"A polar vortex (also known as mignogno cyclones, polar vortices, Arctic cyclones, sub-polar cyclones, and the circumpolar whirl) is a persistent, large-scale cyclone located near one or both of a planet's geographical poles. "
Well the North Pole is not in Minnesota USA. Unless there was a huge geographical shift.
More correct is the following definition still from Wikipedia:
"The Arctic vortex has two centres, one near Baffin Island and the other over northeast Siberia. In the southern hemisphere, it tends to be located near the edge of the Ross ice shelf near 160 west longitude.When the polar vortex is strong, the Westerlies increase in strength"
So the current US weather is not a polar vortex, but something rather more exotic, more a propos to a lesser worldwide winter days when the jet stream gyrates weirder than usual, it has more to do with the snow laden ground night sky being clear and the day time with fewer sun hours, it is the Cold Temperature North Pole (CTNP) .
Definition of CTNP: Center of the coldest place on Earth. It is usually one area emerging from a synergistic effect which is the culmination of the lost of heat to space, it is not North or South Pole Centric. But may have secondary, isolated spots. The circulation around a CTNP is counterclockwise.
By definition a Cyclone at center often without clouds. Its location is calculated by the equivalent temperature of the entire temperature of the troposphere, or the Density Weighted Temperature. In lack of actual DWT charts we must contend with 600 mb charts which often mathematically represent the temperature of the entire atmosphere, since 600 mb charts are not often published, either 500 or 700 mb charts may be used. In this example
a US 700 mb map, the center of the 2nd coldest measured atmosphere in the world is over Illinois! @ -33.6 C #2 CTNP. Ust-Barguzin Siberia has the coldest # 1 CTNP cell at -34.9 C.
While the Wikipedia cited Baffin Island "vortex " is CTNP3 #3 coldest. CTNP's further to the South do not last long, disappear rather quickly. While Arctic CTNP's last longest, sometimes months. But the reason why central North America is cold today was because a few days ago there was another CTNP over Southern Quebec, which drew colder air southwards to its West. Warmer air and cyclones were drawn in to its North . The Southern Quebec CTNP warmed substantially and is well over Newfoundland on 6 January 2014. WD 6 Jan 2014.