By early Saturday, 18 inches (46 centimeters) of snow had fallen in eastern Kentucky. Emergency crews were making their way to those in cars stranded by snow along Interstate 75 to hand out water, fuel and snacks.

The National Weather Service said the winter storm could rank near the top 10 to ever hit the region.

"It does have the potential to be an extremely dangerous storm that can affect more than 50 million people," said Louis Uccellini, director of the weather service. The snowfall, expected to continue into Sunday, could easily cause more than $1 billion in damage and paralyze the eastern third of the nation, he said.

A state of emergency was declared in Tennessee, North Carolina, Virginia, Maryland, Pennsylvania, the District of Columbia, New Jersey and parts of other states. Blizzard warnings or watches were in effect along the storm's path, from Arkansas through Tennessee and Kentucky to the mid-Atlantic states and as far north as New York.

Two feet or more of snowfall is forecast for Washington and Baltimore, and nearly as much for Philadelphia. New York City's expected total was upped to a foot or more.

Flight tracking service FlightAware said airlines canceled about 7,600 flights Friday and Saturday. By Sunday afternoon, airlines hope to be back to full schedule.

College basketball games and concerts were also postponed.

Washington's subway system shut down entirely Friday night and will remain closed through Sunday. About 1,000 track workers are being deployed to keep New York City's subway system moving and 79 trains have "scraper shoes" to reduce the icing on the rails.

The federal government closed its offices at noon Friday. White House spokesman Josh Earnest said President Barack Obama would hunker down at the White House. The US Capitol Police said sledding on Capitol Hill, which only recently became legal, would be welcome for the first time in decades.

In Washington, Baltimore, and Delaware, archdioceses reminded Catholics that dangerous travel conditions are a legitimate excuse for missing Sunday Mass.

Some people, however, were riding out the storm better than others. Passengers on a cruise ship heading back to snowy Baltimore from the Bahamas will get one more day at sea after the Grandeur of the Seas cruise ship decided to land Monday instead of Sunday.

"I was not totally surprised and, frankly, happy to be delayed," said passenger Meg Ryan of Hamilton, New Jersey. "First, it is an extra day of vacation. But more importantly, safety comes first and travel Sunday would be difficult, if not impossible."

And the snowstorm was greeted happily at Virginia's ski resorts.

"We're thrilled," said Hank Thiess, general manager at Wintergreen ski resort in central Virginia, who is expected 40 inches (102 centimeters) of snow. "We're set up to have just a terrific second half of the ski season."