A massive winter storm pounding the northern United States Tuesday grounded 2,600 flights, closed hundreds of schools and made roadways and highways impassible.

At least four people were reportedly killed in accidents on icy and snow covered roads and highways.More than a dozen states from Minnesota to Virginia were in the path of the huge storm, which had already dumped as much as two feet (60 centimeters) of snow in Montana and 15 inches (38 centimeters) in North Dakota.The heavily populated Chicago area was expected to get as much as an inch (2.5 centimeters) of snow an hour during the evening rush, the National Weather Service said.

Hundreds of plows were working the Windy City's roads and freeways, but with up to a foot (30 centimeters) of snow expected, there was no way they could keep up."Consider only traveling if in an emergency," the weather service warned.Eric Jacobson wasn't able to keep up with the snow on his Chicago walkway, but was doing his best to clear it for his neighbors before they came home from work Tuesday evening."It's pretty rugged and pretty intense," 

The snow was so thick and heavy that a woman down the street used a broom to clear off her car.Nearly 900 flights were grounded at Chicago's O'Hare airport -- a major hub -- while another 260 were cancelled at Chicago Midway on Tuesday. Over 100 flights were cancelled in Minneapolis, Minnesota, which helped push the day's total to 1,465, according to FlightAware.Another 1,162 flights scheduled for Wednesday had already been cancelled, mainly in the Washington area.The storm was expected to hit the nation's capital late Tuesday or early Wednesday, and some Congressional meetings were already being called off.

A key vote to keep the federal government funded despite a budget impasse could not be cancelled, however, and was instead rescheduled in hopes of wrapping up work early at the House of Representatives to miss the worst of the weather"We think the system will develop into a more powerful storm as it passes into the mid Atlantic states," Dan Petersen, a meteorologist with the National Weather Service, told AFP."This could be a heavy, wet snow, so there could be tree branches and power lines brought down."

The storm will merge with a second system over the Appalachians Tuesday night and also pull moisture off the Atlantic.Washington will get a slushy mix of rain and about four to eight inches (10 to 20 centimeters) of snow, which could create gridlock if it ends up hitting during the evening or morning commutes."People forget their winter weather driving skills," Petersen, who works at the weather service headquarters in Washington, told AFP.

"We've had people get frustrated and just leave their cars on the road, creating an obstacle."But even those with plenty of experience navigating winter weather got into trouble.A local news channel in Wisconsin reported a truck driver was killed, and his passenger is still missing, after his rig slipped off a Wisconsin highway into a river.And two people were killed in rural Illinois and another in rural Indiana in crashes, an Indiana newspaper reported.