Average trajectory of a ClipperAn 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. Most clippers occur between December and February, but can also occur occasionally in the month of November. 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.
develops into a storm over the Canadian prairies when it becomes entangled with the cold air mass that normally occupies the region in winter. The storm then slides southward and gets caught up in the flow around the mass of high pressure which always inhabits cold polar areas, sending the storm barreling into central and eastern areas of North America.
Ironically, the chinook which in part originates the Alberta clipper usually brings extremely warm weather (often approaching 21C/70F in the depths of winter) to southern Alberta itself, and the term is therefore not in common use in Alberta.
Snowfall amounts with these systems tend to be small (on the order of 1 to 3 inches or 2.5 to 7.5 cm), as the severe lack of moisture and quick movement inhibit substantial snowfall totals. However, several factors could combine to produce somewhat impressive snowfall totals (6 inches/15 cm or more). These factors include access to more moisture (which raises precipitation amounts), slower system movement (which increases snowfall duration), and colder temperatures (which increases the snow to water ratio). The southern and eastern shores of the Great Lakes often receive enhanced snowfall from Alberta clippers during the winter, due to lake enhancement. The lake-effect snow can add substantially to the overall snowfall total.
During the winter, Alberta clippers can occur somewhat frequently, with system intervals on the order of two to four days common during active periods.