Alert archive / Iowa / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 174, NWS Sioux Falls, SD

December 15, 2021O'Brien County, Sioux County, Iowa

NWS Sioux Falls, SD issued this severe thunderstorm warning at Dec 15, 2021, 4:51 PM CST for O'Brien County, Sioux County, Iowa. It was in force for 39 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: Dec 15, 2021, 4:51 PM CST (22:51 UTC)
Expired: Dec 15, 2021, 5:30 PM CST
In force: 39 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Tornado: Possible
Damage threat: Considerable
Hail: 0.75 in
Wind: 70.0 mph

Counties O'Brien County, IA, Sioux County, IA

The radar

The Sioux Falls radar (KFSD), 67 km from the middle of the area, began a volume at 22:54 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
Dec 15, 5:10 PM CST	TSTM WND DMG	2 Sse Sutherland, IA	DESTROYED BUILDING BLOCKING HIGHWAY 10 SOUTH OF SUTHERLAND. TIME ESTIMATED FROM RADAR.
Dec 15, 5:11 PM CST	TSTM WND DMG	Sutherland, IA	LARGE TREE BRANCH DOWN IN TOWN. TIME ESTIMATED FROM RADAR.

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
Dec 15, 1:23 PM CST	Tornado Watch	SPC	7 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 10.9 hours before the alert went out and 196 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: 2165 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 346 m²/s²
0-3 km storm-relative helicity: 384 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

480 
WUUS53 KFSD 152251
SVRFSD
IAC141-167-152330-
/O.NEW.KFSD.SV.W.0174.211215T2251Z-211215T2330Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Sioux Falls SD
451 PM CST Wed Dec 15 2021

The National Weather Service in Sioux Falls has issued a

* Severe Thunderstorm Warning for...
  Sioux County in northwestern Iowa...
  O'Brien County in northwestern Iowa...

* Until 530 PM CST.

* At 450 PM CST, severe thunderstorms were located along a line
  extending from near Ireton to near Cherokee, moving northeast at 70
  mph.

  HAZARD...70 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect considerable tree damage. Damage is likely to 
           mobile homes, roofs, and outbuildings.

* Severe thunderstorms will be near...
  Sioux Center around 505 PM CST.
  Rock Valley, Hull and Sutherland around 510 PM CST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 800 PM CST for northwestern
Iowa...and southeastern South Dakota.

This is a DANGEROUS SITUATION. These storms are producing widespread 
wind damage across parts of Nebraska into Woodbury county. SEEK 
SHELTER NOW inside a sturdy structure and stay away from windows! A 
Tornado Watch remains in effect until 800 PM CST for northwestern 
Iowa...and southeastern South Dakota.

&&

LAT...LON 4291 9539 4291 9654 4296 9650 4298 9652
      4300 9649 4304 9651 4306 9646 4312 9644
      4316 9647 4322 9647 4322 9656 4324 9657
      4325 9655 4325 9539
TIME...MOT...LOC 2250Z 207DEG 59KT 4294 9640 4269 9558 

TORNADO...POSSIBLE
THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

Weisser

1 follow-up statement

057 
WWUS53 KFSD 152325
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
525 PM CST Wed Dec 15 2021

IAC141-167-152334-
/O.EXP.KFSD.SV.W.0174.000000T0000Z-211215T2330Z/
Sioux IA-O'Brien IA-
525 PM CST Wed Dec 15 2021

...THE SEVERE THUNDERSTORM WARNING FOR SIOUX AND O'BRIEN COUNTIES
WILL EXPIRE AT 530 PM CST...
            
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.

A Tornado Watch remains in effect until 800 PM CST for northwestern
Iowa.

LAT...LON 4291 9539 4291 9654 4296 9650 4298 9652
      4300 9649 4304 9651 4306 9646 4312 9644
      4316 9647 4322 9647 4322 9656 4324 9657
      4325 9655 4325 9539
TIME...MOT...LOC 2324Z 207DEG 59KT 4343 9606 4318 9524 

$$

Weisser

The office that day

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

Issued	Product	Office	Counties	Lasted
Dec 15, 2:56 AM CST	Dense Fog Advisory	FSD	Buena Vista, Cherokee, Clay, Dickinson, Ida, Lyon and 5 more	6 hr
Dec 15, 3:23 PM CST	Severe Thunderstorm Warning Considerable damage threat	FSD	Plymouth, Woodbury	67 min
Dec 15, 4:00 PM CST	Tornado Warning	FSD	Woodbury	45 min
Dec 15, 4:05 PM CST	Severe Thunderstorm Warning Considerable damage threat	FSD	Buena Vista, Cherokee, Ida, Plymouth, Woodbury	55 min
Dec 15, 4:17 PM CST	Tornado Warning	FSD	Plymouth, Woodbury	28 min
Dec 15, 4:26 PM CST	Severe Thunderstorm Warning Considerable damage threat	FSD	Plymouth, Woodbury	34 min
Dec 15, 4:31 PM CST	Tornado Warning	FSD	Ida, Plymouth, Woodbury	29 min
Dec 15, 4:32 PM CST	Tornado Warning	FSD	Plymouth, Woodbury	28 min
Dec 15, 4:42 PM CST	Tornado Warning	FSD	Buena Vista, Cherokee, Clay, Ida, O'Brien, Plymouth and 1 more	33 min
Dec 15, 4:56 PM CST	Severe Thunderstorm Warning Destructive damage threat	FSD	Buena Vista, Cherokee, Clay, Ida	46 min
Dec 15, 5:08 PM CST	Tornado Warning	FSD	Buena Vista, Cherokee, Clay	37 min
Dec 15, 5:15 PM CST	Tornado Warning	FSD	Buena Vista, Cherokee, Clay, O'Brien	30 min
Dec 15, 5:29 PM CST	Severe Thunderstorm Warning Considerable damage threat	FSD	Dickinson	46 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.