A series of clipper systems will move over the Midwest the next several days, each with a shot of snow. They systems actually represent some warmer air moving in to replace the brief shot of arctic air the past two days. The shot of arctic air just produced the largest three day temperature swing in Chicago weather history, going from the record high of 63 on Tuesday to zero overnight this morning. The previous record drop was 61 degrees in January 1989.
The first of three clipper systems will spread light snow over parts of the Midwest including the Chicago metro area tonight into Saturday morning. This follows a drop to zero for the overnight low for the city, and readings to -5 in some outlying areas. The moisture is very limited with the system as we sit in arctic air. However, with snow water ratios of around 20 to 1, favorable dendritic snow growth zones of around 9000 feet, the expected moisture will produce from 1.5 to 3.0 inches of fluffy snow for the metro area. A second weak clipper will move thru the area Saturday night. Only a light dusting is expected with this second system. Finally a third system will move through late Sunday night into Monday morning. A couple of inches of fluffy snow look possible with this system.
With the systems will come some warming. From the high today only of 8-12, the highs will jump to highs around 20 Saturday and Sunday and well into the 20s the first part of next week. The graphic from the Chicago Tribune shows the clipper system tonight and the subzero lows so far this winter over the Midwest. So far for Chicago there has been only been one official subzero low, that being -1 on January 22. The monthly average of 26.6 was 2.8 degrees above normal. All the monthly details here.
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