Alert archive / Iowa / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 164, NWS Sioux Falls, SD

September 17, 20218 counties in Iowa; Dakota County, Dixon County, Nebraska; Union County, South Dakota

NWS Sioux Falls, SD issued this severe thunderstorm warning at Sep 17, 2021, 1:11 AM CDT for 8 counties in Iowa; Dakota County, Dixon County, Nebraska; Union County, South Dakota. It was in force for 49 min. 1 report 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: Sep 17, 2021, 1:11 AM CDT (06:11 UTC)
Expired: Sep 17, 2021, 2:00 AM CDT
In force: 49 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Buena Vista County, IA, Cherokee County, IA, Clay County, IA, Ida County, IA, O'Brien County, IA, Plymouth County, IA, Sioux County, IA, Woodbury County, IA, Dakota County, NE, Dixon County, NE, Union County, SD

The radar

The Sioux Falls radar (KFSD), 117 km from the middle of the area, began a volume at 06:14 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
Sep 17, 1:15 AM CDT	TSTM WND DMG	Orange City, IA	CORRECTS TIME OF PREVIOUS TSTM WND DMG REPORT FROM ORANGE CITY. REPORT FROM ORANGE CITY IA, SPOTTER SENT PICTURE OF LARGE TREE BRANCH DOWNED DURING THE STORM.

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

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 6.2 hours before the alert went out and 168 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: 612 J/kg
Mixed-layer CIN: -165 J/kg
Mixed-layer LCL: 2155 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: 19 m²/s²
0-3 km storm-relative helicity: 132 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

035 
WUUS53 KFSD 170611
SVRFSD
IAC021-035-041-093-141-149-167-193-NEC043-051-SDC127-170700-
/O.NEW.KFSD.SV.W.0164.210917T0611Z-210917T0700Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Sioux Falls SD
111 AM CDT Fri Sep 17 2021

The National Weather Service in Sioux Falls has issued a

* Severe Thunderstorm Warning for...
  Cherokee County in northwestern Iowa...
  Northern Woodbury County in west central Iowa...
  Southeastern Sioux County in northwestern Iowa...
  Plymouth County in northwestern Iowa...
  Northwestern Buena Vista County in northwestern Iowa...
  Southwestern Clay County in northwestern Iowa...
  O'Brien County in northwestern Iowa...
  Northwestern Ida County in west central Iowa...
  North central Dakota County in northeastern Nebraska...
  Northeastern Dixon County in northeastern Nebraska...
  Southeastern Union County in southeastern South Dakota...

* Until 200 AM CDT.

* At 110 AM CDT, severe thunderstorms were located along a line
  extending from North Sioux City to Le Mars to 6 miles northeast of
  Sioux Center, moving east at 60 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

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

* Severe thunderstorms will be near...
  Orange City around 115 AM CDT.
  Remsen and Hospers around 120 AM CDT.
  Hinton and Archer around 125 AM CDT.
  Marcus around 130 AM CDT.

Other locations in the path of these severe thunderstorms include
Primghar, Cleghorn, Cherokee, Kingsley, Larrabee, Pierson, Aurelia,
Everly, Royal and Washta.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4250 9552 4277 9524 4316 9507 4315 9627
      4284 9637 4251 9670
TIME...MOT...LOC 0610Z 268DEG 52KT 4253 9652 4280 9615 4311 9606 

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

$$

SG

2 follow-up statements

237 
WWUS53 KFSD 170647
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
147 AM CDT Fri Sep 17 2021

NEC043-051-SDC127-170656-
/O.CAN.KFSD.SV.W.0164.000000T0000Z-210917T0700Z/
Dakota NE-Dixon NE-Union SD-
147 AM CDT Fri Sep 17 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTH CENTRAL DAKOTA...
NORTHEASTERN DIXON AND SOUTHEASTERN UNION COUNTIES IS CANCELLED...

The storms which prompted the warning have moved out of the warned 
area. Therefore, the warning has been cancelled.

LAT...LON 4277 9524 4250 9552 4251 9643 4281 9610
      4315 9600 4316 9507
TIME...MOT...LOC 0646Z 266DEG 45KT 4256 9602 4282 9565 4313 9556 

$$

IAC021-035-041-093-141-149-167-193-170700-
/O.CON.KFSD.SV.W.0164.000000T0000Z-210917T0700Z/
Cherokee IA-Woodbury IA-Sioux IA-Plymouth IA-Buena Vista IA-Clay IA-
O'Brien IA-Ida IA-
147 AM CDT Fri Sep 17 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 200 AM CDT
FOR CHEROKEE...NORTHERN WOODBURY...SOUTHEASTERN SIOUX...EASTERN
PLYMOUTH...NORTHWESTERN BUENA VISTA...SOUTHWESTERN CLAY...O'BRIEN AND
NORTHWESTERN IDA COUNTIES...

At 146 AM CDT, severe thunderstorms were located along a line
extending from near Kingsley to near Cleghorn to near Primghar,
moving east at 50 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

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

Locations impacted include...
  Primghar, Cherokee, Larrabee, Aurelia, Everly, Royal, Peterson, 
  Washta, Spencer In Clay County, Quimby, Linn Grove and Holstein.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4277 9524 4250 9552 4251 9643 4281 9610
      4315 9600 4316 9507
TIME...MOT...LOC 0646Z 266DEG 45KT 4256 9602 4282 9565 4313 9556 

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

$$

SG

451 
WWUS53 KFSD 170657
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
157 AM CDT Fri Sep 17 2021

IAC021-035-041-093-141-149-167-193-170706-
/O.EXP.KFSD.SV.W.0164.000000T0000Z-210917T0700Z/
Cherokee IA-Woodbury IA-Sioux IA-Plymouth IA-Buena Vista IA-Clay IA-
O'Brien IA-Ida IA-
157 AM CDT Fri Sep 17 2021

...THE SEVERE THUNDERSTORM WARNING FOR CHEROKEE...NORTHERN
WOODBURY...SOUTHEASTERN SIOUX...EASTERN PLYMOUTH...NORTHWESTERN BUENA
VISTA...SOUTHWESTERN CLAY...O'BRIEN AND NORTHWESTERN IDA COUNTIES
WILL EXPIRE AT 200 AM CDT...
            
The storms which prompted the warning have weakened below severe
limits, and no longer pose an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However gusty
winds are still possible with these thunderstorms.

Remember, a Severe Thunderstorm Warning still remains in effect for 
portions of Sioux, O'Brien, and Clay counties in northwestern Iowa 
until 230 AM CDT.

LAT...LON 4277 9524 4250 9552 4251 9643 4281 9610
      4315 9600 4316 9507
TIME...MOT...LOC 0656Z 268DEG 52KT 4256 9588 4282 9551 4313 9542 

$$

SG

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 17, 12:29 AM CDT	Severe Thunderstorm Warning	FSD	Plymouth, Sioux	46 min
Sep 17, 12:36 AM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Clay, Dickinson, Lyon, O'Brien, Osceola, Sioux	54 min
Sep 17, 1:23 AM CDT	Severe Thunderstorm Warning	FSD	Clay, Dickinson, Lyon, O'Brien, Osceola, Sioux	67 min
Sep 16, 10:20 PM CDT	Severe Thunderstorm Warning	FSD	Charles Mix, Gregory	25 min
Sep 16, 11:31 PM CDT	Severe Thunderstorm Warning	FSD	Bon Homme, Charles Mix, Hutchinson, Yankton	29 min
Sep 17, 12:10 AM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Brookings, Lake, McCook, Minnehaha, Moody	35 min
Sep 17, 12:34 AM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Minnehaha	56 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2021 Severe Thunderstorm Warnings in Nebraska, 2021 Severe Thunderstorm Warnings in South Dakota, 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.