CHICAGO: 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.

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 2 feet (60 cm) of snow and winds of up to 60 miles (97 km) an hour were expected in some spots during the day and into Thursday, the National Weather Service said.

In Sioux Falls, South Dakota, some 17 inches (43 cm) of snow, wind gusts up to 45 mph (72 kph) and temperatures hovering around 10 degrees Fahrenheit (minus 5 C) punished those going about their daily routines.

"It's really cold, but people still want their coffee and eggs," said Bre Bethke, 37, a manager at M.B. Haskett Delicatessen, after being blasted by the fierce weather each time she opened a drive-through window for a waiting customer.

"Our regulars want to come here and get out of the cold. But not today, no way. This is too much."

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.

"Travel will be near-impossible," he said.

Experts say the growing frequency and intensity of such storms, interspersed with extreme heat and dry spells, are symptoms of climate change. While the East Coast has experienced a relatively mild winter, the Northern Plains has experienced an extreme winter in terms of snowfall and temperatures, according to the weather service.

Among the hardest-hit cities in the Midwest was Minneapolis, where some 20 inches (50 cm) of snow and 45-mph (72-kph) winds were expected to create whiteouts.

"We are bracing for what is likely to be one of the largest snowstorms in Minnesota history," St. Paul Mayor Melvin Carter said at a news conference.

Local officials declared emergencies in Minneapolis and neighboring St. Paul, and motorists were told not to be out on the roads.

Minneapolis' school system said it would hold classes remotely for more than 29,000 pupils for the rest of the week. Dozens of school districts canceled classes in the Dakotas, Colorado and Wyoming.

The storm wreaked havoc on morning air travel. Some 3,500 flights were delayed or canceled across the nation, including 470 flights into and out of Minneapolis, according to Flightaware.com.

It also produced a band of freezing rain stretching from central Iowa through Chicago and into southern Michigan, coating roads, trees and power lines with up to a 1/4 inch (0.6 cm) of ice, the weather service's Pereira said.

The storm hit California on Tuesday and was expected to continue through the end of the week. A rare blizzard warning was issued for Los Angeles County mountains, the first issued by the weather service since 1989.