An upper-level low pressure area moving slowly northeast over the lower deserts, and an associated weak disturbance aloft triggered a slow moving thunderstorm in the lower Coachella Valley near the community of Mecca just after midnight PST. With abundant moisture extending from the surface to 400 mb, and precipitable water values between 1.8 and over 2.2 inches, this storm remained nearly stationary from approximately 0200 through 0800 PST and produced between 3 and 5.5 inches of rainfall near Mecca (approximately 30 miles southeast of Palm Springs, CA). In addition, radar estimates were between 5 and 8 inches. Most of the rain fell between 0200 and 0400 PST, which resulted in a rare and damaging flash flooding in this area. This was eventually found to be a 1000-year flood event.

Flash Flood in RIVERSIDE, CALIFORNIA
From 11-SEP-12 02:00:00 to 11-SEP-12 07:00:00 (PST-8)
Location: MECCA
Flood cause: Heavy Rain
Property damage: 2.00M
Crop damage: 0.00K
Reported by: Fire Department/Rescue

A stationary thunderstorm brought persistent heavy rain in Mecca between 0200 and 0800 PST, resulting in flash flooding of two mobile home parks. Approximately 15 to 20 mobile homes in the Duroville and Saint Anthony's mobile home parks were damaged. The American Red Cross set up an evacuation center at the Mecca Family and Farm Workers Services Facility for the approximately 1500 residents affected. A boil water message was issued for these locations as well. Saul Martinez Elementary School also reported water damage to 15 classrooms, the teachers' lounge and the administration building with 2 to 3 inches of water.

Heavy Rain in RIVERSIDE, CALIFORNIA
From 11-SEP-12 00:00:00 to 11-SEP-12 14:30:00 (PST-8)
Location: MECCA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The ALERT rain gauge at Kent Sea Farms recorded 5.51 inches of rain in 24 hours, 4.18 inches of which was in the past 12 hours. The vast majority of the rain fell between 0000 and 0700 PST.

Flash Flood in RIVERSIDE, CALIFORNIA
From 11-SEP-12 00:45:00 to 11-SEP-12 02:00:00 (PST-8)
Location: MECCA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rain resulted in flooding along 66th Avenue east of Johnson Avenue. County Road Department was dispatched to barricade the roads.
A short distance upstream, the Thermal airport measured 1.42 inches of rain between 0019 and 0316 PST, over an inch of which fell between 0019 and 0236 PST.

Flash Flood in RIVERSIDE, CALIFORNIA
From 11-SEP-12 00:45:00 to 11-SEP-12 04:30:00 (PST-8)
Location: MECCA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Heavy rain resulted in flooding along State Highway 111, just east of the intersection with Colfax Street. The roadway there was covered with 3 feet of water.
A mesonet station, at Kent Sea Farms, just west of this location recorded 3.38 inches of rain between 0050 and 0419 PST.

Flash Flood in RIVERSIDE, CALIFORNIA
From 11-SEP-12 02:00:00 to 11-SEP-12 06:00:00 (PST-8)
Location: MECCA
Flood cause: Heavy Rain
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Fire department and rescue officials in Riverside County reported residential flooding of approximately 4 homes on the 91000 block of 5th Street in Mecca due to heavy downpours. No injuries reported and depth of flood waters was unknown.