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Upper Air Pattern (Polar Vortex) |
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WPC Surface Analysis Feb 14-17 (every 6-hours) |
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What caused the event? The record cold spell and extended period of wintry weather was caused by the upper level polar vortex dropping south from the north pole and then lingering over south central Canada for more than a week. This allowed cold arctic air to gradually spill southward into Texas. At the same time several upper level disturbances riding the jet stream moved through the area providing lift and moisture for winter precipitation. These disturbances show up as waves or dips in the lines that move in from the west. Ahead of each wave upper level lift increases and moisture is drawn up from the south. Since it was already so cold, this precipitation fell as snow, sleet, and freezing rain.