Much of eastern Colorado was hunkered down as the blizzard blew through on a course that will take it across the Great Plains and into the Midwest Monday.
The FAA said air traffic at the Denver airport was seeing at least two-hour delays and some 200 flights canceled. In the city itself, a fleet of snowplows hit the streets Saturday night and motorists were urged to stay home.
A spokeswoman for the city told the Denver Post heavy duty plows were working to keep up with rapid snowfall on main roads. Smaller pickups were working on side streets to prevent ruts and packed, frozen snow tracks from forming, which makes it more difficult to clear later.
"We are trying to stay with it," said Ann Williams, spokeswoman for the city's public works department. "The snow is coming down fairly fast and fairly heavy."
If snowfall increased to more than a foot, the department would have to request funds for additional plowing from city hall.
Next in line for a snow day will be the Texas and Oklahoma Panhandles as well as Kansas and the Kansas City areas. AccuWeather predicted strong winds -- up to 50 mph in some places -- and snowfall rates up to 2 inches per hour, making for likely blizzard conditions.