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Once in a while, you'll hear your local weatherman refer to a winter weather phenomena with a name, one that often times can spell the difference between just snow flurries vs. measurable snow and sub-zero temperatures.  What such phenomena could allude even the most advance weather personnel and put chills down his spine?

None other than the legendary Alberta Clipper!

What is an Alberta Clipper?  In a nutshell, it's an isolated area of Low Pressure, cut-off from the jet stream, which originates from Pacific waters, often times as far north as the Gulf of Alaska.  Once these systems blow onshore, there's limited bodies of water and moisture available to maintain strengthening.  Thus, these systems are often left to keep themselves together, based on the pressure they sustain within their center of circulation.

As the area of Low Pressure becomes entrenched in the Rockies, it produces warming winds on the leeward-side of the mountains, known as the chinook.  This warming effect generates both dynamic and thermodynamic entities within the core of the storm, which in return, interact with a cold, Canadian airmass, producing a snow storm over the Canadian Prairies.  Since this development tends to occur mainly over Alberta, these storms systems commonly dawn the name "Alberta Clipper," although other such systems do exists, including the "Manitoba Maulers" and "Saskatchewan Screamers."

These systems tend to move very fast and on similar tracks, bringing snow to areas of the Dakotas and Upper-Midwest.  Since they are lacking heavily in the moisture department, much of the precipitation generated is confined to the backside of the center of circulation, known as the wrap-around precip.  Thus, although temperatures may drop on the order of some 20-degrees with the passing of the frontal boundary, snow may linger behind for several hundred miles.

Often times as well, when snow reaches lower-levels of the atmosphere, dewpoints are so dry, that any precipitation tends to evaporate before coming into contact with the surface.  This is known as virga.

Thus, snowfall is often the greatest in Snowbelt areas of the Great Lakes.  As the Clipper moves east, winds often shift from the southwest to the northwest, feeding cold, Canadian air across warmer lake waters.  In return, you have lake-enhanced snow, with often a half-foot or more of accumulation possible downstream of the wind flow.

In conclusion, winter storms that effect South Central Kentucky tend to be more southern-based.  Since Clippers are northern-based, just a few miles can mean the difference between only a dusting of snow vs. several inches of accumulation and blizzard-like conditions, along with the headaches that come from forecasting them.