PIERRE, S.D. » The first significant wintry storm of the season will likely bring up to a foot of snow to parts of the Midwest this weekend, with eastern Iowa and northern Illinois bracing for the largest amounts.

The storm system is moving east from Nebraska and will last through Saturday evening when it tails through Michigan, according to Richard Otto, lead forecaster at the National Oceanic and Atmospheric Administration’s Weather Prediction Center.

The snowfall is "right on track" for the season, Otto said. But don’t look for it to be the picturesque light, fluffy snow that often occurs in the dead of winter, he said — much of it will be wet and heavy.

Already, southern South Dakota saw significant snowfall and poor traveling conditions this morning, with a foot or more of snow expected by the time it tapers off.

Tractor-trailers are pulling off slow-moving interstates to park for the day, said Bret Brown, a cashier at Roadway Express truck stop in Sioux Falls.

"A lot of people complaining about it, nobody wants to be out in it," he said. "Interstates are down to 10 miles per hour, the side streets are blocked and there’s a lot of cars in ditches everywhere."

Drivers in central and eastern Iowa will likely have a rough evening commute with six to 10 inches of snow expected, Otto said.

The northwest suburbs of Chicago could see up to 10 inches of snow before noon Saturday, and Otto said southern Wisconsin also will be affected.

"The biggest impacts will be a shovelable snow storm for parts of the Midwest," Otto said.

The weather service also issued a winter storm watch for northern Indiana, saying snow accumulations of 4 to 7 inches are possible. The Indiana Toll Road in the northern part of the state is banning triple-trailer trucks from 7 a.m. Saturday to 1 a.m. Sunday because of dangerous conditions.

Associated Press writer Blake Nicholson in Bismarck, North Dakota, contributed to this report.