SIOUX FALLS, S.D. -- It has been decades since parts of the Midwest experienced a deep freeze like the one expected to arrive Sunday, with potential record-low temperatures heightening fears of frostbite and hypothermia -- even in a region where bundling up is second nature.
This "polar vortex," as one meteorologist calls it, is caused by a counterclockwise-rotating pool of cold, dense air. The frigid air, piled up at the North Pole, will be pushed down to the U.S., funneling it as far south as the Gulf Coast.
Ryan Maue, of Tallahassee, Fla., a meteorologist for Weather Bell, said records will likely be broken during the short yet forceful deep freeze -- a perfect combination of the jet stream, cold surface temperatures and the polar vortex -- that will begin Sunday and extend into early next week.
"All the ingredients are there for a near-record or historic cold outbreak," he said "If you're under 40 (years old), you've not seen this stuff before."
Before the polar plunge, Saturday marked the day Earth is the closest it gets to the sun each year. The planet orbits the sun in an oval and on average is about 93 million miles away. But every January, Earth is at perihelion, and on Saturday, it was only 91.4 million miles from the sun.
But that proximity doesn't affect the planet's temperatures, and the predictions are startling: 25 below zero in Fargo, N.D., minus 31 in International Falls, Minn., and 15 below in Indianapolis and Chicago. At those temperatures, exposed skin can get frostbitten in minutes and hypothermia can quickly set in as wind chills may reach 50, 60 or even 70 below zero.
The cold will sweep through parts of New England, too, where residents will have just dug out from a snowstorm. And fresh powder is expected in parts of the central Midwest and South starting Saturday night -- up to a foot in the St. Louis area, 6 to 8 inches in central Illinois, 8 or more inches in western Kentucky and a half-foot to a foot in southwestern Michigan.
Snow will reduce the sun's heating effect, so nighttime lows will plummet because of strong northwest winds that will deliver the Arctic blast, Maue said. There's no warming effect from the Gulf to counteract the cold air, he said.
Even places accustomed to mild and warmer winters will be affected early next week, including Atlanta where Tuesday's high is expected to hover in the mid-20s.
Sunday's NFL playoff game in Green Bay could be among one of the coldest ever played -- a frigid minus 2 degrees when the Packers and San Francisco 49ers kickoff at Lambeau Field. And ice skaters in Des Moines, Iowa, won't be able to use an outdoor rink, as officials decided to shut it down Sunday and Monday.
States are trying to get ahead of the storm, with Minnesota calling off school Monday for the entire state -- the first such closing in 17 years -- as well as the Wisconsin cities of Milwaukee and Madison.
Though this cold spell will last just a few days, it likely will freeze over the Great Lakes and other bodies of water, meaning frigid temperatures probably won't go away for the rest of the winter, Maue said. He also noted that it's relatively uncommon to have such frigid air blanket so much of the U.S., maybe once a decade or every couple of decades.
But so far, this winter is proving to be a cold one.
"Right now for the winter, we will have had two significant shots of major Arctic air and we're only through the first week of January. And we had a pretty cold December," Maue said.
Associated Press Writer Seth Borenstein in Washington contributed to this report. Contact Carson Walker at http://twitter.com/carsonjw
Wind chill: http://1.usa.gov/19FjvpT