Moist and unstable monsoonal flow triggered scattered showers and thunderstorms across San Diego, San Bernardino and Riverside Counties, a few of which reached severe status with large hail and damaging winds. Localized flash flooding was also reported in a few locations over the 2-day event.

Flash Flood in RIVERSIDE, CALIFORNIA
From 25-AUG-10 13:49:00 to 25-AUG-10 15:00:00 (PST-8)
Location: VALLE VISTA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Highway 74 closed due to flooding until 1600 PDT.

Heavy Rain in RIVERSIDE, CALIFORNIA
From 25-AUG-10 13:36:00 to 25-AUG-10 13:49:00 (PST-8)
Location: VALLE VISTA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The East Hemet Mesonet site reported between 0.50 to 1.01 inches of rain fell between 1336 and 1349 PST.

Heavy Rain in RIVERSIDE, CALIFORNIA
From 25-AUG-10 13:36:00 to 25-AUG-10 13:46:00 (PST-8)
Location: VALLE VISTA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The C4086 mesonet site located in Hemet, CA reported 0.50 inches of rain fell between 1336 and 1346 PST on August 25th.

Heavy Rain in RIVERSIDE, CALIFORNIA
From 26-AUG-10 13:40:00 to 26-AUG-10 14:30:00 (PST-8)
Location: WINCHESTER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

ALERT gauge 248 in Winchester, CA in Riverside County measured 0.49 inches of rain between 1340 and 1430 PST on August 26th. Instantaneous rainfall rates between 1400 and 1415 reached over an inch per hour.

Thunderstorm Wind in SAN DIEGO, CALIFORNIA
From 26-AUG-10 12:20:00 to 26-AUG-10 12:50:00 (PST-8)
Location: LAKE HENSHAW
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Mataguaty SDGE anemometer, located at 6 meters above ground level, measured a peak wind at 1230 PST out of the NNW at 30 MPH with a gust of 60 MPH.  Downdrafts in excess of 40 MPH began shortly after 1220 and continued until 1250 PDT.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 26-AUG-10 13:58:00 to 26-AUG-10 14:29:00 (PST-8)
Location: FAWNSKIN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Fawnskin ALERT gauge in San Bernardino County recorded 1.30 inches of rain in 31 minutes between 1358 and 1429 PST on August 26th.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 25-AUG-10 13:00:00 to 25-AUG-10 15:30:00 (PST-8)
Location: ELSINORE
Magnitude: 52.00 EG
Property damage: 80.00K
Crop damage: 0.00K
Reported by: Newspaper

A severe thunderstorm with estimated wind gusts of 60 MPH brought down ten power poles on Pottery Street in Lake Elsinore. Live power lines fell on a RTA bus around 1330 PST, trapping the driver and 11 passengers for two hours. Trampolines were also picked up and blown into adjacent yards. Street flooding was also reported in Lake Elsinore.

Hail in SAN DIEGO, CALIFORNIA
From 26-AUG-10 11:54:00 to 26-AUG-10 12:30:00 (PST-8)
Location: WARNER SPGS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter SDG173 observed a max hail size of 1 inch in Sunshine Summit (approximately 9 miles NW of Warner Springs), while the average hail size was more like 0.75 inch. Estimated duration for the hail and heaviest part of the thunderstorm was 10 to 15 minutes. Estimated wind gusts of 50 to 60 MPH also accompanied the rain and hail.

Flash Flood in SAN BERNARDINO, CALIFORNIA
From 26-AUG-10 12:00:00 to 26-AUG-10 12:30:00 (PST-8)
Location: VICTORVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Seneca Road from Amargosa Road to El Evado Road was completely washed out due heavy rain on the afternoon of August 26th. Several other roads in Victor Valley, including Palmdale Road and portions of Highway 18 were flooded as well.

Flash Flood in SAN BERNARDINO, CALIFORNIA
From 25-AUG-10 11:50:00 to 25-AUG-10 12:00:00 (PST-8)
Location: FOREST FALLS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A thunderstorm near Forest Falls, CA dumped rain for approximately 45 minutes over the western portion of the community. Trees, boulders and mud were reported flowing down Valley of the Falls Road, causing that portion of the road to be closed to traffic for several hours.

Flash Flood in SAN DIEGO, CALIFORNIA
From 26-AUG-10 11:30:00 to 26-AUG-10 12:30:00 (PST-8)
Location: WARNER SPGS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter SDG173 reported 1.8 inches of rain measured between 1200 and 1256 PST. Mud, debris and rocks were reported flowing across side roads and blocking Highway 79 near Warner Springs.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 25-AUG-10 10:45:00 to 25-AUG-10 11:45:00 (PST-8)
Location: SUGARLOAF
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Big Bear City South Mesonet site reported 1.02 inches of rain fell between 1045 and 1145 PST on August 25th. The storm total for that site was 1.54 inches, which fell between 0945 and 1245 PST.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 25-AUG-10 11:45:00 to 25-AUG-10 11:53:00 (PST-8)
Location: YUCAIPA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Mesonet site at Yucaipa Ridge reported that 0.51 inches of rain fell in 8 minutes between 1145 and 1153 PST on August 25th.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 25-AUG-10 14:00:00 to 25-AUG-10 14:35:00 (PST-8)
Location: WRIGHTWOOD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Wrightwood Mesonet site reported 0.81 inches of rain fell within 35 minutes between 1400 and 1435 PST on August 25th.

Flash Flood in SAN BERNARDINO, CALIFORNIA
From 26-AUG-10 14:00:00 to 26-AUG-10 15:30:00 (PST-8)
Location: CUSHENBURY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter reported 1.73 inches of rain fell between 1400 and 1530 PST on August 26th. The heavy rain flooded Highways 18 and 247 with 2 to 3 feet of water over the roadways.Two swift water rescues were performed, including three people in a car who got washed away, but were saved.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 26-AUG-10 10:48:00 to 26-AUG-10 11:19:00 (PST-8)
Location: FOREST FALLS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

ALERT gauge 2801 at the Oak Glen Watershed measured 0.47 inches of rain between 1048 and 1119 PST on August 26th.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 26-AUG-10 12:30:00 to 26-AUG-10 13:30:00 (PST-8)
Location: HEMET RYAN ARPT
Magnitude: 65.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Media reported downed power lines and trees of 1 to 2 feet in diameter near Hemet, CA on August 26th. Wind gusts estimated between 60-70 mph.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 25-AUG-10 14:00:00 to 25-AUG-10 14:36:00 (PST-8)
Location: WRIGHTWOOD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A member of the public called to report mud, debris and four inch diameter rocks washing down the Sheep Creek Wash at the base of Heath Canyon near Wrightwood, CA on August 25th. Highway 2 was closed between Desert View and Summit Roads due to water, mud and debris washing across the roadway.