Authorities were keeping a wary eye on Highland in San Bernardino County, where about 50 homes remained evacuated after last week’s deluge caused mud to belch from local mountains, overwhelming a drain channel and inundating some homes with feet-deep ooze.

On Tuesday, about 700 shovel-toting volunteers took advantage of sunny weather to clear mud from around dozens of Highland homes.

There was concern about debris basins meant to hold boulders, trees and muddy storm water swept down from the mountains.

"There’s still 50,000-plus cubic yards of debris plugging them up. So we just don’t know how a major rain coming off the mountainside would contain the debris," said Bill Peters, a spokesman for the California Department of Forestry and Fire Protection.

"We’ve been pumping water out of them since last Thursday, 24-7," he added. "They’re down, but still, if we get a catastrophic debris flow like we got last week, it could get interesting."

The fast-moving storm reached the area at about 3 a.m. after hitting Northern California on Tuesday night. Wind, gale and flood warnings were up through the morning from Fresno County south.

The cold northern storm was expected to dump up to an inch of rain in four to five hours, followed by winds gusting to 75 mph in mountains and passes.

The National Weather Service warned that blowing snow and ice could make driving treacherous in the Grapevine area of Interstate 5, the main highway between Southern and Central California.

The rain and strong winds moved into the San Francisco Bay area during the Tuesday evening commute and caused arrival delays of more than two hours at San Francisco International Airport, the Federal Aviation Administration reported.

The storm was fueled by subtropical moisture from north of Hawaii, combined with low pressure over the Northeast Pacific. The previous storms were fed by a similar plume, but it originated from south of the Hawaiian Islands and rained most heavily in the southern half of the state.

The California Department of Transportation was working to repair extensive storm damage to routes in the inland counties east of Los Angeles.

Among the worst damage sites was a section of State Route 330 that slid down a mountain, leaving a huge gap in the road that leads to resorts at Big Bear Lake in the San Bernardino Mountains. There was no estimate of how long it would take to restore the route, Caltrans said.