Scattered monsoon thunderstorms developed across portions of the greater Phoenix area, including east valley communities from Mesa eastward through Superior, during the late afternoon and evening hours on July 21st. Some of the stronger storms produced intense rainfall with peak rain rates between 3 and 4 inches per hour and this led to episodes of flooding and flash flooding in communities such as Apache Junction, located between Phoenix and the higher terrain of southern Gila County. Several Flood Advisory products were issued for the area as well as a Flash Flood Warning; the Weekes Wash in Apache Junction experienced flash flooding although no injuries or water rescues ensued due to the flooding. In addition to the heavy rains, there was a brief episode of dense blowing dust near Queen Creek as strong thunderstorm outflow winds moved through the area stirring up dust and dirt.

Flash Flood in PINAL, ARIZONA
From 21-JUL-17 18:30:00 to 21-JUL-17 21:30:00 (MST-7)
Location: GOLDFIELD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorms with intense rainfall developed across the eastern portion of the greater Phoenix area during the evening hours on July 21st and some of them affected the area around Apache Junction. At 1825MST a trained spotter 4 miles southeast of Apache Junction measured one inch of rain within 15 minutes, implying a rain rate of 4 inches per hour. This intense rainfall led to an episode of flash flooding in the Weekes Wash in Apache Junction. At 1920MST a member of the public reported flash flooding at Weekes Wash and East Lost Dutchman Boulevard, approximately one mile east of Highway 88. Very high flow was noted in the wash; fortunately no vehicles were swept away and water rescues were not needed. A Flash Flood Warning was issued for the area and was in effect during the time of the flooding.

Heavy Rain in PINAL, ARIZONA
From 21-JUL-17 17:30:00 to 21-JUL-17 20:30:00 (MST-7)
Location: SUPERIOR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms with very heavy rain developed across the higher terrain areas well to the east of Phoenix during the late afternoon and evening hours on July 21st and some of the stronger storms affected the community of Superior. At 1900MST a trained spotter located 1 mile northeast of Superior measured 0.74 inches of rain within a 45 minute period. Heavy rain such as reported by the spotter resulted in the issuance of a Flood Advisory for the area around Superior; the advisory was first issued at 1727MST and continued through 2030MST. The flooding resulted in very hazardous driving conditions for motorists in the area, especially since some of the advisory took place at night.

Dust Storm in CENTRAL DESERTS, ARIZONA
From 21-JUL-17 18:30:00 to 21-JUL-17 19:30:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Strong thunderstorms developed across the southeast portion of the greater Phoenix area during the late afternoon hours on July 21st, and some of them produced gusty outflow winds estimated to be at least 40 mph in strength. The winds were sufficient to stir up localized areas of dense blowing dust; at 1837MST a trained spotter located 6 miles northeast of Queen Creek reported a dust storm. The spotter estimated visibility down to one quarter of a mile in dense blowing dust. A Dust Storm Warning was not issued and no accidents were reported due to the sharply restricted visibility.