Alert archive / Iowa / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 88, NWS Sioux Falls, SD

August 20, 2021Cherokee County, Plymouth County, Woodbury County, Iowa

NWS Sioux Falls, SD issued this severe thunderstorm warning at Aug 20, 2021, 6:13 PM CDT for Cherokee County, Plymouth County, Woodbury County, Iowa. It was in force for 32 min. 2 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 20, 2021, 6:13 PM CDT (23:13 UTC)
Expired: Aug 20, 2021, 6:45 PM CDT
In force: 32 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Cherokee County, IA, Plymouth County, IA, Woodbury County, IA

The radar

The Sioux Falls radar (KFSD), 137 km from the middle of the area, began a volume at 23:14 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.

What was reported inside it

Time	Report	Where	Remark
Aug 20, 6:16 PM CDT	TSTM WND DMG	Pierson, IA	LARGE TREE SNAPPED. ALSO HAD 6 INCH DIAMETER TREE BRANCHES DOWN.
Aug 20, 6:22 PM CDT	TSTM WND DMG	3 W Washta, IA	DELAYED REPORT VIA SOCIAL MEDIA. LARGE TREE BRANCH ESTIMATED AT 10 INCHES IN DIAMETER BROKEN. SOME DAMAGE TO CORN CROP ALSO NOTED.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Aug 20, 3:58 PM CDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 11.2 hours before the alert went out and 146 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: 950 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 534 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 121 m²/s²
0-3 km storm-relative helicity: 99 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

034 
WUUS53 KFSD 202313
SVRFSD
IAC035-149-193-202345-
/O.NEW.KFSD.SV.W.0088.210820T2313Z-210820T2345Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Sioux Falls SD
613 PM CDT Fri Aug 20 2021

The National Weather Service in Sioux Falls has issued a

* Severe Thunderstorm Warning for...
  Southwestern Cherokee County in northwestern Iowa...
  Northeastern Woodbury County in west central Iowa...
  Southeastern Plymouth County in northwestern Iowa...

* Until 645 PM CDT.

* At 612 PM CDT, a severe thunderstorm was located over Pierson, or
  20 miles southwest of Cherokee, moving northeast at 30 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect wind damage 
           to roofs, siding, and trees.

* This severe thunderstorm will be near...
  Washta around 625 PM CDT.

Other locations in the path of this severe thunderstorm include
Quimby.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4248 9593 4258 9596 4275 9563 4257 9561
      4256 9574 4253 9579
TIME...MOT...LOC 2312Z 236DEG 25KT 4256 9586 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Schumacher

3 follow-up statements

538 
WWUS53 KFSD 202323
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
623 PM CDT Fri Aug 20 2021

IAC149-193-202333-
/O.CAN.KFSD.SV.W.0088.000000T0000Z-210820T2345Z/
Woodbury IA-Plymouth IA-
623 PM CDT Fri Aug 20 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN WOODBURY AND
SOUTHEASTERN PLYMOUTH COUNTIES IS CANCELLED...
    
The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

A Severe Thunderstorm Watch remains in effect until 1000 PM CDT for
northwestern and west central Iowa.

LAT...LON 4263 9586 4275 9563 4257 9561 4256 9586
TIME...MOT...LOC 2323Z 242DEG 24KT 4259 9577 

$$

IAC035-202345-
/O.CON.KFSD.SV.W.0088.000000T0000Z-210820T2345Z/
Cherokee IA-
623 PM CDT Fri Aug 20 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 645 PM CDT
FOR SOUTHWESTERN CHEROKEE COUNTY...

At 623 PM CDT, a severe thunderstorm was located over Washta, or 15
miles southwest of Cherokee, moving northeast at 30 mph.

HAZARD...60 mph wind gusts and penny size hail.

SOURCE...Radar indicated.

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

Locations impacted include...
  Quimby.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4263 9586 4275 9563 4257 9561 4256 9586
TIME...MOT...LOC 2323Z 242DEG 24KT 4259 9577 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Schumacher

966 
WWUS53 KFSD 202333
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
633 PM CDT Fri Aug 20 2021

IAC035-202345-
/O.CON.KFSD.SV.W.0088.000000T0000Z-210820T2345Z/
Cherokee IA-
633 PM CDT Fri Aug 20 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 645 PM CDT
FOR SOUTHWESTERN CHEROKEE COUNTY...

At 632 PM CDT, a severe thunderstorm was located over Quimby, or 11
miles southwest of Cherokee, moving northeast at 30 mph.

HAZARD...60 mph wind gusts and penny size hail.

SOURCE...Radar indicated. At 616 PM CDT, a weather spotter reported 
         a large tree snapped in Pierson.

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

Locations impacted include...
Quimby and Washta. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4264 9581 4274 9563 4257 9561 4256 9581
TIME...MOT...LOC 2332Z 236DEG 25KT 4263 9570 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

Schumacher

497 
WWUS53 KFSD 202345
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
645 PM CDT Fri Aug 20 2021

IAC035-202354-
/O.EXP.KFSD.SV.W.0088.000000T0000Z-210820T2345Z/
Cherokee IA-
645 PM CDT Fri Aug 20 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHWESTERN CHEROKEE COUNTY
WILL EXPIRE AT 645 PM CDT...
                
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 will be allowed to expire.  However gusty 
winds to 50 mph are still possible with this thunderstorm as it 
moves toward Cherokee.

A Severe Thunderstorm Watch remains in effect until 1000 PM CDT for
northwestern and west central Iowa.

LAT...LON 4264 9581 4274 9563 4257 9561 4256 9581
TIME...MOT...LOC 2344Z 236DEG 25KT 4267 9562 

$$

Schumacher

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 20, 6:31 PM CDT	Severe Thunderstorm Warning	FSD	Ida, Woodbury	29 min

Nearby

Severe Thunderstorm Warnings in Iowa, 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.