The polar vortex has weakened and is in the process of splitting, AccuWeather Lead Long-Range Meteorologist Paul Pastelok explained earlier this week. When the polar vortex is in a strong phase, it tends to hover near the North Pole and the coldest air stays locked up near and north of the Arctic Circle. But, when the polar vortex weakens, there is often a southward discharge of much colder air in part of the U.S.
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