The Alberta Clipper is a well-known, fast-moving, low-pressure system in North America. This extratropical cyclone develops during the cold season, typically from October through March, tracking across the continent and bringing a noticeable shift in winter conditions. The system is defined by its rapid movement and association with cold, dry continental air masses, making it a significant winter storm track affecting the central and eastern portions of the continent.
Meteorological Definition and Origin
An Alberta Clipper is a low-pressure area that forms on the lee side of the Canadian Rocky Mountains, a process known as lee-side cyclogenesis. This formation typically occurs in or near Alberta, giving the system the first part of its name. The process begins when Pacific air flows eastward, encountering the mountains and losing moisture on the western slopes. As this air descends the eastern side of the Rockies, it warms by compression, which helps spin up a small, compact low-pressure center.
This cyclone is characterized by low moisture content and a weaker pressure gradient compared to major coastal storms. It pulls cold, dry continental Arctic air southward from the Canadian Prairies. The term “clipper” was coined in the late 1960s by a U.S. National Weather Service meteorologist, Rheinhart Harms, who noted the system’s rapid movement, paying homage to the sleek, fast-sailing clipper ships.
The system is also sometimes referred to as an Alberta low or Canadian clipper. It remains relatively shallow and compact, unlike a larger, more intense storm. Its track is heavily influenced by the position and strength of the jet stream.
Characteristic Path and Rapid Movement
Following its formation, the Alberta Clipper embarks on a swift, east-southeastward trajectory. This path generally carries it through the Northern Plains states, including the Dakotas and Minnesota, before steering it toward the Great Lakes region. It proceeds toward the Northeast or Mid-Atlantic states, eventually moving off the coast into the North Atlantic Ocean.
The system’s defining trait is its exceptional speed, linked to its position beneath the strong flow of the polar jet stream. Clippers frequently move at speeds ranging from 30 to 45 miles per hour, making them faster than most other winter storms. A clipper system can traverse the distance from the Canadian Rockies to the Atlantic coast in as little as two to four days.
This rapid transit means that weather impacts in any single region are short-lived, often passing through an area in just six to twelve hours. The jet stream provides the steering currents that guide the cyclone quickly across central and eastern North America.
Associated Weather and Environmental Impact
The Alberta Clipper brings a quick burst of light, powdery snow, typically accumulating only 1 to 3 inches. Because the system originates in a cold, dry continental air mass, it lacks the moisture required to produce heavy snowfall. The low moisture content and rapid movement limit the duration and intensity of the precipitation.
The clipper is known for bringing strong winds, gusting up to 40 to 60 miles per hour. These winds combine with the dry, light snow to create blowing and drifting snow. Hazardous travel conditions are more severe than the modest snowfall totals suggest.
The most significant impact is the rapid temperature drop that follows the system’s passage. It ushers in a surge of frigid Arctic air, leading to a sharp cold front. Temperatures can plummet 16°C (29°F) or 30°F in a 10 to 12-hour period, creating a flash-freeze risk on wet roads. It can also enhance lake-effect snow downwind of the Great Lakes.