CURRENT 

CONDITIONS

As California and 

Nevada have moved 

out of the region’s 

primary precipitation 

season (October through 

March), little to no 

change has occurred in 

drought conditions in 

the region. As of July 25, 

8.24% of California and 

none of Nevada remain 

in moderate to severe 

drought (D1-D2) according 

to the U.S. Drought 

Monitor. The ‘Abnormally 

Dry’ (D0) area in southern 

and southeastern Nevada 

has expanded, covering 

about 27% of the state. 

In June 2017, this area showed negative 

Palmer Drought Severity Index (PDSI) 

values, as did the dry or drought areas of 

the southern California coast and those 

near the California-Arizona border.

June and July experienced exceptionally 

warm temperatures. In June 2017, most 

of the region saw temperatures ranging 

from 2-6o F above normal (compared to 

1981-2010), with similar differences in 

July. As discussed in the May 2017 CANV DEWS Drought & Climate Outlook 

Webinar, California and Nevada are 

experiencing an active 

wildfire season. Drying 

conditions are common 

for this time of year and 

precipitation generally 

becomes less important 

for water resource 

planning, with exception 

of southern Nevada and 

southern California which 

typically receive summer 

moisture from the North 

American Monsoon. The 

monsoon is a pronounced 

increase in rainfall over 

the southwestern U.S. 

and northwestern Mexico, 

usually occurring from 

July through September. 

This increase is due to 

intense summer solar 

heating combined with a subsequent 

seasonal wind shift resulting in a flow of 

moisture to the region from the south 

and southwest. For example, Las Vegas 

typically has a summer peak in annual 

precipitation in addition to wintertime 

precipitation. This year, much of the 

region has received below-average 

precipitation, however monsoonal 

moisture has increased in the last few 

weeks of July. 

Melting of snowpack has continued 

throughout the summer. Water stores in 

the 28 western Sierras reservoirs have 

NATIONAL INTEGRATED DROUGHT INFORMATION SYSTEM

CALIFORNIA-NEVADA 

DROUGHT OUTLOOK JULY 2017 

WHAT DOES ABOVE-NORMAL 

PRECIPITATION MEAN FOR 

GROUNDWATER RECHARGE? 

The degree of groundwater recharge is 

determined by several factors including 

soil type, bedrock, surface water 

hydrology, and surface use. California 

Department of Water Resources has 

observed increases of greater than 2.5 

feet in water levels in about 32% of 

4,399 California wells over the last year. 

However, about 47% of 3,657 California 

wells with available data are still 2.5 feet 

or more below their water level of five 

years ago, with 29 percent at least ten 

feet lower. These wells are concentrated 

in the San Joaquin River and Tulare Lake 

hydrologic basins and the Southern 

Central California Coast. Runoff will fade 

into summer and fall, and the degree that 

long-term drought deficits have been 

alleviated varies greatly.

Interested in more Groundwater Data and 

Information? Check out the California 

Department of Water Resources (http://

www.water.ca.gov/groundwater/gwinfo/

index.cfm) and the U.S. Geological Survey 

(https://water.usgs.gov/ogw/).

• Summary maps and reports

• Interactive well locator maps

• Create figures of recent and historic 

well data

• Download one well or all available 

data

Decrease > 10 ft.

Decrease 2.5 to 10 ft.

Change +/- 2.5 ft.

Increase 2.5 to 10 ft.

Increase > 10 ft.

Groundwater Level Change

Spring 2012 - Spring 2017

U.S. Drought Monitor for 

August 1, 2017

Drought intensity

D0: Abnormally dry

D1: Moderate drought

D2: Severe drought

Temperatures: Departure 

from Average (Deg F.)

July 4- Aug. 3, 2017

Precipitation: Percent of Average

July 4- Aug. 3, 2017

http://www.water.ca.gov/

groundwater/maps_and_reports/
increased (see figure above), and 10 

of 12 California Department of Water 

Resources-managed reservoirs are 

above historical averages. Lake Tahoe 

has also rapidly filled since fall of 

2016, when levels were well below 

the natural rim. However, this year 

neither reservoir levels nor reservoirsnowpack combined reached 2011 or 

1983 levels. 

CLIMATE OUTLOOK

ENSO-neutral conditions have 

persisted through early summer 

into July with equatorial sea surface 

temperatures (SSTs) remaining 

near- to above-average across 

the central and east-central 

Pacific Ocean. NOAA’s ENSO alert 

system is currently not active, 

and ENSO-neutral is favored (50 

to ~55% chance) to continue into 

the Northern Hemisphere winter 

2017-2018. Although not favored, 

the official probabilistic ENSO 

forecast as of July 21 shows El Niño 

conditions have an elevated chance 

of occurring (~35-45%) relative 

to the long term average (~25-

35%). However, more than half of 

the IRI/CPC models favor ENSOneutral through the remainder of 

2017. Overall the current ocean 

and atmosphere system remains 

consistent with ENSO-neutral and 

forecasters will continue to watch 

conditions closely.

The Climate Prediction Center 

(CPC) seasonal outlooks for 

California and Nevada as of July 

20 show equal chances of above, 

below, or average precipitation in 

August-September-October (ASO) 

and November-December-January 

(NDJ). There is a 33-60% chance of 

above-normal temperatures through 

the end of summer into fall and 

winter, with the greatest chances 

centered on northeast Nevada in 

ASO. Through October, drought is 

expected to persist in the southern 

central California coast as well 

as near the southern CaliforniaArizona border. 

CAL-ADAPT

California’s 4th California 

Climate Change Assessment, an 

inter-agency effort to implement 

a substantial portion of the state’s 

Climate Change Research Plan, is 

underway and includes scenario 

development, including drought 

scenarios. The California-Nevada 

Applications Program (CNAP), a 

NOAA RISA program, at Scripps 

Institution of Oceanography is 

participating in the assessment 

providing drought scenarios and 

downscaled global climate model 

projections. This includes LOCA, or 

Localized Constructed Analogs, a 

statistical technique that uses past 

history to add improved fine-scale 

detail to global climate models. 

More information and tools can 

be found at Cal-Adapt and see the 

A Scenario of 20 year Drought in 

Northern California presentation by 

Dr. Daniel Cayan (CNAP/SIO) from 

this webinar.

http://www.cpc.ncep.noaa.gov/

ABOUT THIS OUTLOOK

On July 24, 2017 NIDIS and its partners held a 

California-Nevada DEWS Drought & Climate 

Outlook Webinar as part of a series of regular 

drought and climate outlook webinars designed 

to provide stakeholders and other interested 

parties in the region with timely information 

on current drought status and impacts, as well 

as a preview of current and developing climatic 

events like La Niña.

A video of and presentations from this webinar 

can be accessed here: https://www.drought.gov/

drought/calendar/events/california-nevadadrought-climate-outlook-webinar-july-24

CONTRIBUTORS

Julie Kalansky, CNAP/SIO/UCSD

Jordan Goodrich, CNAP/SIO/UCSD

Andrea Bair, NWS

Dan Cayan, CNAP/SIO/UCSD

Amanda Sheffield, NIDIS/SIO/UCSD

OUTLOOK: PRECIPITATION

AUG-SEPT-OCT NOV-DEC-JAN

OUTLOOK: TEMPERATURE

AUG-SEP-OCT NOV-DEC-JAN

EC means equal chances of above, below, and normal

Probability of below-normal precip

33%-40% 40%-50% 50%-60%

Probability of above-normal precip

33%-40% 40%-50% 50%-60%

Probability of above-normal temps

33%-40% 40%-50% 50%-60%

NEW INTERACTIVE OUTLOOKS

The National Weather Service Climate Prediction 

Center has recently launched new interactive maps 

for the U.S. seasonal outlooks. Visit http://www.cpc.

ncep.noaa.gov and click the word “interactive” next to 

any of the outlooks (6-10 day, 8-14 day, One Month, 

or Three Month).

For more details and up-to-date water storage tracking in 

California, visit: https://scripps.ucsd.edu/programs/cnap/

water-storage-tracking-in-california/. NIDIS is working the the 

USGS and CNAP to generate similar figures such as this for the 

northern, central, southern, and eastern Sierras.