About 570 flights were canceled on Friday, with 127 of them at Chicago's O'Hare airport. Kansas City International Airport reopened after being closed on Thursday while crews cleared runways.
The National Weather Service said early in the morning that the storm, headed northeast into the upper Great Lakes, may bring sleet and freezing rain to the Appalachians and mid-Atlantic states, with thunderstorms expected on the storm's southern fringe in the southeastern United States.
Kansas bore the brunt of the bad weather on Thursday, with up to 15 inches of snow in some parts of the state, according to the National Weather Service.
A 200-mile stretch of Interstate 70 in central Kansas was closed and strewn with cars stuck in snow.
National Guard troops riding in Humvees were dispatched to look for stranded motorists along the interstate and other highways, said Sharon Watson, a spokeswoman for Kansas emergency management services.
The fierce storm triggered severe thunderstorms from eastern Texas to Georgia.
Missouri Governor Jay Nixon and Kansas Governor Sam Brownback declared states of emergency because of hazardous travel and possible power outages. Brownback ordered state offices closed because of the storm.
In Nebraska, a 19-year-old woman was killed in a two-car accident on Wednesday on Interstate 80 near Giltner. The Nebraska State Patrol said weather was a factor.
An 18-year-old man died in Oklahoma when his vehicle slid into a tractor-trailer on a slushy state highway, the state's highway patrol said.
Drought-stricken farmers in the Great Plains, one of the world's largest wheat-growing areas, welcomed the moisture brought by the storm, although experts said more rain or snow would be needed to ensure healthy crops.