A strong Pacific low pressure system spread considerable moisture into the central Arizona deserts on March 12th, and the combination of strong forcing, deep moisture and modest instability resulted in scattered to numerous showers and thunderstorms. The storms resulted in areas of moderate to heavy rain, resulting in episodes of flooding and flash flooding that impacted areas near and around the greater Phoenix area. Heavy rain to the southwest of Phoenix led to the morning closure of Highway 238. Afternoon flash flooding near Wittmann led to the closure of Dove Valley Road due to debris. Evening flash flooding southwest of Buckeye and west of Highway 85 led to flowing streams and washes that exceeded action stages. Flowing water led to the closure of old Highway 80 in multiple locations. Multiple Flash Flood Warnings were issued during the day as a result of the heavy rain and flooding impacts.

Flash Flood in MARICOPA, ARIZONA
From 12-MAR-20 08:00:00 to 12-MAR-20 12:00:00 (MST-7)
Location: WITTMANN
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

A powerful Pacific low pressure system spread considerable moisture into the central deserts on March 12th, and aided by modest instability it generated scattered showers and thunderstorms. Some of the stronger storms produced heavy rain sufficient to lead to an episode of flash flooding near the town of Wittmann and to the northwest of Surprise. According to a public report from the town of Surprise, at 1000MST flash flooding occurred about 1 mile northeast of Wittmann. Flooding caused the closure of Dove Valley Road between 203rd and 211th Avenues. The closure was due to debris across the road. A Flash Flood Warning was in effect at the time of the flooding but there were no reports of accidents or injuries.

Flash Flood in MARICOPA, ARIZONA
From 12-MAR-20 21:30:00 to 13-MAR-20 05:00:00 (MST-7)
Location: CRAG
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: County Official

A powerful Pacific low pressure system spread deep moisture into the central deserts on Marcth 12th; aided by modest instability it allowed scattered to numerous showers and thunderstorms to develop during the afternoon and evening hours. Moderate to heavy rain fell with many of the storms, affecting areas to the southwest of central Phoenix. Peak rain rates were well in excess of 1 inch per hour; earlier in the day at about 1100MST a rain gage at Woolsey Peak measured 2.37 inches in a 2 hour period. The heavy rain led to some flash flooding as streams and washes rose rapidly, exceeding alarm stages on gages and causing road closures. At 2303MST county officials reported that Agua Caliente Road was closed as the Cruff Wash reached action stage. The wash crested at flood stage of 4.8 feet. This was about 9 miles south of the Palo Verge Nuclear Generating Station. Shortly after that, at 2324MST, county officials reported that Old Highway 80 was closed at Rainbow Wash as the wash reached action stage. This was about 15 miles southwest of Buckeye. Finally, at 2356MST officials reported that Old Highway 80 was closed due to the Centennial Wash reaching action stage; this occurred about 10 miles south-southeast of the Palo Verde station. Flash Flood Warnings were issued and in effect at the time of the road closures. Fortunately there were no reports of injuries or accidents due to the flooding.