DENVER — A major winter storm today is promising to bring a white Christmas to parts of the West and Midwest, but not without threatening to cause long delays and tough driving conditions for countless holiday travelers.

The storm is expected to dump more than a foot of snow on parts of Colorado and Southern Utah by midday today and blow east into the Plains states through Christmas Day. Blizzard warnings were likely on Christmas Eve in Kansas.

"Pretty much the entire central and southern Rockies are going to get snow, and then it's going east and will drop more snow," said Stan Rose, a National Weather Service meteorologist in Pueblo, Colo.

South Dakota Gov. Mike Rounds declared a state of emergency. The National Weather Service in Sioux Falls, S.D., warned of treacherous travel conditions from today through Friday night, calling the storm "life threatening."

The Nebraska State Patrol urged drivers this morning to use extreme caution when venturing out on the roads across the central third of the state because the roads are slick as freezing rain and snow had started to fall.

In Nevada, multiple wrecks were reported in and around Reno as snow blanketed the area shortly before the Tuesday evening commute.