Dense Fog Images and Facts from Tuesday Night and Wednesday Morning

Persistent Dense Fog Tuesday Night & Wednesday

Dense Fog Photos

Dense fog/low clouds across part of downtown Chicago. Courtesy of Rick DiMaio.	Sun starting to peak through the dense fog in Vernon Hills. Courtesy of Dirk Leahy.	Dense fog at the NWS office in Romeoville.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
340 PM CST WED NOV 21 2012 /440 PM EST WED NOV 21 2012/

...LONG DURATION OF LOW VISIBILITY IN DENSE FOG OBSERVED...

LATE TUESDAY NIGHT INTO WEDNESDAY MORNING BROUGHT WIDESPREAD AND
LONG LASTING DENSE FOG ACROSS THE AREA. VISIBILITY OF UNDER ONE
QUARTER MILE WAS OBSERVED AT ALL AUTOMATED OBSERVATION SITES
ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA. THIS DENSE FOG HAD
SIGNIFICANT IMPACTS AT AIRPORTS...INCLUDING IN CHICAGO AND
ROCKFORD. HERE ARE SOME STATISTICS ABOUT THE LOW VISIBILITY
DURATION AT THESE AIRPORTS.

CHICAGO OHARE INTERNATIONAL AIRPORT...

BELOW 1/4 MILE VISIBILITY...3 HRS 43 MINS FROM 507 AM TO 850 AM.


CHICAGO MIDWAY INTERNATIONAL AIRPORT...

BELOW 1/4 MILE VISIBILITY...6 HRS 9 MINS FROM 340 AM TO 949 AM.
1/16 MILE VISIBILITY...3 HRS 50 MINS FROM MOST OF 535 AM TO 925 AM.


ROCKFORD INTERNATIONAL AIRPORT...

BELOW 1/4 MILE VISIBILITY...12 HRS 59 MINS FROM 937 PM TUESDAY
                            UNTIL 1036 AM WEDNESDAY.
1/16 MILE VISIBILITY...1 HR 25 MINS FROM 815 AM TO 940 AM.

THE NWS WOULD LIKE TO SPECIALLY THANK THE FAA CONTRACT OBSERVERS AT
THESE THREE AIRPORTS FOR COMPILING THIS DATA.


OTHER SITES...

SITE      HOURS BELOW ONE QUARTER OF A MILE     TIME
-------------------------------------------------------
KANKAKEE IL          11 HOURS                10 PM-9 AM
PERU IL              10 HOURS                1 AM-11 AM
ROMEOVILLE IL        13 HOURS               10 PM-11 AM

THIS IS BASED ON ONLY TOP OF THE HOUR MEASUREMENTS TAKEN FROM
AUTOMATED WEATHER OBSERVING SYSTEMS /AWOS/.

$$

RC/MTF

Local Storm Reports

9:15 am Wednesday Visible Satellite Image and Observations Overlaid

The expansive white area on satellite indicates the dense fog area. On the observation sites, the number below the circle indicates the visibility in statute miles. The zeros signify visibility less than one quarter of a mile. It is very rare to see this many observation sites below one quarter of a mile!

Fog Around Terrain...yes, terrain in Illinois!

This is an image of visible satellite on the left and topography with wind farms overlaid (yellow) on the right. Note the stretch of thin or even scattered clearing on the visible satellite channel, and how that lines up with the slightly higher terrain across Bureau and Lee Counties. The fog was only 400-700 ft thick based on atmospheric analysis, and so literally the top of this terrain was above the fog area! It is possible that the wind farms, which are located on the higher elevation, may have helped to mix the atmospheric boundary layer to slightly ease the fog as well, though that is very difficult to tell for certain.

Return to News Archive

National Weather Service Weather Forecast Office

Dense Fog Images and Facts from Tuesday Night and Wednesday Morning