An “epic snowstorm” smacked the nation’s capital and mid-Atlantic states Friday, and a father and son were killed on a slick highway in southwestern Virginia when they stopped to help another motorist.

Virginia State Police said the weather-related accident happened early in the day on Interstate 81 in Wythe County. According to police, a car spun out of control in northbound lanes and came to rest in the left travel lane.

A van carrying the father and son stopped on the right shoulder so one of its passengers — a nurse — could help the injured occupants of the disabled vehicle. Minutes later a northbound tractor-trailer came upon the disabled car. While trying to avoid hitting it, the truck jackknifed and struck the van.

The father and son died at the scene, state police said.

State police said they were “working numerous traffic crashes and responding to multiple disabled vehicles as the winter storm makes its way across the commonwealth.”

Traffic piled up in many cities as motorists tried to get home before the worst of the weather hit. Residents hurried to buy shovels, flashlights and other emergency items.

“An epic snowstorm has the mid-Atlantic region in its crosshairs. At this time, personal safety must be first and foremost,” said a statement from Jane Lubchenco, administrator of the National Oceanic and Atmospheric Administration.

“National Weather Service forecasters have been tracking this storm for the past week and now that the storm is here it must be taken very seriously. Even through the thick of this storm, the public and emergency responders can depend on NOAA for the latest forecast information,” she said.

NOAA is the umbrella agency for the National Weather Service.

Its forecasters posted winter storm warnings from southern Indiana eastward to New York and south to North Carolina, with blizzard warnings for Delaware and the New Jersey coast.

By Friday afternoon, forecasters were predicting that the mountains of West Virginia and Maryland, west of the nation’s capital, would receive the most snow, possibly over 90cms.

Other snowfall predictions included more than 40cms for Washington; over 30cms in Philadelphia, Pennsylvania; and up to 13cms in New York. Forecasters said it could turn out to be one of the heaviest snowfalls Washington has seen.

Delta Air Lines began stopping flights Friday in and out of Washington, Philadelphia and Baltimore, Maryland, said Delta spokesman Anthony Black. There will be limited service to Philadelphia on Saturday, he said. The company hopes to get flights back in service by Sunday.

Southwest Airlines stopped flying into Washington, Baltimore and Philadelphia at 2 p.m. Friday, spokesman Brad Hawkins said. The storm could affect more flights Saturday and Sunday.

Check on flight delays

Amtrak canceled most Friday service from Washington southward, it said.

In Washington, federal employees were given permission to leave work four hours early to avoid commuter problems during rush hour, said Raphael Cook, a public affairs officer for the U.S. State Department.

He said he let his teenage son stay home from school and loaded up on groceries in anticipation of the storm, which is predicted to surpass the record one in the Washington area in mid-December.

The supermarket was packed Thursday night, Cook said. In the parking lot, people were stalking shoppers to grab parking spaces and grocery carts.

He said he already had a flashlight and a shovel.

“I’m ready,” he said with a laugh.

“I have a four-wheel drive SUV and I’m not worried about driving home. I might be worried about getting a parking space,” he said, because he normally parks on a snow emergency route.

Flights canceled, highway crews mobilized

In Maryland, Gov. Martin O’Malley issued an emergency declaration in expectation of the storm. The move qualifies the state for federal assistance, including help from the National Guard and other resources, he said at a news conference.

O’Malley said he was told to expect 70cms of snow, which will most affect the highly populated Interstate 95 corridor.

“This is a great time to curl up with a book … and stay off the roads,” he said, adding that “buses and trains will operate as long as possible.”

The storm will make travel very hazardous or nearly impossible Friday night, the weather service said.

Blizzard conditions were expected in Delaware and eastern New Jersey starting in the afternoon, forecasters said.

Washington Mayor Adrian Fenty put a snow emergency into effect at 9:30 a.m. Friday. It prevents people from parking on major thoroughfares so snow plows can get through.

Virginia snowman is taller than a house

“This will be our second major winter storm,” said Fenty spokeswoman Mafara Hobson. She was referring to a storm that hit a few weeks ago, but the worst snowstorm the capital has seen was in mid-December, when Washington’s Dulles International and Reagan National airports had snow amounts of 46cms and 41cms, respectively — the highest one-day totals for December.

Baltimore-area residents rushed for supplies late Thursday, CNN affiliate WUSA reported.

Shannon Whitehead of College Park, Maryland, said her hardware store had sold out of snow shovels.

“Snowfall totals of 30 to 46cms are expected near the Delaware and central New Jersey coast,” the weather service said, “with up to 56cms possible over southern New Jersey and the central Delmarva,” the Delaware-Maryland-Virginia peninsula.

The blizzard will make travel extremely dangerous in New Jersey, the agency said. Snow, strong wind and poor visibility are likely, leading to white-out conditions.

The storm is the result of a low pressure system moving up the Eastern Seaboard and through the East Atlantic. The system picked up moisture from the Gulf of Mexico and Atlantic Ocean. As a result, the snow it is dropping is wet and compact, said CNN meteorologist Chad Myers.

CNN meteorologist Sean Morris and Jim Tyrrell contributed to this report.

– CNN.COM