As millions of people prepare to travel for the Thanksgiving holiday, two strong storm systems, including the first major winter storm of the season, are forecast to bring snow, wind and rain to much of the United States this week.

More than 25 million people were under winter storm warnings or warnings, the National Weather Service said Monday.

What can you expect this week

According to the National Weather Service’s Weather Prediction Center, the first system, which is expected to bring thunderstorms and possible tornadoes to the central and southern Plains on Monday, will collide with Arctic air as it moves north, bringing widespread snow originated in the Dakotas. , Minnesota and Wisconsin on Tuesday and Wednesday.

Up to a foot of snow is possible in parts of North Dakota, the weather service said, adding that the snowfall “may also be accompanied by gusty winds, resulting in reduced road visibility.”

Snow in the northeast

In addition, a higher-level low-pressure system was forecast to develop over the Great Lakes later this week, resulting in cooler temperatures, cold rain from the Ohio Valley to the East Coast and accumulating snow for the central Appalachians and parts of the Northeast. the weather service said.

Up to 6 inches of snow is possible Thursday and Friday, especially in higher elevations.

• Read more from Foxweer: Snow and rain will lash the US as winter storms intensify ahead of Thanksgiving travel

‘Atmospheric river’ in the northwest

Meanwhile, in the Pacific Northwest, a daylong “atmospheric river event” was expected to bring heavy rain and snow to Oregon and Northern California starting Monday, the weather service said.

“Widespread rainfall of 4 to 7 inches is expected in this region through Wednesday, which could lead to river flooding and an increased risk of mudslides,” the weather service said. “Heavy rainfall and associated weather hazards resulting from this atmospheric river event are expected to continue beyond midweek.”

What about Thanksgiving?

Weather service forecasters have yet to issue forecasts beyond seven days, but the U.S. Climate Prediction Center’s six- to 10-day outlook points to above-average chances of rain in the Pacific Northwest, upper Midwest and Great Lakes early next week. .

Nearly 80 million people are expected to travel more than 50 miles for Thanksgiving next week, with Tuesday and Wednesday expected to be the busiest times to be on the road, according to AAA.

• Read more from NBC News: Nearly 80 million people are expected to make record-breaking trips this Thanksgiving