A WINTER WEATHER ADVISORY will go into effect for Rock and Green counties in south-central Wisconsin and for Jo Daviess County in northwest Illinois at 6am Thursday, lasting through Thursday evening. Several inches of heavy, wet snow are expected to fall in those areas with a sharp cut-off in snowfall amounts further east and southeast.
Low pressure moving through Arkansas Wednesday evening will quickly lift north Wednesday night. As it does, it will rapidly strengthen pulling a significant amount of moisture northward into Illinois. Rain showers are already beginning to move through central Illinois and should cross over into northern Illinois after 9pm/10pm.
Along the leading edge of the showers sleet may initially occur, but it is not expected to last. A steady rain will move in through the night. Low pressure will continue to strengthen as it moves into west-central Illinois Thursday morning. Warm air wrapping in around the low through sunrise will cause a few heavier pockets of rainfall to occur, with the risk of even a couple rumbles of thunder southeast of Rockford.
Colder air to the north will cause heavier bursts of snow to fall, stretching from Wisconsin into northeast Iowa. As the colder air sinks further east a transition over to a rain/snow mix, or just snow, is likely north and west of Rockford. There are likely to be some snow showers that occur in Rockford, but amounts should remain limited to under a couple inches.
Snowfall totals of 2-6 inches are likely stretching from near Janesville to Freeport, down into Carroll County. The freezing line (32-degree line) is very close to north-central Illinois. Any wobble of that line could mean a higher chance for snowfall extending further east/southeast Thursday morning.
Thursday morning’s commute will likely be impacted in some form, whether it be from snow, rain or both. Plan for a little extra time during the morning. By the afternoon a few lingering snow showers may still occur, but winds will pick up from the northwest gusting to 35-40 mph during the afternoon.