A storm out of the Gulf of Alaska invaded the Southland today and will unleash rain, snow, and cold winds through Thanksgiving while causing rough seas and wreaking havoc on the region’s roads, forecasters said.
National Weather Service meteorologists forecast between 1 and 2 inches of rain along the coast and in valleys, 2 to 4 inches in the mountains and foothills, 6 to 12 inches of snow in most mountain locations but between 12 and 24 inches in the San Gabriel Mountains. They warned of significant holiday travel delays and road closures, major snow impacts, roadway flooding at lower elevations, significant flight delays, possible flash floods and debris flows over recent burn areas, and hazardous road conditions.
A winter storm warning signifying an expectation of difficult travel conditions will be in effect in the San Gabriel Mountains from 4 a.m. today until 4 a.m. Friday.
Most mountain areas will get 6 to 12 inches of snow—including 3-6 inches in the Grapevine, which could snarl Interstate 5—but up to 24 inches of snow is expected to accumulate at higher elevations.
The snow level will be at between 5,000 and 7,000 feet this morning but dip down to 3,000 feet tonight, according to the NWS. “Travel could be very difficult to impossible,” warned an NWS statement. “The hazardous conditions could result in temporary road closures. Gusty winds could bring down tree branches and cause power outages.”
A winter storm warning is also scheduled until 10 p.m. Friday in the Santa Ana Mountains, which spread across some of Orange County. Total snowfall accumulations of 3 to 6 inches are expected between 4,000 and 4,500 feet, 6 to 18 inches from 4,500 to 5,500 feet, and from 1 to 3 feet above 5,500 feet, said the NWS. Snowfall at lower elevations below 4,000 feet will be 1 to 3 inches, mostly late Thursday through Friday.
Also forecast in the Santa Anas are strong southwest winds today, with gusts of 50 to 70 mph along the ridges and desert slopes.
“A winter storm warning for snow means severe winter weather conditions are expected. If you must travel, keep an extra flashlight, food and water in your vehicle in case of an emergency,” urged the NWS.
Also in force in Orange County—both inland and coastal areas—is a flash flood watch, from late tonight through tomorrow night.
A high wind warning will be in effect until 10 a.m. in the Antelope Valley, while a less serious wind advisory will be in force until noon in the Santa Monica Recreational area and the Santa Clarita Valley. Southwest winds of 35-35 miles per hour gusting to 65 mph will blow across the Antelope Valley while winds of 15 to 30 mph with gusts of up to 45 mph are expected in the Santa Monicas and the Santa Clarita Valley.
“Damaging winds may blow down trees and power lines. Widespread power outages are possible. Travel will be difficult, especially for operators of high-profile vehicles,” according to an NWS statement.
NWS forecasters said a cold and unstable air mass is hovering over the region this morning, creating the possibility of isolated thunderstorms over the waters northwest of Point Conception, continuing through Thursday evening. “Any thunderstorm that forms will be capable of producing erratic gale-force gusts and rough seas, heavy downpours of rain and hail with reduced visibility, dangerous lightning, and waterspouts, according to an NWS statement.
Mariners should consider staying in port, it said. A small craft advisory, indicating that inexperienced mariners with small vessels should stay on shore, will be in effect until 3 this afternoon.
Also in effect, until 3 this afternoon, is a beach hazards statement, which is slightly less serious than a high surf advisory, issued because surf of 3-6 feet is pounding the L.A. County coast, expected to persist through late tonight.
The NWS forecast rain in L.A. County today and highs of 40 degrees on Mount Wilson; 49 in Palmdale and Lancaster; 53 in Saugus; 56 in San Gabriel; 57 in Pasadena; 58 in Burbank; 60 in Woodland Hills and Avalon; and 61 in Long Beach, Downtown L.A. and at LAX. Temperatures will be a few degrees amid showers on Thursday, then climb slightly amid more showers on Friday.
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