Moderating Temperatures

Middle & upper 20s are in the forecast for today.  By tomorrow, high temperatures will be right around our climatological average for late December—30 degrees.  The mercury will climb a bit more on Saturday, with temperatures reaching the middle 30s and even flirting with 40 in a few spots south of Rockford.

At-or-Above Average Temps Fri & Sat

At-or-Above Average Temps Fri & Sat

Sparing us from the frigid air found over much of northern Canada is the current pattern of our jet stream.  With a general zonal flow—that is, west-to-east—our airmass will originate from the Pacific ocean.  This west-to-east flow allows our air to be modified by a more temperate region (and not by the bitter cold Arctic circle region).

Zonal Flow

Zonal Flow

Things will change by the second half of our weekend and especially around the New Year holiday.  Our large-scale atmospheric pattern will become more meridional.  You may have guessed that meridional flow is characterized by a more north-to-south jet stream pattern. This will open the gates for Arctic air to slide south, sending air temperatures well below average and below zero.

Thursday Midday Canada Temps

Thursday Midday Canada Temps

Oh, Canada.

-Joe

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Posted under 13 Climate Authority, weather

This post was written by qni_it on December 26, 2013

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