Pedestrians walk on a snowy street on Sunday, November 25, 2018 in Kansas City, Missouri. Conditions similar to the snowstorm closed highways and delayed air traffic when a winter storm was moving in the Midwest. (AP Photo / Charlie Riedel) ORG XMIT: MOCR108(Photo: Charlie Riedel, AP)

Travelers from the Upper Midwest rushed Sunday to return home before a major winter storm, bringing heavy snow, high winds and headaches to travel over much of the region, including Chicago's O & ## airports. 39, Hare and Midway.

The storm caused blizzard conditions in the hardest-hit areas on Sunday, which is expected to be the busiest travel day of the Thanksgiving weekend.

Generalized snowfall of 6 to 12 inches was expected from the central Mississippi Valley to the Great Lakes, the National Weather Service said. Parts of Illinois have experienced whiteout conditions, bursts of 45 mph and up to 2 inches of snow per hour.

Heavy snow hit the Chicago metropolitan area later on Sunday, causing nearly 800 flight cancellations and at least 446 flight delays at the O. Hare International Airport, a major hub. Airlines delays at the Chicago entrance or exit have had repercussions on the entire national system.

Nationally, 1,777 flights were canceled and 4,867 were delayed at 10:45 pm EST, according to the FlightAware Flight Tracker. Most cancellations took place in Chicago and Kansas City. Dallas-Fort Worth, Denver and Boston were among other affected airports. The weather has caused most major airlines to waive the change fee.

"It has been snowing for some time in the Rockies, but it is heading to Chicago," said Paul Walker, Senior Meteorologist at AccuWeather.

More: Snow! Airlines waive change fees for post-Thanksgiving storm

More: Snow: More than 650 flights canceled by the storm after Thanksgiving Sunday

The snow has dropped nearly 10 inches in parts of Idaho and Wyoming Saturday night through Sunday. Jackson, Wyoming, was hit with 9 inches.

According to Walker, blizzard and near-blizzard conditions are likely from Topeka (Kansas) to Omaha (Nebraska), Des Moines (Iowa) and Madison (Wisconsin). The main highways between small country roads could see dangerous driving conditions, he warned.

Kansas Governor Jeff Colyer said a state-wide disaster emergency situation. Parts of Interstate 70 were ordered closed in the state.

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"The Kansas Department of Transportation has announced the closure of several roads because of visibility," said Colyer. "We strongly recommend postponing travel plans due to conditions, if possible."

In Nebraska, parts of I-80 were closed when snow and accidents took over the road.

A mix of freezing rain, sleet and slush in Washington could lead to dangerous driving conditions until Tuesday morning, the National Weather Service said. Snow is likely to reach 8 inches in the Cascades.

The rapid storm is expected to bring heavy snow to parts of New England by Tuesday, one foot or more in northern New Hampshire and Maine. Temperatures will fall Monday and Tuesday from the Ohio Valley to the east coast. The conditions could be 15 to 30 degrees below normal, especially in the central Mississippi Valley and in parts of the Ohio Valley.

Contributors: Ben Mutzabaugh and Kristin Lam

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