THE SNOW EATERS

FACTS AND FICTION ABOUT CHINOOKS THAT OCCUR ON THE INTERIOR PLAINS

• What are Chinooks?• How are Chinooks created?• Legends and Folklore• What Do Chinooks Look Like—

The Chinook Arch• Where Chinooks occur• Historical Facts about Chinooks

TABLE OF CONTENTS

An Alberta Experience

• They flow off the mountain ridges, rushing winds that are very hot and very dry. Along the eastern slope of the Rocky Mountains, they have been called "Snow Eaters" but today are more commonly known by their First Nations name: Chinook.

What Are Chinooks?

• In popular myth, Chinook is supposed to mean "snow eater", as a strong Chinook can make a foot of snow all but vanish inside of one day. The snow partially melts, and partially evaporates in the dry wind.

• However, the true origin of the name is that "Chinook Wind" in the local language of the fur traders meant that the wind came from the direction of the country of the Chinooks (the lower Columbia River in British Columbia and Washington, i.e. from across the Rocky Mountains).

• A strong Chinook can make snow one foot deep almost vanish in one day. The snow partly melts and partly evaporates in the dry wind. Chinook winds have been observed to raise winter temperature, often from below −20°C (−4°F) to as high as 10°C to 20°C (50°F to 68°F) for a few hours or days, then temperatures plummet to their base levels.

How Chinooks Are Created• A chinook is a wind most notable in the northern high plains (Southern

Alberta) that brings in drier and warmer weather. One of the main reasons for the change in the weather is the sloped elevation. When air moves from the higher elevations of the west (mountains in the Cordillera region) it downslopes as it moves east. Since the air is downsloping the temperature and relative humidity of the air will change adiabatically. Sinking air warms at the dry adiabatic lapse rate. When this warmer air replaces a very cold polar air mass the temperature increase can be dramatic. Another name for the chinook is "snow eater" since the warm and dry air quickly melts and evaporates snow away that is on the ground. The air at the high elevations tends to be dry (low dewpoint). When air downslopes it dries the air even more since the relative humidity decreases. As the temperature of air warms as it downslopes the temperature and dewpoint diverge (dewpoint depression becomes greater). As the dewpoint depression increases the relative humidity decreases.

• A Chinook is produced by a downsloping wind (the wind is following the slope down the mountain). As air downslopes it warms adiabatically (the air cools when it rises in the atmosphere and warms up when it drops in the atmosphere) and decreases in relative humidity (loses moisture it becomes drier). The Chinook is common in the western foothills of Southern Alberta in winter.

Legends and Folklore• Among the native peoples,

one legend tells of a girl, Chinook-Wind who married Glacier and left with him to his land in the cold mountainous region where glaciers are found.

• She longed for the warm currents of the Pacific Ocean where she grew up and was told by spirits that they would come for her.

• They came for her in the form of snowflakes. They argued with Glacier and took Chinook-Wind with them to return to her home.

• This legend in a way parodies the events which happen during a Chinook wind. A light snow may fall from the unexpended wind not quite devoid of its moisture followed by the warming trend which both melts and sublimates the snow.

Legends and Folklore from Southern Alberta

• A man rode his horse to church, only to find just the steeple sticking out of the snow. So, he tied his horse to the steeple with the other horses, and went down the snow tunnel to attend services. When everybody emerged from the church, they found that a chinook had melted all of the snow, and their horses were now all dangling from the church steeple.

• A man was riding his sleigh to town when a chinook overcame him. He kept pace with the wind, and while the horses were running belly deep in snow, the sleigh rails were running in mud up to the buckboard. The cow that was tied behind was kicking up dust.

More Folklore

• A man and his wife were out during a Chinook. The wife was heavily dressed and the man was wearing summer clothes. When the couple had returned home, the man had frostbite, and the woman had heatstroke.

What do Chinooks Look Like?Below is a Chinook Arch over Calgary

The Chinook Arch• One of the most striking

features of the chinook is the chinook arch, which is a band of stationary stratus clouds caused by air rippling over the mountains due to orographic lifting. To those unfamiliar with the chinook, the chinook arch may look like a threatening storm cloud at times. However, they rarely produce rain or snow. They can also create stunning sunrises and sunsets.

• The stunning colours seen in the Chinook arch are quite common. Typically the colours will change throughout the day, starting with yellow, orange, red and pink shades in the morning as the sun comes up, grey shades in the mid day changing to pink/red colours, and then orange/yellow hues just before the sun sets.

Chinook Arch Over Calgary

Cochrane Alberta

Historical Events and Facts

• Chinooks are most prevalent over southern Alberta in Canada, especially in a belt from Pincher Creek and Crowsnest Pass through Lethbridge, which get 30 to 35 chinook days per year on average. Chinooks become less frequent further south in the United States, and are not as common north of Red Deer. But they can and do occur as far north as Grande Prairie in northwestern Alberta and Fort St. John in northeastern British Columbia.

• The most impressive chinook winds blowing off the Rockies can reach speeds of between 65 and 95 km/h (40-60 mph) with gusts exceeding 160 km/h (100 mph). When blowing at those speeds, the chinook can tip railcars off the tracks and blow semi-trailer units off the road.

• In Lethbridge, Chinook winds can gust in excess of hurricane force (120 km/h or 75 mph). On November 19, 1962, an especially powerful chinook there gusted to 171 km/h (107 mph).

• When, on February 25, 1986, a chinook descended on Lethbridge, Alberta with winds gusting to 166 km/h (104 mph), it fully removed a snow pack of 107 cm (42 inches) in depth in eight hours. Lethbridge was left with substantial wind damage and new lakes standing in the surrounding fields and pastures.

• Trains have been known to be derailed by chinook winds there. During the winter, driving can be treacherous as the wind blows snow across roadways sometimes causing roads to vanish and snowdrifts to pile up higher than 1 meter. Empty semi trucks driving along Highway 3 and other routes in Southern Alberta have been blown over by the high gusts of wind caused by chinooks.

• Impressive as the chinook is as a wind, the temperature changes it brings can be astonishing, often as much as 20-25 Celsius degrees (36-45 F degrees) in an hour.

• The greatest chinook temperature jump ever recorded occurred on January 22, 1943, when a chinook shot the temperature in Spearfish, South Dakota, from a chilling minus 4oF (-20oC) at 7:30 AM to 47oF (8.3oC) just two minutes later!

• In Pincher Creek, Alberta, a chinook jacked the temperature 21 Celsius degrees (37.8 F degrees) in four minutes on January 6, 1966.

• Four years earlier in Pincher Creek AB, the temperature rose by 41°C (from -19°C to 22°C) in one hour in 1962.

• Calgary also gets many chinooks - the Bow Valley in the Canadian Rockies west of the city acts as a natural wind tunnel funneling the chinook winds.

• In February 1992, Claresholm, Alberta hit 24°C (75°F) - one of Canada's highest February temperatures.

• No wonder, the chinook has the reputation its name "Snow Eater" engenders. The deadly-to-snow combination of high temperature and dry air rushing by at high speeds can literally remove a foot (30 cm) of snow in a few hours. And it may not just melt the snow but evaporate it as well, often all in one single process called sublimation, without leaving a liquid pool behind. The very dry air soaks up the liquid like a sponge, replenishing some of the water vapour lost in the mountain traverses.

• Chinook winds may last from only a few hours to a few days, sometimes even persisting for several weeks. They can be welcome visitors during the winter, giving a respite to residents of the cold Prairies. But in other seasons, the searing dry winds can desiccate vegetation, raise soil into dust storms, and rapidly increase the danger of grass and forest fires.

• For many living under the chinook influence, its winds bring debilitating physical effects ranging from sleeplessness to anxiety and severe migraine headaches.

All of this wind and heat is giving me a

headache!

Summary

• Chinooks are a weather phenomena that have impacted regions to the east of the Rocky Mountains so much that legends and folklore have been created.

• Caused by weather systems leaving the Cordillera region that evolve into fast moving warm winds that can “eat snow”, Chinooks influence the lives of plants and animals on the western edge of the interior plains.