A major winter storm battered the Northern Plains and Upper Midwest with high winds and heavy snow on Wednesday, forcing hundreds of schools to close, grounding air travel and making road travel difficult - if not impossible - in some U.S. areas, writes Reuters.

More than 50 million Americans were under winter weather advisories on Wednesday morning as the storm moved across a wide swath of the western and northern United States and into the East. Up to 60 cm of snow were expected in some spots during the day and into Thursday, the National Weather Service said.

The storm also pounded California and brought a mix of snow and sleet to the East, including New England, where forecasters warned motorists to beware slick roads.

Snow-covered roads also will make travel treacherous in the Upper Midwest, and ice-covered power lines and falling trees could cause power outages late on Wednesday and into Thursday, said Frank Pereira, a forecaster with the weather service"s Weather Prediction Center in College Park, Maryland.