Alert archive / Wisconsin / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 88, NWS Milwaukee, WI

September 20, 2021Dane County, Jefferson County, Wisconsin

NWS Milwaukee, WI issued this severe thunderstorm warning at Sep 20, 2021, 10:41 PM CDT for Dane County, Jefferson County, Wisconsin. It was in force for 20 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Sep 20, 2021, 10:41 PM CDT (03:41 UTC)
Expired: Sep 20, 2021, 11:01 PM CDT
In force: 20 min
Issued by: NWS Milwaukee, WI
Area: Storm-based polygon
Tornado: Possible
Hail: 0.75 in
Wind: 60.0 mph

Counties Dane County, WI, Jefferson County, WI

The radar

The Milwaukee radar (KMKX), 26 km from the middle of the area, began a volume at 03:43 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

Green Bay/Straub, WI (KGRB), launched 00:00Z, 3.7 hours before the alert went out and 170 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: 429 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 735 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 194 m²/s²
0-3 km storm-relative helicity: 212 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 2.0

Open this sounding in Storm Lab

The text

As transmitted.

494 
WUUS53 KMKX 210341
SVRMKX
WIC025-055-210415-
/O.NEW.KMKX.SV.W.0088.210921T0341Z-210921T0415Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Milwaukee/Sullivan WI
1041 PM CDT Mon Sep 20 2021

The National Weather Service in Milwaukee/Sullivan has issued a

* Severe Thunderstorm Warning for...
  Southeastern Dane County in south central Wisconsin...
  Northern Jefferson County in southeastern Wisconsin...

* Until 1115 PM CDT.

* At 1041 PM CDT, a severe thunderstorm was located over Cambridge,
  or 9 miles southwest of Lake Mills, moving northeast at 40 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
  Watertown, Jefferson, Lake Mills, Johnson Creek, Deerfield,
  Cambridge, Lake Ripley, Ixonia, Milford, Utica, Rockdale,
  Hubbleton, Pipersville and Helenville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4288 8908 4304 8920 4320 8888 4320 8863
      4308 8854 4305 8854
TIME...MOT...LOC 0341Z 240DEG 33KT 4300 8905 

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

STUMPF

2 follow-up statements

497 
WWUS53 KMKX 210352
SVSMKX

Severe Weather Statement
National Weather Service Milwaukee/Sullivan WI
1052 PM CDT Mon Sep 20 2021

WIC025-210401-
/O.CAN.KMKX.SV.W.0088.000000T0000Z-210921T0415Z/
Dane WI-
1052 PM CDT Mon Sep 20 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN DANE COUNTY IS
CANCELLED...
    
The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

LAT...LON 4313 8901 4320 8888 4320 8863 4308 8854
      4305 8854 4290 8901
TIME...MOT...LOC 0351Z 240DEG 33KT 4305 8893 

$$

WIC055-210415-
/O.CON.KMKX.SV.W.0088.000000T0000Z-210921T0415Z/
Jefferson WI-
1052 PM CDT Mon Sep 20 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1115 PM CDT
FOR NORTHERN JEFFERSON COUNTY...

At 1051 PM CDT, a severe thunderstorm was located over Lake Mills,
moving northeast at 40 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
Watertown, Jefferson, Lake Mills, Johnson Creek, Lake Ripley, Ixonia,
Milford, Pipersville, Hubbleton and Helenville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4313 8901 4320 8888 4320 8863 4308 8854
      4305 8854 4290 8901
TIME...MOT...LOC 0351Z 240DEG 33KT 4305 8893 

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

STUMPF

958 
WWUS53 KMKX 210401
SVSMKX

Severe Weather Statement
National Weather Service Milwaukee/Sullivan WI
1101 PM CDT Mon Sep 20 2021

WIC055-210411-
/O.CAN.KMKX.SV.W.0088.000000T0000Z-210921T0415Z/
Jefferson WI-
1101 PM CDT Mon Sep 20 2021

...THE SEVERE THUNDERSTORM WARNING FOR CENTRAL JEFFERSON COUNTY IS
CANCELLED...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been cancelled.  However gusty winds are
still possible with this thunderstorm.

LAT...LON 4313 8901 4320 8888 4320 8863 4308 8854
      4305 8854 4290 8901
TIME...MOT...LOC 0358Z 240DEG 33KT 4310 8881 

$$

STUMPF

The office that day

Everything else NWS Milwaukee, WI issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 20, 7:22 PM CDT	Severe Thunderstorm Warning	MKX	Iowa, Sauk	38 min
Sep 20, 7:46 PM CDT	Severe Thunderstorm Warning	MKX	Columbia, Sauk	44 min
Sep 20, 7:59 PM CDT	Special Weather Statement	MKX	Iowa	31 min
Sep 20, 8:23 PM CDT	Special Weather Statement	MKX	Marquette	37 min
Sep 20, 8:37 PM CDT	Special Weather Statement	MKX	Columbia, Sauk	38 min
Sep 20, 9:14 PM CDT	Special Weather Statement	MKX	Lafayette	46 min
Sep 20, 9:21 PM CDT	Severe Thunderstorm Warning	MKX	Columbia, Dodge	24 min
Sep 20, 9:22 PM CDT	Severe Thunderstorm Warning	MKX	Dane, Green, Iowa, Lafayette	38 min
Sep 20, 9:24 PM CDT	Tornado Warning	MKX	Dane, Green, Iowa, Lafayette	24 min
Sep 20, 9:44 PM CDT	Special Weather Statement	MKX	Green Lake	46 min
Sep 20, 10:04 PM CDT	Special Weather Statement	MKX	Green	41 min
Sep 20, 10:27 PM CDT	Special Weather Statement	MKX	Jefferson	48 min
Sep 21, 3:04 AM CDT	Gale Watch	MKX		11 hr
Sep 21, 1:48 PM CDT	Gale Warning	MKX		50 hr
Sep 21, 1:48 PM CDT	Small Craft Advisory	MKX		17 hr
Sep 21, 1:51 PM CDT	Beach Hazards Statement	MKX	Kenosha, Milwaukee, Ozaukee, Racine, Sheboygan	58 hr

Nearby

Severe Thunderstorm Warnings in Wisconsin, 2021 Every severe thunderstorm warning 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.