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    What is a Polar Vortex?

    By Jillian MacMath, AccuWeather.com Staff Writer
    November 12, 2014; 2:25 AM ET
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    "The polar vortex is not a recently discovered phenomenon; in fact, it has been talked about in the meteorological world for decades," AccuWeather.com Senior Meteorologist Bernie Rayno said.

    A polar vortex is a large pocket of very cold air, typically the coldest air in the Northern Hemisphere, which sits over the polar region during the winter season.

    The frigid air can find its way into the United States when the polar vortex is pushed farther south, occasionally reaching southern Canada and the northern Plains, Midwest and northeastern portions of the United States.

    A large, powerful high pressure system originating in the Eastern or Western Pacific and stretching to the North Pole is required to displace the pocket of cold air.

    "These high pressure systems can reach Alaska, but it is not typical to stretch all the way to the North Pole," according to AccuWeather.com Senior Meteorologist Brett Anderson.

    The vortex is capable of delivering subzero temperatures to the United States and Canada for several days at a time.

    When the strong air from the Eastern or Western Pacific weakens and falls apart, the polar vortex will retreat into place near the North Pole.

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