A cold storm struck the Southland Thursday, creating what National Weather Service forecasters described as a risk of urban flooding and of mud and debris flows down slopes denuded by wildfires.
The NWS issued an urban and small stream flood advisory for eastern L.A County that was initially scheduled to be in effect until 9:15 a.m., but then extended it until 12:15 p.m.
A statement said the move was in response to Doppler radar indicating “moderate to heavy rain over eastern Los Angeles County, with heavy rain moving in soon from the west. Minor flooding is expected in the portions of Los Angeles County into the afternoon, including low-lying roads or parking lots and small streams.”
Forecasters urged motorists who encounter flooding to immediately turn around.
“Most flood deaths occur in vehicles,” noted an NWS statement.
The NWS forecast between a half-inch and an inch of rain in most Southland areas and between an inch and 1.5 inches in the mountains and foothills.
In the San Gabriel Mountains, snow levels will generally range between 5,000 and 5,500 feet through Thursday, then rapidly lower to 3,500 feet tonight into early Friday, when there is the potential for snow showers accompanied by snow accumulations and the formation of ice on Interstate 5 near The Grapevine, said an NWS statement.
A winter weather advisory, which indicates challenging travel conditions, will be in effect in the San Gabriel Mountains in Los Angeles County until 9 a.m. Friday, with the heaviest snow expected this afternoon.
Four to eight inches of snow are expected above 5,500 feet through early Friday, with accumulation of up to a foot on higher peaks, an NWS statement said, and between 1 and 2 inches are possible as low as 3,500 feet tonight into early Friday. At the same time, winds of between 20 and 30 mph will sweep the mountains, gusting to 45 mph, forecasters said.
Mountain conditions for motorist could include falling snow, blowing snow and snow and ice on roads, forecasters said.
There is a slight chance of thunderstorms in Los Angeles County this afternoon, creating the potential for mud and debris flows in recent burn areas, and there could be urban roadway flooding during the peak of the storm, the statement said. A flash flood watch will be in effect in the San Gabriel Mountains and the Santa Clarita and San Gabriel valleys through tonight.
Along the coast, a beach hazard statement will be in force until 10 a.m. in L.A. and Orange counties. Expected is surf of three to five feet with sets of up to seven feet. Ocean conditions Thursday will create a risk of drowning for swimmers and surfers, forecasters warned. Anyone caught in a rip current should stay calm and swim parallel to shore until able to break free.
The storm is expected to linger until Friday morning.
The NWS forecast highs in L.A. County Thursday of 45 degrees Fahrenheit on Mount Wilson; 49 in Palmdale and Lancaster; 53 in Saugus; 56 in Pasadena and Burbank; 57 in San Gabriel and Woodland Hills; 59 in Downtown L.A. and at LAX; and 60 in Long Beach and Avalon.
In Orange County, where the forecast is mostly for cloudy skies, the NWS said highs would be 57 in Mission Viejo; 58 in Yorba Linda; 59 in Laguna Beach and Fullerton; 60 in Newport Beach, San Clemente and Anaheim; and 61 in Irvine.
Temperatures in L.A. and Orange counties will be roughly the same Friday under cloudy skies and climb by around 6-7 degrees in several communities — 11 degrees on Mount Wilson, amid sunny skies Saturday. The sun will stick around until at least Monday.
—City News Service