An Early Chinook: When the Snow Eater Comes

The wind came in around midnight, warm and dry. I heard it, sort of dimly noted that the heater had not run for a while, and went back to sleep. Indeed, come dawn, the last of the snow had completely disappeared from yards, including the remains of snowmen. Now abandoned, damp, knit hats and scarves lay on the lawn, empty of their former contents. The chinook wind had arrived.

Chinook wind takes the name from the Chinook people of the Pacific coast. The usage inside the Rocky Mountains is taken from a different Blackfeet word meaning “snow eater.” One the coast, the wind [chin-ook] blows in from over the Pacific and brings warmer air and lots of moisture. The chinook wind of the inland plains [shin-ook] devours moisture as it races down the slope of the eastern front of the mountains. The classic chinook is that of Montana and Alberta, as Ian Tyson so eloquently described in “Springtime.” Down in the High Plains, it tends to be more out of the southwest, but does the same thing as the wind blows downslope off the southern Rockies.

Downslope winds tend to be warm, and dry, no matter what you call them. Image from:

We don’t get that many true chinook winds. In winter, our winds tend to be northwest (slightly mild to bitterly cold), due north (good Lord, that’s cold!”) northeast (“Not so bad, and the snow’s nice”) and south. (“Go back to sleep, plants, please go back to sleep!”)

This past one melted the snow in the night, leaving moist spots in the lawn and garden. The snow all sank in for once, and will help a lot with the prospects for a solid start to the winter wheat crop. There are hints that we might get more moisture this coming week. Or we will get howling winds and no moisture. It just depends on what happens when the forecast computers shake the Magic Eight Ball™, er, that is, run the next model.


5 thoughts on “An Early Chinook: When the Snow Eater Comes

  1. Adiabatic cooling rate.
    For anyone who’s unfamiliar with the mechanics…
    When air is forced upwards by encountering a mountain range, it cools at a rate of 5-1/2 degrees per thousand feet elevation*.
    Warm air holds more moisture than cool air. When the air cools enough to reach 100% humidity, it sheds moisture as precipitation, and cools at the lower rate of 3-1/3 degrees per thousand feet*.
    When it tops the mountain and starts descending, it immediately starts warming, and because warmer air can hold more moisture, it warms at the rate of 5-1/2 degrees per thousand feet the whole way down, creating the rain shadow effect.

    The strong, hot downslope wind is a separate, but related phenomenon, and I honestly don’t remember the details very well. It’s the Chinook Wind in the Rockies, the Santa Ana Wind in California, and likely a lot of other names in other places.

    I can tell you that it’s rather surreal to watch a couple feet of snow disappear in a few hours of a roaring Chinook Wind. It seriously messes with your head. Not to mention, it’s suddenly warm, but wind chill remains a thing…

    *These are the values the internet currently provides. I was taught 4.6 and 2.3 more than thirty years ago (I regret doing that math), so expect the numbers to be ironclad or precise.

  2. In SW Oregon, we get a similar dry wind when the Chetco Effect is in play. Chetco is the river in SW Oregon, and when a well-placed Low sets the winds from the NE, it’s warm hot and dry. Brookings, at the SW coast, is usually moist and cool, frequently in the 50s in the summer and winter. When the Chetco Effect is in play, it can find the 80s in summer. The Effect isn’t so noticeable in winter.

    I live a bit less than 1000′ below and east of the Cascades passes, so any moisture coming from due west gets dumped in the mountains. OTOH, cold storms from the NW can make it through the gaps, and SW to S is pretty open to the wet snow I call Cascade Concrete. Seems to be a moot point this year; La Nina’s minions are pushing all the moisture either well north or well south of us. Sigh.

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