What is an "Alberta Clipper"?

     You may have heard the term "Alberta Clipper" this winter, especially as of recently.  The term "clipper" in meteorology means a quickly moving low pressure system.  An Alberta Clipper refers to one of these systems that originates over or near that provincial region of Canada.

    Some common characteristics of Alberta Clippers include:

  • This typical upper weather pattern:

Typical Upper Level Pattern

 

  • When in a pattern favoring Alberta Clippers, most typically late autumn through winter, temperatures across northern Illinois and northwest Indiana are often overall cooler than normal, however such a pattern provides regular temperature fluctuations, such as we are seeing this week.
  • The strong jet stream and even the low pressure iteslf often progress onshore from the Pacfic, but take better shape just beyond the Rockies hence the Alberta reference.
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  • The counterclockwise nature of the winds around the low pressure center of an Alberta Clipper often lead to Pacific air advancing eastward.  This tends to be warmer than the inherent air mass ahead of the clipper, so warmer and even more moist air comes with a shift to southwest or west winds, such as we experienced Wednesday Night.  This can be even more pronounced in the Plains states where westerly winds are that of downslope off the higher terrain and thus the air warms even more so.  To the right is an example of a surface weather map showing this warm air wrapping eastward around the low center in Saskatchewan.
  • The cold front of an Alberta Clipper turns the wind to the northwest or north and often brings sharply colder air into areas.
  • The progressive nature of these systems can often induce strong winds, which if accompanying snowfall or quickly follows fresh snowfall, can create widespread blowing snow.
  • Precipitation is commonly found on the northern side of these systems, while the southern side typically struggles to see much precipitation due to lack of deep saturation.
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    Surface Weather Map Showing an Alberta Clipper

    Surface Weather Map

     

    Two Day Loop of Water Vapor Satellite

    Water Vapor Loop

    Multiple circulations are indicated moving southeast from Canada through the duration of this loop.  These are Alberta Clippers.

       The forecast through this weekend calls for more Alberta Clippers, including one on Saturday that is further south than its predecessors.  Because of such a path, it could bring a "shovelable" snow to the local area.

    Clipper Forecast



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