The strongest storm to hit Southwest California in several years is expected to bring torrential rain, flash flooding and powerful winds on Friday, forecasters say.

The storm is expected to dump up to 6 inches of rain on Los Angeles County beaches and valleys and 5 to 10 inches on south-facing foothills and coastal mountain slopes, according to the National Weather Service. A flash flood watch has been issued for Santa Barbara, Ventura and Los Angeles counties from Friday morning through Saturday morning.

Much of that rainfall is expected to fall within a short time Friday afternoon and evening, with rain potentially falling at a rate of more than an inch an hour, forecasters said.

“The Friday morning commute is definitely going to be wet,” but the rain is just going to get heavier as the day progresses, said Kathy Hoxsie, a meteorologist with the National Weather Service in Oxnard.


“The afternoon commute is going to be a mess,” Hoxsie said. “Hopefully people can take a half day off. Being a Friday, I know a lot of people do that anyway. … The evening is shaping up to be nasty.”

The storm is likely the strongest to hit the region within the last six years, according to the weather service.

Rainfall began falling on the Central Coast early Thursday and is expected to move into Southern California overnight, Hoxsie said.

Wildfire burn scars in Duarte and Azusa are particularly vulnerable with this storm, she said.


The system also is bringing powerful southerly winds that will increase dramatically on Friday, with gusts up to 60 to 70 mph likely over high elevations in Ventura, San Luis Obispo and Los Angeles counties, as well as the Channel Islands and Santa Catalina Island, according to the weather service. Damaging wind gusts are also possible in the Antelope Valley.

“It’s going to be blowing really well,” Hoxsie said. “We’re trying to tell folks, don’t just do your usual preparation for rain, but also, if you’ve got anything outside that could be moved into the garage, this would be the storm where you should do that.”

Snow levels are anticipated to be at 8,000 feet Friday night, lowering to 6,000 feet on Saturday, according to the weather service. Because of the heavy precipitation, 1 to 2 feet of snow could fall above 8,000 feet in Los Angeles and Ventura counties, and 6 to 12 inches are possible above 6,000 feet.

Coastal waters will be dangerous Friday night and through the weekend, Hoxsie said. Swells of 6 to 9 feet are expected off the coast of Los Angeles County on Thursday, and the waves are expected to peak Saturday at 8 to 13 feet, she said.


After a brief respite Sunday, another storm system is expected to move into the region early next week, bringing several more days of rain, forecasters said.

“The storm door stays open for a while,” Hoxsie said.

hailey.branson@latimes.com

Twitter: @haileybranson