One of the places that could be hit the hardest is Springfield, Missouri. Among the hazards expected there Wednesday: lightning, wind and ice, with a little snow and sleet thrown on top for good measure.
The biggest threat of heavy snow lies in parts of Kansas, Nebraska and Missouri, with the possibility of whiteout conditions in some places, he said.
In Kansas, where the storm had already started, the National Weather Service was predicting as much as 18 inches of snow. The agency said parts of Nebraska could see more than a foot of snow, with drifts making some roads impassable.
CNN affiliate KSNW in Wichita reported that crews had treated roads Monday but no matter how much salt and sand they had spread, by Wednesday morning, primary roads were snow-packed and slick. Side streets were worse.
There was a break in the weather that allowed crews to get out before the afternoon rush hour and clear some of the major thoroughfares, the station reported.
Kansas State University announced on its website that Thursday classes were canceled.
Forecasters were predicting as much as 2 inches of snow in St. Louis, with the precipitation turning into sleet and freezing rain Thursday. The conditions will have "a significant impact on travel," the weather service warned.
North of where the most snow will fall, Chicago could receive what would be its largest single snowfall of the year -- 4 inches, Miller said. The city usually gets up to 4 feet of snow a year. So far this year, only about a foot has fallen, he said.
South of the snow belt, dangerously icy conditions are possible in parts of northern Arkansas and southern Missouri, he said. That includes Springfield, where windy conditions will precede the possibility of up to 3 inches of snow and sleet Thursday, with the possibility of a quarter of an inch or more of ice to boot.
Heavy rains forecast