Officials reported as many as six people may have died in weather-related crashes on Nebraska roads. Three more died in Oklahoma where the governor declared an emergency, and at least one death was reported in Minnesota.
Heavy snows also resulted in 260 flights being canceled at Chicago airports and about 100 canceled in Minneapolis.
The worst was yet to come in the Omaha and Lincoln areas of Nebraska, forecasters said. Blizzard-like conditions were expected by nightfall.
"Travel will be treacherous, and in some locations impossible, over the Christmas holiday," Barbara Mayes, a meteorologist with the National Weather Service in Valley, told the Omaha World-Herald.
The storm system was expected to intensify as it moves up the Missouri Valley and strikes the Midwest, forecasters said. Freezing rain was causing travel problems in Iowa, Illinois, central Wisconsin and western Michigan. An ice storm warning was in effect in the Chicago area.
The Minnesota forecast called for one of the deepest Christmas snows on record across the region. The storm was expected to linger into Saturday, bringing 48 to 60 hours of snowfall with accumulations of possibly 16 to 22 inches in a wide band from the Iowa border through the Twin Cities to Duluth and the Arrowhead.
Travel was expected to be hazardous in northwest and north-central Iowa with up to 14 inches of blowing snow.
South Dakota officials declared a state of emergency and said they expect part of their interstate highway system will be closed.
The Tulsa World reported three people died in a crash near Sand Springs where sleet had been reported. The Minneapolis Star Tribune reported a Wisconsin woman died in a car-pickup truck crash near Morton, Minn.
KTEN-TV, Ada, Okla., reported Oklahoma Gov. Brad Henry declared a statewide emergency. He said state troopers, National Guard troops and other emergency personnel had been pressed into service.
The Star Tribune reported the state patrol said it had recorded about 250 crashes on state roads, with about 400 more vehicles in ditches. The state Transportation Department was recommending no unnecessary travel. Most of the Minneapolis-St. Paul metropolitan area had gotten at least a half-foot of snow with 9.4 reported in Chaska.
"If you wanted a white Christmas, you got it!" Andrew Maggio, who was shoveling the drive of his Minneapolis home, told the Star Tribune.
National Public Radio reported traffic had slowed to a crawl in Mason City, Iowa, and about 1,300 homes in Iowa were without power. Heavy snow also was reported in Arizona, Colorado, Kansas and South Dakota.
"As we go into Christmas Day, we expect some very heavy snow and some blizzard-like conditions across parts of the upper Midwest," Bruce Sullivan, a National Weather Service forecaster, told NPR. "With winds expected to increase to over 30 mph, in some spots to over 40 mph, that could produce some white-out conditions for travelers."
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