LOS ANGELES — A storm out of the Gulf of Alaska will slide into Southern California today — Wednesday, Nov. 27 — and unleash rain, snow and cold winds through Thanksgiving while causing rough seas and wreaking havoc on the region’s roads, forecasters said.

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.

Graphic courtesy of the National Weather Service

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 5500 feet, said the NWS. Snowfall at lower elevations below 4,000 feet will be of 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, San Bernardino and Riverside counties  — 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.

LA Daily News