Friday snow potential update

Thunderstorms are developing in central Illinois along a warm front that will help pull moisture northward.  Look for rain, possibly mixing with snow, to develop later this morning before quickly changing to snow this afternoon.  Road conditions will likely deteriorate for your evening commute.  Still looking at 3" to 6" - keep in mind that there will likely be locally higher snowfall totals.

6:30am Update: A Winter Storm Warning has been issued for Green, Rock and Walworth counties in southern Wisconsin.  A Winter Weather Advisory has been issued for Stephenson, Jo Daviess, Carroll and Whiteside counties while a Winter Storm Watch has been issued for Winnebago, Boone, McHenry and Ogle counties.  All three of these will go into affect this afternoon and last through tonight.

This storm system will have two sides to it:  a warm side which will produce thunderstorms and potentially severe weather in East-Central Illinois as well as points east and south, and a cold side which could potentially bring a heavy, wet snow right along the Wisconsin/Illinois border.   Low pressure is currently moving out of Kansas and into Missouri this morning which has been producing some strong thunderstorms across central Missouri.  That low will move through central Illinois around noon bringing with it light rain showers before intensifying as it moves into southwest Michigan by this evening.  The rain will spread in from the southwest to northeast and don't be surprised if there is a mixture of sleet and snow with some of the rain..  By mid-afternoon, likely after 3pm, the rain will begin to change to snow from west to east as the second low moves into the Upper Great Lakes and pulls down cooler weather.  Temperatures will be falling into the mid-30s so the snow that does fall will likely be heavy and wet which will reduce visibility this evening.  Snowfall rates could be heavy at times as cooling aloft allows the temperatures to fall quickly.  This system will quickly move northeast into Michigan by Saturday morning.  Winds will increase from the northwest tonight which may cause some blowing and drifting.

As far as snow totals go - this gets a little complicated.  Totals will likely be less south and southeast of Rockford as more of a mixture of rain/snow will occur.  Further north, right along the Wisconsin/Illinois border totals will likely be higher due to more cooling.  Roughly west of a line from Rockford to Dixon could see some of the heavier totals: 3" to 6".  Southeast of that line totals could be less.  Further north in Wisconsin has the best potential to pick up on higher totals and that's why a Winter Storm Warning has been issued.

Any slight deviation in the track will change the outcome of precipitation.  We'll continue to provide update here throughout the day as needed.