Heavy equipment is used by the Los Angeles Fire Department to clear a mudflow in a residential area in Los Angeles following heavy rain.
LOS ANGELES - Hundreds of California residents were ordered to evacuate their homes on Wednesday as rain from a powerful Pacific storm raised the risk of mudslides in areas hit by recent wildfires.
Some areas around Los Angeles could see over 13cm of rain from the storm, which is being channeled to the coast by a flow of atmospheric moisture known as the "Pineapple Express."
The storm, the wettest to hit California this winter, was set to peak on Thursday and has already sparked flood watches from Arizona to Washington.
Residents of Lake Elsinore, 90km east of Los Angeles got mandatory evacuation orders over risks nearby hillsides scorched by fire in 2018 could turn into rivers of mud and debris that could carry away cars and homes.
"It's going to be heavy and fast," said Bob Oravec, a meteorologist with the NWS's Weather Prediction Center in College Park, Maryland. "Debris flows and mudslides are a risk in any area scorched by the wildfires. There's little to no vegetation to slow that water down."
Among the hardest hit areas was northern California, with rain driven by winds of up to 75 miles per hour (120 km per hour) pounding parts of Sonoma County's wine country.
Cars plowed through standing water on San Francisco streets and water reached the wing mirrors of an abandoned car on a flooded Santa Cruz road.
The Pineapple Express weather system gets its name from a flow of moisture, known as an atmospheric river, that heads east from waters near Hawaii to soak the U.S. West Coast.
The NWS expected over 2.4 meters of snow in some areas of the Sierra Nevada mountains.
"The big thing that we could see as life-threatening would be mountain travel that will become very dangerous," said NWS meteorologist Cory Mueller.
It is one of a string of storms that have swelled snowpack in California to above-average levels, delighting farmers and skiers following years of drought.