Thanksgiving travelers are already facing snowy conditions, with forecasts indicating more inclement weather on the way this holiday weekend. Winter storm warnings were issued on Saturday, affecting much of the northern United States.

The National Weather Service has extended storm warnings and advisories from Montana across to New York. The snow was predicted to begin Friday, continuing through the weekend, particularly impacting Iowa and Illinois with significant snowfall. West-central Illinois is expected to see between six inches and a foot of snow from Friday night through Saturday night.

While the conditions are severe, meteorologists have noted that they do not currently meet the criteria for a blizzard warning, which would require winds of at least 35 mph, visibilities under a quarter mile, and duration over three hours.

A storm that had already brought snow to parts of the northern Plains and the Great Lakes region persisted on Friday. By the storm’s end, snowfall could exceed a foot in some places, especially downwind of Lake Superior in Michigan’s northern Lower Peninsula, as well as areas near lakes Erie and Ontario. Central New York state is also forecasted to receive a foot of snow.

Saturday’s predictions from the weather service suggest that parts of Iowa, Illinois, Wisconsin, and Michigan could see more than a foot of snow, potentially complicating travel plans during this busy holiday period.

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.