A large convective complex formed over south central Arizona during the early morning hours on August 23rd, a result of a weather disturbance acting on a very humid and unstable airmass. The complex of thunderstorms produced locally heavy rain across much of south central Arizona, including the greater Phoenix metropolitan area, beginning shortly after midnight and persisting through sunrise. Peak rainfall rates were between 3 and 4 inches per hour, and the heavy rain led to episodes of flooding and flash flooding, affecting areas from Witmann and New River south through the central portions of Phoenix. Several Urban and Small Stream Flood Advisories were issued for the event, but no Flash Flood Warnings were issued, despite the fact that a Flash Flood Watch remained in effect through 5 am.

Heavy Rain in MARICOPA, ARIZONA
From 23-AUG-12 01:30:00 to 23-AUG-12 03:45:00 (MST-7)
Location: PHOENIX
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A large convective complex developed across south central Arizona, including the entire Phoenix metropolitan area, during the early morning hours on August 23rd. The combination of a weak weather disturbance and a very moist and unstable airmass led to widespread thunderstorms with very heavy rain. At 157 AM, a Flood Control District rain gage 3 miles southeast of central Phoenix measured 1.1 inches of rain within a 30 minute period. The gage was located at the Durango Complex. Another rain gage near Sky Harbor Airport recorded 1.14 inches in 30 minutes as well. The heavy rains led to significant urban flooding and prompted the issuance of an Urban and Small Stream Flood Advisory for the greater Phoenix area from 145 AM until 345 AM.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-12 03:00:00 to 23-AUG-12 06:00:00 (MST-7)
Location: WITTMANN
Flood cause: Heavy Rain
Property damage: 40.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

A large convective complex developed across the greater Phoenix metropolitan area, including the community of Wittman, during the very early morning hours on August 23rd. The combination of a weather disturbance and a very humid and unstable airmass allowed the thunderstorms to produce locally heavy rainfall, with peak rain rates in excess of 2 inches per hour. The first rains began shortly after midnight, and continued into the early morning hours. At approximately 350 AM, local Fire Department and Rescue units reported a water rescue at 211th Avenu and West Montgomery Road, one mile southeast of the town of Wittman. A vehicle was stuck in rapidly rising water, and the occupants needed to be rescued. Although no Flash Flood Warning were in effect at the time, an Urban and Small Stream Flood Advisory was in effect and continued through 4 AM. No injures were reported due to the flash flooding.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-12 02:00:00 to 23-AUG-12 06:00:00 (MST-7)
Location: SCOTTSDALE
Flood cause: Heavy Rain
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A convective complex developed across the greater Phoenix metropolitan area during the early morning hours on August 23rd. The combination of a passing weather disturbance and a very humid and unstable airmass allowed the thunderstorms to produce copious rainfall with peak rain rates well in excess of 2 inches per hour. Heavy rain began in central Phoenix around 130 AM and continued into the early morning hours. According to broadcast media reports, a van became stuck in a flooded wash at 7700 East Roosevelt Street at about 452 AM. The wash was located about 3 miles east of Papago Park. As a result, the Scottsdale Fire and Rescue Unit performed a water rescue to save the occupants of the van from the flood waters. No Flash Flood Warnings were in effect at the time, however a Flash Flood Watch was in effect through 5 AM, and Urban and Small Stream Flood Advisories had been issued earlier for the area. Fortunately, no injuries were reported as a result of the flash flooding.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-12 03:00:00 to 23-AUG-12 06:00:00 (MST-7)
Location: WEST END
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Department of Highways

A large convective complex developed across the greater Phoenix metropolitan area during the early morning hours on August 23rd. The combination of a passing weather disturbance and a very humid airmass allowed thunderstorms to produce excessive rainfall with peak rain rates in excess of 2 inches per hour. Heavy rains began in the central Phoenix area by 130 AM, and persisted into the early morning hours. According to the local Department of Highways, mud and debris were blocking the right 3 lanes of eastbound Interstate 10 at about 515 AM. The debris flow was a result of flash flooding. The blockage was located 2 miles east of Tolleson. Although Flash Flood Warnings were not issued, a Flash Flood Watch was in effect through 5 AM. Earlier, Urban and Small Stream Flood Advisories were issued for the central Phoenix area.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-12 05:00:00 to 23-AUG-12 08:00:00 (MST-7)
Location: WITTMANN
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large convective complex developed across south central Arizona, including the greater Phoenix area, during the early morning hours on August 23rd. The combination of a passing weather disturbance and a very humid airmass allowed thunderstorms to produce excessive rain, with peak rain rates in excess of 2 inches per hour. The heavy rains initially developed in the Wittmann area after 130 AM, but they persisted off and on through sunrise. According to a trained weather spotter 2 miles southwest of Wittmann, at about 6 AM flooding was reported along Patton Road. Water up to 6 inches deep was reported to be flowing across the road for at least a one mile stretch of the roadway. Flash Flood Warnings were not in effect at the time, but an Urban and Small Stream Flood Advisory had been issued and was in effect through 9 AM. No injuries were reported in association with the flash flooding.

Thunderstorm Wind in MARICOPA, ARIZONA
From 23-AUG-12 01:58:00 to 23-AUG-12 01:58:00 (MST-7)
Location: PHOENIX DEER VLY ARP
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A thunderstorm complex developed over the greater Phoenix metropolitan area during the early morning hours on August 23rd. Most of the storms produced locally heavy rainfall, however a few produced strong, gusty wet microburst winds. At 158 AM, the official ASOS weather station at Deer Valley airport measured a peak wind gust to 52 knots, or 60 mph. No damage reports were received as a result of the strong winds.

Heavy Rain in MARICOPA, ARIZONA
From 23-AUG-12 02:00:00 to 23-AUG-12 04:15:00 (MST-7)
Location: NEW RIVER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A convective complex developed across south central Arizona, including the entire Phoenix metropolitan area, during the early morning hours on August 23rd. The storms persisted through sunrise and produced locally heavy rain with rainfall rates in excess of 2 inches per hour. At 225 AM, a Flood Control District rain gage 3 miles northeast of New River measured 1.37 inches of rain in 30 minutes. The gage was located in Skunk Creek. At 320 AM, another rain gage in Cave Creek measured 1.18 inches of rain within a one hour period. The heavy rain led to the issuance of an Urban and Small Stream Flood Advisory for northern Maricopa county, from 222 AM through 415 AM. The rains led to significant urban flooding of roads, washes and low lying areas.

Heavy Rain in MARICOPA, ARIZONA
From 23-AUG-12 00:25:00 to 23-AUG-12 04:00:00 (MST-7)
Location: MORRISTOWN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A convective complex developed across south central Arizona during the early morning hours on August 23rd, and it affected the entire Phoenix metropolitan area, including the community of Wittmann. The storms produced locally heavy rainfall which led to flooding of streets, washes and low lying areas. An Urban and Small Stream Flood Advisory was issued for northwest Maricopa county, including Wittmann, beginning at 1 am and continuing through 4 am. At 125 AM, a Flood Control District rain gage located 10 miles northwest of Wittmann, measured 1.73 inches of rain at Daggs Wash. The rain fell in a one hour period of time.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-12 02:00:00 to 23-AUG-12 04:00:00 (MST-7)
Location: KENDALL
Flood cause: Heavy Rain
Property damage: 40.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large convective complex developed across the greater Phoenix metropolitan area during the early morning hours on August 23rd. The combination of a weather disturbance and a very humid and unstable airmass allowed the thunderstorms to produce copious amounts of rainfall, with peak rain rates well in excess of 2 inches per hour. Heavy rain began around 130 AM and persisted into the early morning. At 255 AM, a trained weather spotter about 2 miles northeast of Phoenix Sky Harbor Airport reported that he had measured 2 inches of rain since 2 AM. The excessive rain led to significant urban flooding as well as flash flooding; water was reported to be flowing into at least one home in the area. Although no Flash Flood Warnings were in effect at the time, a Flash Flood Watch was in effect through 5 AM, and Urban and Small Stream Flood Advisories were also in effect for central Phoenix. No injuries were reported as a result of the flooding.