Residents of Grand Forks, N.D., started their Wednesday with a temperature of minus-13 degrees and a wind chill of minus-49. Temperatures fell from near freezing to minus-9 in six hours amid 50 mph gusts and a "ground blizzard," the edge of bone-chilling Arctic air that's sweeping east.
The deep freeze will mark the coldest stretch of the season for some, with temperatures plummeting more than 40 degrees in 12 to 24 hours in many spots. Grand Forks hit a low of minus-28 early Thursday (some locations nearby fell as low as minus-37) as wind chill alerts stretch across much of the Upper Midwest and Northern Plains.
The National Weather Service warned that "the dangerously cold wind chills could cause frostbite on exposed skin in as little as 10 minutes." And the wind chill in northern Minnesota fell as low as minus-50 early Thursday.
Eventually, this intense, albeit brief, icy air mass will make it all the way to the Mid-Atlantic and New England — though in a moderated form.
Along the cold shot's southern periphery, moisture from the Deep South was helping make for a narrow strip of snow from the Chicagoland area to Maine. Earlier on, a so-called ground blizzard had raged in the Red River Valley of the Dakotas, where strong winds lofted previously fallen snow.
The instigator behind the impending cold is not a low-pressure system, the type of setup usually associated with unwelcome weather — including storms. Instead, the culprit for the cold is a dome of high pressure sagging south from Manitoba, Canada. The air it transports has origins as far away as the East Siberian Sea in the Arctic Ocean.
That high-pressure air Thursday morning was anchored over the Dakotas, spilling the coldest air south over the Upper Midwest, Corn Belt and central/northern Plains. Minneapolis plunged to minus-10 (with a wind chill of minus-30) and Kansas City dropped to 3 degrees early Thursday, the coldest temperature observed there this season. The temperature fell swiftly since midnight, at which time the mercury stood at 19 degrees.
In Omaha, the temperature fell to minus-4 overnight, also its coldest reading of the season. It's nowhere near a record though — the city hit minus-22 degrees on Feb. 13, 1905.
The cold front had made it as far south as Oklahoma by Thursday morning. Broken Bow, in the state's southeastern corner, stood at a comparatively balmy 40 degrees, while Newkirk, about 275 miles to the north-northwest, had nose-dived to just 10 degrees.
By Friday morning, the high will be anchored over the central Mississippi Valley as it inches into Illinois. Morning lows hit minus-7 in Sioux City, Iowa, and minus-27 in Park Rapids, Minnesota, on Thursday morning. The most severe cold will soon head toward the Great Lakes. Chicago is forecast to approach zero degrees early Friday morning. The Windy City has not dipped below 2 degrees this season.
Indianapolis and Detroit could also find themselves in the single digits to start their Friday.
Ahead of the cold, a bit of light snow had developed along the southern and eastern fringes of Lake Michigan.
In the East, cuddle weather arrives just in time for Valentine's Day. The abrupt cold front will pass through Washington, Philadelphia, Baltimore and New York on Friday. That will make early Saturday the chilliest.
In Plattsburgh, N.Y., it was 32 degrees as the sun rose Thursday morning; on Friday, it could be 5 degrees below zero.