Blizzard Conditions Disrupt Travel Across Northern and Central Plains

Parts of South Dakota were expected to receive up to 13 inches of snow, with wind gusts as high as 55 miles per hour, according to the National Weather Service.

More than a million people across the Northern and Central Plains were under blizzard or ice storm warnings early Tuesday, as heavy snow, freezing rain and powerful winds created treacherous road conditions that forecasters said could last through early Wednesday.

As of Tuesday morning, parts of Nebraska and South Dakota had recorded about four inches of snow, though strong winds prevented accurate readings, said Amanda Viken, a meteorologist at the National Weather Service’s office in North Platte, Neb. Some towns in southeastern South Dakota had received up to a foot of snow since Monday, according to the National Oceanic and Atmospheric Administration.

Before the storm tapers off on Tuesday night into Wednesday, up to four more inches of snow are expected in western South Dakota, western Nebraska, far eastern Wyoming and northeastern Colorado, the National Weather Service said. In areas where snowfall has stopped or slowed, freezing temperatures and wind gusts of more than 55 miles per hour could cause icy roads and whiteout conditions throughout the day, forecasters said.

“It’s pretty slick out, and the visibility restrictions that we’re seeing with this strong wind aren’t helping,” Ms. Viken said.

Snow showers and blustery north winds were sweeping across northwest Nebraska late Tuesday morning, causing visibility to be below one mile in some areas, the National Weather Service said on social media.

A blizzard warning

A storm is a blizzard when it contains large amounts of snow, winds over 35 m.p.h. and visibility of less than a quarter mile for at least three hours.

More than half a million people were also under an ice storm warning early Tuesday in the Dakotas and a slice of western Minnesota. A dangerous mix of sleet and freezing rain was expected to blanket the Dakotas and northern Minnesota on Tuesday, bringing ice accumulation totals above a half inch and creating hazardous travel conditions, the Weather Service said.

As the storm exits the Plains, a wintry mix will likely follow into a portion of the Mississippi Valley on Wednesday.

On Monday, the South Dakota Department of Transportation said in a news release that conditions were “approaching near zero visibility” on roads covered in snow and ice, prompting officials to close parts of Interstate 90 through Tuesday morning.

An accident involving several jackknifed tractor-trailers forced a section of eastbound Interstate 80 near York, Neb., to close for about three hours on Monday afternoon, the Nebraska State Patrol said. There were no injuries in the accident, which was partly caused by blowing snow and slick road conditions, Cody Thomas, a spokesman for the Nebraska State Patrol, said in a statement.

“Be safe and take it slow if you’re traveling today,” the Nebraska State Patrol said on social media on Tuesday.

In Kansas, state transportation officials temporarily closed Interstate 70 from Goodland, in northwestern Kansas, west to the Colorado state line and warned that roads were “partially covered or snow-packed” on Tuesday morning. Interstate 70 has been reopened, but parts of other roads remain closed, according to transportation officials.

Mr. Thomas said that there had been about 60 “weather-related incidents” on Interstate 80 in Nebraska on Monday, mostly between Lincoln and North Platte.

Forecasters warned that power outages were possible, particularly in South Dakota, as strong winds could damage trees and knock down power lines. As of early Tuesday, though, there were no reports of widespread power outages, according to PowerOutage.us, which tracks the utility industry.

The impact on air travel appeared to be relatively modest at the outset of the storm. About 80 flights within, into or out of the United States on Tuesday had been canceled as of late morning, according to FlightAware. About 2,700 flights across the country had been delayed.

Holiday travelers who planned to hit the road on Tuesday should take caution on the road, said Matthew Meyers, a meteorologist at the Weather Service office in Sioux Falls, S.D. In the southeastern part of the state, temperatures were expected to remain below freezing, causing much of the rain that had fallen overnight to refreeze.

“If they can they should take it pretty slow,” he said. “It’s going to be slick out there.”

Johnny Diaz, Eduardo Medina and Derrick Bryson Taylor contributed reporting.