Chinook wind

Chinook winds /ʃɪˈnʊk/, or simply Chinooks, are föhn winds in the interior West of North America, where the Canadian Prairies and Great Plains meet various mountain ranges, although the original usage is in reference to wet, warm coastal winds in the Pacific Northwest.Chinook arch over Calgary, 6 January 2003The extreme colours of a Chinook archChinook arch in Calgary, Alberta, 19 November 2005Chinook arch over Calgary, March 2007Chinook arch over Kelowna, BC, Canada, 2 October 2007 Chinook winds /ʃɪˈnʊk/, or simply Chinooks, are föhn winds in the interior West of North America, where the Canadian Prairies and Great Plains meet various mountain ranges, although the original usage is in reference to wet, warm coastal winds in the Pacific Northwest. The Blackfoot people term this wind 'Snow Eater'; however, the more commonly used term 'Chinook' originates from the language spoken by the eponymous people in the region where the usage was first derived (the Chinook people lived near the ocean, along the lower Columbia River). The reference to a wind or weather system, simply 'a Chinook', originally meant a warming wind from the ocean into the interior regions of the Pacific Northwest of the USA. A strong föhn wind can make snow one foot (30 cm) deep almost vanish in one day. The snow partly melts and partly sublimates in the dry wind. Chinook winds have been observed to raise winter temperature, often from below −20 °C (−4 °F) to as high as 10–20 °C (50–68 °F) for a few hours or days, then temperatures plummet to their base levels. The greatest recorded temperature change in 24 hours was caused by Chinook winds on 15 January 1972, in Loma, Montana; the temperature rose from −48 to 9 °C (−54 to 49 °F). Chinooks are most prevalent over southern Alberta in Canada, especially in a belt from Pincher Creek and Crowsnest Pass through Lethbridge, which get 30–35 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 annually as far north as High Level in northwestern Alberta and Fort St. John in northeastern British Columbia, and as far south as Las Vegas, Nevada, and occasionally to Carlsbad, in eastern New Mexico. In southwestern Alberta, Chinook winds can gust in excess of hurricane force 120 km/h (75 mph). On 19–November 1962, an especially powerful Chinook in Lethbridge gusted to 171 km/h (106 mph). In Pincher Creek, the temperature rose by 41 °C (74 °F), from −19 to 22 °C (−2 to 72 °F), in one hour in 1962. Trains have been known to be derailed by Chinook winds. 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 a metre. Empty semitrailer trucks driving along Highway 3 and other routes in southern Alberta have been blown over by the high gusts of wind caused by Chinooks. Calgary, Alberta 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. On 27 February 1992, Claresholm, Alberta a small city just south of Calgary; recorded a temperature of 24 °C (75 °F) again the next day 21 °C (70 °F) was recorded. These are some of Canada's highest February temperatures. The Chinook can seem to do battle with the Arctic air mass at times. It is not unheard of for people in Lethbridge to complain of −20 °C (−4 °F) temperatures while those in desert region, just 77 km (48 mi) down the road, enjoy 10 °C (50 °F) temperatures. This clash of temperatures can remain stationary, or move back and forth, in the latter case causing such fluctuations as a warm morning, a bitterly cold afternoon, and a warm evening. A curtain of fog often accompanies the clash between warm to the west and cold to the east.