We are still several days away from this potential weather system but some numerical model guidance over the last 36 to 48 hours has continued to show the threat of a swath of a accumulating snow this coming weekend. This would be associated with an area of low pressure moving through the Midwest with what looks like just enough cold air to produce an area of accumulating snow northwest of the weather system as you'll see below. Whether that accumulating snow occurs in a small part of Illinois, a larger part of the state or completely misses Illinois remains to be seen but the potential is there. Some early thoughts and details follow below....
The system responsible for this potential snow event is still out over the northern Pacific Ocean at this time but will eventually come ashore the western U.S. and make its way down into and near the Four Corners region by Friday afternoon as shown below. Beyond that, this upper level low is forecast to come out into the central and southern plains before coming east and northeast into portions of the Midwest.
This upper level low will lead to the development of an area of low pressure at the surface initially across Oklahoma at the beginning of the loop below. As of now and subject to change, it is forecast to come northeast into and through portions of Illinois from late Friday night through Saturday afternoon. With what looks like just enough cold air on the northwest side, model guidance continues to advertise a swath of snow possible across portions of the state. The location of this and also potential snow amounts is still well up in the air and will be determined by the strength and track of that surface low as model guidance gets a better handle on it over the next few days.
One thing to note is that surface temperatures look to be quite marginal for the majority of this event as things stand now and this could make snow accumulations verify on the lower side and would have to get some heavier precipitation/higher snowfall rates to get snow to really accumulate well. That said, some model guidance is indeed hinting at the potential for a band of heavier snow Saturday morning and afternoon. These heavier rates would offset marginal temperatures near or just above freezing. Right now, areas further northwest across the state and northern Illinois would stand the best chance for snow accumulations where as areas further southeast closer to the center of the surface low will see warmer temperatures.
It is still early in the game but below is our latest thinking. Keep an eye out for future forecasts.