Chinook winds blow in from the Pacific in late winter and early spring. Their moisture evaporates as they pass over the Rocky Mountains. Once the winds come down from the mountains onto the high plains, the air can be quite mild and extremely dry,. When a Chinook takes effect local temperatures can warm up from as low as 5 degrees below zero to 60 or 70 degrees Fahrenheit. The air is so dry that when it hits snow, it sucks up the moisture, changing the snow directly into water vapor, bypassing the liquid phasethat slushy phase-- entirely. Called sublimation, this is a common way for snow to disappear quickly in arid climates. www.weathernotebook.org/transcripts/2001/03/14.html

A Chinook wind is a dry warm to hot wind that flows down the leeward (eastern) side of the Rocky Mountains. It is a type of katabatic wind. The Chinook wind is caused by pacific winds climbing the windward (western) Rocky Mountains and loosing moisture and temperature as it climbs. This brings moisture and causes storms on the windward side of the Rockies but as it crests the mountains it is devoid of moisture and as this dry air descends the leeward side of the mountain it rapidly increases in temperature and so will dry out and warm up this leeward side and this area east of the Rockies. It causes snow to sublimate (turn from solid state to a gaseous state). It can dry out plants and soil and will sometimes trigger early sprouting that will then be killed off in a freeze or will not have adequate water as this usually occurs during the cold season and the ground stays frozen or does not get the moisture from the sublimated snow. It can kill off some types of plants and trees that cannot cope with rapid temperature change and can melt valuable snow pack that is a water source later in the season. It has been known to cause strange attitudes and reactions in animals and people in the effected areas too. During a Chinook wind a cloud cap often sits on top of the mountains while the hot wind comes down the mountain and across the plains. The heat will melt the snow and can often trigger an “Indian Summer”. The name Chinook comes from the native Chinook tribe and means “Snow Eater”. They’ve been known to raise temperatures 50+ degrees Fahrenheit in just a few minutes. People find a Chinook to be a pleasant break from winter but, its effects on people often can seem like a city of manic-depressives that will be giddy and happy or cranky and testy. It’s a strange phenomenon that’s a neat experience but can be devastating to the area. Chinooks can cause “Red Belt” an area of dead or damaged trees and vegetation caused by the rapid dry out. It can cause avalanches by making large areas of snow unstable. The dryness and heat creates a perfect fire hazard environment and can spread fires…well … like wildfire. It can even cause wire fences to become electrified due to strong positive electrical charges in the dry hot wind. The Chinook is the katabatic wind of the Rocky Mountains but there are other similar winds found all over the world: In the European Alps there is the Foehn. In the Andes the Puelche. In Argentina they have the Zonda and Pampero. In India they have the Bhoot. In Hawaii there is the Kona. Let’s not forget the Santa Ana in California. As a Rocky Mountain native I can tell you it is a rather neat phenomenon and hopefully you’ll get a chance to experience it… when your teeth are chattering and all you want is a warm blast of air.