December 12 Snow and Strong Winds

 An intense winter storm brought a variety of weather to central and southeast Illinois during the weekend of December 11-12.  A low pressure system strengthened as it tracked from Nebraska east into the lower Great Lakes.  With the low passing just north of the area, we were on the "warm" side of the system on Saturday with a widespread quarter to one inch rain, heaviest in eastern Illinois.  During this time very heavy snow of 8-20" fell from northern Iowa and Minnesota east into Wisconsin.  A strong cold front swept through the state Saturday evening and northwest winds brought plummeting temperatures which quickly froze any water from the earlier rains.  The "dry slot" of cyclone affected most of the area Saturday night while snow continued to our north. 

By early Sunday morning the wrap-around snow on the back side of the low pressure system rotated southeast into central Illinois.  Light to moderate, with occasionally heavy pockets of snow fell for much of Sunday.  Due to a very tight pressure gradient between the low pressure to our east, and an Arctic high poised over the northern Plains, sustained northwest winds blew at 25 to 35 mph and gusted over 50 mph.  These winds combined with the falling snow and snow on the ground to produce white-out conditions with near zero visibility from time to time.  Numerous traffic accidents were reported with several highways and interstates closed for periods of time. Snow amounts were generally 1 to 3 inches, with a few areas affected by heavier snow bands seeing 4 to 5 inches.  As the Arctic air moved in and high winds remained over the area Sunday night, dangerously cold wind chills of -10 to -20 were common into Monday morning.

The map below shows snowfall reports from the Significant Weather Observation Program (SWOP).  Note the variability in snow amounts even across short distances.  This is indicative of the banded nature of the snow, with brief heavier snow bursts occurring within the general light to moderate snow area.

   

Here is a brief summary of the peak wind gusts reported over parts of central through southeast Illinois on Sunday.

52 mph...Morton 
52 mph...5 miles south of Champaign
50 mph...Ogden
50 mph...2 miles north of Homer 
50 mph...Mattoon (ASOS)
50 mph...Champaign (ASOS)
48 mph...Lawrenceville (ASOS)
46 mph...Decatur (ASOS)
46 mph...Bloomington airport



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