With enhanced easterlies on the south end of the monsoon high and embedded weak perturbation waves rolling west across southern Arizona, scattered strong to severe thunderstorms developed in a moist unstable environment throughout the afternoon and evening on the 21st. Most storms in the afternoon developed across southwest Arizona, between Phoenix and the Colorado River, with sporadic storm motions driven by outflows and cell mergers. In the evening, new showers and thunderstorms developed and spread through south-central Arizona, including in the Phoenix metro area. With high moisture content and strong forcing, thunderstorms produced very heavy rain with rainfall rates around 1.5-2.0 inches per hour with briefly higher rates for short periods. Thunderstorms also produced damaging winds, which generated dense blowing dust in open desert areas. One storm produced a severe microburst in the small town of Tacna in Yuma county that caused significant damage. The American Red Cross Disaster Relief and Yuma County Sheriffs Office was called in to support those impacted by the storm.

Flash Flood in MARICOPA, ARIZONA
From 21-JUL-21 17:10:00 to 21-JUL-21 17:30:00 (MST-7)
Location: WICKENBURG
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

Hassayampa River Preserve closed several trails due to water/debris with a sudden rise in the Hassayampa River. Palm Lake in the reserve reportedly rose by 3 feet due to flood waters and video from the day after the heavy rain showed evidence of 1-3 feet of flow in the typically dry river bed. A USGS streamflow gage a few miles downstream measured a rapid 1 foot rise in 30 minutes. No damages or injuries were reported.

Flash Flood in MARICOPA, ARIZONA
From 21-JUL-21 16:37:00 to 21-JUL-21 17:00:00 (MST-7)
Location: WICKENBURG
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

A Maricopa County Flood Control District streamflow gage on Powder House wash near Powder House Wash Road reached alarm stage and flood waters continued into and down Constellation Road and flooded the intersection with Jack Burden Road. A nearby rain gage measured 2.09 inches of rain in 56 minutes. The Public Works Department had to remove sand and debris from the road the following day. No damages or injuries were reported.

Thunderstorm Wind in YUMA, ARIZONA
From 21-JUL-21 16:00:00 to 21-JUL-21 16:00:00 (MST-7)
Location: TACNA
Magnitude: 65.00 EG
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Public

Multiple photos, videos, and media coverage show considerable damage around the small rural town of Tacna due to a microburst from a strong thunderstorm. Numerous trees were downed or broken. There were several downed or snapped power poles, causing a power outage to the area. Some trees and power poles fell on residential property, causing additional damage. There was extensive damage to residences and businesses. Several homes had their roof torn off by the winds. Yuma County Sheriff's Offices and the American Red Cross Disaster Relief Unit were dispatched for search and rescue efforts and to provide assistance to impacted individuals and families. Three families reportedly received additional assistance. Shelters were set up for displaced individuals and families. Additional reported damages include four electric car charging stations, a car window being blown out by flying debris, an overturned semi-truck on I-8, and a couple stacks of thousand-pound hay bales being blown over. Wind gusts estimated around 65-75 mph based on damage reports. Timing based on radar. Fortunately, no injuries were reported. No official damage estimates provided.