Some of the coldest air the nation has seen in years is spilling down, spreading across the region as dangerously cold wind chill values become life-threatening to anyone caught in them. Approximately seventy percent of the continental US will see temperatures fall below freezing at some point this week.
This brutal cold snap is all thanks to the breakdown of something called the “Polar Vortex.” To keep it nice and simple, you can think of the polar vortex as a circulation of strong upper-level winds that usually are surrounding parts of the north pole.
These winds act to keep this bitterly cold air trapped into parts of the Arctic regions of the northern hemisphere.
When this circulation weakens or is interrupted by a change in wind speeds, for example, this circulation becomes more distorted. Once the circulation becomes distorted, the jet stream plunges very far south, allowing for sections of the frigid air associated with the polar vortex to spill southward.
The last notable visit from the polar vortex, which made headlines across the nation, occurred in the winter of 2014 as an arctic airmass impacted millions of people in North America.