Latest model data is showing a conflicting signal for a snowfall event in the Chicago area.  The European model is backing off the idea of a snowfall threat while the GFS is showing a fairly significant snowstorm for portions of WI into N IL.  The main piece of energy that will lead to this event is still in the Pacific so its no surprise we are seeing these differences:

Notice the European model splits the energy into two different pieces and does not bring these pieces together in time for a storm to form and produce a significant snowfall.  The European model does put an emphasis on the s/w energy to the north as it phases with another s/w energy leading to the develop of a northern stream low that develops or begins to develop over Michigan.  

My one problem with this is the uper levels really do not match up with the surface even with a northern stream dependent system.  

GFS

GFS is much more align with the northern and southern stream and we see a much more significant threat for snowfall across portions of N Illinois inot WI and IA.  Notice the southern stream does not get sheared out as much and the system takes on a neutral axis quicker resulting in a stronger more dynamic system.  The dry slot behind the convection along the cold front sets up the cold sector in a dynamic snow event.

Still a lot of details, as you can see the handling of the Pacific energy is key here and hopefully we can gather some more model agreement over the next day or so.