Residents across the western Plains of the U.S. northward to the western portions of the Canadian Prairies are well aware of the term chinook wind. Chinook winds are most common across southern Alberta, where they have an average occurrence of 30 to 35 days per year. These winds bring mild weather, but also can bring strong, damaging winds.
The term chinook comes from the Chinook people who once lived in the Columbia River region of the Pacific Northwest. These people claimed that the term means "eater" and during current times the chinook is sometimes called a "snow eater". Meteorologists refer to the chinook as foehn winds that typically blow from the West, cross the Rockies, then move downhill onto the Prairies.
These winds deposit much of their moisture on the west slopes of the mountains as the wind moves uphill, but as the winds move over the ridge of the mountain range and head downhill the air dries out and warms by an average of 5.5 degrees F (3.3 degrees C) per thousand feet. This process results in weather much milder to the east of a mountain range than to the west at the same elevation.
These winds tend to accelerate as they move downhill, sometimes reaching or exceeding hurricane force in some areas.
Very cold weather has been in place nearly nonstop across the Prairies during the past six weeks or so, but for the next several days it appears that a few episodes of chinook winds may bring much milder weather than we have seen for some time. The effect of the chinook diminishes the further one moves away from the mountains, so eastern Saskatchewan and Manitoba may not reap as much of a benefit from the warming west winds.
The higher temperatures and dry air could melt or evaporate some of the protective snow cover across the Prairies during the next several days, but it does not appear that all of the snow will melt. A return of colder weather is indicated by the middle of next week as arctic air once again begins to shift south from Western Canada. The return of colder weather and more of an upslope wind flow could be accompanied by some snow at that time, but no major storms are yet expected.
Further down the road, some of the climate computer models indicate that very to extremely cold weather may return to the Prairies around the middle of January and it could last for much of the remainder of the month. So, for the time being, enjoy the break in the arctic cold and hope that when it does turn colder some snow returns to help protect winter grain crops and bring moisture for spring.
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