UPDATE 9PM: Steady and heavy, but a fine snow, continue to fall across much of northern Illinois, now moving into southern Wisconsin. The snow has caused visibility to fall to around a mile in most locations, but down to a quarter of a mile in the open and rural areas. North winds will remain strong through the night with blowing and drifting snow remaining a concern through Tuesday morning. The snow will come to an end early Tuesday, but the impacts will still be felt through the morning commute.
A Winter Weather Advisory has been issued for Winnebago, Boone, McHenry, Ogle, Lee, DeKalb and Whiteside counties, lasting through 9am Tuesday. A rather strong storm system moving along the Gulf has pushed enough moisture northward into the Great Lakes to allow accumulating snow to take place Monday evening and overnight.
The band of snow is already lifting north from southern and central Illinois and is expected to move into northern Illinois between 5-7pm. Even though radar is showing light snow currently over a portion of the area, dry air is still present and needs to be overcome a little further before the snow reaches the ground. This may take until after sunset to occur. But once it does a steady snow is then expected to continue through at least Midnight, with a few flurries lasting into early Tuesday morning.
Snow accumulations will range between 2-4 inches for Rockford and points east and south, with 1-2 inches occurring northwest. Strong North winds throughout much of the afternoon Monday has caused some significant blowing and drifting snow on east/west roads, with drifts nearly taking over the entire road in some locations.
Winds are expected to remain rather blustery through the night keeping the risk high for blowing and drifting snow, with conditions only deteriorating once the snow does begin to fall. Winds will ease a bit by Tuesday morning but impacts from the lingering snow and wind gusts to 15-20 mph early on could cause some problems for the morning commute.