Chinooks

Chinooks are strong warm winds the Plains Indians called

A Chinook is an unusually strong westerly or south westerly wind that sweeps over the Rockies and onto the plains states of the Wyoming, Colorado and Montana. These warm, dry winds are also very common in regions of western Canada, particularly in the extreme southwestern corner of the province of Alberta. The Chinook is named after the Chinook Indians who lived along the Columbia River, and who were the first people to tell stories of "the great south wind", or, in their language, the "Snow Eater".

Chinooks are formed when very moist air moves in from the Pacific Ocean and condenses, depositing heavy rain on the western, or leeside slope of the Rockies. This air, already warm, continues heating, rushes over the mountains and surges down the eastern slopes, gaining velocity and eventually turning into strong winds. These warm winds usually maintain a speed of between 40-60 miles per hour, sweeping down mountain valleys and onto the plains, creating drastic and almost instantaneous temperature changes. Chinook winds have been known to melt a foot of snow or more in a single day. Temperature variations can be extreme, as much as 20-25 degrees Celsius (or 36-40F) in an hour. These mild winds last from a few hours to a few days, sometimes even several weeks.

Some of the most extreme Chinook effects have been observed in the Crowsnest Pass region in southern Alberta. This area records around 30-35 Chinook days per year. In 1962 the weather office at Pincher Creek recorded a temperature of 20 degrees below zero. Between midnight and 1AM a welcome Chinook blew in and in a little under an hour the temperature had risen by almost 60 degrees.



In this same area the Chinook winds have been recorded at gusts exceeding 120 kilometres an hour, near hurricane velocity. Railcars have been flung off tracks and semi-trailer units tipped over. It's not uncommon for the RCMP to shut down certain sections of highways until the winds have abated. Nor are the Chinooks always as warm as predicted. Instead of melting the snow, the gusts set snowdrifts in motion, creating "white-outs" that are as bad or worse than any plains blizzard. When these winds gust for longer than a day or two, fields are left without protective snow cover and precious topsoil begins to move and drift, and again, obscure visibility, sometimes as much as 100%.

Lingering Chinooks can also cause trees and tulips to become confused and think it's Spring and to blossom in January or February. Unfortunately this mild weather is almost always followed by a cold snap where early blossoms freeze. Gardening in a Chinook zone is a real challenge. Fruit trees are almost impossible to grow and rose bushes must be well protected to survive lack of snow cover and the fluctuating winter temperatures. Even then they often succumb to winterkill during a particularly harsh winter.

The neurology department at the University of Calgary has also conducted a study and concluded that high velocity winds are a cause of migraines. Seventy five patients were asked to keep dairies for 2 years. When their headache records were compared against meteorological data, it was concluded that sufferers did indeed experience migraines to a greater degree when high winds were a factor. Other people are affected by Chinooks in other ways: sleeplessness, mood swings or severe depression. Chinooks may also cause temperature inversions that trap emissions and pollution, making breathing very uncomfortable for people with asthma or other respiratory disorders. In Switzerland, where similar warm winds called "foehns" occur, law courts actually recognise that fluctuating

barometric conditions can drive people temporarily insane.

Winter Chinooks have also spawned their fair share of tall tales. What else did cowboys or early settlers have to do during those long, cold winter nights - or to flabbergast gullible greenhorns? There were stories of winter snows that were so deep that when people attended Sunday services the only hitching post they could find was the church steeple. They had to tunnel through the snow to get inside. While services were in progress a Chinook blew in. By lunch time the snow was gone, it felt like April and the settlers horses were dangling off the church roof.

Another tale tells of a couple travelling to Calgary on a winter trail across the open plains. Halfway there they were chased by a howling Chinook wind. The husband was riding in the front of the sleigh and drove his team hard to stay on the snow. If they got bogged down in the water and mud the Chinook would create, they could be stranded for days or weeks. When the couple arrived in Calgary, the man had frostbite and his poor wife, riding in the back of the sleigh, had sunstroke.

The early Blackfoot tribes that lived in what is now Banff National Park told this tale of the Chinook - the Great South Wind had a small blind daughter who remained in hiding somewhere in the mountains. Every so often during the coldest times of winter she would wander away from her safe mountain home and smile upon the frigid plains, turning harsh winter into brief spring. Sometimes she would stay and play long enough to make lilacs bloom in January; other times she passed by quickly and old man winter would return as suddenly as he had disappeared.

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