As one storm system moved through the region Saturday, a second, more powerful system was expected to hit the area Sunday, forecasters said.
The first storm drenched the region, dropping more than an inch of rain in Redwood City, about 24 miles south of San Francisco, in a little more than six hours early Saturday, said National Weather Service forecaster Diana Henderson.
To the east in the Sierra Nevada, Interstate 80, the main route between Sacramento and Reno, Nev., was shut down for about three hours after snowy roads caused several spinouts, but was reopened later in the afternoon, state highway officials said.
Officials said tire chains were mandatory for all vehicles except four-wheel drives on all three major mountain highways between the Sacramento and Reno areas—I-80 over Donner Summit, U.S. 50 over Echo Summit and State Highway 88 through Carson Pass, which was also briefly shut down.
Up to 5 feet of snow is expected in the higher elevations of the Sierra Nevada before the weekend is over.
Interstate 5 near the Oregon border was open to cars and truck with chains. It had been shut down late Tuesday for about 12 hours after a 60-car pileup near Yreka then closed again Friday when a storm dropped several inches of snow in some areas of Siskiyou and Shasta counties.
The second storm was expected to arrive early Sunday. "It's expected to bring some sustained winds, with a possibility of thunderstorms and moderate to heavy rain," Henderson said.
The weather was causing delays Saturday at San Francisco International Airport but was affecting mostly regional flights, airport duty manager Shannon Wilson said.
Arriving flights were being delayed up to 45 minutes Saturday afternoon, and about 12 flights had been canceled because of a change in the direction of prevailing winds, Wilson said.
With the wind coming from the south instead of the west, only two of the airport's four runways were being used for takeoffs and departures, Wilson said.
"It's an unusual wind for us," he said.
North of San Francisco, more than 6 inches of rain fell Friday in the tiny Sonoma County community of Venado. And with a second storm approaching, officials were paying close attention to the rising levels of the Russian River.
The river was expected to peak just below "monitor stage" on Christmas Eve, said National Weather Service hydrologist Allan Takamoto. That's about 3 feet below flood stage but high enough that officials had a "heightened awareness of what's going on," Takamoto said.
The heavy rain caused problems on local highways, forcing officials to close a section of Highway 128 in Napa County near Lake Berryessa.
In Mendocino County, Highway 162, which connects the community of Covelo with Highway 101, was closed because of a washout.
Along the beaches, waves up to 16 feet were expected. Forecasters were urging people walking along beaches or jetties to watch for large breaking waves.
Associated Press writer Martin Griffith in Reno, Nev., contributed to this report.