Fast-moving thunderstorms brought new waves of rain on Sunday to Southern California, following days of drenching weather and heavy mountain snowfall.

Up to 2 inches of rain had fallen by early afternoon in valley and coastal areas since nightfall Saturday, with about double that in the mountains, the National Weather Service said.

"We're not completely done with this storm yet," forecaster Steve Vanderurg said.

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Officials said the rain brought a threat of serious slides on hillsides stripped of vegetation by last year's wildfires. Mud and minor rock slides prompted authorities to shut a highway through a San Diego-area burned between Ramona and Escondido.

The Los Angeles County and Orange County fire departments were on standby for possible flash floods and slides. Flash flood watches remained in effect through Sunday night for Los Angeles, Ventura and San Bernardino counties.

In downtown Los Angeles, Sunday's basketball game between the Los Angeles Lakers and Cleveland Cavaliers was delayed 12 minutes after a small leak in the Staples Center roof allowed a steady flow of raindrops to fall on the court.

The Santa Anita race track in Arcadia, meanwhile, canceled horse races for the sixth day this month because of wet conditions on the synthetic track.

The storm system also soaked parts of Northern California and the weather service posted winter storm warnings for parts of the Sierra Nevada.

A highway was closed in the mountains south of San Francisco, and Pacific Gas and Electric (PCGPI) said about 2,700 homes and businesses were still blacked out because of earlier storms.

A series of fierce storms has caused deadly avalanches, flooded streets and set off mud and rock slides in recent days. Some areas have received more moisture in a week than during the entire rainy season last year.

Three skiers were killed Friday by a trio of avalanches that swept through canyons outside the trails of Mountain High ski resort at Wrightwood, northeast of Los Angeles in the San Gabriel Mountains. A fourth man escaped the avalanches.

One of the skiers, 60-year-old actor Christopher Allport of Santa Monica was found Saturday morning after a trio of avalanches swept through off-trail canyons outside the Mountain High ski resort in Wrightwood.

Allport was a veteran character actor who had appeared on such TV shows as "ER," "Felicity," and "Matlock."

Allport wrote a story that appeared in the Los Angeles Times in 2004 about the pleasures of backcountry skiing. "Any excursion into the mountains requires awareness," he wrote. "Have fun, but be careful."

Avalanches are unusual in the San Gabriel Mountains, but the peaks had been hit by 3 feet or more of new snow this past week, drawing thousands of skiers and snowboarders.