This past week, while the Inland Northwest was trapped under a veil of low clouds and fog, and all outside objects shimmered with a daily coating of fresh ice, it might be hard to believe that not too far away, at elevations above 3,500 feet, folks were walking around in short sleeves.
Folks in Billings, were doing just that earlier this week, where highs were in the mid-50s to low 60s. Calgary, Alberta, saw similar warmth. The same ridge of high pressure that kept us in the cold and fog, resulted in near record highs for several locations east of the Rockies. The key was being on the right side of the mountain range.
I’ve often talked about the effects that the Rockies and the Cascades have on precipitation amounts. On the windward side of the mountains, air rising over the terrain enhances precipitation resulting in a lush climate. In stark contrast is the leeward side of the mountains, where sinking air, all its moisture wrung out on the west side, continues to dry and warm as it descends in elevation.
This “rain shadow” effect results in much more desertlike conditions, such as what is seen across central Washington. Just as the terrain can affect precipitation, it can exert a great influence on temperatures as well. chinook winds, experienced just east of the Rockies, are a prime example of that.
How many times have you read stories about the latest blizzard to hit Denver, only to find out days later that temperatures were in the 50s and all their snow had disappeared? Similar scenarios occur in places like Billings, Salt Lake City and Calgary.
Chinook winds are responsible, and can result in drastic warming of as much as 50 degrees in a matter of minutes. The chinook is often called a “snow eater” because the warmth of the wind quickly melts snow, and the dryness of the wind contributes additionally to evaporating snow. The characteristics of chinook winds are due to the effect of downsloping. As air descends the mountains, the pressure increases, which results in compressional warming.
Unfortunately, the effects of chinooks are not always positive. Often times these warm winds can reach great speeds as they descend the mountains. Less than a month ago, chinook winds battered towns in the front range of the Rockies from Fort Collins to Colorado Springs, Colo. More than $2 million in damage was reported as downed trees toppled onto cars and power lines. Wind speeds were measured as high as 111 mph.
Regionwide, the warmth has ended for our neighbors in Montana. Though locally, we’re finally out of the foggy and stagnant weather pattern, we, too, will see a return to more active winter weather. It looks like snowy weather will be in the picture for the middle and toward the end of next week. Just in case you were starting to miss it.
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