DETROIT — The Arctic chill that has gripped the Upper Midwest and Rockies is spreading.

Other parts of the U.S. are expecting sharp drops in temperature in the coming days from a powerful weather system that hit Alaska with hurricane-force winds over the weekend. The system has dumped 3 feet of snow in some places.

Meteorologists are adamant the weather isn’t because of the polar vortex, a giant upper air pattern that normally pens in cold air in the Arctic in the winter. Instead, they say it’s being pushed in by a different weather phenomenon more related to the remnants of a powerful typhoon.

“The polar vortex itself has not moved south. It’s still in the Arctic where it always is,” said National Weather Service spokeswoman Susan Buchanan.

Whatever the case, the cold is expected to linger. Some regions will go from record warm to record cold in just two days, with temperatures dropping 15 to 20 degrees below normal on the East Coast Friday and Saturday. Freezing temperatures will likely dip as far south as Atlanta on Friday, said Jeff Masters, meteorology director of the Weather Underground.

As much as 3 feet of snow blanketed parts of Michigan’s Upper Peninsula, with temperatures in the 20s and 30s early Wednesday. Up to 18 inches fell in northern Wisconsin and parts of central Minnesota saw more than 16.

Many roads were snow-covered and slippery Wednesday morning in the Upper Peninsula, where residents are accustomed to snowy conditions. Of his drive into work, meteorologist Justin Titus said that roads were “just rutted out and kind of felt like you were driving over a washboard.”

The National Weather Service said some lake-effect snow, mainly in Michigan, is forecast through the weekend.