Dense fog and slick spots this morning

12:50pm Update: This is the sounding from the NWS in Davenport, IA and it shows a pretty strong inversion just above the surface with light winds through about 900 mb.  An inversion is when the air at the surface is cooler than the air above.  The layer is also fairly saturated so it's no wonder the fog has stuck around for so long.  With limited atmospheric mixing the fog isn't able dissapate easily.  Temperatures as a result will remain in the upper 30s to near 40° today. 

(9:02:06 AM) nwsbot: LOT extends Dense Fog Advisory for Boone, De Kalb, DuPage, Ford, Grundy, Iroquois, Kane, Kankakee, Kendall, La Salle, Lee, Livingston, McHenry, Ogle, Will, Winnebago [IL] till 3:00 PM CST

A Dense Fog Advisory continues through 10am for southern Wisconsin and northern Illinois.  Calm winds and clear skies late last night allowed the thick, dense fog to develop and expand eastward.  Visibility in almost all locations through Wisconsin and Illinois have dropped to less than a quarter mile.  Another concern this morning have been the temperatures.  A few slick spots have been reported from some of our weather watchers due to the fact temperatures have fallen below freezing.  Be sure to give yourself plenty of time this morning and watch for those slick spots; especially on bridges, overpasses, sidewalks and parking lots.  Those are most likely to become slippery. 

Despite high pressure overhead the atmosphere is fairly 'calm'.  This leads me to believe the fog is going to have a hard time lifting as we go through the morning so it's possible we could still be dealing with the fog through noon.  This will play an impact on our temperatures today, especially if the fog holds.  I did lower highs this morning to 41° rather than the 45° I had yesterday.  Should the fog lift sooner, we will have a better shot of reaching the warmer temperatures, but if it holds then we'll remain cooler.