The National Weather Service has declared a winter storm warning for the D.C. region, with up to a foot of snow expected to fall by Monday afternoon.
The warning is in effect until 2 p.m. Monday. Approximately 5 to 9 inches of snow is expected overnight, with wind gusts as high as 36 mph, the weather service said.
An additional 1 to 2 inches of snow is possible for the Monday morning commute, before tapering off early afternoon.
D.C.'s Department of Transportation and Department of Public Works have deployed nearly 200 pieces of equipment, including heavy and light plows and sprayer trucks. Crews began treating surfaces and roadways late Saturday evening.
Lon Anderson, a spokesman for the AAA Mid-Atlantic motor club, urged motorists to avoid driving Monday morning and use mass transit.
"If we get the six to 10 inches or more of snow accumulation being forecast, driving in much of our region will be very difficult, and certainly very treacherous," Mr. Anderson said. "Our best advice is to just stay home if possible or take mass transit."
Eastern seaboard cities along a corridor arcing through Washington to Boston and beyond braced amid forecasts of potentially heavy snow accumulations early in the week as the storm began a trek up out of the Southeast.
A powerful March snowstorm blanketed much of Alabama and then marched across Georgia on Sunday, forcing some flight cancellations in Atlanta.
Scott Unger of the National Weather Service in Birmingham said a winter storm warning was in effect until 3 p.m. Sunday mostly for several northern and eastern counties of Alabama, with much of the rest of the state under a winter storm advisory.
He said snow accumulations could reach up to 5 inches in some areas of Alabama, where some churches canceled Sunday services and cold, blustery winds whipped even the usually balmy Gulf Coast.
The weather service said winter storm warnings are in effect from northern Georgia and the Carolinas through the Mid-Atlantic states into New England. Forecasters warn that 8 to 14 inches of snow are possible in the Philadelphia area.
At Hartsfield-Jackson Atlanta International Airport, Delta and AirTran airlines canceled some Sunday flights.
AirTran spokesman Tad Hutcheson said flights out of Atlanta into the Northeast also may be canceled Sunday night as the messy, developing storm took aim at walloping at wide swath of the East Coast up through Maine.
"I expect the Northeast will be hit pretty hard tonight, so our expectations is that people flying into Washington, D.C., and Boston will need to call or check our Web site for possible cancellations," Mr. Hutcheson told the Atlanta Journal-Constitution.
Delta spokesman Brian Kruse said the airline is monitoring the weather and asking customers flying to, from or through Atlanta to call Delta or check its Web site for updates.
Despite above-freezing temperatures, a heavy flurry of snow fell on downtown Atlanta, blanketing cars and creating slushy streets and sidewalks. It hadn't snowed in Atlanta for more than a year — the area received 1.4 inches of snow in January 2008, said Laura Griffith of the National Weather Service in Peachtree City, Ga.
Outside the CNN Center in downtown Atlanta, Flori Kwon of Claremont, Calif., took some time to take pictures of her son Jake, 5, playing in the snow.
"He wants to make a snowman, but I don't think there's enough snow," Ms. Kwon said while large snowflakes landed in her hair. "We're kind of surprised it's snowing."
Meanwhile, tornado watches were in effect from northern Florida into coastal Georgia and southern South Carolina.
In Pennsylvania, the National Weather Service warned that Philadelphia and its suburban counties could expect as much as 8 to 14 inches of snow starting sometime Sunday evening. The snow in that region may mix with a little sleet at the onset as forecasters issued a winter storm warning for much of eastern Pennsylvania starting at 6 p.m. Sunday and lasting through 4 p.m. Monday.
• This article is based in part on wire service reports.