Heavy rain, pounding waves and plenty of snow in the mountains are all in the forecast as Northern Californians brace for a weekend of wintry weather.

Forecasters say as one storm system moves through the region Saturday, a second system is expected to hit the area Sunday.

With steady rain expected through Saturday, and heavy to moderate rain for Sunday, the National Weather Service has issued a "hazardous weather outlook" for the San Francisco Bay area.

Bay Area roadways bore the brunt of the overnight storm.

Both directions of state Highway 1 in Marin County near Olema were blocked Saturday morning because of a fallen tree and downed power lines, according to the California Highway Patrol, but it reopened 10 a.m. Saturday.

A mudslide blocked state Highway 128 in Napa County Saturday morning following heavy rainfall overnight, according to the California Highway Patrol.

Both directions of state Highway 128 were blocked near Wragg Canyon Road, just south of Lake Berryessa, according to the CHP.

The California Highway Patrol is urging drivers to slow down. CHP said Saturday morning it's already responded to dozens of accidents Saturday morning, many of them weather related.

On Highway 580, near Castro Valley, a driver said she lost control of her car because of the weather around 7 a.m. and drove up an embankment and flipped over.

A truck ended up on its side early Saturday morning on southbound 880 in Oakland. 

A driver also fled the scene after a crashing a car into a tree on 580 near the Coolidge exit in Oakland.

Officers said many people are driving too fast during this new set of storms.

Along the coast, waves up to 16 feet are expected.  Forecasters are urging people walking along beaches or jetties to watch for large breaking waves.

The wet weather is also having an impact on holiday travel at Bay Area airports.

The San Francisco International Airport is seeing delays of around 45 minutes Saturday.

On Friday some passengers saw delays of as much as two hours due to the weather.

More than 100 flights were cancelled by the end of the day.

The storm is expected to end Sunday night, but another system could arrive by the evening of Christmas Day.

"There will be some breaks in there," Cross said. "It looks like probably Monday will be a nice enough day, but overall it will be pretty wet and cold."

Pacific Gas and Electric officials say Sunday's storm, in particular, could cause problems including power outages.

"We're expecting windy conditions especially in the higher elevations, in the North Bay, Peninsula and portions of the East Bay as well," said PG&E spokesman Joe Molica. "We urge folks to be prepared out there."

Molica noted that anyone experiencing a power outage should use flashlights and battery-operated radios, not candles. A phone with a cord is also good to have, he noted.

"A cordless phone won't work in a power outage, and a cell phone might work only for a limited period of time," Molica said.

Residents are encouraged to freeze water in 2-liter bottles ahead of the storm so that they can keep items in the refrigerator cool if the power goes out, Molica said.

In addition, anyone who spots a downed power line should assume it is live and call 911 and PG&E immediately.

In the mountains, heavy snow is expected Saturday and Sunday, with up to four feet predicted to fall in the higher elevations of the Sierra Nevada.