Winter Storm Watches Issued in Anticipation of Snow Thursday and Friday

A Winter Storm Watch has been issued for all of northern Illinois and southern Wisconsin beginning Thursday evening, lasting through Friday evening.  A long duration snow event is expected to take place during that time, possibly bringing snow totals up over nine or ten inches when all said and done.


Skies have been clearing from west to east Wednesday evening and this has allowed temperatures to fall back into the single digits in many locations.  Our skies will remain dry tonight, but clouds move back in Thursday morning as the atmosphere begins to saturate a little more.


There are a few light snow showers moving out of South Dakota and into northwest Iowa Wednesday evening.  Those are expected to move in Thursday morning, but will not be impactful during the day Thursday.

A warm front will lift northward Thursday afternoon and evening.  This will help pull warm air northward, moving up over top very cold air near the surface.  It'll also bring more moisture with it, helping to produce snow showers by Thursday evening.


In the mid and upper levels of the atmosphere there isn't much occurring during the day Thursday to help initiate much snow, other than a few flurries or light snow showers.  But as we get further into the evening and overnight several mid-level disturbances (think of these as mini low pressure systems) begin to move in from west to east.  As this occurs, snowfall will pick up in intensity between 7pm and 10pm with moderate to heavy snow falling during the overnight.  Snowfall rates up to one inch per hour are very well possible underneath the heavy snow bands through Friday morning.

Once the snow begins to fall not only will it quickly begin to stick to the roads, but it will quickly begin to accumulate.  By Friday morning, anywhere from four to six inches of snow may already be on the ground.  This will cause roads to become difficult to travel and remain very slick and snow covered throughout the day Friday.  Additional bands of moderate snow will be likely during the day Friday, adding another two to four inches, possibly five inches, to what has already fallen.  If those moderate bands of snow occur during the day Friday, significant impacts to the afternoon and evening commutes will be likely.


The storm event is a little under 24 hours away still and it's possible for forecasts to shift the heavier snow north or south.  But wherever those snow bands occurs, those places could receive over ten inches of snow by Friday evening.  Travel will become increasingly more difficult Thursday night and Friday morning, with snow lasting through the day Friday.


Another round of light snow is possible Saturday afternoon and evening before moving out by Sunday.