Cindy Graham remembers the blizzard of 1996, when it took six days to clear her street. So yesterday, with snow predicted, she was taking no chances.

"Comfort food," she said, pointing to her shopping cart crammed with treats: fresh veggies for homemade soup, freshly baked French loaves for garlic bread, whipped cream for hot cocoa, bottled water, hamburger fixings and a 12-pack of beer. It came to more than $150.

Across the region yesterday, folks prepared for what could be the biggest winter storm in nearly three years, a system that meteorologists said could dump as much as a half-foot of snow before ending early this afternoon. Convoys of salt trucks were loaded and lined up. School officials eyed the latest weather reports, and Montgomery County was the first school system to announce, shortly after 9 p.m., that classes would be canceled today. Metro was preparing to keep its tracks cleared and buses rolling. And markets saw everything from bottled water to horse feed fly off the shelves.

For Lee Kauffman, preparing for the worst meant stopping at a Lowe's hardware store to load up on 800 pounds of salt and two plastic snow shovels for his Clifton homeowners association. "I'm ready to roll," said Kauffman, 35.

The National Weather Service is predicting an early, potent winter storm that will blanket the District of Columbia and close-in suburbs with three to six inches of snow and sleet and leave northern and western suburbs with as much as eight inches on the ground.

The lower total at the core of the region was because slightly higher temperatures might result in freezing rain rather than snow in the latter part of the storm, said Richard Hitchens, a meteorologist in the Weather Service's Sterling office. "If that doesn't happen," he added, "then a four to eight total for the District might even work."

By 10 p.m., six to 10 inches of snow had fallen in far southwestern Virginia, with Blacksburg measuring seven inches, Hitchens said. By early today, the snow had begun to move into the Washington area, leaving parked cars in St. Mary's County with a thickening blanket of white.

Today could mark the region's deepest snowfall since Jan. 25, 2000, when 10.3 inches fell on the Washington area, the National Weather Service said. Last winter, the only measurable snowfall was a puny 2.6 inches Jan. 19.

For drivers, the worst conditions are expected to the south, where freezing rain could spread a dangerously slick coating on roads in Charles, St. Mary's and Calvert counties in Maryland and King George County, Va. Nearly 2,000 Dominion Virginia Power workers were poised to repair downed power lines if necessary, a spokeswoman said.

Yesterday, school officials were putting the final touches on their systems to notify parents about closings. Most will make the call shortly after 5 a.m. and then scramble to get the word out, notifying media outlets. Some, such as Prince William schools, will post closings on their Web sites.

Fairfax County schools will for the first time spread the word using its e-mail alert program. More than 17,000 families have signed up for the new system.

"We haven't done it yet for snow -- but we did it for snipers," said Paul Regnier, a schools spokesman, referring to closings in October.

District agencies, as well as Metro, spent most of yesterday gearing up for snow. The city declared a snow emergency at midnight, a move that banned parking along snow emergency routes marked with red and white signs. Last night, the city opened about 100 more beds at emergency shelters and called in extra road-clearing crews.

In Prince George's, County Executive Jack B. Johnson (D) faced his first challenge after only three days on the job. "We're ready to go," he said at a news conference called to outline snow plans. The county began de-icing roads and bridges two days ago.

To keep Metro running, the transit agency was scheduled to run "polishing trains" all night to keep tracks from freezing, said Metro spokesman Steven Taubenkibel. Switch heaters also were to be turned on.

Virginia's Department of Transportation had nearly 1,400 salt trucks and plows ready to clear more than 15,000 lane-miles of roadway in Northern Virginia. VDOT had about 85,000 tons of salt on hand.

"We've called in everybody and every piece of equipment," said Joan Morris, a VDOT spokeswoman. "It's better to be overprepared. We've had it pretty easy for the past several years."

Montgomery County officials reminded property owners that they, too, have snow responsibilities and must clear public sidewalks adjacent to their property within 24 hours. Other municipalities, such as Rockville, Gaithersburg and Takoma Park, have similar snow-clearing requirements.

Staff writers Michele Clock, Michael H. Cottman, Susan DeFord, Sylvia Moreno, Paul Schwartzman, Ian Shapira and Debbi Wilgoren contributed to this report.