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Alberta Clipper
Mon Mar 31, 2003
Listen in RealAudio 
Out of the Canadian Prairies they come, sweeping down on the wind like the square-rigged
sailing ships of old, bringing their frigid cargo eastward: The Alberta Clipper. Hi, I'm Bryan
Yeaton, and this is The Weather Notebook.
Alberta Clippers are storms born east of the Canadian Rockies on Alberta's high plains. Once
formed, Clippers sail southeastward into the Dakotas and Minnesota, and then steer across the
Great Lakes toward the Atlantic Coast. This track leaves them hundreds of miles away from the
moisture sources of the Atlantic and Gulf of Mexico, so Clippers generally don't deposit huge
snowfalls, usually just a few inches of light, powdery flakes. Still, their strong, frigid
winds produce true blizzard conditions, due to severe blowing and drifting. A mature Clipper
can sport winds of 40 miles per hour, with gusts to 60.
Alberta Clippers sail under the push of a northwesterly jet stream. Often they are followed by
bitter outbreaks of polar air, known as the Siberian Express, which continue for days after
the low has moved off. Strong northerly winds and bitterly cold temperatures leave behind
dangerous windchills, ground blizzards, and days of whiteout conditions where surface
visibility is nearly zero.
When a Siberian Express follows a Clipper over the Great Lakes, major lake-effect snowfalls
may strike the lee shores with its cold, gusty northwest winds.
A Clipper can even produce heavy snow over New England and Maritime Canada; after crossing the
Appalachians, it becomes energized by warm Atlantic coastal waters and is reborn a Nor'easter.
Thanks to our contributing writer, meteorologist Keith Heidorn. The Weather Notebook is
produced by the Mount Washington Observatory, and supported by Subaru and The National Science
Foundation. Thanks also today to Davis Instruments, makers of the Vantage Pro Weather Station,
on the web at www.Davisnet.com.
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