Dec7, 2012 Extended Outlook
There is a cold front that will be at its strongest as it is passing our area Sunday night into Monday morning. The strength of the thermal gradient is apparent looking at the equivalent potential temperature predicted by GFS (below at 850mb 06Z monday). The temperature Tuesday 0Z from the ECMWF is around 12 degrees cooler at 850mb than the temperaure 0Z monday before the frontal passage (GFS agrees on this). GFS shows as the front is passing a moderate amount of precip associated with the front, including a lobe of precipitation extending well into the cold air, meaning snow is very likely for Minnesota, Wisconsin, Michigan. Sleet and snow is also a possibility for Northern Illinois and Indiana as the precip moves out early monday morning. At the upper levels the jet will be in position for upper level convergence aloft at the same time as the arrival of the cold air working to shut off precipitation sooner, while PVA at 500 looks to come a little too late to keep precipitation going longer. Most model soundings show conditions favorable for snow for at least a few hours of light snow or ice pellets overnight. The very cold air moving in can also mean roadway icing.