The Chinook is a Warm Wind
East of the Rockies, the Warm Wind From the West is a Chinook
The Chinook wind is a warm, drying wind blowing down from off of the Rocky Mountains in western Canada and the inland northwest of the United States.
The Chinook wind is a warm wind blowing off of the Rocky Mountains in the western Canadian province of Alberta and the state of Montana. First Nations people called it Snow Eater.
The General Picture of How Moist Air Moves from West to East
On a map of North America, in Canada the Rocky Mountains form the boundary between the provinces of British Columbia (on the west) and Alberta.
British Columbia has the Pacific Ocean as its western boundary. The warm Pacific water is absorbed by the air masses on the west coast.
This air then rises as it flows from west to east, away from the ocean and toward inland Canada.
The same pattern holds in the north-western United States. The cities of Seattle, Washington, and Vancouver, British Columbia are not far apart and share similar weather.
How the Mountains Affect the Air Mass
All things being equal, a gain in altitude produces a drop in the temperature of the air, at a rate of 3 Fahrenheit degrees for every 1,000 feet of altitude gained.
As air cools, its capacity to hold moisture becomes less, and the result is precipitation - rain, snow, fog - on the uphill slope of the mountains. In Canada and the U.S. Pacific Northwest, some of the biggest trees and lushest forests are found in these very wet places.
The air mass continues moving from west to east, but after it crosses a mountain range and starts down the other side, the air is dry. It heats up as it descends, gathering up the moisture on the lee side of the mountains.
Aerial photos of mountain ranges often show a dramatic difference in the vegetation on the wet side of the mountains as compared to the dry side.
What a Chinook is
The Chinook wind in southern Alberta and Montana is a well-known regional climatic phenomenon which amazes weather watchers and residents.
In the middle of winter, the air temperature might rise by 20 Farenheit degrees or more in the space of a day. It can be bitterly cold in the morning and balmy by afternoon. The snow can melt away leaving the ground dry in the space of a few hours.
The Chinook wind often moves at a high speed. It is most noticeable in winter, when its warm temperature contrasts so dramatically with the ambient cold air.
The Chinook is one of those winds from off the mountains, famous in legends around the world, but known by many names: Mistral, Foehn, Santa Ana wind are some of them. Not all of these winds are warm. The Mistral, for example, is a cold wind. However, like the Chinook it flows down off of the mountains.
Chinooks and Health
Every legendary wind has probably been blamed for causing people to act strangely - even to go mad. While the Chinook does not have the dire reputation of the Mistral on this account, there are many people who claim the wind affects their health. It's not unusual to hear people say the Chinook gives them a headache, although such people are a small minority of the population.
Chinooks also have a mood-lifting effect. In the middle of winter, the presence of a Chinook in southern Alberta means a relief from the grip of winter's cold, and perhaps a day when the snow will shovel itself.
Chinooks and Plants
The Chinook wind has a drying effect which is not particularly good for plants. There is an art to gardening in Chinook country. It includes watering trees and shrubs very well in the fall, and wrapping tender plants (e.g. rose bushes) to prevent their drying out. The native plants of the region have adapted to the cycle of warm and cold air alternating over the course of a winter, and tend to be somewhat drought-resistant.
Gardening Under the Arch is the name of a local gardening book, produced by people who have learned to work with Nature's fickle ways in the Chinook region of southern Alberta.
The Chinook Arch
The Chinook almost always is accompanied by a band of flat cloud up high in the sky. Locals call this the Chinook arch. It can be a terrible tease to farmers hoping for a little more moisture on the fields, because these clouds drop no rain and the Chinook wind itself sucks the moisture off the fields and out of the soil.
For photographers and others who love the beauty of nature, the Chinook arch can be a stunning sight, particularly at sunset when the clouds take on shades of yellow, orange and red.
