What the heck is a polar vortex?

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Americans in two dozen states from the Midwest to the Southeast and Northeast are shivering this week courtesy of a distorted polar vortex. The rush of cold air it's sending southward is the biggest visitor from the North Pole since Santa Claus.http://feeds.feedburner.com/~ff/rss/cnn_us?d=yIl2AUoC8zA</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=drLieyfksMc:ly-NqsmelJE:yIl2AUoC8zA) http://feeds.feedburner.com/~ff/rss/cnn_us?d=7Q72WNTAKBA</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=drLieyfksMc:ly-NqsmelJE:7Q72WNTAKBA) http://feeds.feedburner.com/~ff/rss/cnn_us?i=drLieyfksMc:ly-NqsmelJE:V_sGLiPBpWU</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=drLieyfksMc:ly-NqsmelJE:V_sGLiPBpWU) http://feeds.feedburner.com/~ff/rss/cnn_us?d=qj6IDK7rITs</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=drLieyfksMc:ly-NqsmelJE:qj6IDK7rITs) http://feeds.feedburner.com/~ff/rss/cnn_us?i=drLieyfksMc:ly-NqsmelJE:gIN9vFwOqvQ</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=drLieyfksMc:ly-NqsmelJE:gIN9vFwOqvQ)
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