Dust off your hoodie.
After a mild December, a polar vortex is set to send an arctic blast into the United States later this week.
“That polar jet is going to be pushed further south, and can you imagine what that's going to do? It's going to open the freezer door,” said FOX Weather meteorologist Kendall Smith. “So all that cold arctic air that's trapped right over Canada, right over the North Pole, is going to blow directly into Arctic Circle 48.”
This will likely be the coldest air ever felt across the Lower 48 this winter, according to the FOX Prediction Center.
Cold air will begin in the western West later this week and move into the central United States early next week.
The cold air will continue for a while.
How cold will it get?
Temperatures over the weekend could drop into the 30s to 50s below average for this time of year in some locations.
Wind chills can approach -50 degrees in some places.
Temperatures in Minneapolis, Kansas City, Little Rock, Arkansas, Nashville, Tennessee, and Chicago will remain well below average through January 18, according to the Climate Prediction Center's temperature outlook.
Why are winters so warm and what is changing?
El Niño is partly to blame for the warm winters that the United States has had so far.
According to NOAA, during El Niño winters, temperatures in the northern United States are typically warmer and drier than average. The jet stream generally flows from west to east.
“We were pretty lucky for a good part of December and into early January, but now we've kind of turned the page, completely flipped the script, so to speak,” Smith said. Told. “Because now we're starting to see cold air trapped over Canada and the Arctic. That's going to start to change.”
About two weeks ago, the Arctic experienced a sudden, small-scale stratospheric warming.
They wrote that the air in the stratosphere, a layer of Earth's atmosphere about 30 miles above the Earth's surface, warmed by 55 degrees over six days. Amy Butler, NOAA Chemical Science Institute. As a result, the polar vortex winds weakened.
Approximately every year, weather phenomena in the lower atmosphere send strong atmospheric waves into the stratosphere, where they interact with the polar vortex.
A polar vortex is a belt of strong winds that orbits the North Pole. The constant steady rotation of these winds locks the Arctic atmosphere in place.
When the wind weakens and becomes unstable, the vortex wobbles, just like the top.
According to Judah Cohen, an atmospheric scientist at Verisk Atmospheric and Environmental, stratospheric weather can lead our weather by up to two weeks.
“The collapse of the polar vortex is called sudden stratospheric warming, where there is a very dramatic warming in the north pole of the stratosphere, and then the polar vortex moves south, away from where the north pole is normally located. “I do,” Cohen said. “The cold air can then move south, and then often manifests itself as a negative Arctic Oscillation at the surface.”
During the Great Texas Freeze in February 2021, the Arctic Oscillation reached its lowest and most negative value in eight years.
According to NOAA, the nor'easter is also associated with a negative oscillation phase in the Arctic.
How long will the dangerous cold last?
After a week, it's still unclear how long the cold air will remain in place.
“However, considerable uncertainty remains about how the polar vortex will evolve after mid-January,” Butler wrote. “On the other hand, there are signs that even this small warming could predispose some regions to colder weather over the coming weeks. Stay tuned!”
