A blast of Arctic air gripped much of the central and eastern portions of the U.S. on Friday in sub-freezing temperatures well below normal for this time of year, setting records from Iowa and Michigan to New York.
The frigid weather pattern stemmed from a fluctuation in the clockwise circulation of polar air, also known as the polar vortex, that was drawing icy air from Canada into northern tier of the U.S., according to meteorologist Marc Chenard of the U.S. Weather Prediction Center outside Washington.
