LOS ANGELES (Reuters) – A winter storm that dumped heavy snow on the U.S. Midwest, stranding some motorists in Missouri and cancelling dozens of flights, marched east toward Washington on Saturday.

The weather system is forecast to affect an 1,800-mile (2,900 km) corridor of the United States from Colorado to the mid-Atlantic. It started as rain from Mexico and turned to snow as it met icy air.

The storm hit Kansas and Missouri on Friday and continued pummeling those states on Saturday, as it extended into parts of Iowa, Illinois, Indiana and Ohio, said U.S. Weather Prediction Center meteorologist Andrew Orrison.

The storm is dumping its heaviest snowfall on areas west of St. Louis, where about a foot and a half of snow was recorded, with more still falling on Saturday, Orrison said.

More than 1,200 motorists in Missouri were stranded and there were four deaths on the roads, the Missouri State Highway Patrol said in a tweet on Saturday.

It was not immediately clear if the fatalities were all weather-related and a representative for the Missouri Department of Public Safety could not immediately be reached for comment.

Dozens of flights were canceled at St. Louis Lambert International Airport, which described the onslaught of snow, in a message on Twitter, as one of its biggest single-day winter storms in years.

Snow is forecast for the Appalachian Mountains and the mid-Atlantic on Saturday evening and Sunday.

“Given how cold it is across the Midwest and even in the mid-Atlantic region, certainly people who are going to be out are going to want to dress in layered clothing,” Orrison said.

“To the extent that it’s snowing outside, travel will be hazardous and outright dangerous in some areas,” he said.

Washington, where many federal government offices are closed because of the U.S. government shutdown, is expected to receive 6 to 8 inches (15 cm to 20 cm) of snow when the storm arrives there, according to the National Weather Service.

Central and northern Virginia will receive even more, with up to 10 inches (25 cm) of snow possible in some places.

Bands of icy rain are forecast for areas farther south, including parts of Virginia and South Carolina.

But the storm will bypass New York City and other parts of the Northeast. Philadelphia is expected to receive a few inches of snow, but areas north of there are expected to be spared, Orrison said.