Mon, Oct 19th Surprise Snow Event

(12:45PM - 10/19/20) A disturbance moving through the region will bring a surprise snow event to portions of Northern Illinois this afternoon.

Summary...
A disturbance moving through the region will bring a surprise snow event to portions of Northern Illinois this afternoon. This event has not been well modeled, as most model guidance had little to no precipitation, let alone snow. (Kudos to the GFS model for consistently being the model to show some snow).

An area of snow has been moving across Iowa this morning into early this afternoon, with a swath of accumulation across the heart of Iowa...Upwards of 3-8" in some areas north of Des Moines. While temperatures have been well above freezing this morning across Northwest Illinois, dynamic and evaporative cooling is accruing, which will allow precipitation to fall as snow. This area of snow is now entering Northwest Illinois, where a period of moderate to heavy snow is likely this afternoon. Accumulation is possible, if not likely, in a swath across portions of Northwest Illinois...Where upwards of 1-4" may be possible in the heaviest axis. Outside of this axis, only up to a dusting is possible. Further east, warmer temperatures will into the 40's exist across North-Central and Northeast Illinois. While some cooling of temperatures may occur due to the aforementioned dynamic  and evaporative cooling processes occurring, not enough cooling will be possible...Thus, across North-Central Illinois rain may only  change over to snow or a rain/snow mix for a short time and only rain is expected across Northeast Illinois.

​Below is the snowfall forecast for this snow event.

JP