What Is the Polar Vortex?

Denver (CBS)- The term "Polar Vortex" has been widely used to describe the dangerously cold temperatures that have been plunging into the U.S. from Canada. In fact, some of the wind chill readings from northern Minnesota were as cold as 70 below zero on Wednesday morning!!

The term "Polar Vortex" has been around in forecasting literature since the 1800's but, has become popular in the media in the last few years.

The Polar Vortex is a big, cold area of low pressure that forms over the north pole during Winter. The vortex part of this system refers to the counter-clockwise rotation of the low. Typically, this cold air is contained by a jet stream flow called the Arctic Oscillation. This is when the Vortex is stable and the bitter cold stays bottled up around the poles.

But, on occasion the oscillation will get a ripple or a wave that opens the door for the Arctic deep freeze to ooze south into the U.S. This is termed an unstable or wavy Vortex.

This current wave is bringing some of the coldest air in generations to the mid-west.