Update 3:15 pm CST…
Dense Fog Advisory shifts north – now in effect until later this evening for Illinois counties along and north of Interstate-80. Visibility has dropped to near zero in many locations with moist air positioned over the wet snow cover. The afternoon/evening commute will be significantly impacted, so prepare for a slow commute with sudden loss in visibility for extended distances. Conditions have improved considerably well south of Interstate-80.
Refer to the visibility map below for latest values.
A Dense Fog Advisory is in effect until this Friday evening for portions of the Chicago area in Illinois south of Interstate-80. Actually patchy dense fog with visibility less than quarter-mile is also occurring along the Lake Michigan shoreline due to on-shore easterly winds bringing moisture off the lake waters. If traveling, be prepared to possibly encounter pockets of dense fog and a sudden drop in visibility.
With low pressure approaching from the south, low-level moisture is increasing under the existing and lowering cloud layer. The combination of scattered light drizzle/rain from the low-hanging clouds and the increase in moisture has caused fog to form and visibility to drop in many areas along and south of Interstate-80.
Latest Visibility values across the Chicago area…