Obviously has been just about all snow in much of the Chicago metro thus far, but the R/S line is finally crashing south of RFD and west towards Rt 47, for other portions of the LOT CWA.
It's not subsidence. More of the issue with drier air flowing in from the east across NE IL.
Further west across the DVN this issue doesn't exist, due to less dry air at the start.
The good news is that the ARW/NMM/NSSL WRF all are much wetter and snowier than the NAM/3KM NAM.
Usually wouldn't mention them much in the winter, but might be of some use this go around.