Name: Dense Fog in Wisconsin, April 8, 2020
Start: 2020-04-08T02:00
End: 2020-04-08T07:30
Location: Wisconsin

Where it happened

Every event with a place to put it; 1 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: 1
Injuries: 0
Property damage: $20,000
Crop damage: None recorded
Events: 1

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 ARX wrote it up.

One person was killed in a two vehicle accident near Potosi (Grant County) on the morning of April 8th. The driver of a pickup failed to stop for a stop sign at an intersection on U.S. Highway 61, collided with a semi-truck, and was thrown from the vehicle. According to the accident report, the incident occurred during dense fog. The automated weather observing equipment at the Platteville (Grant County) and Dubuque (Dubuque County) airports were both reporting dense fog with a quarter mile or less visibility.

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 La Crosse, WI wrote its last area forecast discussion before the first event at Apr 7, 4:10 PM CST, 9 hours 50 minutes earlier.

Area forecast discussion, Apr 7, 4:10 PM CST, 9 hours 50 minutes before

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Hazardous weather outlook, Apr 7, 1:35 PM CST, 12 hours 25 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

1 dense fog. Local standard time, as filed.

Dense Fog, Grant

When: April 8, 2:00 AM CST to 7:30 AM CST
Where: Grant forecast zone
Deaths: 0 direct, 1 indirect
Property damage: $20,000
Reported by: Broadcast Media
Coordinates: 42.868, -90.706 (the zone’s center; the record gives no point)

The driver of a pickup failed to stop for a stop sign at an intersection along U.S. Highway 61 near Potosi, collided with a semi-truck and was thrown from the vehicle. According to the accident report, the driver was pronounced dead at the scene of the accident and that dense fog was a contributing factor. The automated weather observing equipment at the Platteville and Dubuque airports were both reporting dense fog with a visibility of a quarter mile or less at the time of the accident.

The people who died

As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.

Event	Date	Age	Sex	Where	Kind
Dense Fog, Grant	2020-04-08	42	Male	Vehicle/Towed Trailer	Indirect

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 2020 Every state in 2020 This day in weather history Warnings in Wisconsin, April 2020

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 2026-09-30. Each event’s entry at NCEI: 884482.