I thought this was interesting. This is the first time I have heard the term "Polar vortex", but apparently it has been around for many years. http://wonkwire.rollcall.com/2014/01/30/theres-global-warming-cold/
From what I have been reading the polar vortex is always there, it's the permanent circulation in the polar regions but every so often it slips south and brings colder air into Canada and the U.S. Sometimes it sets up the conditions for a McFarland Signature to form which brings the cold air all the way down to Mexico.
