SACRAMENTO - Howling winds, pelting rain and heavy snow pummeled Northern California on Friday, toppling trees, flipping trucks and cutting power to more than a million people.

Flights were grounded as gusts reached 80 mph during the second wave of an arctic storm that sent trees crashing onto houses, cars and roads. Forecasters expected the storm to dump as much as 10 feet of snow in the Sierra Nevada by Sunday.

The heavy snow was slowing search efforts for a family believed to be missing in the mountains, authorities said.

"A huge tree, over 100 years old, just fell across the house. It just wrecked the whole thing," said Faye Reed, whose daughter Teenia owns the damaged home north of Sacramento. "They won't be able to live in it. The whole ceiling fell in, and now it's raining inside."

Highways from Sacramento to the San Francisco were closed because of debris or toppled tractor-trailers blocking lanes, and local roads were flooded.

More than a million people from the Bay Area to the Central Valley were in the dark. Crews worked to restore power, but it could be days before all the lights are on, said Pacific Gas & Electric spokeswoman Darlene Chiu.

In Southern California, authorities in Orange County urged residents of three fire-scarred canyons - Modjeska, Silverado and Williams - to leave beginning Friday afternoon. The order also called for the mandatory evacuation of large animals from the mudslide-prone canyons, where 15 homes burned last fall in a 28,000-acre wildfire.

"It's too late once the rain starts. These areas are extremely vulnerable. You're risking your life and your family's life fundamentally" by ignoring orders, said Steve Sellers of the governor's Office of Emergency Services.

Riverside and San Bernardino counties, east of Los Angeles, have deployed swift-water rescue teams in case torrential rains bring flash floods and mudslides. The state opened its emergency operations center Friday morning to coordinate storm response, and Gov. Arnold Schwarzenegger said he had spoken with Homeland Security Secretary Michael Chertoff by phone.

"Preparation is really the heart of this whole thing," Schwarzenegger said after touring the state emergency operation center at the Los Alamitos Joint Training Base.

Homeowners in Southern California stacked sandbags and hay bales around their homes while residents in the low-lying areas of the Central Valley - California's inland breadbasket - piled sandbags to barricade their homes from streams and creeks that forecasters warned might swell.

Yosemite National Park rangers and sheriff's deputies combed the Sierra foothills and mountain snow camps Friday afternoon searching for a missing Clovis man and his two children, said Clovis police spokeswoman Janet Stoll-Lee.

John Hopper, 64, a volunteer chaplain with the Clovis police, left town Thursday morning with his 15-year-old twins Matt and Sarah to "go play in the snow," Stoll-Lee said.

The family didn't give any indication of where they were heading, and law enforcers heard they were missing only when Hopper's ex-wife reported they hadn't returned late Thursday, she said.

"We're pretty concerned because there isn't that much time until darkness is going to fall and we've got this bad storm headed our way," Stoll-Lee said. "Even knowing the county where they were heading would have been helpful."

Travelers saw their flight plans put on hold when airlines delayed or canceled flights in Sacramento and the San Francisco Bay Area. Ferry service in the San Francisco Bay was interrupted, as well, and the state Legislature in Sacramento closed offices and sent employees home early.

The wind was expected to continue throughout the afternoon, with gusts between 30 and 50 mph. The winds are expected to weaken as the third storm moves into the area Saturday, said Kathy Hoxsie, a meteorologist with the National Weather Service in Sacramento.

As the storm continues to move east into the Sierras, forecasters hope the temperature will drop enough so that the precipitation falls as snow and doesn't form ice.

Authorities in Nevada warned truckers as far east as Wyoming not to cross over the Sierra Nevada into California, where blizzard-like conditions forced ski resorts and local businesses to shut down.

"State officials have been working closely with trucking companies and truck stops to let them know, 'Stay put,"' said Nevada Highway Patrol Trooper Chuck Allen.