Alert archive / South Dakota / Dense Fog Advisories in 2021

Dense Fog Advisory 8, NWS Sioux Falls, SD

February 21, 202111 counties in South Dakota; 10 counties in Iowa; 8 counties in Minnesota

NWS Sioux Falls, SD issued this dense fog advisory at Feb 21, 2021, 8:24 PM CST for 11 counties in South Dakota; 10 counties in Iowa; 8 counties in Minnesota. It was in force for 7 hr.

The area

The counties it named.

The facts

Issued: Feb 21, 2021, 8:24 PM CST (02:24 UTC)
Expired: Feb 22, 2021, 3:18 AM CST
In force: 7 hr
Issued by: NWS Sioux Falls, SD

All 29 counties

Buena Vista County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Ida County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Sioux County, IA, Cottonwood County, MN, Jackson County, MN, Lincoln County, MN, Lyon County, MN, Murray County, MN, Nobles County, MN, Pipestone County, MN, Rock County, MN, Brookings County, SD, Clay County, SD, Kingsbury County, SD, Lake County, SD, Lincoln County, SD, McCook County, SD, Miner County, SD, Minnehaha County, SD, Moody County, SD, Turner County, SD, Union County, SD

The radar

The Sioux Falls radar (KFSD), 42 km from the middle of the area, began a volume at 02:25 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Minneapolis, MN (KMPX), launched 00:00Z, 2.4 hours before the alert went out and 255 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 578 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: 36 m²/s²
0-3 km storm-relative helicity: 32 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this dense fog advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Sioux Falls, SD wrote its last area forecast discussion before this dense fog advisory went out at Feb 21, 4:57 PM CST, 3 hours 27 minutes earlier.

Area forecast discussion, Feb 21, 4:57 PM CST, 3 hours 27 minutes before

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Hazardous weather outlook, Feb 21, 4:49 PM CST, 3 hours 35 minutes before

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In the hours before

Local storm report, Feb 21, 3:02 PM CST, 5 hours 22 minutes before

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Local storm report, Feb 21, 3:43 PM CST, 4 hours 41 minutes before

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Local storm report, Feb 21, 3:44 PM CST, 4 hours 40 minutes before

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Local storm report, Feb 21, 3:56 PM CST, 4 hours 28 minutes before

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Local storm report, Feb 21, 5:00 PM CST, 3 hours 24 minutes before

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Local storm report, Feb 21, 5:02 PM CST, 3 hours 22 minutes before

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      <p id="message1">
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      <p id="message2">
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      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
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The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 22, 3:18 AM CST	Wind Advisory	FSD	Aurora, Beadle, Brule, Charles Mix, Davison, Douglas and 3 more	15 hr

Nearby

Dense Fog Advisories in South Dakota, 2021 Dense Fog Advisories in Iowa, 2021 Dense Fog Advisories in Minnesota, 2021 Every dense fog advisory in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.