More rain fell in the Southland today amid isolated thunderstorms and forecasters warned of high surf, some coastal flooding and the possibility of mud flows over fire-denuded slopes.
"The big story today will be the high surf," said National Weather Service meteorologist Curt Kaplan, noting surf of 8 to 12 feet is in the forecast, with maximum sets of 16 feet.
The current storm — the third weather system to hit Southern California this week — slammed into the Southland late yesterday morning and was dissipating today, with Kaplan saying the next bout of rain should come Saturday.
He said that so far, the latest storm has produced between a half-inch and an inch-and a third of rain in metropolitan Los Angeles, between 1 and 3 inches in the foothills, almost 2 inches in the valleys, and roughly between a third of an inch and more than three-fourths in the valleys.
"Scattered showers and isolated thunderstorms will persist across the burn areas of Ventura and Los Angeles counties through today," an NWS statement said, warning of a possibility of a half-inch to three quarters of an inch per hour near the sites of thunderstorms — rainfall rates able to cause flash flooding and debris flows, especially over slopes previously stripped bare by wildfires.
A flash flood watch was in effect until noon today for the burn areas in the San Gabriel and Santa Clarita valleys, the San Gabriel Mountains and several areas of Ventura County.
In the San Gabriel Mountains, conditions appeared to ease somewhat this morning. A winter storm warning was cancelled and replaced with a winter weather advisory scheduled to expire at noon.
Still, periods of moderate to heavy snowfall were likely this morning, with snow accumulation above 4,000 feet expected to range from 3 to 6 inches, according to the NWS. Generally, the snow level will be around 4,000 feet but could climb down to 3,500 feet in heavier showers or thunderstorms.
Combined with winds of between 20 and 30 mph, the snow could produce whiteout conditions today, forecasters said. Black ice could also be a problem
"Travel will be treacherous at times on mountain highways this morning such as Angeles Crest Highway, Highway 39, Interstate 5 near The Grapevine, and Highway 14 near Soledad Canyon Pass," a statement said, urging motorists using mountain roads to pack an emergency kit including tire chains.
The coastline, meanwhile, was being battered by what an NWS statement called "very large damaging surf."
A high surf warning will be in force in Los Angeles County until 4 a.m. Friday, and a coastal flood advisory is due to expire at noon today. NWS forecasters warned that the surf will build to between 10 and 14 feet, with sets of 16 feet expected this morning.
In Orange County, a high surf warning was in effect until 10 p.m. Friday, and a flash flood watch will be in effect until noon today.
The combination of high astronomical tides, onshore winds and very large surf will cause minor overflow of sea water into low-lying areas today, especially during the times of highest today," an NWS statement said.
The NWS blamed the high surf on a series of long-period westerly swells.
"A high surf warning means that large and battering surf could damage coastal structures and will make swimming and rock jetties very dangerous," a statement said. It added that swimmers who become trapped in rip currents should swim parallel to shore until able to free themselves.
Three El Nino-caused weather systems hit Southern California this week, including one that slammed into the region late yesterday morning. The next storm is now forecast for Saturday.
The NWS forecast mostly showers today and highs of 44 on Mount Wilson; 48 in Palmdale; 49 in Lancaster; 50 in Saugus; 56 in Burbank; 57 in Yorba Linda, Woodland Hills and Pasadena; 58 in San Gabriel, San Clemente and Irvine; and 59 in Downtown L.A., Long Beach,Avalon, Newport Beach, Laguna Beach, Fullerton, Anaheim and at LAX.
Friday is forecast to be partly cloudy, with temperatures marginally higher than today. Rain is forecast Saturday, followed by several partly cloudy days, with highs in the low 60s.