Wisconsin, 2009

Dense Fog in Wisconsin, September 12 to 13, 2009

September 12 to 13, 2009 · NWS MKX · 7 events in 7 counties and zones

The combination of high pressure over the Great Lakes Region, light winds, clear skies, and a moist layer of air that moved west from Lake Michigan allowed for the development of dense fog overnight over the southeast corner of Wisconsin and the area from around Madison west-northwest to the Wisconsin River Valley. Visibilities were reduced to 1/8 to 1/4 mile.

Where it happened

Every event with a place to put it; 7 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

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The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
7

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS MKX wrote it up.

The combination of high pressure over the Great Lakes Region, light winds, clear skies, and a moist layer of air that moved west from Lake Michigan allowed for the development of dense fog overnight over the southeast corner of Wisconsin and the area from around Madison west-northwest to the Wisconsin River Valley. Visibilities were reduced to 1/8 to 1/4 mile. In between the two highlighted areas, visibilities dropped to only 1/2 to 2 miles, or only briefly dropped to 1/4 mile. Newspaper articles indicated that there were a few vehicle accidents, and there were some delays in aircraft departures at some airports.

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

7 dense fog. Local standard time, as filed.

Dense Fog, Waukesha

When
September 12, 8:00 PM CST to September 13, 7:00 AM CST
Where
Waukesha forecast zone
Reported by
ASOS
Coordinates
43.018, -88.304 (the zone’s center; the record gives no point)

Dense Fog, Sauk

When
September 12, 8:00 PM CST to September 13, 7:00 AM CST
Where
Sauk forecast zone
Reported by
ASOS
Coordinates
43.427, -89.948 (the zone’s center; the record gives no point)

Dense Fog, Iowa

When
September 12, 8:00 PM CST to September 13, 7:00 AM CST
Where
Iowa forecast zone
Reported by
ASOS
Coordinates
43.001, -90.135 (the zone’s center; the record gives no point)

Dense Fog, Dane

When
September 12, 8:00 PM CST to September 13, 7:00 AM CST
Where
Dane forecast zone
Reported by
ASOS
Coordinates
43.067, -89.418 (the zone’s center; the record gives no point)

Dense Fog, Walworth

When
September 12, 8:00 PM CST to September 13, 7:00 AM CST
Where
Walworth forecast zone
Reported by
ASOS
Coordinates
42.669, -88.542 (the zone’s center; the record gives no point)

Dense Fog, Racine

When
September 12, 8:00 PM CST to September 13, 7:00 AM CST
Where
Racine forecast zone
Reported by
ASOS
Coordinates
42.730, -87.812 (the zone’s center; the record gives no point)

Dense Fog, Kenosha

When
September 12, 8:00 PM CST to September 13, 7:00 AM CST
Where
Kenosha forecast zone
Reported by
ASOS
Coordinates
42.573, -87.840 (the zone’s center; the record gives no point)

What these are

Dense Fog
Fog reducing visibility to a quarter mile or less, filed where it caused accidents or disruption.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Wisconsin in 2009Every state in 2009This day in weather historyWarnings in Wisconsin, September 2009

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 196697, 196698, 196699, 196700, 196701, 196702, 196703.