Flash Flood — San Bernardino, California
2014-08-03 · near Adelanto Hlndale Arp, San Bernardino, California
Event narrative
CHP reported a flooded wash with multiple cars stuck in the area. 4 inches of rain recorded in gauge within 2 hours on the steep slope of big Mt Baldy. A hiker parked their car in the small town of Mt Baldy and hiked to the top. Hail and lightning caused them to go back down the mountain early. They used the dry creek to go back
down and were swept away in a flash flood over 10 feet, per NWS Storm Survey of high water marks on trees. The hiker's car was found the next
day during the NWS Storm Survey. The car was destroyed and the person drowned somewhere along the middle or bottom of the creek, just on the San Bernardino County side. LA County Fire department led the search and rescue. Since Mt Baldy
town, where the car was parked, is in San Bernardino County they ended up having a unified command with Los Angeles County, San Bernardino Fire, and Town of
Mt Baldy. At least 2 vehicles were towed out of the creek. We were told at the survey that the cars were on the Los Angeles County side of the mountain but washed downstream, and across the San Bernardino County side of the mountain, where the one fatality of a 48-yr old man from El Segundo, occurred.
Wider weather episode
An upper-level low from Baja cut underneath a large area of seasonably strong high pressure aloft, tapping into lingering monsoonal moisture to produce showers and thunderstorms over the mountains and deserts, as well as a few along the coastal areas, with heavy rain at times. The activity on the 2nd consisted of elevated thunderstorms with lightning along the coast during the morning and a few thunderstorms over the San Bernardino County mountains. Rain and rapid cooling in one of these storms resulted in several bicyclists being treated for hypothermia during the Tour de Big Bear race. This elevated convection became intense and transitioned into numerous strong thunderstorms on the 3rd, focusing more on the mountains and deserts and closing several roadways due to flooding. Rainfall of 2 to 4 inches occurred in less than 3 hours across steep terrain in the San Bernardino County mountains. The hardest hit areas were Mt Baldy, Forest Falls and Oak Glen where numerous debris flows occurred causing road damage and closures. Incident Command Posts were set up at both Mt Baldy and Valley of the Falls. A weather station in Mt Baldy reported 4 inches of rain in less than 2 hours. Swift water rescues were performed in Mt Baldy along the LA County line. There was also a large area of 1 to 2.5 inches of rain in low-lying areas and deserts, including 2.73 inches in one hour at the Borrego ALERT gage. The Fish Creek RAWS in the San Diego County desert recorded 2.77 inches of rain in one hour, resulting in moderate flooding and the subsequent closure of Fish Creek Road through August 8th. Heavy rain west of the mountains produced flash flooding in Redlands and Ramona. A large sink hole developed in Redland due to heavy rainfall. San Bernardino County was the hardest hit with flash flooding, with 25 homes damaged and approximately $11 million in damage county-wide for this event. Full storm surveys were done from Mill Creek near Forest Falls, to Oak Glen, to Lytle Creek and through out Mt Baldy on August 4th.
View location on OpenStreetMap → (34.7275, -117.5269)
Source: NOAA Storm Events Database, event_id 539354. Narrative written by the NWS forecast office that issued the report.