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Alberta Clipper
Fri Jan 14, 2005
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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