Dense Fog in Wisconsin, May 25 to 26, 2001

Name: Dense Fog in Wisconsin, May 25 to 26, 2001
Start: 2001-05-25T20:30
End: 2001-05-26T06:30
Location: Wisconsin

May 25 to 26, 2001 · NWS MKX · 5 events in 5 counties and zones

Dense fog developed over southeast Wisconsin after light winds off Lake Michigan pulled moist air into the region. Clear skies aided in the nighttime radiational cooling.

Where it happened

Every event with a place to put it; 5 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: 5

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.

Dense fog developed over southeast Wisconsin after light winds off Lake Michigan pulled moist air into the region. Clear skies aided in the nighttime radiational cooling. Visibilities were reduced to 1/8 to 1/4 mile. About two dozen vehicle accidents were noted and local airport traffic was delayed.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Milwaukee, WI wrote its last area forecast discussion before the first event at May 25, 1:30 PM CST, 7 hours earlier.

Area forecast discussion, May 25, 1:30 PM CST, 7 hours before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
230 PM CDT FRI MAY 25 2001

FCST CHALLENGE IS WHETHER SHOWERS AND STORMS ASSOCIATED WITH THE
UPPER LOW WILL BE OVER ON MEMORIAL DAY. SECOND CHALLENGE IS
TEMPERATURES DUE TO WIDE VARIATIONS IN CLOUD COVER. THIRD CHALLENGE
IS NIGHT TIME AND EARLY MORNING FOG.

LARGE UPPER LOW CONTINUES TO SPIN ACROSS THE WESTERN GREAT LAKES.
APPEARS THAT TIMING OF AREAS OF VERTICAL MOTION CONTINUES TO BE
PROBLEMATIC DUE TO THE NATURE OF THESE TYPES OF SYSTEMS. MODELS
TYPICALLY DO NOT HANDLE THE TIMING OF PRECIPITATION VERY WELL AND
THIS COMPLICATES ANY TIMING OF PRECIPITATION...AS WELL AS MAX
TEMPERATURES DURING THE DAY...AS SEEN TODAY WITH SOME AREAS IN THE
40S WITH THUNDERSTORMS AND OTHERS THAT ARE IN THE SUN AND AROUND 60
DEGREES.

AND WITH THIS VARIED CLOUD COVER TYPICAL OF THIS PATTERN COMES
CLEAR SKIES IN MANY LOCALES AT NIGHT...AND WITH LIGHT WINDS AND
MOISTURE AT LOW LEVELS FROM DAYTIME SHOWERS...FOG FORMATION WILL BE
COMMON OVER THE NEXT THREE NIGHTS.

IN ANY CASE...IT IS APPARENT THAT THE LOW WILL CONTINUE TO INFLUENCE
THE WEATHER ACROSS SOUTHERN WISCONSIN THROUGH SUNDAY AND EVEN INTO
MEMORIAL DAY. AVN POINTS TOWARDS LIGHT PRECIP AMOUNTS ON MEMORIAL
DAY AND AS AREA REMAINS UNDER CYCLONIC FLOW AND HIGH PRESSURE
PUSHING DRY AIR IN BEHIND TROF/COLD FRONT...MAY BE ENOUGH LIFT AND
INSTABILITY LEFT OVER AND COMBINED WITH DAYTIME HEATING FOR A FEW
BRIEF SHOWERS ON MEMORIAL DAY.

WILL KEEP COOLER TEMPS PER AVN MOS.

.MKX...NONE.

EISE

In the hours before

Special weather statement, May 25, 4:38 PM CST, 3 hours 52 minutes before

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The radar

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

Open the radar archive at this moment

Event by event

5 dense fog. Local standard time, as filed.

Dense Fog, Sheboygan

When: May 25, 8:30 PM CST to May 26, 6:30 AM CST
Where: Sheboygan forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.756, -87.800 (the zone’s center; the record gives no point)

Dense Fog, Ozaukee

When: May 25, 8:30 PM CST to May 26, 6:30 AM CST
Where: Ozaukee forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.403, -87.891 (the zone’s center; the record gives no point)

Dense Fog, Milwaukee

When: May 25, 8:30 PM CST to May 26, 6:30 AM CST
Where: Milwaukee forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.022, -87.929 (the zone’s center; the record gives no point)

Dense Fog, Racine

When: May 25, 8:30 PM CST to May 26, 6:30 AM CST
Where: Racine forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 42.730, -87.812 (the zone’s center; the record gives no point)

Dense Fog, Kenosha

When: May 25, 8:30 PM CST to May 26, 6:30 AM CST
Where: Kenosha forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
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

Every storm in Wisconsin in 2001 Every state in 2001 This day in weather history Warnings in Wisconsin, May 2001

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: 5248303, 5248304, 5248305, 5248306, 5248307.