© AFP/Getty Images/Scott HalleranA pizza delivery man crosses a street in the falling snow to make a delivery in the Montford neighborhood in Asheville, North Carolina. Northeastern United States from North Carolina to Connecticut was under a winter storm warning Friday, as a major storm system threatens to dump up to 16 inches (40 centimeters) of snow in the region, weather forecasters said.
A major storm moving up the Atlantic Coast on the last shopping weekend before Christmas threatened to shut down much of the region as officials warned of up to 20 inches of snow and significant power outages.

People stocked up on groceries and other staples Friday after the National Weather Service issued winter storm warnings from the Carolinas to Rhode Island.

In Virginia, Gov. Tim Kaine declared a state of emergency ahead of the storm, placing the National Guard and other agencies on standby. Philadelphia officials also declared a state of emergency and the school district canceled all weekend activities. Maryland Gov. Martin O'Malley urged motorists to stay home if possible.

Some shoppers were trying to get their holiday buying done before the snow hit.

"Most of them are coming in this morning to shop before they get snowed in," said Kayla Mahr at the Bath and Body shop at the River Ridge Mall in Lynchburg, Va.

The Federal Aviation Administration said departing flights at Hartsfield-Jackson Atlanta International Airport were delayed by as much as an hour Friday because of rain and wind. United Airlines said it had already canceled more than 140 Saturday flights on the East Coast ahead of Saturday's weather.

Forecasters expected up to 20 inches of snow through late Saturday from the Washington metro area to West Virginia. They said 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.

The Archdiocese of Washington says dangerous travel conditions caused by bad weather is a legitimate excuse from attending Sunday Mass.

Up to a foot of snow was forecast in parts of Tennessee, North Carolina, Pennsylvania and New Jersey.

Appalachian Power, which serves 1 million customers in Tennessee, Virginia and West Virginia, warned of the potential for an extended power outage.

The Potomac Mills Mall, with more than 200 stores in Woodbridge, Va., planned to conduct regular weekend business hours while keeping a close watch on the storm, spokeswoman Lauren Horsley said.

"The plan is still to go ahead as usual and it if becomes necessary, we'll handle that as it comes," she said.

In southern West Virginia, Ron Hart's hardware store was swamped Friday as customers bought heaters and other emergency supplies just a week after a wind storm had knocked out electricity and spawned an earlier emergency shopping surge.

"People are having to spend money on bare essentials versus Christmas," Hart said. "Our Christmas sales are considerably down because of what people are having to buy."

Jim Weintraub, owner of Ace Hardware in Asheville, N.C., where a foot or more of snow was expected, said he picked up 1,500 pounds of rock salt Friday morning. An hour-and-a-half later, "I'm just about out," he said.

But customers were thinking fun, too.

"I've been told we're the only store around with sleds," Weintraub said. "As I was driving back up to the store, my wife was calling me and saying, 'Where are you? People are waiting for sleds!'"

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. Delaware crews were to be sent home in the afternoon to rest up for what one official said would be a long weekend.

Dozens of accidents were reported Friday in Virginia as roads became slick.

Amtrak spokeswoman Karina Romero said the railway was putting extra crews on duty, in part to keep ice from forming on the overhead lines that power electric trains. Extra locomotives equipped with snow plows would also be available.

Some universities in Virginia and Maryland canceled final exams and weekend commencement exercises.

On the Tennessee-North Carolina line, the National Park Service closed a road through Newfound Gap in the Great Smoky Mountains after it got 4 inches of snow.

Ski operators were basking in the forecast, as long as motorists didn't get stuck en route to the slopes.

"The problem we have is not the customers, it's our staff getting here," said Brad Moretz, general manager of North Carolina's Appalachian Ski Mountain.

After a warm start to the ski season that delayed openings of many resorts, the storm arrived just in time for Winterplace Ski Resort's season debut Friday in southern West Virginia.

"It's perfect timing," said Winterplace President Terry Pfeiffer. "With the new snow coming in, there's not going to be much better skiing."

Police shut down many roads leading to downtown Charleston, S.C., as heavy rains across the coast and an approaching high tide flooded at least two dozen streets.

The Coast Guard sent an airplane to fly from North Carolina to New Jersey warning boaters by radio to stay in port if they didn't have an urgent need to be on the water.

The National Weather Service issued a flash flood warning for west Alabama, where rivers were still swollen from heavy rains earlier this week and as much as 3 more inches of rain was possible.

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