As millions prepare to hit the roads or skies ahead of Christmas Day, a winter storm is plowing through several parts of the country Thursday morning, threatening to hamper many travelers' plans.
Nearly 20 inches of snow has already been reported in Colorado, just west of Denver, while in Des Moines, Iowa, a foot of the white stuff has accumulated.
Fifteen states are currently under winter storm watches or warnings, with blizzard warnings in effect for seven states.
The storm is expected to strengthen as it moves over Chicago on Thursday, changing rain to snow there and dumping up to a half a foot in the Windy City.
The system will move eastward Thursday night, spreading rain into the Northeast, with some areas from Washington, D.C., to Boston getting up to 3 inches. Cold air will then come in from behind the storm Friday night, changing rain to snow in western Pennsylvania, Maryland, New York and West Virginia, where 3 to as much as 14 inches could accumulate in the highest elevations.
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