Fri-Sat, Dec 11-12th Snow Event Update #4

(12:30PM - 12/11/20) A storm system moving hrough the region today through Saturday will bring accumulating snow to portions of far Northern Illinois, this Friday afternoon through Saturday evening.

Summary...
A storm system moving through the region today through Saturday will bring accumulating snow to portions of far Northern Illinois, this Friday afternoon through Saturday evening. Model guidance continues to hold lock step in overall agreement regarding this event. With this update the biggest change is to continue to tighten the north and south gradient, on either side of the snowfall axis...As well as adding the mention of locally higher snowfall amounts in excess of 5" being possible in the heaviest snowfall axis. A developing storm system is ejecting out from the Plains today, and will northeastward, into the Great Lakes on Saturday. Marginal cold air will be in place, and when combined with the favorable storm track, will lead to a swath of accumulating snow across portions of the region and state.

​Forecast...
Precipitation, in the form of rain, has spread into portions of Northern and Central Illinois this morning and early this afternoon. As the storm system further develops and some colder air filters in, rain will turn to rain/snow or all snow for areas of far Northern and Northwest Illinois, near the Illinois/Wisconsin border. Rain/snow and snow will then continue in varying intensity for far Northern and Northwest Illinois, near the Illinois/Wisconsin border, through Saturday evening. Further south across other portions of Northern Illinois, as the storm system wraps up and passes the area, enough cold air will wrap in allowing for rain to change over to rain/snow or all snow further south across more of Northern Illinois...Generally along and north of I-88, from Saturday morning through Saturday evening.

Final snowfall totals in the main snowfall axis, which will clip portions of northwest and Northern Illinois near the IL/WI border, will be in the 2-5" range...However, locally higher amounts in excess of 5" are possible in that axis. There will be a quick drop off in snowfall totals south of this main axis, to 1-3" and a dusting to 1" over a very short distance across far Northern Illinois. Temperatures are expected to be marginal during this event, with temperatures staying in the mid 30's for much of this event for most impacted areas...Thus, this will lead to a lot of melting and compaction as the snow falls. This will be one of those events where official measurements will say 2-5" of snow fell, but only 1-3" might be on the ground after the event is over.

​Below is the snowfall forecast for this event.

JP