Rocks and debris trapped cars on Los Angeles area roadways and fears of muslides forced dozens out of their homes as California was hit with a wintry storm that inundated lowland areas with rain and threatened the mountains with heavy snow.

Residents of 44 houses in a Los Angeles County area scorched by a recent massive wildfire remained evacuated as a precaution against landslides while the rain continued.

Parts of a 12-mile stretch of the Angeles Crest Highway just north of Los Angeles were buried by mud and rock Saturday, leaving 90 vehicles stranded as authorities closed the road and crews cleared the scene, said county fire Capt. Frank Reynoso. No injuries were reported.

Seventy of the stranded vehicles had been freed Saturday night, but another 20 would be forced to remain overnight, authorities said.

About 50 of the stranded motorists gathered at Newcomb's Ranch Restaurant off the highway.

"Everybody was just looking to get down off the mountain," restaurant manager Mike Noxin told the Los Angeles Times.

Several small slides were reported on the highway between La Canada Flintridge and Mount Wilson, and the road was to remain closed indefinitely, the California Highway Patrol said.

Debris flows can occur because the ground in recently burned areas has little ability to absorb rain, which instead instantly runs off, carrying ash, mud, boulders and vegetation.

Rain was expected to fall at rates up to three-quarters of an inch per hour through early Sunday.

Flooding shut down a three-mile section of the Pacific Coast Highway in Huntington Beach, authorities said. The stretch along Bolsa Chica State Beach was expected to remain closed until Sunday.

About 16,000 utility customers throughout Southern California were sporadically without electricity, mostly because of downed branches crashing onto power lines.

Snows between 8 and 16 inches were expected by Sunday morning above 6,000 feet in the Southern California mountains. Winds were blowing at 25 to 35 mph.

The National Weather Service issued a winter storm watch through Sunday night for western Plumas County and the west slope of the Sierra Nevada in the north of the state and the mountains of Ventura and Los Angeles counties in the south.

"It looks like we'll be getting a lot of precipitation," said George Cline, a National Weather Service forecaster in Sacramento.

He expected the storm to bring an inch of rain to the Central Valley, with wind gusts up to 60 mph. Gusts up to 90 mph were expected on mountain ridges.

The California Department of Transportation was requiring chains for travel on all major highways over the Sierra. Chains were also required for Interstate 80 through most of Nevada.

Forecasters said the new snow would also bring extreme avalanche danger to the alpine backcountry.

Snow was falling at elevations of 6,000 feet Saturday and was expected to dip to 4,500 by Sunday morning.

Cline said most soils in the northern part of the state aren't saturated this early in the winter, minimizing the danger of mudslides even in burned areas.

"We don't anticipate anything really unusual from it yet," Cline said. "We're keeping an eye on the burn scar areas. Things have been so dry, it's still soaking into the ground."