Showers doused the Southland for a second straight day Thursday, triggering some unexpected mudslides and debris flows.
A thunderstorm may develop over the Southland Thursday afternoon, said National Weather Service Curt Kaplan.
Forecasters said they still believe there will not be mud slides or debris flows in area denuded by wildfires but conceded they are marginally less confident of it then Wednesday. Their optimism tuned out to have been unwarranted.
The rain fell at a rate of around a third of an inch per hour Thursday morning in areas of Ventura County stricken by the ”Hill Fire” and areas of L.A. and Ventura counties affected by the Woolsey Fire, prompting the Nationl Weather Service in Oxnard to issue a flash flood warning in effect until 10:45 a.m..
Mud and debris flows struck Highway 1, which was shut down at Leo Carrillo State Beach. Additionally, a mudslide prompted closure of the eastbound Victory Boulevard offramp from the southbound Hollywood Freeway in the Valley Glen area of the San Fernando Valley.
With scattered showers having fallen in several areas overnight, Thursday morning’s commute was challenging, as was the case Wednesday, when, according to the California Highway Patrol, there were 119 accidents reported on Los Angeles County freeways between 5 a.m. and 10 a.m., compared to 93 under dry conditions a week earlier. Forecasters said motorists must be particularly vigilant on canyon roads.
The conditions did not spare Orange County. The NWS office in San Diego issued a flash flood watch covering the Santa Ana Mountains and Foothills and inland Orange County, including Santa Ana, Anaheim, Garden Grove, Irvine, Orange, Fullerton, and Mission Viejo. The watch also applied to parts of Riverside County hit by the Holy Fire, as was Orange County.
The NWS said rainfall rates of 1/2 inch in an hour will be likely later Thursday, adding: “This could lead to mud and debris flows in and below the recent burn scars. The period of greatest concern will be from late Thursday morning through late this evening. Additional rainfall totals could range from 1 to 2 inches by midnight.”
In mountain areas, the slow-moving low-pressure system will bring snow to higher elevations of the San Gabriel Mountains in Los Angeles and Ventura counties through late this evening, according to the NWS.
Forecasters said six inches of snow would fall above 6,500 feet, 10 inches above 7,500 feet and one to two inches between 5,500 and 6,500 feet. At the same time, the mountains will be swept by winds of 15-25 miles per hour, with 40-mph gusts.
A winter weather advisory will be in force in the San Gabriels until midnight.
Forecasters urged motorists to brace for slippery road conditions but said snow would not be an issue along the Interstate 5 corridor through the Tejon Pass and the Grapevine.
The NWS forecast showers in L.A. County Thursday and highs of 47 in Palmdale and Lancaster; 48 on Mount Wilson; 52 in Saugus; 56 in Yorba Linda; 59 in Burbank; 60 in San Gabriel, Pasadena and Woodland Hills; 61 in downtown L.A. and at LAX; 62 in Long Beach and Avalon. Temperatures will be up to eight degrees warmer Friday.
Showers were also forecast in Orange County, along with highs of 43 on Santiago Peak; 50 in Ortega Highway at 2,600 feet; 56 in Yorba Linda; 59 in Anaheim and Mission Viejo; 60 in Laguna Beach, San Clemente, Fullerton and Irvine; and 61 in Newport Beach. Friday’s temperatures will be up to nine degrees higher.