Alert archive / Wisconsin / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 31, NWS Milwaukee, WI

August 7, 2021Jefferson County, Waukesha County, Wisconsin

NWS Milwaukee, WI issued this severe thunderstorm warning at Aug 7, 2021, 12:54 PM CDT for Jefferson County, Waukesha County, Wisconsin. It was in force for 45 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
Aug 7, 2021, 12:54 PM CDT (17:54 UTC)
Expired
Aug 7, 2021, 1:39 PM CDT
In force
45 min
Issued by
NWS Milwaukee, WI
Area
Storm-based polygon
Hail
0.75 in
Wind
60.0 mph

Counties Jefferson County, WI, Waukesha County, WI

The radar

The Milwaukee radar (KMKX), 10 km from the middle of the area, began a volume at 17:56 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 12:00Z, 5.9 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-pSkew-T log-p diagram, Green Bay/Straub, WI at 12:00Z on 2021-08-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 20 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Green Bay/Straub, WI at 12:00Z on 2021-08-07The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 72 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
20 J/kg
Mixed-layer CIN
-32 J/kg
Mixed-layer LCL
656 m above ground
0-6 km bulk shear
17 kt
0-1 km storm-relative helicity
72 m²/s²
0-3 km storm-relative helicity
103 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

310 
WUUS53 KMKX 071754
SVRMKX
WIC055-133-071900-
/O.NEW.KMKX.SV.W.0031.210807T1754Z-210807T1900Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Milwaukee/Sullivan WI
1254 PM CDT Sat Aug 7 2021

The National Weather Service in Milwaukee/Sullivan has issued a

* Severe Thunderstorm Warning for...
  Western Waukesha County in southeastern Wisconsin...
  East central Jefferson County in southeastern Wisconsin...

* Until 200 PM CDT.

* At 1253 PM CDT, a severe thunderstorm was located near Lac La
  Belle, or 8 miles southeast of Watertown, moving southeast at 20
  mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

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

* Locations impacted include...
  Waukesha, Pewaukee, Hartland, Delafield, Wales, Okauchee Lake,
  Oconomowoc, Ottawa, Dousman, North Prairie, Lac La Belle, Eagle,
  Nashotah, Waterville, Oconomowoc Lake, Chenequa, Summit, Genesee
  Depot, Genesee and Lapham Peak St Park.

People attending The Waukesha Mud Girl Run should seek safe shelter
immediately!

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4284 8841 4293 8857 4319 8856 4307 8821
TIME...MOT...LOC 1753Z 299DEG 19KT 4311 8861 

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

$$

HANSEN
2 follow-up statements
125 
WWUS53 KMKX 071824
SVSMKX

Severe Weather Statement
National Weather Service Milwaukee/Sullivan WI
124 PM CDT Sat Aug 7 2021

WIC055-071832-
/O.CAN.KMKX.SV.W.0031.000000T0000Z-210807T1900Z/
Jefferson WI-
124 PM CDT Sat Aug 7 2021

...THE SEVERE THUNDERSTORM WARNING FOR EAST CENTRAL JEFFERSON 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 4288 8838 4296 8854 4311 8854 4305 8823
TIME...MOT...LOC 1822Z 299DEG 19KT 4303 8842 

$$

WIC133-071900-
/O.CON.KMKX.SV.W.0031.000000T0000Z-210807T1900Z/
Waukesha WI-
124 PM CDT Sat Aug 7 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 200 PM CDT
FOR SOUTHWESTERN WAUKESHA COUNTY...

At 122 PM CDT, a severe thunderstorm was located over Dousman, or
near Delafield, moving southeast at 20 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

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

Locations impacted include...
Waukesha, Pewaukee, Delafield, Wales, Oconomowoc, Ottawa, Dousman,
North Prairie, Nashotah, Waterville, Oconomowoc Lake, Summit, Genesee
Depot, Genesee and Lapham Peak St Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4288 8838 4296 8854 4311 8854 4305 8823
TIME...MOT...LOC 1822Z 299DEG 19KT 4303 8842 

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

$$

HANSEN
741 
WWUS53 KMKX 071839
SVSMKX

Severe Weather Statement
National Weather Service Milwaukee/Sullivan WI
139 PM CDT Sat Aug 7 2021

WIC133-071849-
/O.CAN.KMKX.SV.W.0031.000000T0000Z-210807T1900Z/
Waukesha WI-
139 PM CDT Sat Aug 7 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHWESTERN WAUKESHA 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 4288 8838 4296 8854 4311 8854 4305 8823
TIME...MOT...LOC 1836Z 299DEG 19KT 4299 8831 

$$

HANSEN

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 6, 7:34 PM CDTAreal Flood AdvisoryMKXMilwaukee, Waukesha119 min
Aug 6, 7:38 PM CDTSevere Thunderstorm WarningMKXJefferson37 min
Aug 6, 7:55 PM CDTSpecial Marine WarningMKX50 min
Aug 6, 7:57 PM CDTSpecial Weather StatementMKXKenosha, Racine, Walworth63 min
Aug 6, 8:00 PM CDTAreal Flood AdvisoryMKXJefferson, Rock, Walworth2 hr
Aug 6, 8:14 PM CDTSevere Thunderstorm WarningMKXRock, Walworth31 min
Aug 6, 8:51 PM CDTSpecial Weather StatementMKXRock, Walworth54 min
Aug 6, 9:45 PM CDTSevere Thunderstorm WarningMKXDane30 min
Aug 6, 10:15 PM CDTSpecial Weather StatementMKXDane30 min
Aug 7, 10:06 AM CDTSpecial Weather StatementMKXColumbia, Marquette54 min
Aug 7, 11:01 AM CDTSpecial Weather StatementMKXColumbia, Green Lake59 min
Aug 7, 11:47 AM CDTSpecial Weather StatementMKXDodge, Jefferson58 min
Aug 7, 12:32 PM CDTSevere Thunderstorm WarningMKXJefferson43 min
Aug 7, 1:48 PM CDTSevere Thunderstorm WarningMKXSauk42 min
Aug 7, 3:53 PM CDTSevere Thunderstorm Warning Considerable damage threatMKXSauk52 min
Aug 7, 4:33 PM CDTSevere Thunderstorm Warning Considerable damage threatMKXColumbia, Dane, Iowa, Sauk57 min
Aug 7, 4:38 PM CDTTornado Warning Tornado observedMKXIowa67 min
Aug 7, 5:17 PM CDTSevere Thunderstorm WarningMKXColumbia, Green Lake, Marquette, Sauk58 min
Aug 7, 5:26 PM CDTTornado WarningMKXColumbia39 min
Aug 7, 5:31 PM CDTSevere Thunderstorm WarningMKXColumbia, Dane59 min
Aug 7, 5:33 PM CDTTornado WarningMKXIowa57 min
Aug 7, 6:03 PM CDTSpecial Weather StatementMKXDodge, Fond du Lac, Green Lake42 min
Aug 7, 6:09 PM CDTSevere Thunderstorm WarningMKXDane66 min
Aug 7, 6:25 PM CDTSevere Thunderstorm WarningMKXDane50 min
Aug 7, 6:40 PM CDTSpecial Weather StatementMKXJefferson50 min

Nearby

Severe Thunderstorm Warnings in Wisconsin, 2021Every 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.