Cold blast to bring lake effect snow to multiple states as post-Thanksgiving travel underway

The first big snowstorm of the season is threatening to bury New York towns along lakes Erie and Ontario during a hectic holiday travel and shopping weekend.

An Arctic outbreak of cold air will expand south and east and bring "dangerously cold wind chills" into the Northern Plains and Upper Midwest, the National Weather Service said Saturday, while heavy lake-effect snow could make travel "very difficult to impossible" into next week.

"Temperatures will be 15 to 20 degrees below average over parts of the Northern Plains and temperatures will be about 10 degrees below average over parts of the eastern third of the country," the weather service reported.