Saturday Night Snow

Good afternoon! Our winter storm is making progress today with an eventual track from Southern Illinois to Valparaiso, Indiana and then up to the eastern UP of Michigan.

Rain is likely for much of Saturday as warm southerly winds accompany the first phase of this storm system. Up to a half inch of rain is possible before we cool the column of air above us in order to support snowfall.

Once that switchover occurs, snow will pile up efficiently and quickly. With a stormtrack that goes almost due south to north, the highest accumulations will be in a swath in the same direction. The highest accumulations appear likely for areas west of Rockford. There is a potential for up to 10 inches of snow in a 60 mile swath along the Mississippi (perhaps just west). For NW Illinois (Jo Daviess, Carroll, Whiteside, and Stephenson) there will be a few snow totals that go above a half foot. On the other side of the coin, for those of you in DeKalb and McHenry County, you're getting the least amount. I ran a snowfall forecasting tool (BUFKIT) that only gives O'Hare around an inch of snow. For areas along Illinois Hwy 23, look for around 2 inches with an isolated 4 (should we get cold enough to allow the switchover to occur earlier). For the Rockford metro I am going with 3-6 inches.

However, I am going to caution you about two things. #1: It's extremely difficult forecast snowfall amounts when you start with rain and change to snow. If we don't receive precisely the forecasted amount of rain before it changes to snow, the snowfall accumulations will vary (either high or low). #2: Storms that go south to north produce narrow bands of heavy snow. Should the track go just fifty miles further west, we'll be held in the rain longer before the changeover...fifty miles east and we'll changeover sooner and snowfall amounts will be higher. Right now, I am forecasting that changeover to occur around 7pm.

An update will come with the evening computer models (around 10pm). -ERIC

p.s. To our commenters, please try not to speculate or forecast based on what you observe on the computer models. Our team has a lot of experience forecasting weather of this nature and I don't want our casual observers to get the wrong information. I appreciate your comments, hopes, and questions though. Let's try to keep the arm chair quarterbacking to the Bears-Packers game this weekend. Thanks!