(CNN) -- California is bracing for a series of powerful winter storms poised to deliver a one-two-three punch to the West Coast, bringing snow, rain and high wind throughout the Golden State, forecasters said.
The effects of the storms were already being felt Thursday.
But the National Weather Service warned a second and more powerful storm front was expected to move in Friday, and a third wave was forecast for the weekend.
Up to 4 feet of snow is possible at elevations above 5,000 feet by Saturday morning and wind gusts of up to 80 mph are possible in the region Friday, the weather service said.
"The combination of heavy snow and powerful winds will likely cause frequent whiteout conditions at the highest elevations," forecasters said.
"Travel over the higher passes will be very difficult, if not impossible, at times between Friday evening and Saturday morning."
In addition, up to 10 inches of precipitation was forecast for other parts of the state -- rain at the lower elevations and snow in the mountains.
Forecasters warned it could be the most significant rainfall Southern California has seen since January 2005. Flash-flood watches were in effect around Los Angeles, and the possibility of mudslides loomed for hillsides scorched bare by wildfires last year.
Authorities advised homeowners in those areas to have plenty of sandbags on hand and watch for signs of flooding, The Associated Press reported.
The mission to prepare for the storms was already under way, with members of the Orange County Conservation Corps placing gravel-filled bags along an area burned last fall, according to the AP.
Gov. Arnold Schwarzenegger ordered the state Office of Emergency Services to prepare for the bad weather.
"The state is expecting a powerful series of storms that could produce blizzard conditions in the higher elevations of the Sierra, with wind gusts of more than 100 mph and 8 to 10 feet of snow forecast at above 7,000 feet," a news release from Schwarzenegger's office said.
High wind watches and warnings covered much of California Thursday, along with a winter storm warning and a blizzard warning for the northeastern part of the state.
Rain was falling Thursday at some of the state's lower elevations, but there was snow in the mountains, said CNN meteorologist Bonnie Schneider.
The weather already disrupted air traffic. Flights into San Francisco were delayed more than two hours Thursday because of conditions in the area, affecting air traffic throughout the country, the Federal Aviation Administration said. Shorter delays were reported in Los Angeles.
Gusty winds were reported as the front moved in. The weather service said a remote site at an elevation of 5,300 feet recorded a 70-mph wind gust early Thursday -- just below hurricane strength. An offshore Coast Guard station reported a 61-mph wind gust Wednesday night.
Winds of up to 55 mph were forecast for some sites Thursday, and winds of up to 60 mph on Friday, the weather service said. "Winds this strong will make driving difficult, especially for high-profile vehicles. Use extra caution."
Light to moderate rain was forecast in southern California on Thursday. But as the stronger front moves in Friday, it will bring "significantly higher" rainfall totals to the southern part of the state Friday and into Saturday morning, the weather service said.
In addition, the storm will bring high surf and coastal flooding, forecasters said. E-mail to a friend
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