Polar Vortex Round 2? - KMSP-TV

Polar Vortex Round 2?

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By Derek Kevra
FOX 2 Meteorologist

(WJBK) -- You likely heard the term "polar vortex" a lot… but do you know what it really means?  Let's jump into a little science lesson.

The polar vortex is nothing new.  In fact, quite the opposite.  Ever since we've had weather, we've had the polar vortex.   In the simplest terms, it is an area of low pressure high in the atmosphere that rests over the North Pole (in fact, over the South Pole too).   It is always there and gets strongest in the winter.

Obviously the air in the polar vortex is quite cold (duh).   From time to time, the polar vortex will be forced from its normal position and move south.  Likewise, a chuck of the cold air may break free and travel south.  Whatever the case, the outcome is the same… polar air infiltrates southern regions.

A couple weeks ago the second scenario happened:  a big chunk of very cold air broke off and moved our way.   It stuck around for about 48 hours before kicking east.  This time around a different situation is setting up.  Is it technically a "polar vortex"?  Well, no, not really.  But it's still quite interesting to talk about.

Surrounding the polar vortex is a lot of cold air that is technically different than that of the P.V.   (See the image below)

This week an area of high pressure is building in the Pacific Northwest (topical joke: nothing to do with Richard Sherman! Ok, I'm done) which is pushing the jet stream north. 

As it does this it is allowing the arctic Canadian air to flood south, making for a cold snap. 

The problem this time around is some strong high pressure in the Atlantic Ocean is keeping the cold air bottled up right over us.  Think of it as a sandwich… the high pressure is the bread, keeping the cold air (which is, say sliced turkey) held in place directly over us. 

This is the reason we are in for a prolonged cold snap this time around.  Morning lows all the way through Friday will range between -5 and 5 degrees.

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