A potent and fast-moving Pacific storm will hit the Southland this afternoon, bringing stiff winds and a chance of mud flows over fire-stripped slopes, the National Weather Service said.
The storm is expected to bring a period of moderate to occasionally heavy rain lasting three to five hours, followed by scattered showers, an NWS statement said.
The rain will start at the Central Coast by mid-morning, then reach the Los Angeles basin during the mid to late afternoon hours, turning to showers mid-evening, it said. The showers will end by late tonight.
Also expected Friday afternoon and evening are gusty winds, especially in the San Gabriel Mountains and the Antelope Valley, according to the NWS.
As colder air flows into the region, the atmosphere will become increasingly unstable, creating a slight chance this afternoon and evening of thunderstorms that could unleash small hail, it said, adding there is also a slight chance of waterspouts. “Rainfall rates may be high enough, especially in thunderstorms, to pose a threat of mud and debris flows near recent burn areas,” it said.
Rainfall totals are expected to average a half-inch to 1.5 inch, with the higher amounts expected in the Central Coast. In the Antelope Valley, a quarter-inch to a half-inch is expected.
NWS forecasters said the snow level will start at around 6,500 feet, then fall to between 4,500 and 5,000 feet this afternoon, although it could drop to 4,000 in case of thunderstorms.
Between three and five inches of snow are expected to accumulate from 5,000 to 6,500 feet, and between five and 10 inches above 6,500 feet.
“Be prepared for snow-covered roads and limited visibility, and use caution when driving,” an NWS statement said, urging motorists to keep emergency supplies on hand if they venture into mountain areas.
Forecasters said south-to-southwest winds of between 25 and 35 miles per hour gusting to 50 mph would blow through mountain areas today while winds of between 20 and 30 mph, gusting to 45 mph, will sweep the Antelope Valley. In Los Angeles and around beach cities, forecasters expect winds of between 15 and 25 mph gusting at up to 40 mph.
A winter weather advisory denoting perilous travel conditions will be in effect in the San Gabriels from 1 this afternoon until 6 a.m. Saturday.
A wind advisory will be in effect in the Antelope Valley from noon until 10 p.m. and, from 3 p.m. to 9 p.m., on Santa Catalina Island and in L.A. County beach cities, metropolitan Los Angeles, the downtown area, and the Hollywood Hills. In Orange County, a wind advisory will be in effect from 4 p.m. until 4 a.m. Saturday.
High surf is also in the forecast, and a high surf advisory will be in force in L.A. County from 4 p.m. today unto midnight Sunday. Off the coast, a small craft advisory will be in effect from 1 p.m. today until 3 a.m. Sunday.
The NWS forecast a sharp cooldown today and highs of 54 on Mount Wilson; 61 at LAX; 62 in Long Beach, Palmdale, Saugus and San Clemente; 63 in Lancaster, Burbank, Avalon, Anaheim, Laguna Beach and Newport Beach; 64 in downtown L.A., San Gabriel, Fullerton and Fullerton; 66 in Pasadena and Woodland Hills; and 67 in Yorba Linda and Mission Viejo.
Temperatures will be similar under dry skies Saturday and Sunday, but showers are forecast Monday. A warming trend taking highs back into the 70s is expected Tuesday, with temperatures reaching the 80s Wednesday.
