An MCS developed in the afternoon in western Arizona and spread southwest through Riverside and Imperial counties during the evening and early overnight hours. In an otherwise week steering wind, the MCS was partially maintained by strong low level wind shear as it progressed downslope through a moisture-rich environment. The MCS produced widespread 40 plus mph wind gusts, locally higher, with multiple damaging wind reports. The strong winds also generated dense blowing dust. There were numerous reports of power outages across Imperial County and unconfirmed reports of trees falling on vehicles. Given the high moisture content, storms with the MCS and the slow-moving storms that developed well out ahead of the MCS produced very heavy rainfall, leading to areas of flash flooding. Radar estimated rainfall was upwards of 2 to 3 inches in 1 hour for many areas, with locally higher amounts.

Flash Flood in IMPERIAL, CALIFORNIA
From 10-AUG-21 23:00:00 to 11-AUG-21 01:00:00 (PST-8)
Location: OGILBY
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: County Official

An Imperial County Public Works official reported there were multiple washouts along Ogilby Road, after heavy rain impacted the area, that would take a few days to repair. Ogilby Road had to be closed to traffic as a result. There were two areas east of the road with radar estimated rainfall of around 2 inches and several washes flow toward and across Ogilby road. The specific locations of flooding impacts and extent of damages to the road were not shared. Timing estimated from radar. No injuries reported.

Dust Storm in PALO VERDE VALLEY, CALIFORNIA
From 10-AUG-21 19:30:00 to 10-AUG-21 20:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A couple of trained spotters in Blythe reported less then 1/4 mile visibility in blowing dust with estimated 40-50 mph winds. No damages or injuries were reported.

Thunderstorm Wind in IMPERIAL, CALIFORNIA
From 10-AUG-21 22:40:00 to 10-AUG-21 22:40:00 (PST-8)
Location: CALEXICO
Magnitude: 43.00 EG
Property damage: 8.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

A tree fell in the area of Sterling Court and Rockwood Avenue due to strong winds. The tree reportedly fell through a fence and took down a power pole. Wind gusts estimated around 45-50 mph based on area weather stations and radar. Timing estimated from radar. No injuries were reported.

Thunderstorm Wind in IMPERIAL, CALIFORNIA
From 10-AUG-21 22:40:00 to 10-AUG-21 22:40:00 (PST-8)
Location: CALEXICO
Magnitude: 43.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

A tree fell into a home due to strong winds near Encanto Drive and 8th street. The tree caused very minor damage to the eaves of the home and the resident suffered minor injuries that did not need to be treated by authorities. Additional details of the injury were not provided. Winds were estimated around 45-50 mph based on area weather stations and radar. Timing estimated from radar.

Thunderstorm Wind in IMPERIAL, CALIFORNIA
From 10-AUG-21 22:40:00 to 10-AUG-21 22:40:00 (PST-8)
Location: CALEXICO
Magnitude: 43.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Local Official

Calexico Public Works Department reported a couple street lights/lamps came down in strong winds, with one on the 800 block of Third Street and the other on Emilia Drive. Winds were estimated around 45-50 mph based on area weather stations and radar. Timing estimated from radar. No injuries reported.

Flash Flood in IMPERIAL, CALIFORNIA
From 10-AUG-21 21:40:00 to 10-AUG-21 23:30:00 (PST-8)
Location: PALO VERDE
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Department of Highways

Highway 78 was closed due to flooding, first reported at 2237MST by California Highway Patrol. Imperial County Public Works also received unconfirmed reports of damages to county roads in Palo Verde Valley. Onset of flooding impacts estimated from radar. No injuries were reported.