEST NEW MEXICO WHERE DEWPOINTS 

HAVE INCREASED INTO THE MIDDLE/UPPER 40S...THOUGH JUST ENTERING FAR 

SOUTHEAST ARIZONA WHERE KDUG REMAINS WITH LOWER 30 DEWPOINTS. 

BOTH OPERATIONAL AND HIGH RESOLUTION DIRECT CONVECTIVE ALLOWING 

MODELS HAVE VARYING SOLUTIONS REGARDING CONVECTIVE EVOLUTION THIS 

AFTERNOON AND EVENING. GIVEN THE SYNOPTIC ENVIRONMENT WITH DEEP 

SOUTHERLY FLOW...CONCEPTUALLY WOULD EXPECT ELEVATED HIGH TERRAIN 

CONVECTION TO BLOSSOM ACROSS SOUTHEAST ARIZONA THIS AFTERNOON...AND 

HAVE DISCOUNTED MODELS WITH LACK OF CONVECTIVE RESPONSE (I.E. LOCAL 

6KM NMM CORE). AT THE OTHER END OF THE SPECTRUM...A DRIER WESTERLY 

FETCH IN THE LOW TERRAIN REGIONS OF CENTRAL ARIZONA SHOULD LIMIT THE 

EXTENT OF ORGANIZED CONVECTIVE PROPAGATION TO THE NORTHWEST...AND 

HAVE ELIMINATED MODELS SHOWING PRECIPITATION IN THIS AREA (I.E. GFS 

CORES). HAVE MOSTLY UTILIZED SREF PROBABILISTIC OUTPUT ALONG WITH 

THE OPERATIONAL NAM AND THE NCEP 4KM WRF-NMM HIGH RESOLUTION MODEL 

TARGETING FAR SOUTHEAST ARIZONA THROUGH WEST CENTRAL NEW MEXICO WITH 

THE STRONGEST SIGNALS FOR PERSISTENT CONVECTION. 

THESE AREAS JUST OUTSIDE THE SOUTHERN AND EASTERN PERIPHERY OF THE 

FORECAST AREA SHOULD BE CHARACTERIZED BY MUCAPES EXCEEDING 500 

J/KG...DEEPLY MIXED BOUNDARY LAYERS WITH MIXING RATIOS NEAR 6 

G/KG...AND CLASSIC INVERTED-V SOUNDINGS WITH CLOUD BASES AROUND 

600MB. SREF PROBABILITIES FOR CONVECTIVE 0.01 PRECIP TOTALS 

JUXTAPOSED WITH MIDLEVEL UVV AND THUNDERSTORM GUIDANCE ARE 

UNQUESTIONABLY HIGH...YIELDING BETTER CONFIDENCE IN THESE AREAS FOR 

AT LEAST SOME ORGANIZED THUNDERSTORMS. MEAN FLOW VECTORS FROM THE 

S/SW IN THE MAJORITY OF THE CLOUD BEARING LAYER SHOULD ALLOW 

ELEVATED CONVECTIVE ELEMENTS TO PROPAGATE TOWARDS GILA 

COUNTY...THOUGH ECHOES MAY REMAIN PRIMARILY VIRGA...AND HAVE KEPT 

JUST A MEAGER MENTION OF POPS AT THE HIGHEST ELEVATIONS. GIVEN THE 

HIGH CLOUD BASES AND LARGE DCAPE VALUES ON THE WESTERN EDGE OF THE 

THETA-E GRADIENT...STILL CANNOT RULE OUT THAT OUTFLOW GENERATION 

COULD STIR UP BLOWING DUST INTO PINAL AND NORTHEAST MARICOPA 

COUNTIES. HOWEVER...CONFIDENCE IN THIS SCENARIO IS STILL TOO LOW TO 

INTRODUCE INTO THE GRIDDED DATABASE. 

BY SUNDAY...THE INFLUENCE OF THE CUTOFF SYSTEM WILL LARGELY HAVE 

DRIFTED WESTWARD...WITH MUCH STRONGER SUBSIDENCE ALOFT AND A 

PREVAILING WESTERLY FETCH SHUNTING ANY DIURNAL CONVECTION WELL TO 

THE EAST. H5 HEIGHTS WILL RAPIDLY INCREASE AOA 588DM WITH H7 

TEMPERATURES IN A +12C TO +15C RANGE...YIELDING HIGHS MUCH ABOVE 

AVERAGE. HAVE KEPT THE FORECAST FOR LOWER ELEVATIONS IN A 105F-115F 
RANGE...WITH THE MAJOR METROPOLITAN AREAS STILL JUST SHORT OF 

EXCESSIVE HEAT CRITERIA. NEVERTHELESS...THE PERSISTENCE AND 

MAGNITUDE OF THE HEAT SHOULD NOT BE TAKEN LIGHTLY...AND WILL 

MAINTAIN MENTIONS IN THE HAZARDOUS WEATHER OUTLOOK AND WEBPAGE.

HEIGHTS AND TEMPERATURES ALOFT WILL BE DAMPENED SLIGHTLY ON TUESDAY 

AS A WAVE PASSES THROUGH THE NRN/CNTRL ROCKIES...HOWEVER THIS WILL 

ONLY BE A TEMPORARY REPRIEVE...AS STRONG RIDGING BUILDS RAPIDLY OVER 

THE FOUR CORNERS REGION WITH H5 HEIGHTS EXCEEDING 590DM BY 

WEDNESDAY. HAVE STAYED SOMEWHAT CONSERVATIVE FORECASTING HIGHS 

EITHER SIDE OF 110F FOR THE LAST SEVERAL DAYS OF THE WEEK...AGAIN 

STILL JUST SHORT OF EXCESSIVE HEAT CRITERIA. IF THE RIDGE CENTER 

BECOME SITUATED CLOSER TO THE FORECAST AREA AND COMPRESSIONAL 

EFFECTS MORE PRONOUNCED...THEN THE FORECAST HIGHS MAY NEED TO BE 

INCREASED CLOSER TO WARNING THRESHOLDS.

&&

.AVIATION...

SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL...AND 

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

MOSTLY CLEAR SKIES AND LIGHT DIURNAL WINDS EXPECTED ACROSS THE 

REGION AT ALL THE PHOENIX TERMINALS. MORNING SURFACE WINDS AT KPHX 

WILL BE LIGHT AND VARIABLE...WITH A MORE PROMINENT EASTERLY FLOW 

ALOFT. LATEST READINGS FROM TPHX VAD WIND SHOW 10 TO 15 KTS OUT OF 

THE EAST ABOVE 3KFT. WEST-SOUTHWEST WINDS WILL GRADUALLY DEVELOP 

DURING THE AFTERNOON...LINGERING UNTIL AFTER SUNSET. 

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

ALONG THE LOWER COLORADO RIVER VALLEY...CONTINUED CLEAR SKIES AND 

SOME BRIEF GUSTY WINDS CAN BE EXPECTED AS THE WEAK UPPER LEVEL LOW 

MOVES WEST. NOT ENOUGH CONFIDENCE AT THIS TIME TO INCLUDE IN THE 

TAFS AS GUSTINESS SHOULD BE BRIEF. WINDS EXPECTED FROM THE 

EAST-SOUTHEAST THROUGH MUCH OF THE MORNING...BEFORE BECOMING MORE 

DIURNAL IN DIRECTION IN THE EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

MONDAY THROUGH FRIDAY...

A STRONG UPPER RIDGE WILL BUILD ACROSS THE AREA AND REMAIN IN PLACE 

THROUGH THE MIDDLE OF NEXT WEEK. THIS WILL KEEP CONDITIONS HOT AND 

DRY...WITH HUMIDITY VALUES DROPPING INTO THE SINGLE DIGITS EACH 

AFTERNOON FOLLOWED BY GENERALLY POOR OVERNIGHT RECOVERY. 

OVERALL...WINDS WILL BE LIGHT IN THE EARLY MORNING HOURS...WITH 

UPSLOPE FLOW BECOMING GUSTY EACH AFTERNOON TO AROUND 25 MPH DUE TO 

STRONG SURFACE HEATING. AFTERNOON WEST WINDS WILL BE STRONGEST 

TUESDAY AS AN AREA OF LOW PRESSURE AND JET STREAM ENERGY PASSES 

THROUGH THE GREAT BASIN AND CENTRAL ROCKIES. 

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.

CA...NONE.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...AJ/MO

AVIATION...NOLTE/CDEWEY

FIRE WEATHER...MEYERS/MO

267 

FXUS65 KPSR 162218

AFDPSR

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE PHOENIX AZ

315 PM MST SAT JUN 16 2012

.SYNOPSIS...

PRIMARILY HOT AND DRY WEATHER WILL CONTINUE ACROSS MUCH OF THE 

REGION THROUGH NEXT WEEK. AREAS OF BLOWING DUST WILL BE POSSIBLE 

LATE THIS AFTERNOON AND EARLY EVENING OVER THE SOUTH-CENTRAL ARIZONA 

DESERTS. THERE IS A SLIGHT CHANCE OF THUNDERSTORMS OVER SOUTHERN 

GILA COUNTY TONIGHT WITH MORE NUMEROUS STORMS OVER SOUTHEAST 

ARIZONA. HOWEVER...A LACK OF MOISTURE WILL LIMIT REDEVELOPMENT OVER 

THE CENTRAL DESERTS. HIGH TEMPERATURES WILL JUMP SEVERAL DEGREES 

SUNDAY WITH SOME SLIGHT ADDITIONAL WARMING MONDAY...REACHING 110 

DEGREES...OR SLIGHTLY MORE...FOR LOW DESERT LOCATIONS. THE ABOVE 

NORMAL TEMPERATURES WILL CONTINUE THROUGH MOST OF NEXT WEEK. 

&&

.DISCUSSION...

REST OF TODAY THROUGH TUESDAY...SCATTERED THUNDERSTORMS HAVE 

DEVELOPED OVER THE SOUTHEAST QUARTER OF ARIZONA EARLY THIS 

AFTERNOON...ISOLATED OVER FAR EAST-CENTRAL ARIZONA. AREAS OF BLOWING 

DUST WERE ADDED TO PORTIONS OF THE SOUTH-CENTRAL ARIZONA DESERTS FOR 

EARLY THIS EVENING IN ANTICIPATION OF DISTANT THUNDERSTORMS SENDING 

OUTFLOW TOWARD US AND PICKING UP DUST ALONG THE WAY. GIVEN THE EARLY 

STORM DEVELOPMENT...WILL START DUST POSSIBILITIES A LITTLE EARLIER. 

DOESNT LOOK LIKE THERE IS ENOUGH CAPE TO GENERATE STORMS OVER OUR 

LOWER DESERTS BUT A SLIGHT CHANCE REMAINS FOR SOUTHERN GILA 

COUNTY/ZONE 24. LATEST MODELS ARE SHOWING AN INCREASE IN 

PRECIPITABLE WATER SPREADING ALL THE WAY INTO SOUTHEAST CALIFORNIA 

TONIGHT AND LINGERING SUNDAY. HOWEVER...WARMING ALOFT WILL MAKE FOR 

EVEN LESS CAPE. THUS HELD OFF ON INTRODUCING ANY POPS FOR OUR AREA 

SUNDAY. THERE WILL ALSO BE WARMING IN THE LOWER LEVELS BY SEVERAL 

DEGREES AS THE UPPER LOW DRIFTS AWAY AND HIGH PRESSURE STRENGTHENS. 

ANTICIPATE TEMPS TO REMAIN BELOW EXCESSIVE HEAT WARNING THRESHOLDS. 
ANTICIPATE LITTLE CHANGE IN TEMPS BUT WITH LESS PRECIPTITABLE WATER 

AS THE RIDGE STARTS TO WEAKEN DUE TO A SYSTEM PASSING TO THE NORTH. 

HOWEVER...TEMPS WILL BE JUST A LITTLE WARMER...CLOSE TO EXCESSIVE 

HEAT THRESHOLDS. AFTERNOON AND EVENING BREEZINESS WILL BE STRONGER. 

ON TUESDAY...THE LOWER LEVELS WILL BE COOLER BY AT LEAST A FEW

DEGREES DUE TO THE WEAKENED RIDGE WITH HIGHS DROPPING BELOW 110 ON 

THE LOW DESERTS. 

WEDNESDAY THROUGH SATURDAY...RIDGING BEGINS TO STRENGTHEN AGAIN 

WEDNESDAY AND HIGHS REBOUND BY AT LEAST A FEW DEGREES. ECMWF BUILDS 

THE RIDGE MORE QUICKLY THAN THE GFS AND IS CENTERED A BIT FURTHER 

NORTH. THIS LEADS TO ANOTHER DIFFERENCE IN SOLUTIONS WHEREIN THE 

ECMWF BRINGS IN MORE MOISTURE FROM THE EAST TOWARD THE END OF NEXT 

WEEK. TAKING A BLENDED APPROACH...THURSDAY LOOKS TO BE THE WARMEST 

DAY...JUST REACHING EXCESSIVE HEAT CRITERIA. ALSO...HELD OFF 

INTRODUCING ANY POPS IN THE EXTENDED BUT SHOWED A SUBTLE DECREASE IN 

MAX TEMPS. 

&&

.AVIATION...

SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL...AND 

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

MOSTLY CLEAR SKIES AND LIGHT DIURNAL WINDS EXPECTED ACROSS THE 

REGION AT ALL THE PHOENIX TERMINALS. MORNING SURFACE WINDS AT KPHX 

WILL BE LIGHT AND VARIABLE...WITH A MORE PROMINENT EASTERLY FLOW 

ALOFT. LATEST READINGS FROM TPHX VAD WIND SHOW 10 TO 15 KTS OUT OF 

THE EAST ABOVE 3KFT. WEST-SOUTHWEST WINDS WILL GRADUALLY DEVELOP 

DURING THE AFTERNOON...LINGERING UNTIL AFTER SUNSET. 

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

ALONG THE LOWER COLORADO RIVER VALLEY...CONTINUED CLEAR SKIES AND 

SOME BRIEF GUSTY WINDS CAN BE EXPECTED AS THE WEAK UPPER LEVEL LOW 

MOVES WEST. NOT ENOUGH CONFIDENCE AT THIS TIME TO INCLUDE IN THE 

TAFS AS GUSTINESS SHOULD BE BRIEF. WINDS EXPECTED FROM THE 

EAST-SOUTHEAST THROUGH MUCH OF THE MORNING...BEFORE BECOMING MORE 

DIURNAL IN DIRECTION IN THE EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

MONDAY THROUGH FRIDAY...

A STRONG UPPER RIDGE WILL BUILD ACROSS THE AREA AND REMAIN IN PLACE 

THROUGH THE MIDDLE OF NEXT WEEK. THIS WILL KEEP CONDITIONS HOT AND 

DRY...WITH HUMIDITY VALUES DROPPING INTO THE SINGLE DIGITS EACH 

AFTERNOON FOLLOWED BY GENERALLY POOR OVERNIGHT RECOVERY. 

OVERALL...WINDS WILL BE LIGHT IN THE EARLY MORNING HOURS...WITH 

UPSLOPE FLOW BECOMING GUSTY EACH AFTERNOON TO AROUND 25 MPH DUE TO 

STRONG SURFACE HEATING. AFTERNOON WEST WINDS WILL BE STRONGEST 

TUESDAY AS AN AREA OF LOW PRESSURE AND JET STREAM ENERGY PASSES 

THROUGH THE GREAT BASIN AND CENTRAL ROCKIES. 

&&
.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...AJ

AVIATION...NOLTE/CDEWEY

FIRE WEATHER...MEYERS/MO

130 

FXUS65 KPSR 162237

AFDPSR

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE PHOENIX AZ

337 PM MST SAT JUN 16 2012

.UPDATE...TO AVIATION AND FIRE WEATHER DISCUSSIONS...

&&

...

&&

.AVIATION...

SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL...AND 

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

LIGHT AND VARIABLE WINDS WILL GIVE WAY TO WEST-SOUTHWEST WINDS FOR 

THE KPHX TERMINALS...GENERALLY AFTER 17/0000. CONVECTIVE ACTIVITY TO 

OUR SOUTH NEAR TUCSON EXPECTED TO GENERATE OUTFLOW BOUNDARY MOVEMENT 

INTO THE PHOENIX AREA THIS EVENING MAINLY FROM THE SOUTH-SOUTHEAST 

AS WELL AS SCATTERED TO BROKEN MID TO HIGH LEVEL CLOUD DECKS THIS 

EVENING. AT THIS TIME...HAVE NO MENTION OF WX IN THE TAFS...BUT 

CANNOT RULE OUT SOME BLOWING DUST DECREASING VISIBILITIES FOR A 

SHORT PERIOD THIS EVENING.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

ALONG THE LOWER COLORADO RIVER VALLEY...CONTINUED CLEAR SKIES AND 

SOME BRIEF GUSTY WINDS CAN BE EXPECTED AS THE WEAK UPPER LEVEL LOW 

MOVES WEST. PERIODIC GUSTS UP TO 15 KTS POSSIBLE...BUT OTHER WISE 

WINDS WILL STAY UNDER 10 KTS. EAST-SOUTHEAST WINDS TO CONTINUE 

THROUGH THE EARLY EVENING...BEFORE BECOMING MORE DIURNAL IN 

DIRECTION IN THE EARLY EVENING AND VERY LIGHT NEAR SUNRISE.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&

...

854 

FXUS65 KPSR 170345

AFDPSR

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE PHOENIX AZ

840 PM MST SAT JUN 16 2012

.SYNOPSIS...

PRIMARILY HOT AND DRY WEATHER WILL CONTINUE ACROSS MUCH OF THE 

REGION THROUGH NEXT WEEK. AREAS OF BLOWING DUST WILL BE POSSIBLE 

LATE THIS AFTERNOON AND EARLY EVENING OVER THE SOUTH-CENTRAL ARIZONA 

DESERTS. THERE IS A SLIGHT CHANCE OF THUNDERSTORMS OVER SOUTHERN 

GILA COUNTY TONIGHT WITH MORE NUMEROUS STORMS OVER SOUTHEAST 

ARIZONA. HOWEVER...A LACK OF MOISTURE WILL LIMIT REDEVELOPMENT OVER 

THE CENTRAL DESERTS. HIGH TEMPERATURES WILL JUMP SEVERAL DEGREES 

SUNDAY WITH SOME SLIGHT ADDITIONAL WARMING MONDAY...REACHING 110 

DEGREES...OR SLIGHTLY MORE...FOR LOW DESERT LOCATIONS. THE ABOVE 

NORMAL TEMPERATURES WILL CONTINUE THROUGH MOST OF NEXT WEEK. 

&&

.DISCUSSION...

SCATTERED STRONG THUNDERSTORMS THAT DEVELOPED OVER SOUTHEAST AZ 

SATURDAY AFTERNOON...AND PUSHED CONVECTIVE OUTFLOW BOUNDARIES AND 

DUST STORMS INTO PHOENIX...WAS A FUNCTION OF UPPER LEVEL 

DYNAMICS/DIFLUENT FLOW IN SOUTHEAST AZ. THIS PROVIDED GOOD UPPER 

LEVEL STORM SUPPORT...WHICH WORKED IN CONJUNCTION WITH A SURGE OF

BOUNDARY LAYER MOISTURE WHICH PUSHED INTO SOUTHEAST AZ LATE FRIDAY 

NIGHT/SATURDAY MORNING FROM SOUTHERN NEW MEXICO.

03Z VAD WIND PROFILERS AT PHOENIX AND TUCSON SHOWED A DEEP FETCH OF 

SOUTHEASTERLY FLOW BELOW 12 THSD FEET...WHICH WILL CONTINUE TO 

ADVECT MOISTURE NORTHWARD ACROSS SOUTH CENTRAL AZ TONIGHT. 

HOWEVER...AS 300/250 MB CLOSED LOW JUST OFF THE NORTHERN BAJA COAST 

MOVES WESTWARD TONIGHT...A STRONG 300/250 MB ANTI-CYCLONE WILL SHIFT 

NORTH INTO AZ SUNDAY AND ESSENTIALLY STABILIZE THE ATMOSPHERE. 

THEREFORE...THERE WILL BE NO REPEAT THUNDERSTORM PERFORMANCE ON 

SUNDAY IN SOUTHEAST AZ. 

A 300/250 MB DEFORMATION ZONE HOWEVER DOES DEVELOP FROM LAS VEGAS TO 

THE WHITE MOUNTAINS IN EAST CENTRAL AZ MONDAY...PROVIDING RENEWED 

UPPER LEVEL SUPPORT FOR MOUNTAIN CONVECTION EAST OF OUR ZONE 24.

OTHERWISE...MINOR UPDATES FOR TONIGHTS FORECAST WILL REMOVE THE 

MENTION OF BLOWING DUST...AND SLIGHT THUNDERSTORM THREATS IN ZONE 

24. REMAINDER OF FORECASTS LOOK OK.

PREVIOUS DISCUSSION...

REST OF TODAY THROUGH TUESDAY...SCATTERED THUNDERSTORMS HAVE 

DEVELOPED OVER THE SOUTHEAST QUARTER OF ARIZONA EARLY THIS 
AFTERNOON...ISOLATED OVER FAR EAST-CENTRAL ARIZONA. AREAS OF BLOWING 

DUST WERE ADDED TO PORTIONS OF THE SOUTH-CENTRAL ARIZONA DESERTS FOR 

EARLY THIS EVENING IN ANTICIPATION OF DISTANT THUNDERSTORMS SENDING 

OUTFLOW TOWARD US AND PICKING UP DUST ALONG THE WAY. GIVEN THE EARLY 

STORM DEVELOPMENT...WILL START DUST POSSIBILITIES A LITTLE EARLIER. 

DOESNT LOOK LIKE THERE IS ENOUGH CAPE TO GENERATE STORMS OVER OUR 

LOWER DESERTS BUT A SLIGHT CHANCE REMAINS FOR SOUTHERN GILA 

COUNTY/ZONE 24. LATEST MODELS ARE SHOWING AN INCREASE IN 

PRECIPITABLE WATER SPREADING ALL THE WAY INTO SOUTHEAST CALIFORNIA 

TONIGHT AND LINGERING SUNDAY. HOWEVER...WARMING ALOFT WILL MAKE FOR 

EVEN LESS CAPE. THUS HELD OFF ON INTRODUCING ANY POPS FOR OUR AREA 

SUNDAY. THERE WILL ALSO BE WARMING IN THE LOWER LEVELS BY SEVERAL 

DEGREES AS THE UPPER LOW DRIFTS AWAY AND HIGH PRESSURE STRENGTHENS. 

ANTICIPATE TEMPS TO REMAIN BELOW EXCESSIVE HEAT WARNING THRESHOLDS. 

ANTICIPATE LITTLE CHANGE IN TEMPS BUT WITH LESS PRECIPITABLE WATER 

AS THE RIDGE STARTS TO WEAKEN DUE TO A SYSTEM PASSING TO THE NORTH. 

HOWEVER...TEMPS WILL BE JUST A LITTLE WARMER...CLOSE TO EXCESSIVE 

HEAT THRESHOLDS. AFTERNOON AND EVENING BREEZINESS WILL BE STRONGER. 

ON TUESDAY...THE LOWER LEVELS WILL BE COOLER BY AT LEAST A FEW 

DEGREES DUE TO THE WEAKENED RIDGE WITH HIGHS DROPPING BELOW 110 ON 

THE LOW DESERTS. 

WEDNESDAY THROUGH SATURDAY...RIDGING BEGINS TO STRENGTHEN AGAIN 

WEDNESDAY AND HIGHS REBOUND BY AT LEAST A FEW DEGREES. ECMWF BUILDS 

THE RIDGE MORE QUICKLY THAN THE GFS AND IS CENTERED A BIT FURTHER 

NORTH. THIS LEADS TO ANOTHER DIFFERENCE IN SOLUTIONS WHEREIN THE 

ECMWF BRINGS IN MORE MOISTURE FROM THE EAST TOWARD THE END OF NEXT 

WEEK. TAKING A BLENDED APPROACH...THURSDAY LOOKS TO BE THE WARMEST 

DAY...JUST REACHING EXCESSIVE HEAT CRITERIA. ALSO...HELD OFF 

INTRODUCING ANY POPS IN THE EXTENDED BUT SHOWED A SUBTLE DECREASE IN 

MAX TEMPS. 

&&

.AVIATION...

SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL... 

THROUGH 10Z SUN...GENERALLY BKN CLOUDS AOA 20 THSD FT. SOUTHEAST 

WIND 5 TO 15 KNOTS. FROM 10Z SUN TO 23Z SUN...SCT CLOUDS NEAR 20 

THSD. LIGHT WINDS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

THROUGH 20Z SUN...CLEAR SKIES AND LIGHT WIND UNDER 10 KNOTS. 

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

TUESDAY THROUGH SATURDAY...

UPPER LEVEL RIDGING WILL RETURN TO THE DESERT SOUTHWEST AND SUPPORT 

WELL ABOVE NORMAL TEMPERATURES THROUGH THE WEEK. CONDITIONS WILL 

REMAIN HOT AND DRY UNDER THIS RIDGING...WITH HUMIDITY VALUES 

CONTINUING TO DRY INTO THE SINGLE DIGITS. OVERALL...WINDS WILL BE 

LIGHT IN THE EARLY MORNING HOURS...WITH UPSLOPE FLOW BECOMING GUSTY 

EACH AFTERNOON TO AROUND 25 MPH DUE TO STRONG SURFACE HEATING. 
AFTERNOON WEST WINDS WILL BE STRONGEST TUESDAY AS AN AREA OF LOW 

PRESSURE AND JET STREAM ENERGY PASSES THROUGH THE GREAT BASIN AND 

CENTRAL ROCKIES. EXTENDED MODELS INDICATE SOME ENHANCED LOW TO MID 

LEVEL MOISTURE MOVING INTO THE REGION FROM THE SOUTHEAST EARLY INTO 

THE WEEKEND POTENTIALLY INCREASE HUMIDITIES WHILE ALSO INCREASING 

AFTERNOON/EVENING CONVECTIVE POTENTIAL. 

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ/AJ

AVIATION...VASQUEZ

FIRE WEATHER...NOLTE

732 

FPUS75 KPSR 162239

NOWPSR

SHORT TERM FORECAST

NATIONAL WEATHER SERVICE PHOENIX AZ

339 PM MST SAT JUN 16 2012

AZZ028-170030-

NORTHWEST AND NORTH CENTRAL PINAL COUNTYINCLUDING THE CITIES OF...APACHE JUNCTION...CASA GRANDE...COOLIDGE...

AND FLORENCE

339 PM MST SAT JUN 16 2012

.NOW...

...STRONG GUSTY WINDS AND BLOWING DUST...

STRONG THUNDERSTORMS THAT DEVELOPED NEAR TUCSON HAVE GENERATED A

NORTHWESTWARD MOVING OUTFLOW BOUNDARY. A LARGE AREA OF GUSTY WINDS IN

THE 25 TO 35 MPH RANGE...WITH ISOLATED GUSTS TO 40 MPH...WILL LIKELY

SWEEP THROUGH LOCATIONS NEAR FLORENCE...COOLIDGE...AND CASA GRANDE

BETWEEN 425 AND 530 PM. THIS INCLUDES PORTIONS OF INTERSTATES 8 AND

10. AREAS OF BLOWING DUST ARE ALSO LIKELY...WITH VISIBILITIES LESS

THAN 1 MILE AT TIMES.

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
WEATHER.GOV/PHOENIX

240 

FPUS75 KPSR 170044

NOWPSR

SHORT TERM FORECAST

NATIONAL WEATHER SERVICE PHOENIX AZ

544 PM MST SAT JUN 16 2012

AZZ028-170245-

NORTHWEST AND NORTH CENTRAL PINAL COUNTYINCLUDING THE CITIES OF...APACHE JUNCTION...CASA GRANDE...COOLIDGE...

AND FLORENCE

544 PM MST SAT JUN 16 2012

.NOW...

...GUSTY WINDS AND BLOWING DUST IN PHOENIX...

A LARGE AREA OF GUSTY WINDS IN THE 20 TO 30 MPH RANGE...WITH ISOLATED

GUSTS TO 40 MPH...GENERATED FROM EARLIER THUNDERSTORMS NEAR

TUCSON...WILL SWEEP THROUGH THE ENTIRE GREATER PHOENIX AREA THROUGH

7 PM. AREAS OF VISIBILITIES UNDER A MILE AT TIMES WILL ALSO ACCOMPANY

THE WIND GUSTS.

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

745 

FLUS45 KPSR 152155

HWOPSR

HAZARDOUS WEATHER OUTLOOK

NATIONAL WEATHER SERVICE PHOENIX AZ

255 PM MST FRI JUN 15 2012

AZZ023-028-162200-

GREATER PHOENIX AREA-NORTHWEST AND NORTH CENTRAL PINAL COUNTY255 PM MST FRI JUN 15 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH-CENTRAL ARIZONA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

THERE IS A SLIGHT CHANCE OF LATE AFTERNOON AND EVENING BLOWING DUST

SATURDAY DUE TO THE POSSIBILITY OF DISTANT THUNDERSTORMS OVER

SOUTHEAST ARIZONA. SUNDAY THROUGH THURSDAY...TEMPERATURES WILL BE

WELL ABOVE NORMAL...EXCEPT PERHAPS TUESDAY...AND WILL APPROACH

EXCESSIVE HEAT THRESHOLDS. 
.SPOTTER INFORMATION STATEMENT...

SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.

$$

785 

FLUS45 KPSR 161200

HWOPSR

HAZARDOUS WEATHER OUTLOOK

NATIONAL WEATHER SERVICE PHOENIX AZ

500 AM MST SAT JUN 16 2012

AZZ023-028-171230-

GREATER PHOENIX AREA-NORTHWEST AND NORTH CENTRAL PINAL COUNTY500 AM MST SAT JUN 16 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH-CENTRAL ARIZONA.

.DAY ONE...TODAY AND TONIGHT.

THERE IS A SLIGHT CHANCE FOR BLOWING DUST LATE THIS AFTERNOON AND

EVENING ACROSS NORTHERN PINAL AND SOUTHEAST MARICOPA COUNTIES DUE TO

THE POTENTIAL FOR DISTANT THUNDERSTORMS OVER SOUTHEAST ARIZONA. 

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

TEMPERATURES WILL BE WELL ABOVE NORMAL SUNDAY AND MONDAY...AS WELL AS

WEDNESDAY THROUGH FRIDAY. HIGHS AROUND THE PHOENIX METROPOLITAN AREA

WILL BE NEAR OR SLIGHTLY ABOVE 110 DEGREES...AND APPROACHING EXCESSIVE

HEAT WARNING THRESHOLDS. 

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

$$

968 

WWUS75 KPSR 162342

NPWPSR

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

442 PM MST SAT JUN 16 2012

AZZ028-170100-

/O.NEW.KPSR.DS.W.0003.120616T2342Z-120617T0100Z/

NORTHWEST AND NORTH CENTRAL PINAL COUNTYINCLUDING THE CITIES OF...APACHE JUNCTION...CASA GRANDE...

FLORENCE
442 PM MST SAT JUN 16 2012

...DUST STORM WARNING IN EFFECT UNTIL 6 PM MST THIS EVENING...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A DUST STORM

WARNING...WHICH IS IN EFFECT UNTIL 6 PM MST THIS EVENING. 

* AFFECTED AREA...CASA GRANDE...COOLIDGE...FLORENCE...AND SURROUNDING

 COMMUNITIES...INCLUDING INTERSTATES 8 AND 10 NEAR CASA GRANDE.

* TIMING...THROUGH 6 PM MST.

* WINDS...SOUTH WIND 25 TO 35 MPH WITH ISOLATED GUSTS TO 45 MPH.

* VISIBILITY...AREAS OF LESS THAN 1/4 MILE IN BLOWING DUST.

* IMPACTS...DANGERS TO VEHICULAR TRAVEL...ESPECIALLY ON THE

 INTERSTATES 8 AND 10. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DUST STORM WARNING IS ISSUED WHEN WINDS HAVE GENERATED LARGE

AREAS OF BLOWING DUST OR BLOWING SAND THAT HAVE SUBSTANTIALLY

REDUCED VISIBILITIES...TO 1/4 MILE OR LESS...RESULTING IN

HAZARDOUS DRIVING CONDITIONS IN SOME AREAS. BE READY FOR A SUDDEN

DROP IN VISIBILITY TO NEAR ZERO. USE EXTRA CAUTION AND SLOW DOWN

WHILE DRIVING...AS OBJECTS ON AND NEAR ROADWAYS WILL BE SEEN ONLY

AT CLOSE RANGE. IF YOU ENCOUNTER BLOWING DUST OR BLOWING SAND ON

THE ROADWAY OR SEE IT APPROACHING...PULL OFF THE ROAD AS FAR AS

POSSIBLE AND PUT YOUR VEHICLE IN PARK. TURN THE LIGHTS ALL THE

WAY OFF AND KEEP YOUR FOOT OFF THE BRAKE PEDAL.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

432 

WWUS75 KPSR 170009

NPWPSR

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

509 PM MST SAT JUN 16 2012

AZZ023-170115-

/O.EXA.KPSR.DS.W.0003.000000T0000Z-120617T0100Z/

GREATER PHOENIX AREAINCLUDING THE CITIES OF...MESA...PHOENIX

509 PM MST SAT JUN 16 2012

...DUST STORM WARNING IN EFFECT UNTIL 6 PM MST THIS EVENING...
THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A DUST STORM

WARNING...WHICH IS IN EFFECT UNTIL 6 PM MST THIS EVENING. 

* AFFECTED AREA...SOUTHERN PORTIONS OF THE EAST VALLEY...INCLUDING

 QUEEN CREEK...GILBERT AND CHANDLER.

* TIMING...THROUGH 6 PM MST.

* WINDS...SOUTH WIND 25 TO 35 MPH WITH ISOLATED GUSTS TO 45 MPH.

* VISIBILITY...AREAS OF LESS THAN 1/4 MILE IN BLOWING DUST.

* IMPACTS...DANGERS TO VEHICULAR TRAVEL...ESPECIALLY ON INTERSTATE

 10 AND THE LOOP 202 SANTAN FREEWAY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DUST STORM WARNING IS ISSUED WHEN WINDS HAVE GENERATED LARGE

AREAS OF BLOWING DUST OR BLOWING SAND THAT HAVE SUBSTANTIALLY

REDUCED VISIBILITIES...TO 1/4 MILE OR LESS...RESULTING IN

HAZARDOUS DRIVING CONDITIONS IN SOME AREAS. BE READY FOR A SUDDEN

DROP IN VISIBILITY TO NEAR ZERO. USE EXTRA CAUTION AND SLOW DOWN

WHILE DRIVING...AS OBJECTS ON AND NEAR ROADWAYS WILL BE SEEN ONLY

AT CLOSE RANGE. IF YOU ENCOUNTER BLOWING DUST OR BLOWING SAND ON

THE ROADWAY OR SEE IT APPROACHING...PULL OFF THE ROAD AS FAR AS

POSSIBLE AND PUT YOUR VEHICLE IN PARK. TURN THE LIGHTS ALL THE

WAY OFF AND KEEP YOUR FOOT OFF THE BRAKE PEDAL.

&&

$$

AZZ028-170115-

/O.CON.KPSR.DS.W.0003.000000T0000Z-120617T0100Z/

NORTHWEST AND NORTH CENTRAL PINAL COUNTYINCLUDING THE CITIES OF...APACHE JUNCTION...CASA GRANDE...

FLORENCE

509 PM MST SAT JUN 16 2012

...DUST STORM WARNING REMAINS IN EFFECT UNTIL 6 PM MST THIS

EVENING...

A DUST STORM WARNING REMAINS IN EFFECT UNTIL 6 PM MST THIS

EVENING. 

* AFFECTED AREA...CASA GRANDE...COOLIDGE...FLORENCE...AND 

 SURROUNDING COMMUNITIES...INCLUDING INTERSTATES 8 AND 10 NEAR 

 CASA GRANDE. 

* TIMING...THROUGH 6 PM MST.

* WINDS...SOUTH WIND 25 TO 35 MPH WITH ISOLATED GUSTS TO 45 MPH.

* VISIBILITY...AREAS OF LESS THAN 1/4 MILE IN BLOWING DUST.

* IMPACTS...DANGERS TO VEHICULAR TRAVEL...ESPECIALLY ON THE 

 INTERSTATES 8 AND 10. 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DUST STORM WARNING IS ISSUED WHEN WINDS HAVE GENERATED LARGE

AREAS OF BLOWING DUST OR BLOWING SAND THAT HAVE SUBSTANTIALLY

REDUCED VISIBILITIES...TO 1/4 MILE OR LESS...RESULTING IN

HAZARDOUS DRIVING CONDITIONS IN SOME AREAS. BE READY FOR A SUDDEN

DROP IN VISIBILITY TO NEAR ZERO. USE EXTRA CAUTION AND SLOW DOWN

WHILE DRIVING...AS OBJECTS ON AND NEAR ROADWAYS WILL BE SEEN ONLY

AT CLOSE RANGE. IF YOU ENCOUNTER BLOWING DUST OR BLOWING SAND ON

THE ROADWAY OR SEE IT APPROACHING...PULL OFF THE ROAD AS FAR AS

POSSIBLE AND PUT YOUR VEHICLE IN PARK. TURN THE LIGHTS ALL THE

WAY OFF AND KEEP YOUR FOOT OFF THE BRAKE PEDAL.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

505 

WWUS75 KPSR 170054

NPWPSR

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

554 PM MST SAT JUN 16 2012

AZZ028-170200-

/O.CAN.KPSR.DS.W.0003.000000T0000Z-120617T0100Z/

NORTHWEST AND NORTH CENTRAL PINAL COUNTYINCLUDING THE CITIES OF...APACHE JUNCTION...CASA GRANDE...

FLORENCE

554 PM MST SAT JUN 16 2012

...DUST STORM WARNING IS CANCELLED...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS CANCELLED THE DUST

STORM WARNING. 

VISIBILITIES HAVE IMPROVED BUT STILL REMAIN BELOW ONE AND A HALF

MILES IN SPOTS.

$$

AZZ023-170200-

/O.EXT.KPSR.DS.W.0003.000000T0000Z-120617T0200Z/

GREATER PHOENIX AREAINCLUDING THE CITIES OF...MESA...PHOENIX

554 PM MST SAT JUN 16 2012

...DUST STORM WARNING NOW IN EFFECT UNTIL 7 PM MST THIS

EVENING...
THE DUST STORM WARNING IS NOW IN EFFECT UNTIL 7 PM MST THIS

EVENING. 

* AFFECTED AREA...THE PHOENIX METRO AREA...INCLUDING DOWNTOWN PHOENIX

 AND THE EAST VALLEY.

* TIMING...THROUGH 6 PM MST.

* WINDS...SOUTH WIND 25 TO 35 MPH WITH ISOLATED GUSTS TO 45 MPH.

* VISIBILITY...AREAS OF LESS THAN 1/4 MILE IN BLOWING DUST.

* IMPACTS...DANGERS TO VEHICULAR TRAVEL...ESPECIALLY ON VALLEY FREEWAYS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DUST STORM WARNING IS ISSUED WHEN WINDS HAVE GENERATED LARGE

AREAS OF BLOWING DUST OR BLOWING SAND THAT HAVE SUBSTANTIALLY

REDUCED VISIBILITIES...TO 1/4 MILE OR LESS...RESULTING IN

HAZARDOUS DRIVING CONDITIONS IN SOME AREAS. BE READY FOR A SUDDEN

DROP IN VISIBILITY TO NEAR ZERO. USE EXTRA CAUTION AND SLOW DOWN

WHILE DRIVING...AS OBJECTS ON AND NEAR ROADWAYS WILL BE SEEN ONLY

AT CLOSE RANGE. IF YOU ENCOUNTER BLOWING DUST OR BLOWING SAND ON

THE ROADWAY OR SEE IT APPROACHING...PULL OFF THE ROAD AS FAR AS

POSSIBLE AND PUT YOUR VEHICLE IN PARK. TURN THE LIGHTS ALL THE

WAY OFF AND KEEP YOUR FOOT OFF THE BRAKE PEDAL.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

788 

WWUS75 KPSR 170149

NPWPSR

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

649 PM MST SAT JUN 16 2012

AZZ023-170300-

/O.EXP.KPSR.DS.W.0003.000000T0000Z-120617T0200Z/

GREATER PHOENIX AREAINCLUDING THE CITIES OF...MESA...PHOENIX

649 PM MST SAT JUN 16 2012

...DUST STORM WARNING WILL EXPIRE AT 7 PM MST THIS EVENING...

THE DUST STORM WARNING WILL EXPIRE AT 7 PM MST THIS EVENING. 

AREAS OF BLOWING DUST ARE STILL BEING REPORTED ACROSS THE PHOENIX
METRO AREA. HOWEVER...CONDITIONS HAVE IMPROVED WITH VISIBILITIES

INCREASING TO BETWEEN ONE HALF OF A MILE AND ONE MILE.

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

749 

WWUS85 KPSR 162324

SPSPSR

SPECIAL WEATHER STATEMENT

NATIONAL WEATHER SERVICE PHOENIX AZ

424 PM MST SAT JUN 16 2012

AZZ028-170015-

PINAL AZ424 PM MST SAT JUN 16 2012

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...

 CENTRAL PINAL COUNTY IN SOUTH CENTRAL ARIZONA

UNTIL 515 PM MST

AT 413 PM MST...A LARGE AREA OF GUSTY WINDS IN THE 25 TO 35 MPH 

RANGE WITH ISOLATED GUSTS TO NEAR 45 MPH...GENERATED FROM STRONG 

THUNDERSTORMS NEAR TUCSON...WAS MOVING NORTH TOWARD THE CITIES OF 

FLORENCE...COOLIDGE...AND CASA GRANDE. THE AREA OF GUSTY WINDS WILL 

MOVE THROUGH THE REGION BETWEEN 430 AND 530 PM. AREAS OF BLOWING 

DUSTS WITH VISIBILITIES UNDER 1 MILE WILL ALSO ACCOMPANY THE WIND 

GUSTS. LOW VISIBILITIES IN BLOWING DUST COULD BE DANGEROUS TO 

VEHICULAR TRAVEL...ESPECIALLY ALONG PORTIONS OF INTERSTATES 8 AND 10 

NEAR CASA GRANDE.

SOME UNSECURED OBJECTS COULD BE BLOWN AROUND. SEEK SHELTER INDOORS 

UNTIL THE WIND STORM PASSES.

LOCALLY DENSE BLOWING DUST IS POSSIBLE. IF YOU ENCOUNTER BLOWING DUST

WHILE DRIVING...PULL OVER AS FAR OFF THE ROADWAY AS POSSIBLE AND

PARK. TURN OFF YOUR HEADLIGHTS AND KEEP YOUR FOOT OFF THE BRAKE.

LAT...LON 3275 11175 3276 11178 3279 11179 3279 11186

 3305 11200 3315 11156 3330 11132 3304 11123

 3273 11166 3272 11173

TIME...MOT...LOC 2318Z 160DEG 10KT 3290 11148

$$

HV
876 

WWUS85 KPSR 162350

SPSPSR

SPECIAL WEATHER STATEMENT

NATIONAL WEATHER SERVICE PHOENIX AZ

450 PM MST SAT JUN 16 2012

AZZ023-024-028-170100-

PINAL AZ-MARICOPA AZ450 PM MST SAT JUN 16 2012

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...

 CENTRAL MARICOPA COUNTY IN SOUTH CENTRAL ARIZONA

 NORTH CENTRAL PINAL COUNTY IN SOUTH CENTRAL ARIZONA

UNTIL 600 PM MST

AT 446 PM MST...A LARGE AREA OF GUSTY WINDS...GENERATED FROM EARLIER 

THUNDERSTORMS NEAR TUCSON...WILL SWEEP THROUGH THE PHOENIX EAST 

VALLEY BETWEEN 515 PM AND 630 PM. SOUTH WINDS IN THE 25 TO 35 MPH 

RANGE...WITH AREAS OF VISIBILITIES LESS THAN 2 MILES IN BLOWING 

DUST...WILL MOVE THROUGH THE EAST VALLEY COMMUNITIES OF QUEEN 

CREEK...APACHE JUNCTION...CHANDLER...GILBERT...MESA...AND TEMPE.

A FEW ISOLATED WIND GUSTS UP TO 40 MPH ARE EXPECTED.

LOCALLY DENSE BLOWING DUST IS POSSIBLE AND MAY HAMPER VEHICULAR 

TRAVEL...ESPECIALLY ALONG INTERSTATE 10. IF YOU ENCOUNTER BLOWING

DUST WHILE DRIVING...PULL OVER AS FAR OFF THE ROADWAY AS POSSIBLE 

AND PARK. TURN OFF YOUR HEADLIGHTS AND KEEP YOUR FOOT OFF THE BRAKE.

LAT...LON 3342 11201 3350 11156 3326 11141 3318 11161

 3316 11208

TIME...MOT...LOC 2346Z 168DEG 10KT 3325 11167

$$

HV

692 

WWUS85 KPSR 170048

AWWPHX

AZZ023-170700-

AIRPORT WEATHER WARNING FOR SKY HARBOR AIRPORT

NATIONAL WEATHER SERVICE PHOENIX AZ

548 PM MST SAT JUN 16 2012

...AIRPORT WEATHER WARNING FOR SKY HARBOR AIRPORT IN EFFECT UNTIL

745 PM MST...
THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED AN AIRPORT WEATHER

WARNING FOR SKY HARBOR AIRPORT FOR BLOWING DUST.

A DUST STORM WARNING HAS BEEN ISSUED FOR THE GREATER PHOENIX AREA...

INCLUDING SKY HARBOR INTERNATIONAL AIRPORT.

STRONG GUSTY WINDS UP TO 35 KT HAVE CREATED AREAS OF DENSE BLOWING

DUST THAT HAVE THE POTENTIAL TO RAPIDLY LOWER VISIBILITY TO LESS THAN

1/4 MILE AT TIMES. THE DUST WILL AFFECT THE AIRPORT THROUGH AT LEAST 745

PM.

$$
APPENDIX E

ADDITIONAL NATIONAL WEATHER SERVICE METEOROLOGICAL 

DATA TABLES FOR PHOENIX-AREA AIRPORTS
Elevation: 1243 ft. above sea level

Latitude: 33.268

Longitude: -111.812

Data Version: VER2

Dynamically generated Tue Oct 02 14:40:02 EDT 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD
Elevation: 1066 ft. above sea level

Latitude: 33.527

Longitude: -112.295

Data Version: VER2

Dynamically generated Tue Oct 02 14:43:22 EDT 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD
Elevation: 968 ft. above sea level

Latitude: 33.416

Longitude: -112.383

Data Version: VER2

Dynamically generated Tue Oct 02 16:08:23 EDT 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD
Elevation: 1085 ft. above sea level

Latitude: 33.55

Longitude: -112.366

Data Version: VER2

Dynamically generated Tue Oct 02 16:06:13 EDT 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD
Elevation: 1380 ft. above sea level

Latitude: 33.466

Longitude: -111.733

Data Version: VER2

Dynamically generated Tue Oct 02 16:10:30 EDT 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD
Elevation: 1473 ft. above sea level

Latitude: 33.622

Longitude: -111.910

Data Version: VER2

Dynamically generated Tue Oct 02 16:47:02 EDT 2012 via http://cdo.ncdc.noaa.gov/qclcd/QCLCD