A Winter Storm Watch has been issued for Stephenson, Jo Daviess, Carroll and Whiteside counties ahead of a winter storm that will impact northern Illinois and southern Wisconsin with snow, sleet, freezing rain and rain Friday into Saturday. The watch goes into effect Friday morning, lasting through Saturday afternoon.
Models are coming into a little better agreement with the overall track, but there is still plenty of room for that track to shift. Right now, it looks like low pressure will develop east of the Rockies Friday, moving through the Plains during the afternoon and into Iowa by Friday evening. By Saturday morning the low is forecast to be over northwest Illinois and southwest Wisconsin. Moisture will increase during the day Friday, but there will be a very dry air mass down near the surface. This should keep the first half of the day Friday dry. As moisture increases, light snow will then develop by the evening (perhaps late afternoon west and southwest of Rockford) continuing into the early overnight. Temperatures Friday will be in the 20s but are expected to rise near freezing as warm air is pulled into the Stateline after Midnight, and then above freezing by Saturday morning. This brings the likely potential for a mixture of sleet and freezing rain Friday night, with possibly just rain by Saturday morning.
Right now it looks like the heaviest snow will fall from Minnesota to Wisconsin, with at least a few inches accumulating over northern Illinois. Friday into Saturday definitely has the potential to be messy with impacts into Saturday morning. After that, it gets cold and fast. Temperatures will fall quickly by Saturday night with highs only in the teens Sunday through next Tuesday.