A new storm headed toward the Southland Friday, threatening to generate heavy rain, snow on Interstate 5 in the San Gabriel Mountains, wind gusts of 80 miles per hour, challenging travel conditions in the mountains, whiteouts, flooding, debris flows and rockslides in several burn areas, and rough seas, according to the National Weather Service.

The storm hails from the Gulf of Alaska and will tap into a band of moisture stretching from Hawaii to California as a low pressure system parks itself over California, said NWS meteorologist Todd Hall. Heavy rain is expected starting daybreak Saturday, he said.

Rain is expected starting late Friday evening or early Saturday, NWS forecasters said. Coastal and valley areas are forecast to receive between 1.5 and 3 inches of rain, the NWS said on its website, adding that the snow level in the San Gabriels will fall to 5,000 feet amid winds of between 40 and 60 miles per hour.

The impacts expected to result from the storm include flooding, downed trees and power outages, increased accidents and travel delays, shallow debris flows, with more significant flows and flash-flooding possible, rockslides on canyon roads, and winter weather driving conditions in the San Gabriel Mountains late Monday-Tuesday, the NWS said.

“A powerful winter storm will move into southwestern California tonight and Saturday. Very strong and damaging southerly winds will likely accompany this storm system across many portions of Southwest California. This has the potential to be one of the strongest southerly wind events in recent years associated with a

storm system” according to an NWS statement.

The approaching storm could produce rainfall rates of between a half-inch and an inch of rain, forecasters saud, describing a situation that could trigger flows and slides.

The storm could trigger mudslides and debris flows down slopes previously denuded by wildfires, including the Woolsey, Hill, Thomas, La Tuna, South and Stone fires, said NWS meteorologist Curt Kaplan.

In the San Gabriel Mountains, a winter storm watch will be in effect in Los Angeles and Ventura counties from Friday evening through Saturday afternoon, according to the NWS.

“A Winter Storm Watch means there is potential for significant snow, sleet or ice accumulations that may impact travel,” explained the statement.

“A powerful winter storm is forecast to move into southwestern California Friday night and Saturday, bringing heavy snow and potentially damaging winds to the higher mountain elevations,” warned an NWS statement. “Snowfall of 8 to 16 inches with locally higher amounts will be possible through Saturday above 6,500 to 7,000 feet. Very strong south to southeast winds of 40 to 55 mph with the potential for damaging gusts of up to 80 mph can also be expected. These very strong southerly winds could bring dangerous driving conditions across Interstate 5 near the Grapevine. The combination of heavy snow and very strong winds will likely create whiteout conditions and be dangerous for travelers into the high mountain elevations.”

The snow levels is expected to be at 7,000 to 7,500 feet through Saturday morning and drop to around 6,000 feet by Saturday evening, to between 5,000 and 5,500 feet late Saturday night and Sunday, according to an NWS statement. At times, snow may fall as low as 4500 feet.

Disruptions are also expected at lower elevations, including “significant wind impacts possible for Interstate 5 near the Grapevine, where very strong gusts of 70 to 80 mph will be possible.”

Along the coast, a small craft advisory will be in force from 2 p.m. to 11 p.m. Friday, and a gale watch will be in effect from Friday evening through Saturday morning. Combined seas of 10 to 13 feet are expected.

The NWS forecast mostly cloudy skies Friday and highs of 51 on Mount Wilson; 57 in Lancaster; 58 in Palmdale; 59 in Avalon; 60 in Saugus; 61 in San Gabriel; 62 in Burbank and at LAX; 63 in Woodland Hills, Long Beach and Pasadena; and 64 in Downtown L.A. Temperatures mostly — but not universally — will be marginally lower Saturday amid rain and remain at roughly the same levels amid showers on Sunday, Monday and Tuesday.

Partly cloudy skies are forecast in Orange County, along with highs of 47 on Santiago Peak; 56 on Ortega Highway at 2,600 feet; 58 in Fremont Canyon; 61 in Trabuco Canyon, San Clemente and Yorba Linda; 63 in Laguna Beach; 64 in Newport Beach, Anaheim and Mission Viejo; and 65 in Fullerton and Irvine. Temperatures will be roughly the same amid rain Saturday and showers on Sunday and Monday.

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