A quick-moving storm was clearing out of the Southland this morning—more rapidly than forecasters had expected—but a stronger one was expected tonight, threatening heavy rain, thunderstorms, waterspouts, fierce winds, high surf, flash flooding in areas denuded by wildfire and snow above 5,000 feet.
The storm that arrived Wednesday night had been expected to produce between a half-inch and an inch of rain in coastal and valley areas of Los Angeles County, between 1 and 2 inches in the mountains and foothills, and up to 3 inches along some slopes, according to the NWS. How much precipitation it will have generated in the end was not immediately known.
Rainfall volumes associated with the second storm "could be very impressive" -- 1-3 inches in coastal and valley areas, 3-6 inches in the mountains and foothills and up to 8 inches along some south-facing slopes, according to the agency.
Along the L.A. County coast, a high surf advisory will be in effect until 5 a.m. Sunday while in Orange County, a less serious beach hazard statement will be in effect from Friday morning through late Saturday night along with a coastal flood watch. Also in effect in Orange County will be a flash flood watch from late tonight through Saturday afternoon.
The wind is also a major aspect of this week's storms. A wind advisory was scheduled to be in effect until midnight tonight in the San Gabriel mountains and the Antelope Valley. An even more serious high wind watch will be in effect in the Antelope Valley from late tonight through Friday evening.
The National Weather Service forecast south-to-southwest winds of between 20 and 30 miles per hour with gusts of between 45 and 50 mph in the Antelope Valley and the L.A. County portion of the San Gabriel mountains through tonight, followed by winds of between 25 and 40 mph gusting to up to 60 mph in the Antelope Valley.
Traffic on the Antelope Valley (14) Freeway and Pearblossom Highway, SR138—particularly high-profile vehicles—could be affected by the high winds, and visibility may be sharply restricted by blowing sand and dust, forecasters said.
In Orange County, a wind advisory will be in effect from 4 a.m. Friday to 1 p.m. Saturday. The county's coastal areas and inland valleys were expected to be swept by south-to-southwest winds of between 20 and 30 mph with 50-mph gusts.
In the San Gabriels in both Los Angeles and Ventura counties, a winter storm watch will be in effect from late tonight through late Saturday night.
The snow level will begin at 8,000 feet tonight, then drop to between 5,500 and 6,500 feet Friday afternoon through Saturday night, according to a National Weather Service advisory.
Between 5,500 and 7,000 feet, snow accumulation from the second storm will range between 6 and 12 inches -- up to 18 inches in some spots -- forecasters said. Above 7,000 feet, between 1 and 3 feet of snow is expected, and up to 4 feet of snow could accumulate on the higher peaks.
South winds of between 25 and 40 mph gusting to 60 mph will sweep the San Gabriel mountains, which, mixed with falling snow, will make travel hazardous, while below 5,000 feet, heavy rain likely will cause road flooding and may trigger rock slides, forecasters said. People should travel in the mountains today, Friday and Saturday only in an emergency, they said.
"If you must travel, check the latest road reports before departing," urged an NWS advisory. "Keep an emergency kit in your vehicle which includes a flashlight, food and water, extra clothes and blankets and tire chains.
In areas denuded by wildfires, there could be flows of mud and debris, they said. Of special concern are the sites of the 1,952-acre Colby Fire in the hills above Glendora and Azusa in January, the 250-acre Madre Fire in the Angeles National Forest, also in January, the 125-acre Madison Fire in the Monrovia area in April , the 22-242-acre Powerhouse Fire in the Angeles National Forest in June and the 28,000-acre Springs Fire in Ventura County in May.
A flash flood watch will be in effect from late tonight through Saturday evening in the region's so-called burn areas.
During that time, thunderstorms and heavy rain are expected, according to an NWS advisory, which said that there could be between a half-inch and an inch of rain an hour, which would trigger the flow of mud and debris. Also possible are waterspouts skimming in coastal waters, forecasters said.
Voluntary evacuations have been reported in Glendora due to fears of mud flows from the Colby Fire burn area.
"Southern California residents in or below recently burned areas are urged to take the steps necessary to protect their property," warned the NWS advisory.
The NWS forecast highs today of 54 on Mount Wilson; 57 in Avalon; 61 at LAX; 62 in Saugus, Palmdale and Lancaster; 63 in Long Beach and San Gabriel; 64 in Pasadena, Burbank; Newport Beach; 65 in downtown L.A and Woodland Hills; 67 in Anaheim;
Temperatures will be generally similar Friday, when thunderstorms are also in the forecast.