What Are Alberta Clippers? | WeatherBug
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What Are Alberta Clippers?

January 31, 2017
By WeatherBug Meteorologist, Andrew Rosenthal
Alberta Clipper is a funny sounding name. No, it's not a type of haircut. It's not one of your father's power tools either. No, it's also not a hockey team from Canada, but you'd be close. It's a winter storm system that usually starts just north of Montana, in the Canadian province of Alberta.

Alberta Clippers typically form just east of the Canadian Rocky Mountains. Since they form well away from a body of water, Alberta Clippers tend to not have much moisture associated with them, so they are not big snow producers. However, they do bring cold, Canadian air that can drop the temperature by 30-degrees or more.

So, where do they come from? The name, "Alberta Clipper," comes from the fact that the storm quickly clips across the northern tier of the U.S., similar to how fast 19th-century sailing ships known as "clippers" sped across the seas. The rest of the name comes from where they generally form, Alberta, Canada.

Areas of low pressure moving from Alaska and the Pacific Northwest tend to fall apart as they cross the northern Rockies, unable to strengthen in the dry air of the Canadian Prairies. However, the energy in them isn't lost, it keeps moving along. This then forms into a new storm system that sets out on a path southeastward into the northern U.S.

Several ingredients are needed for an Alberta Clipper to form. Typically, high pressure is in place along the Pacific Coast, forcing the atmospheric energy to speed northward along the jet stream into Canada. A fresh area of low pressure forms as the energy passes over the Rockies and moves into the Prairies. This pulls Arctic air southward from northern Canada, causing a building upper-level trough across the central U.S. to deepen.

At this point, the Clipper starts to move. The low slides along the building trough into the U.S. Northern Tier, dragging a cold front behind it. It often only takes a day or two for the Clipper to reach the Eastern Seaboard, but a huge change in the weather often occurs. While the weather ahead of an Alberta Clipper tends to be mild, it is often replaced by a winter-like chill and in the mid-winter, an arctic outbreak.

Thanks to the lack of moisture along the storm system, heavy snow is not typically a major aspect of a Clipper. However, the strong northwesterly winds that follow the Alberta Clipper's passage will cross the relatively warmer waters of the Great Lakes, firing up the lake-effect snow machine. While the storm itself might average two or three inches from the Upper Midwest to the Mid-Atlantic and New England, the lake-effect snow might produce localized snowfall totals on the order of a foot or more southeast of the Great Lakes.

A Clipper is typically followed by Arctic high pressure, bringing very chilly temperatures for a couple of days. After the high pressure passes, winds shift around from the south, sweeping out the cold air and bringing a return to milder weather.

However, Alberta Clippers occasionally open the doors to major snowstorms, especially on the East Coast. These storms build in the American Rockies, and then follow right behind the Clipper, feeding off the cold air. By the time it reaches the East Coast and speeds northward along the Seaboard, the ingredients are in place for a major snow-maker. For example, one such storm in January 1996, dropped 2 feet of snow in the Mid-Atlantic.

So the next time you hear the buzz building of an Alberta Clipper, get ready for a bit of snow and a dose of frigid temperatures.

Image: Aqua MODIS satellite imagery of an Alberta Clipper on January 25, 2015 (NASA)