Dense Freezing Fog to continue until late morning over western and southernmost portions of the Chicago area
Dense fog formed overnight over western and southernmost portions of the Chicago area and is expected to persist into the later morning hours with visibility near zero in some areas. With temperatures again in the upper teens to lower 20s and 100% relative humidity in these areas, freezing fog has condensed on untreated roads, sidewalks, parking lots and side-streets, so in addition to very poor visibility, slick spots are making conditions even more dangerous.
At 9AM CST visibility was a quarter-mile or much less at official airport sites in Sterling/Rock Falls, Rochelle, Rockford, Peru/Ottawa, Kankakee, Morris and Pontiac.
The current areas of poor visibility is depicted on the map below…