Thanksgiving travelers are already facing snow and cold temperatures, with more severe weather anticipated throughout the holiday weekend. On Saturday, winter storm warnings were issued for much of the northern United States.

The National Weather Service has extended storm warnings and advisories from Montana all the way to New York. Snowfall is expected to begin on Friday and continue through the weekend in several areas, with Iowa and Illinois likely to experience the most significant impact. West-central Illinois could see snow accumulations ranging from six inches (approximately 15 centimeters) to a foot (30 centimeters) or more from Friday night through Saturday night.

Currently, meteorologists note that the forecast conditions do not meet the criteria for a blizzard warning, which requires winds of at least 35 mph (56 kph), visibility reduced to less than a quarter mile (400 meters), and these conditions persisting for over three hours.

A storm system that has already delivered snow to parts of the northern Plains and the Great Lakes region continued on Friday. By the storm’s conclusion, snowfall totals are expected to reach at least a foot, especially in areas located downwind of Lake Superior across Michigan’s northern Lower Peninsula and downwind of lakes Erie and Ontario. Central New York state could also receive up to a foot (30 centimeters) of snow.

The weather service predicts that parts of Iowa, Illinois, Wisconsin, and Michigan could see over a foot (30 centimeters) of snow on Saturday.

Snow squalls Friday bringing quick bursts of heavy snow and dangerous, whiteout conditions for driving were possible across the interior Northeast, the weather service said. Its winter storm severity index warned of highly dangerous driving conditions in eastern Iowa and northwestern Illinois from Friday afternoon until midnight.

In the Pacific Northwest and the Rockies, a combination of snow and rain was expected Friday. By Saturday, the snow will taper off for the Rockies and northern Plains, but continue on to the Midwest.

To the south, storms — some of them heavy — are in the forecast, with some flash flooding possible Saturday in the western Gulf Coast.

Temperatures were well below average in the eastern and central parts of the country, with highs Friday expected in the 20s degrees F and 30s degrees F in the Midwest, the 30s and 40s in New England and Mid-Atlantic areas, and the 40s and 50s in the Southeast.

The snowy weather on Thanksgiving brought a number of vehicle crashes in western Michigan.