WASHINGTON — The polar vortex dumped snow and cold Arctic air on parts of the northeast United States and Canada over Mother's Day weekend, the Associated Press reports.<br /><br />According to the National Oceanic and Atmospheric Administration, the polar vortex is a band of low pressure Arctic air normally centered around the North Pole. It is located in the middle and upper tropospheres and extends into the stratosphere.<br /><br />The polar vortex is usually held in place by a current called the jet stream. Disturbances in the jet stream can push frigid, wintry air to parts of Canada and the U.S., while high-pressure systems of warmer air bulge northwards elsewhere.
