Shoppers jammed aisles and emptied stores of milk, bread and shovels Friday as a massive snowstorm blew into the Mid-Atlantic. Forecasters predicted a record 30 inches or more for the nation's capital, and authorities already were blaming the storm for the deaths of father-son Samaritans in Virginia.

The region's second snow storm in less than two months could be "extremely dangerous," and heavy, wet snow and strong winds threatened to knock out power, the National Weather Service said.

Flakes started falling around noon in Washington, where the federal government sent workers home early. The storm's wide swath and predictions of historic proportions for an area ill-equipped for snow had airlines canceling flights and school districts closing hours before any snow arrived.

The last time D.C. got at least 28 inches of snow was in 1922. The city has seen more than a foot only 13 times since 1870, according to the National Weather Service. The storm was expected to track through Virginia and West Virginia, across Maryland into southern New Jersey and Pennsylvania.

At a Trader Joe's in Falls Church, Va., Errol Bailey, a 55-year-old tailor who works in northern Virginia, said he'd already stocked up on food at his home in Largo, Md., but realized he should have provisions at work too.

"I've got some cashews, some orange juice, some bread, cheese and I'm about to pick up a bottle of wine here now," said Bailey. "I hope I'll be enjoying the wine at home, but if it gets real bad maybe I'll have to pop that open at work."

Many residents scrambling for food and supplies found they were too late.

In Alexandria, Va., James Ivery, 60, and his wife had already bought supplies but were back at a Harris Teeter supermarket to get out of the house one last time before the storm. Many shelves and bins were emptied of milk, vegetables, eggs and cold cuts.

"It just seems like people are panicking. I don't think it's going to be too bad," Ivery said. "As long as I got power and satellite service, I'll be fine."

Metro, the Washington-area rail system, said ridership Friday morning was down about one-fourth from the same day last week, a sign people were heeding official warnings to stay home. Metro warned it would likely have to close all but the underground portions of the system during the storm.

In western Virginia, a tractor-trailer struck and killed a father and son who had stopped to help another driver who had wrecked in snow on Interstate 81, Virginia State Police said. William Edward Smith Jr., 25, of Morresburg, Tenn., and 54-year-old William Edward Smith Sr. of Sylva, N.C., died at the scene, authorities said.

Across the region, transportation officials were deploying thousands of trucks and workers and had hundreds of thousands of tons of salt at the ready.

"This is not a good mix," said Joan Morris, a spokeswoman for the Virginia Department of Transportation. "Heavy, wet snow with gusting winds is going to make it a very tough storm for us. I expect visibility will be very poor in spots, and we'll have to deal with drifting snow."

Blizzard warnings were in effect for much of Delaware and southern New Jersey from Friday afternoon to Saturday night, with strong winds and blowing, drifting snow.

Philadelphia could get about a foot of snow and up to 20 inches was expected in the Pittsburgh area.

The second big storm comes less than two months after a Dec. 19 storm dumped more than 16 inches of snow on Washington. Snowfalls of this magnitude _ let alone two in one season _ are rare in the area. According to the National Weather Service, Washington has gotten more than a foot of snow only 13 times since 1870.

The heaviest on record was 28 inches in January 1922. The biggest snowfall for the Washington-Baltimore area is believed to have occurred in 1772, before official records were kept, when as much as 3 feet fell in the Washington-Baltimore area, an epic event George Washington and Thomas Jefferson mentioned in their diaries.

Some flights at Reagan National Airport were delayed Friday morning. At least 18 afternoon flights were canceled, including those run by Delta and US Airways. Southwest Airlines canceled Friday afternoon flights at Baltimore, Philadelphia and Washington airports. Amtrak canceled most trains heading south from Washington.

Virginia's General Assembly, 100 miles south in Richmond, canceled Friday's floor sessions and committee meetings, the first time anyone could remember that the threat of snow had sent the whole Legislature home.

Virginia Gov. Bob McDonnell, who has been in office less than a month, declared his second snow emergency, authorizing state agencies to assist local governments. The assistance includes deploying National Guard soldiers and emergency response teams.

Between the December storm and several smaller snowfalls, the region's road crews have had plenty of practice in the past two months.

Maryland highway officials said they have spent about $50 million so far clearing and treating roads this winter. That's almost twice the $26 million that had been budgeted.

The Virginia Department of Transportation said it already spent the $79 million budgeted for statewide snow removal and was tapping into emergency maintenance funds. Once that $25 million reserve is exhausted, the department said it will have to dip into other programs to cover its costs.

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Associated Press writers Kathleen Miller in Falls Church, Va., and Steve Szkotak in Richmond, Va., contributed to this report.