It's a clash of warm and cold air

Winter Storm Watches and Winter Weather Advisories have been issued extending from Michigan southwest through Wisconsin and central Iowa.  A heavy, wet snow is expected across northern Wisconsin and Michigan where totals could top out over 6".  Further to the south anywhere between 2"-4" could be possible in areas highlighted by the Winter Storm Watch and Winter Weather Advisory. 

It's a battle between the cold air to the north and warm, moist air to the south.  A developing low currently in north Texas will lift northeast through Oklahoma and just north of St. Louis by tonight and almost directly overhead Chicago by early Wednesday morning.  The low will continue to draw moisture northward and that moisture will mix with the very cold air in the upper Midwest and Great Lakes.  We will remain on the 'warmer' side of this low with heavy rainfall still expected for us.  However, as the low moves over Lake Michigan by Wednesday afternoon there may be enough cold air wrapping in behind the system to cause our column of air to cool enough that any leftover moisture could mix with or change to a few snowflakes.  No accumulations would be expected for us, however, just northwest of Dubuque may experience a little accumulation on grassy surfaces.