Update 6:45AM CDT…
Visibilities have improved significantly and the threat of dense fog has ended early this Tuesday morning over the Chicago area. The spread between the temperatures and dew-points has widened, as temperatures begin to warm and winds slowly pick up out of the south.
Under clear skies and nearly calm winds, the difference between temperatures and dew-points has narrowed to the point where patches of very dense fog will lower visibility to below a quarter-mile and locally near zero in some portions of the Chicago area overnight into the early morning hours Tuesday. Most likely affected areas look to be along and north of Interstate-80.
The visibility map below highlights current spots with lowest visibility. If you are going to be on the road during the overnight hours into early morning Tuesday, drive carefully and be prepared to possibility encounter sudden reduced visibility to near zero in affected locales.
Winds should pick up around sunrise or a little after, enabling the fog to lift or break up, but until then be alert to the dense fog potential around our area.