A major late-season snowstorm was projected to last through Wednesday night and dump plowable snow on the Washington area for the first time in two years after burying the Midwest under more than a foot.
The National Weather Service said the District could get equally walloped by Old Man Winter, but a more likely scenario was a daylong storm and two very snarled commutes.
The storm was projected to hit the mid-Atlantic region late Tuesday night in the form of a wintry mix of snow and rain and continue throughout Wednesday with heavy, wet snow. Up to 6 inches were predicted for the immediate Washington area.
"It all depends on when the rain turns over to snow," meteorologist Jared Klein said Tuesday. "It does look like it will be throughout the day [Wednesday], both in the morning and afternoon rush hours. That's doubly a concern. The afternoon rush hour has more certainty of snowing, and it's going to be a heavy, wet snow."
The storm is the product of two low-pressure systems moving across the country, one moving eastward, that wreaked havoc on the Dakotas and most recently Minnesota and Chicago, where schools and about 1,000 flights were canceled.
Chicago was hit Tuesday by a storm expected to dump as much as 10 inches of snow in the area before the end of the day — the most since the 2011 blizzard and its more than 20 inches of snow.
The system moved across the Dakotas and Minnesota on Monday, dropping up to a foot of snow in some areas and freezing rain in others.
Another low pressure system was making its way up from the Carolinas and into Virginia, and while Mr. Klein assured that the combination of the two storms would not result in another superstorm, it was still shaping up to be strong.
"Merging of storms happens all the time," Mr. Klein said. "It's like waves in an ocean. Sometimes two waves hit each other and become a stronger, higher wave. But if they're not in sync, they can cancel each other out. This time it's going to be stronger."
Hundreds of flights in and out of area airports were canceled Tuesday afternoon in advance of the storm. As of 7 p.m. Tuesday, the federal government had not announced whether it would close Wednesday.
Though it has been two years since the last major snow storm, area power companies were drawing on experience to prepare their crews for the strong possibility of outages.
"Wet snow can weigh heavily," Dominion Virginia Power spokeswoman Le-Ha Anderson said. The power company had additional crews on standby and en route from the eastern and central regions of the state, as well as the Carolinas.
"At about 5 to 6 inches of wet snow, we can expect that trees will bend or break onto power lines," Ms. Anderson said. Along with heavy snow weighing down lines, there's also the concern of high winds snapping limbs that have been weakened by the snowfall, as well as slippery roads causing car collisions with utility poles.
If there's a silver lining to the forecast, it's the relatively warm temperatures predicted for the coming days.
Weather Service science and operations officer Steve Zubrick said that while Tuesday's temperatures hovered in the mid-40s, the thermometer could drop to 33 degrees overnight.
"It can snow very well at 33 degrees, but it's not going to be the horrible impact on the roads if it were 15 degrees out," Mr. Zubrick said.
Temperatures throughout the rest of the week should stay in the 40s, which means "there's going to be a lot of melting," Mr. Zubrick said.
"There could be a small threat of localized flooding," he added, "just not anything really substantial."
The 2012-13 winter has been relatively mild and snow-free. Only 1.5 inches of snow had fallen in the D.C. area this winter before this week's storm, compared to an average 15 inches in one winter. Tuesday night and throughout Wednesday, the storm's rain-snow line will fall along the Interstate 95.
"Areas to the west will get more snow. They're looking at 10 to 15 inches," Mr. Klein said. "The east side, it will take longer for [the rain] to change over to snow. Then it will be a wet snow mix."
Areas farthest east might not see any snow until Wednesday morning or afternoon.
By early Tuesday afternoon, snow was already falling at Snowshoe Mountain Ski Resort in eastern West Virginia.
"We're definitely excited," spokeswoman Sarah Eilers said. "We average about 180 inches a year, and right now we're around 140. So we're hoping this will get us to the end of March."
Despite the threat of 10 inches of snow, residents of Shenandoah, Va., were less concerned with shovels than propane tanks.
Marsha Downey of Shenandoah Hardware said the store had a run on the gas tanks but little interest in snow removal tools.
"Two years ago, when we had that really bad winter, we must have sold 10,000 shovels. I guess people still have them," she said with a laugh. "A lot of people here have gas stoves and they want to make sure they're prepared. I guess if they can't go anywhere, at least they can eat."
• This article is based in part on wire service reports.
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