A slow-moving storm system slid over the Southland Wednesday — albeit later than expected — bringing rain to most areas and snow to the mountains, beginning what forecasters expect to be two days of wet conditions.
A winter storm warning will be in effect until 4 a.m. Friday in the Los Angeles County mountains, excluding the Santa Monica range. According to the National Weather Service, “heavy snow” is possible, with 1 to 3 feet accumulating above 5,000 feet, and “light snow” falling as low as 4,000 feet. The snow will be accompanied by winds gusting up to 45 to 50 mph, with higher-elevation gusts of up to 60 mph.
“Travel could be very difficult to impossible,” according to the NWS.
The weather service said some mountain roadways that could be affected by snowfall include Angeles Crest Highway, Mount Baldy Road and Highway 39.
Caltrans reminded motorists that chains will be required on the Angeles Crest Highway north of La Canada Flintridge, and the agency urged motorists to be aware of road conditions and anticipate possible closures due to impending snow. Caltrans also advised that snow could impact travel through the Grapevine area on the Golden State (5) Freeway in northern Los Angeles County.
Gusting winds were also impacting the Antelope Valley, where the NWS issued a wind advisory through 10 p.m. Forecasters said the area should expect winds of 15 to 30 mph, with gusts up to 45 mph, potentially reducing visibility for motorists and blowing dust across roadways.
Meanwhile, in Orange County, voluntary evacuation warnings went into effect at 10 a.m. for the Silverado, Williams and Modjeska canyon areas in the Bond Fire burn area due to fears of possible debris flows. The same areas were subjected to mandatory evacuations during last week’s storm.
The NWS issued a flash flood watch for Orange County coastal and inland areas and the Santa Ana Mountains, including the Bond Fire burn area. The watch will be in effect through Thursday afternoon.
“Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations,” according to the NWS. “Flooding may occur in poor drainage and urban areas. Flash flooding and debris flows are possible, especially near recent burn scars.”
NWS forecasters for Orange County said the area could receive up to 2.5 inches of rain along the coast and as much as 6 inches in the mountains below 5,000 feet, with hourly rainfall amount of 0.6 to 0.7 inches possible.
A flash flood watch will take effect at 6 p.m. and continue through Thursday afternoon for Los Angeles County burn areas from the Lake, Bobcat, Dam and Ranch 2 fires. Forecasters said the areas could experience “several hours of moderate to heavy rain … which could lead to flash flooding and debris flows.”
According to the NWS, 2 to 4 inches of rain could fall in L.A. County coastal and valley areas, with 3 to 7 inches falling in the mountains.
The storm was originally expected to begin dumping rain and snow on the area overnight. But it moved slower than anticipated, with heavier rain not expected to begin until later Wednesday afternoon.
“By (Thursday), the steadier precipitation should hang on over LA County through at least the morning hours then become more showery in the afternoon,” according to the NWS.
Forecasters said there will be a chance of some thunderstorms Wednesday night and Thursday morning.
Temperatures will also remain “significantly below average” across the region, according to the NWS.
On Tuesday, Anaheim recorded its lowest daytime temperature for that date at 56 degrees, breaking the old record of 59 set in 2007.
The rainy weather is expected to continue through Thursday, with dry — but cool — conditions anticipated starting Friday and lasting through the holiday weekend.