Early this Sunday morning dense fog with visibility near zero has developed over the portion of the Chicago area well west and south of Lake Michigan and the city of Chicago. Closer-in conditions are a little hazy, but visibility is relatively unaffected. A dense Fog Advisory is in effect until 9AM CDT for the gray-shaded area on the headlined map.
Note local airport visibility on the map below. Conditions should improve rapidly between 8 and 9AM where fog is occurring.