Glossary: Arctic Outflow
Arctic Outflow
Arctic outflow is only a concern for the west coast. Normally in Canada, air comes inland off the Pacific Ocean and flows from west to east carrying in mild and moist air. During an Arctic outflow, cold Arctic air comes down from the north and gets trapped on the western side of the Rockies. As more cold air pushes down, this parcel of air is pushed further south and forced into the valleys. Valleys with a west to east orientation, normally filled with mild moist air off the Pacific, are now filled with cold dry Arctic air. Weather-wise, an Arctic outflow sitting in these valleys can cause drastic changes in temperature.
There are two main concerns associated with Arctic outflows. First, Arctic outflows cool the air over the water near the shore. When the mild air tries to move onto the coast it collides with the cool air, causing snow or freezing precipitation. Second, high wind chill levels tend to result from cold air rushing out of the valleys.
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