A major storm system brought a mix of bad weather on Tuesday to much of the central United States, with a possibly dangerous tornado in Alabama and heavy snow in the northern Midwest.

Connor Baird, a forecaster with the National Weather Service in Birmingham, Alabama, said all or parts of three counties — Tuscaloosa, Pickens and Carroll — were under tornado warnings.

“It looks pretty large, but we don’t have an exact measure of it,” he said. “It is a particularly hazardous tornado.”

Baird said there were reports of trees down and building damage from the storm.

There were six reports of tornadoes in eastern Mississippi, with roofs blown off, mobile homes flipped and trees down, the weather service said. Tornado watches were in effect for central Tennessee and central Kentucky, which means conditions exist for a possible tornado.

Winter storm and blizzard warnings were in effect from the central Rocky Mountains to northern Michigan, the weather service said. Northern Wisconsin and Michigan are forecast to receive the highest amounts, with up to 12 inches of snow, according to the weather service.

The Twin Cities of St. Paul and Minneapolis, Minnesota, have declared a snow emergency, with parking restrictions, while state government offices in several counties of southeast South Dakota closed early on Tuesday due to snow and high winds.

Stormy weather has affected U.S. air travel, with 2,114 flight delays and 658 cancellations, with airports in Minneapolis, Chicago and Denver hit the hardest, according to the FlightAware website.