OMAHA, Neb. >> A “highly impactful” winter storm is expected to deliver a punch to the country’s midsection today and into Tuesday, with blizzard conditions dumping as much as a foot or more of snow and shutting down schools and highways in several Midwest states.

Snow as deep as 8 to 12 inches (20 to 30 centimeters) could blanket a broad area stretching from southeastern Colorado all the way to the upper peninsula of Michigan, including western Kansas, eastern Nebraska, large parts of Iowa, northern Missouri and northwestern Illinois, said Bob Oravec, a forecaster with the National Weather Service in College Park, Maryland.

“So a very, very highly impactful event coming forward,” Oravec said.

There were widespread school closures across Nebraska and Kansas on Monday ahead of the storm, where forecasters predicted 5 to 8 inches (12 to 20 centimeters) of snow. The district that includes Nebraska’s capital, Lincoln, told students to stay home. Lines were long Sunday at a Target Store drive-up in Omaha as residents stocked up on milk, bread and booze ahead of the storm.

Whiteout conditions in central Nebraska closed a long stretch of Interstate 80. Kansas closed Interstate 70 from the central city of Russell all the way to the Colorado border due to dangerous travel conditions, as well as many secondary roads in northwestern Kansas. Several vehicles slid off I-70 in northeastern Kansas.

Federal courts in Omaha and Lincoln closed at noon Monday. The U.S. Army Corps of Engineers began increasing the flow through a Missouri River dam that sits on the Nebraska-South Dakota border near Yankton by 2,000 cubic feet per second to reduce the chance of ice jams forming.

The National Weather Service office in Des Moines, Iowa, warned of the potential for “widespread heavy, possibly extreme, snowfall,” with up to 9 to 15 inches (23 to 38 centimeters), and warned that commuters on Monday evening and Tuesday morning would face “significant impacts,” with possible whiteout conditions at times. Dubuque, on Iowa’s eastern border with Illinois, closed its city offices Tuesday. Schools in Cedar Rapids in eastern Iowa were among those closing Tuesday.

The threatening weather has already affected campaigning for Iowa’s Jan. 15 precinct caucuses, where the snow is expected to be followed by frigid temperatures that could drift below zero degrees (minus 18 Celsius) by caucus day next week. It forced former President Donald Trump’s campaign to cancel multiple appearances by Arkansas Gov. Sarah Sanders and her father, former Arkansas Gov. Mike Huckabee, who had been scheduled to court Iowa voters on Trump’s behalf Monday.

In South Dakota, Sioux Falls Mayor Paul TenHaken urged residents not to travel Monday if they did not have to, and to give snowplows time and patience so they can clear the roads.

The Illinois Tollway, a state agency that maintains nearly 300 miles (480 kilometers) of toll roads across 12 northern Illinois counties, urged drives to take a similar “go it slow” attitude. The agency plans to deploy its entire fleet of 196 snowplows to clear snow and ice and help stranded drivers.

Parts of northern Missouri braced for up to a foot of snow. Officials in Kansas City, Missouri, said City Hall would be closed Tuesday and municipal courts would operate remotely. But the Missouri Department of Transportation said it was ready for its first big snowfall of the season, with at least 100 new employees after a shortage of snowplow drivers last winter.

Much of western and southern Minnesota as well as west-central Wisconsin were under winter storm warnings or advisories with snow accumulations of up to 10 inches (25 centimeters) predicted.

In Wisconsin, cancellations started Monday morning, with the state Homeland Security Council calling off a Tuesday meeting in Madison. The council advises Gov. Tony Evers on security issues. The state’s capital city was under a winter storm warning until early Wednesday morning with as much as 9 inches (23 centimeters) of snow and 40 mph (64 kph) winds on tap. City officials canceled garbage collection Tuesday morning to prevent residents from putting trash cans along curbs and making it difficult for snowplows to navigate.

Northwestern Illinois was also under a winter storm warning with forecasts calling or 7 to 12 inches (18 to 30 centimeters) of snow by early Wednesday morning. The Chicago area as well as Gary, Indiana, were under winter storm advisories, with forecasts calling for up to 6 inches (15 centimeters) of snow by Tuesday evening and wind gusts of up to 30 mph (48 kph) in Chicago. Snowfall rates could exceed an inch per hour during the day Tuesday, the weather service said.

The disruptions extended as far south as the Oklahoma panhandle, where Cimmaron County emergency managers asked citizens to stay home. More than a dozen motorists were stranded there Monday afternoon, with whipping winds and blizzard conditions leading to near-zero visibility, said Lea Lavielle, the county’s emergency management director.

Roads and major highways were closed “from every corner of our county and in between,” Lavielle said. “At this point in time, we are advising individuals to shelter in place the best they can.”

A blizzard warning remained in effect through Tuesday morning for the Oklahoma Panhandle and northern and western parts of the Texas Panhandle, with snowfall accumulations of up to 8 inches expected along with wind gusts up to 75 mph.

The Gulf Coast in southeastern Louisiana and Mississippi was under a tornado watch, as residents in New Orleans and other communities braced for storm weather, and several school systems dismissed classes early Monday.

New York’s governor is warning that heavy rains and high winds on Tuesday could lead to major power outages throughout the state and flash flooding, especially in the Hudson Valley.

The storm follows a separate storm that has moved offshore after dumping over a foot of snow Sunday on parts of Pennsylvania, New York state and portions of New England, Oravec said.

And another storm is on the way that will affect the Pacific Northwest into the northern Rockies, he said. Blizzard warnings were out for much of the Cascade and Olympic ranges in Washington and Oregon.