Heavy rain, pounding waves and plenty of snow in the mountains were all in the forecast as Northern Californians braced for a weekend of wintry weather and potential delays in holiday travel.

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.

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 Lafayette, a drain backed up on the Pleasant Hill onramp to Highway 24 and flooded the roadway.

In Mendocino County, Highway 162, which connects the community of Covelo with Highway 101, was closed because of a washout.

Caltrans said Sunday could be worse.

“They say heavy rains more tomorrow, I thought this was going to be the lighter storm, so we'll see,” said John Camm, with Caltrans.

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.

In the mountains, where up to 5 feet of snow was expected in the higher elevations of the Sierra Nevada, the storm was causing major delays Saturday for holiday travelers.

Officials said tire chains were mandatory for all vehicles except four-wheel drives on all three major mountain highways connecting the Sacramento and Reno, Nev., areas -- Interstate 80 over Donner Summit, U.S. 50 over Echo Summit and State Highway 88 through Carson Pass.

Interstate 5 in far Northern California was open to cars and truck with snow chains Saturday. 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.