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Chinooks - Snow Eaters

Chinook clipartA Chinook, or snow-eater, is a unique type of wind whose influence is especially strong in the Grasslands, although the effect can occasionally be felt as far north as Edmonton and as far east as Winnipeg. The influence of Chinooks are most apparent during the winter months and are very important because the temperatures of the interior are often so low during that period.  

A Chinook wind is the result of the extreme influence of the Rocky Mountains on air masses. The prevailing winds in western Canada are westerly and air flowing in from the Pacific often has a high moisture content. As Pacific air is forced over the Rockies, it expands, grows colder and loses its moisture in the form of precipitation. As the air descends to the plains it picks up speed, compresses, and warms up. As a result, its ability to hold water increases. When a Chinook hits southern Alberta the temperature may increase 20 degrees Celsius in ten minutes, and large volumes of surface and soil moisture can be lost very quickly. During the winter, a thick snow cover can be reduced to slush and water in a matter of hours. As the ground under the snow is frozen, the water from the melted snow cannot be absorbed by the soil, and is rapidly evaporated by the dry wind. This adds to the dryness of the region. Elsewhere in the province, the melting of the snowpack in the spring provides moisture that vegetation needs to start the growing season. In this region, snow does not generally stay on the ground very long. The sight of completely bare ground in the middle of winter is common in the Grasslands Natural Region. Chinook winds greatly influence the climate, vegetation, and resource development of the Grasslands Natural Region.

Reprinted from Alberta Natural Regions Poster Series Manual with the permission of Alberta Provincial Parks and Protected Areas.

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