This cold blast could be relatively short-lived, with a return to more typical wintry temperatures by later in December.
What is the polar vortex? How it can impact snow, freezes in the U.S.
The polar vortex is a large area of circulating cold air above the North Pole. Strong winds keep it contained, but when it weakens, it can wobble and stretch.
Ready for some serious cold?
The planet’s most extreme cold air will be barreling into the central and eastern United States this coming weekend “like a wrecking ball,” said Weather Trader meteorologist Ryan Maue in a post on X on Dec. 9.
Maue called it a “textbook ‘Polar Vortex’ mega-dump of western Canadian cold.”
“Some of the coldest, if not the coldest, temperatures across the entire globe will cover the central and eastern U.S. over the weekend and into early next week,” said climatologist Judah Cohen, a research scientist at the Massachusetts Institute of Technology, in an email to USA TODAY.
“It also seems that the most expansive and continuous area of below normal temperatures across the globe will extend from Alaska to the eastern U.S. this upcoming week,” he said.
But in a shred of good news for those who hate the frigid weather, this cold blast could be relatively short-lived. Forecasts expect a return to more typical wintry temperatures by later in the month and into the new year as the polar vortex retreats back to the north – and La Niña returns to prominence.
How cold will it get?
In Chicago, for instance, wind chills could “make a run at 20 below at some point this coming weekend,” the National Weather Service said. Even colder wind chills approaching 45 below are possible in the Dakotas.
Wind chills that low can cause frostbite to exposed skin within 10 minutes, the weather service said.
Temperatures will dip to as much as 30 degrees below the seasonal average in many locations, according to the weather service.
Cold courtesy of the polar vortex
The blast of cold will come from the polar vortex, which is a large upper-level, low-pressure area or circulation that typically resides above the Arctic Circle. When this storm is strong, it tends to keep the coldest air in the Northern Hemisphere locked up over the pole.
“However, when it weakens or stretches, frigid air can move south,” said AccuWeather meteorologist Alex Sosnowski in an online forecast.
Pulses or “lobes” of the polar vortex can pinwheel south over the United States, which is what will happen this week, according to Maue.
This type of on-again-off-again behavior from a disrupted polar vortex – with “waves” or “lobes” spinning off down into the United States, bringing transient cold blasts – isn’t unusual, AccuWeather meteorologist Paul Pastelok told USA TODAY.
He said this particular lobe should persist up until “the 18th or 19th of the month.”
“We believe that two to three more rounds of intense cold are possible from the Midwest to much of the East, spanning Dec. 10 to 19,” Pastelok said. “There is a chance for a frost or freeze late next week as far south as central Florida.”
When will the U.S. get relief from the cold?
After that, the vortex should retreat toward the North Pole for the immediate future, experts predict.
“There’s a change in the pattern globally, with some moderation in temperatures [for the U.S.] later in December and into January,” Pastelok said.
Cohen agreed, saying, “I believe that the entire cycle of a weak or disrupted polar vortex that began at the end of November is coming to its conclusion by the end of next week… Clearly, the polar vortex is strengthening and some period of milder weather in the central and eastern U.S. looks inevitable to me.”
‘More normal pattern of La Niña’
With the polar vortex in retreat later this month, U.S. winter weather will be guided more by natural climate troublemaker La Niña, Pastelok said.
“This should favor a return to the more normal pattern of La Niña,” he said.
According to the Climate Prediction Center’s winter forecast, which used La Niña as a primary guide, a warmer-than-average winter is most likely across the southern tier of the nation, as well as in California and along much of the East Coast and Florida. Colder-than-normal conditions are expected in the Pacific Northwest and across the upper Midwest.
