Dense Fog in Wisconsin, April 7, 2001

Name: Dense Fog in Wisconsin, April 7, 2001
Start: 2001-04-07T02:00
End: 2001-04-07T08:30
Location: Wisconsin

April 7, 2001 · NWS MKX · 17 events in 17 counties and zones

Dense fog developed overnight, reducing visibilities to 1/8 to 1/4 mile. About 3 dozen vehicle accidents were reported.

Where it happened

Every event with a place to put it; 17 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
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Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 17

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 overnight, reducing visibilities to 1/8 to 1/4 mile. About 3 dozen vehicle accidents were reported. Numerous airline flights were delayed or canceled at local airports.

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 Apr 6, 1:59 PM CST, 12 hours 1 minute earlier.

Area forecast discussion, Apr 6, 1:59 PM CST, 12 hours 1 minute before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
300 PM CDT SAT APR 7 2001

FCST FOCUS ON SHOWERS/STORMS TONIGHT...STRONG WIND EVENT FOR
SATURDAY.

INTENSE LOW TRACKS NE OUT OF THE PLAINS TONIGHT...PUSHING A SFC WARM
FRONT INTO THE CWA BY MORNING.  LOTS OF SLOPE TO THE WARM FRONT AS
EVIDENCED BY THE H8 BNDRY REACHING INTO CNTRL WI AT THAT TIME.
TYPICALLY LIKE TO TIME THE ASSOCIATED PCPN ALNG AND JUST SOUTH OF
THE H8 BNDRY...WHICH MEANS MUCH OF THE CWA WILL BE CLEAR OF PCPN BY
12Z SAT.  SOME QUESTION AS TO HOW MUCH PCPN WE WILL SEE TONIGHT.
THE BEST DEEP FORCING IS CLEARLY WELL OUT TO OUR WEST...BUT IT IS
LIKELY SOME CONVECTION WILL FIRE ON WARM FRONT AND TRACK EAST/NE
ALONG IT.  HOW FAR IT TRACKS EAST AND HOW MUCH INTENSITY IT
MAINTAINS IS UNCERTAIN.  PROG SOUNDINGS DONT SHOW MUCH INSTABILTIY
...EVEN ELEVATED...AND THE MID LEVEL RDG IS OVRHD.  BEST CHANCE
FOR RAINFALL WILL BE WEST OF MADISON.

DRY SLOT ARRIVES FOR SATURDAY AND SO DO SOME IMPRESSIVE WINDS. SPC
IS HANGING ONTO A SLGT CHC FOR SVR THROUGH ABOUT MID-DAY/EARLY
AFTN AND THIS LOOKS GUD...THO POPS RATHER SMALL. THE COLD FRONT IS
SWINGING THROUGH...A NARROW BAND OF DEEPER RH IS ASSOCIATED WITH
IT...AND THERE IS A TAIL OF THE MID LEVEL S/W REACHING ACROSS THE
CWA. IN ADDITION...TEMPS AND DWPNTS WILL BE UNSEASONABLY WARM  BIG
THING WORKING AGAINST IT ARE THE VERY STRONG LINEAR WINDS THAT
COULD TEAR APART THE DVLPG CONVECTIVE TOWERS BEFORE THEY CAN MATURE.

LOWEST 5KFT GOES DRY ADIABATIC ON SATURDAY GIVING MOMENTUM TRANSFER
POTENTIAL OF 50-60 MPH /+-/.  WILL HOIST A HIGH WIND WATCH FOR
SATURDAY IN ANTICIPATION OF A HIGH WIND WARNING BEING ISSUED LATER.
NEXT FCSTR WILL ASSESS WITH THE NEXT RUN.

IT THEN QUIET DOWN FOR A WHILE...THOUGH NOISY SW FLOW WILL KEEP
THINGS UNSEASONABLY MILD INTO MID WEEK WITH TIMING ISSUES ON
LIGHTER PCPN CHCS COMING UP.

.MKX...HIGH WIND WATCH...ALL OF CWA 46..47..51..52..56>72.

DAVIS

In the hours before

Local storm report, Apr 7, 1:45 AM CST, 15 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

17 dense fog. Local standard time, as filed.

Dense Fog, Marquette

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Marquette forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.820, -89.399 (the zone’s center; the record gives no point)

Dense Fog, Green Lake

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Green Lake forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.800, -89.045 (the zone’s center; the record gives no point)

Dense Fog, Sauk

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Sauk forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.427, -89.948 (the zone’s center; the record gives no point)

Dense Fog, Columbia

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Columbia forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.467, -89.334 (the zone’s center; the record gives no point)

Dense Fog, Dodge

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Dodge forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.416, -88.707 (the zone’s center; the record gives no point)

Dense Fog, Washington

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Washington forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.369, -88.231 (the zone’s center; the record gives no point)

Dense Fog, Iowa

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Iowa forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.001, -90.135 (the zone’s center; the record gives no point)

Dense Fog, Dane

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Dane forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.067, -89.418 (the zone’s center; the record gives no point)

Dense Fog, Jefferson

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Jefferson forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.021, -88.776 (the zone’s center; the record gives no point)

Dense Fog, Waukesha

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Waukesha forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 43.018, -88.304 (the zone’s center; the record gives no point)

Dense Fog, Milwaukee

When: April 7, 2:00 AM CST to 8:30 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, Lafayette

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Lafayette forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 42.661, -90.132 (the zone’s center; the record gives no point)

Dense Fog, Green

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Green forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 42.680, -89.602 (the zone’s center; the record gives no point)

Dense Fog, Rock

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Rock forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 42.671, -89.072 (the zone’s center; the record gives no point)

Dense Fog, Walworth

When: April 7, 2:00 AM CST to 8:30 AM CST
Where: Walworth forecast zone
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 42.669, -88.542 (the zone’s center; the record gives no point)

Dense Fog, Racine

When: April 7, 2:00 AM CST to 8:30 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: April 7, 2:00 AM CST to 8:30 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, April 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: 5240189, 5240190, 5240191, 5240192, 5240193, 5240194, 5240195, 5240196, 5240197, 5240198, 5240199, 5240200, 5240201, 5240277, 5240278, 5240279, 5240280.