More moderate brand of chill replaces Friday’s bitter arctic temps/wind chills as snow ebbs

A wave of snow swept across the Chicago area overnight—the first in a series of snow-generating disturbances predicted to impact the metro area in the more active pattern taking shape over the coming week.



Snowfall tapers to sporadic flurries and even ends at times Saturday. But additional snow is in the metro area’s future. It’s possible more snow will fall in a string of three additional systems likely to impact Chicago between now and midweek, than the 3.5 inches which had fallen over the ENTIRE 2012-13 season up to the time snowfall commenced last night.



Friday night’s snow followed a day in which daytime temperatures rose no higher than 12-degrees at O’Hare and remained in single digits in most western suburbs. The frigid daytime readings came on the heels of a 0-degree low at O’Hare, reached at 7:08am Friday morning. That reading marked only the second time this winter an official 0-degree or lower reading has occurred here this winter.



Models point to Sunday night/Monday system as the next disturbance capable of producing a significant accumulation



Flurries may flutter to earth from time to time Saturday, but serious accumulations aren’t expected.  And, while snowfall may pick up as the next in a series of disturbance passes late Saturday night into early Sunday, it’s the late Sunday night/Monday system most likely to lay down an additional several inches of snow.  And an equally vigorous system may produce still another wave of snowfall Tuesday capable of accumulation.



Snowy disturbances develop and straddle sharp northwest to southeast temp contrast zone draped across the Lower 48



The sudden spate of snow-generating systems in the next week is the product of a zone of highly varied temperatures which has developed along the western flank of the huge mass of frigid arctic air which descended into the eastern U.S. late this past week.



Such regions of widely varied temperatures also support vigorous jet streams within which precipitation-generating disturbances are embedded. The approach of each disturbance encourages winds to blow up and over the western flank of the large reservoir of cold air resulting in cloud and precipitation formation. Such regions in the atmosphere can become notoriously active.



It’s not unheard of for February to be Chicago’s snowiest month



An in house analysis we produced several weeks ago, looking at the Februarys and Marches which have followed lackluster snow seasons, like the one we’ve had in place across Chicago, indicated a tendency toward more frequent late-winter snows. A number of these Februarys and Marches ended up with impressive monthly snow totals.



Late season snow tallies reveal some impressive late-winter accumulations have occurred here. In fact, in 32 of the 128 seasons for which snow observations are available—that 25% of all the snow seasons on record in Chicago—the month with the largest snow accumulation has been February.



An average of 43% of Chicago’s seasonal snow has fallen beyond this date



Though days continue to lengthen and normal temperatures are on the upswing, snow has been no stranger in Chicago from this date forward. Just under half (43%) of the snow which has fallen here has done so from this date forward. This leaves plenty of time for additional snowfall to occur.



Groundhog Day blizzard of February, 2011 was winding down 2 years ago after producing the city’s third-heaviest snow



The final snows of the infamous Groundhog Day Blizzard of 2011 were winding down on this date two years ago, having buried Chicago under its third heaviest snow on record. The storm, which generated howling wind gusts clocked to 70 mph along Lake Michigan, produced 21.2” of snow here.  The mammoth system’s reach was extensive and not limited to the Midwest. On a nationwide basis, it produced $1.8-billion dollars in storm damage and led to the loss of 36 lives.

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