WASHINGTON — A blizzard-like storm rocked the Mid-Atlantic and Northeast on Saturday, crippling travel across the region and causing tens of thousands of power outages.

Those who did venture out were treated to nearly desolate stores on what is usually one of the busiest shopping days of the year. There were virtually no lines to get a picture with a mall Santa on the last weekend before Christmas.

The National Guard used Humvees to rescue stranded motorists in Virginia and some 500 people had sought warmth and refuge in emergency shelters. At least one person was killed in a traffic accident in Virginia.

"The snow has not stopped falling, the storm isn't over, and folks should not think this is crying wolf," said Laura Southard, a spokeswoman for the Virginia Department of Emergency Management.

Nearly two feet of snow fell in some areas, and the nation's capital was under a blizzard warning. Public transportation nearly ground to a halt, but it wasn't enough to keep senators from staying in session to debate health care reform. The slow-moving storm was headed to the northeast.

Snowplows cleared the runway at Andrews Air Force Base in suburban Washington as President Barack Obama returned from climate talks in Copenhagen. The White House said Obama rode in a motorcade back to the White House, instead of taking his helicopter, because of the conditions.

Forecasts called for up to 20 inches of snow across the region, which was virtually a sea of white. The Smithsonian Institution closed its museums, and the National Mall, which normally would be swarming with tourists, instead was the scene of snowball fights and cross-country skiers.

For Chris and Kelly Fitzpatrick, who were visiting from Clearwater, Fla., the winter wonderland came at the perfect time.

"It's her fault that we're out so long. She wants to walk and walk and walk," said Chris Fitzpatrick, 38.

In western Virginia, officials said several hundred motorists became stranded and had to be rescued by four-wheeled-drive vehicles.

"Some folks have decided to stay in vehicles, others have been taken to shelters," said Virginia Department of Emergency Management spokesman Bob Spieldenner. "We're definitely trying to keep people off the roads."

Virginia State Police spokeswoman Corinne Geller said traffic was moving, though slowly. There were reports of jackknifed tractor-trailers and some semis on their sides. Troopers had responded to more than 4,000 traffic crashes and disabled vehicles.

"It's looks probably a lot worse than it is," she said.

At Crump's Store at the intersection of two country roads outside Richmond, Va., owner Suzanne Rudd stood with a man dressed as Santa and waved to the few motorists who dared to hit the slick roads. Rudd said only six children had come by midmorning to visit with Santa.

"Normally we'd have a long line here but people are having a hard time getting out," Rudd said.

The same was true at the Cherry Hill Mall in New Jersey, which would typically be a place where down-to-the-wire Christmas shoppers would create a mob scene. Instead, parking spots were plentiful.

Inside, there was no line for a picture with Santa.

"It was fantastic," said Chris Bailey, who got pictures of his 4-year-old daughter Olivia.

Mayors in Washington and Philadelphia declared snow emergencies and forecasters said the conditions could worsen. Governors in Virginia and West Virginia declared states of emergency.

"It's going to be an all day thing. It's going to be on and off," said National Weather Service meteorologist Kevin Witt in Sterling, Va.

Most of the flights at Reagan National Airport and Dulles International Airport had been canceled, creating a ripple effect of delays across the country. The runways at Reagan were closed until 6 a.m. Sunday. Dulles had one runway open, but were expecting many, if any, flights.

"It's going to be very challenging for people who weren't able to get out today to rebook on flights this week," said Tara Hamilton, a spokeswoman for the Metropolitan Washington Airports Authority.

Joy Rood, 20, played solitaire as she waited at Reagan for a flight to visit family in Los Angeles with her husband, who was asleep at a table outside an airport cafe.

"We had a canceled flight at Dulles at 6 yesterday because the plane had difficulties," she said. "So they cabbed us over here to — uh, what airport am I at?"

Forecasters said the storm system was expected to generate winds up to 35 miles per hour, which could cause near-whiteout conditions. It could be the most snow in the nation's capital since a February 2003 storm dumped nearly 27 inches at Baltimore-Washington International Airport.

At a Walmart in the Richmond, Va., area, Nnika White took advantage of the few shoppers, buying a drum set for her 2½ year old son. White, dressed in a toboggan, scarf and flannel-like jacket, said she works long hours at the law firm she owns and doesn't get much time to shop.

"It's nice because no one's here. For shopping, it's great, but the roads are very, very bad," she said.

Snow, ice and freezing rain also hit western North Carolina on Friday, knocking out power to almost 60,000 customers around the Asheville area.

After a warm start to the ski season that delayed openings of many resorts, the storm arrived just in time for West Virginia, dumping more than 20 inches on some slopes, said Joe Stevens, a spokesman for the area's ski association.

"These are midseason conditions," he said. "The storm couldn't have come at a better time."

Highway crews in Maryland, Delaware and the District of Columbia were spraying brine on heavily traveled roads to help prevent snow and ice from sticking.

The storm came from the Gulf and drenched South Florida with rain starting late Thursday, leaving flooded homes and stranded drivers.