Alberta clipper

An Alberta clipper (also known as a Canadian Clipper) is a fast moving low pressure area which generally affects the central provinces of Canada and parts of the Upper Midwest and Great Lakes regions of the United States, precipitating a sudden temperature drop and sharp winds. Alberta clippers take their name from Alberta, Canada, the province from which they appear to descend, and from clipper ships of the 19th century, one of the fastest ships of that time.

A clipper originates when warm, moist winds from the Pacific Ocean come into contact with the mountains in the provinces of British Columbia and then Alberta. The air travels down the lee side of the mountains, often forming a chinook in Alberta, then develops into a storm over the Canadian prairies when it becomes entangled with the cold air mass that normally occupies that region in winter. The storm then slides southward and gets caught up in the jet stream, sending the storm barreling into central and eastern areas of North America.

Ironically, the chinook which in part originates the Alberta clipper usually brings relatively warm weather (often approaching 10 °C/50 °F in the depths of winter) to southern Alberta itself, and the term is therefore not used in Alberta.

The storms sweep in at high speed over whatever land they encounter, usually bringing with them sharp cold fronts and drastically lower temperatures. It is not uncommon for an Alberta clipper to cause temperatures to drop by 16 °C (30 °F) in as little as 10 to 12 hours. Often, the storms bring biting winds with them, only increasing the effect of the lower temperatures. Winds in advance of and during an Alberta clipper are frequently as high as 56 to 72 km/h (35 to 45 mph). These conditions would cause wind chill values to drop into the −30 to −45 Celsius (−20 to −50 Fahrenheit) range.

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Wikipedia