High pressure moves in Monday following a weak cold front Sunday evening. Skies will remain partly to mostly cloudy leading up to sunrise Monday, but plenty of sunshine is expected for Monday afternoon. High temperatures will reach the low to mid 40s. Clouds will, however, be on the increase ahead of a rather strong storm system that will move in from the west beginning Monday night, bringing the majority of the Stateline the first accumulating snow of the season.
The majority of Monday night will be dry and cool. Temperatures will fall just below freezing, before rising heading into Tuesday morning. A quick surge of moisture thanks to strong southwest winds (the low level jet) will allow the atmosphere to become saturated quickly Tuesday morning. A period of snow will be likely, starting just before sunrise Tuesday, lasting through early afternoon for some. At times, the snow will be heavy and reduce visibility through the morning commute. This could slow you down a bit as you’re out on the roads. As warm air moves in from the south mid to late morning sleet could mix in with some of the snow, until changing over to all rain by the afternoon. For folks closer to the state line, and in southern Wisconsin, the snow/sleet mixture could last a little longer into the early afternoon.
Any accumulations are most likely to remain on grassy surfaces, but roads could be sloppy Tuesday morning. As for snow accumulations, 1-2 inches are possible for north-central and northwest Illinois, as well as for south-central Wisconsin, with perhaps a few spots getting close to 3 inches. It’s in those areas that the snow will be coming down for a longer period of time. Any snow that does fall will more than likely melt away by the evening as temperatures, and dew points, rise above freezing and rain falls through Wednesday.