Blizzard conditions and heavy snow are threatening tens of millions of people across the central and eastern United States, with winter storms putting a long stretch of Midwest-to-Northeast highways at risk of dangerous whiteouts and ice.

A Michigan winter storm could bring up to 20 inches of snow to parts of the state, say National Weather Service snowfall accumulation predictions.

A winter storm system is expected to intensify Saturday morning, bringing steady snow showers and creating potentially hazardous travel conditions across Illinois, Missouri, Iowa, Wisconsin and Michigan. Chicago, Minneapolis, Milwaukee, St. Louis, Indianapolis, Detroit and Roanoke, Virginia, are a few of the cities at risk through the weekend.

In a post early Friday, the Weather Prediction Center (WPC) said the "significant" winter storm would develop on Friday, bringing with it a "broad area of moderate to heavy snow" from the eastern Plains and through the western Great Lakes area.

Thanksgiving in Iowa was sunny but colder than normal, with morning temperatures in the teens and highs in the mid-30s. A strong winter storm will bring heavy snow starting Friday afternoon, spreading across most of the state and making travel difficult.

A major winter storm is blasting the Central U.S. with heavy snow this weekend, causing travel headaches for millions of people as they return home from Thanksgiving plans.