WASHINGTON — Stores ran low on milk, bread and snow shovels and federal workers were sent home early Friday as the second major snow storm in less than two months bore down on the Mid-Atlantic.

Up to 28 inches of heavy, wet snow accompanied by powerful winds were forecast in Washington, Baltimore and surroundings. That could be a historic snowfall for the nation’s capital, where the record stands at 28 inches in January, 1922.

Airlines canceled flights across the region and school districts closed for the day ahead of the winter storm forecast from Virginia and West Virginia across Maryland into southern New Jersey and Pennsylvania. It was already snowing hard in Richmond, Va., on Friday morning.

Residents in the Washington area scrambled for food and supplies, but many found they were too late.

“As you see, I’m in front of Whole Foods and half of the food is gone already,” Denise Wright said on a shopping trip for staples.

Colleen Sport, who just moved to the area from Atlanta, was at the Home Depot in Falls Church, Va.

“I was looking for salt and shovels and of course they’re out,” said Sport, 42. “Now I’m just hoping to get shelving and work inside.”

In Alexandria, Va., James Ivery, 60, and his wife had already bought supplies but were back at a Harris Teeter supermarket Friday morning 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.”

The federal government, the region’s largest employer, told workers they could take Friday off as unplanned leave and prepared to shut offices four hours early.

Metro, the Washington-area rail system, warned it would likely have to close all but the underground portions of the system during the storm. Trains cannot operate outside when snow accumulations reach 8 inches because the snow cuts off access to the electrified third rail that powers the trains.

Across the region, state officials were deploying thousands of trucks and employees 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.”

The National Weather Service warned snow accumulations of 18 inches to 28 inches are expected from Baltimore to northern Virginia and parts of West Virginia.

Blizzard warnings were in effect in 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 12 to 20 inches are expected in the Pittsburgh area.

The combination of wet snow and strong winds could make conditions even more treacherous than the Dec. 19 storm, which 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 biggest snowfall is believed to have occurred in 1772, before official records were kept. As much as 3 feet fell in the Washington-Baltimore area during that storm, and both George Washington and Thomas Jefferson mentioned the event in their diaries, according to the weather service.

Virginia’s General Assembly 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. Officials urged people to stock up on supplies Thursday night and warned of a tough evening commute Friday.

Virginia Del. Tim Hugo was hurrying out of a Thursday afternoon committee meeting so he could get home to Fairfax County, a Washington suburb that’s supposed to get hit.

“I’m heading out of here now because I don’t want my wife stranded at home with 2 feet of snow in the drive,” he said.

Southwest Airlines canceled Friday afternoon flights at Baltimore, Philadelphia and Washington airports. Amtrak canceled most trains heading south from Washington, D.C.

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.

WEATHER

A winter weather advisory remains in effect for Vermilion County until 6 a.m. today, according to the National Weather Service.

Friday’s snowfall caused few accidents as drivers navigated the slick roads. Almost 2.5 inches of snow had fallen as of 5 p.m. Friday. The weather prompted school officials in Indiana to end classes early Friday. Several high school basketball games, including Decatur Eisenhower at Danville High, were canceled.

The Illinois Department of transportation reported Interstate 74 was about 75 percent covered with snow and ice from Champaign east to the state line Friday night.