Alert archive / Iowa / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 171, NWS Sioux Falls, SD

December 15, 2021Plymouth County, Woodbury County, Iowa; Dakota County, Dixon County, Nebraska; Union County, South Dakota

NWS Sioux Falls, SD issued this severe thunderstorm warning at Dec 15, 2021, 3:23 PM CST for Plymouth County, Woodbury County, Iowa; Dakota County, Dixon County, Nebraska; Union County, South Dakota. It was in force for 67 min. 13 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, 3:23 PM CST (21:23 UTC)
Expired: Dec 15, 2021, 4:30 PM CST
In force: 67 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 Plymouth County, IA, Woodbury County, IA, Dakota County, NE, Dixon County, NE, Union County, SD

The radar

The Sioux Falls radar (KFSD), 121 km from the middle of the area, began a volume at 21:23 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, 4:10 PM CST	TSTM WND DMG	Homer, NE	ELECTRIC POLE BLOWN DOWN. TIME ESTIMATED FROM RADAR.
Dec 15, 4:17 PM CST	TORNADO	2 S Salix, IA
Dec 15, 4:17 PM CST	TORNADO	2 Sw Bronson, IA
Dec 15, 4:19 PM CST	TSTM WND DMG	Hornick, IA	OVERTURNED PROPANE TANKS. TIME ESTIMATED FROM RADAR.
Dec 15, 4:20 PM CST	TSTM WND DMG	4 W Bronson, IA	BUILDING DAMAGED. TIME ESTIMATED FROM RADAR.
Dec 15, 4:21 PM CST	TSTM WND DMG	2 E Sergeant Bluff, IA	ROOFS OFF A COUPLE OF HOMES BETWEEN SERGEANT BLUFF AND BRONSON. TIME ESTIMATED FROM RADAR.
Dec 15, 4:21 PM CST	TSTM WND DMG	5 Wnw Sioux City, IA	TREE UPROOTED. REPORT VIA SOCIAL MEDIA AND TIME ESTIMATED FROM RADAR.
Dec 15, 4:23 PM CST	TSTM WND GST 82	1 Wsw Sergeant Bluff, IA
Dec 15, 4:24 PM CST	TSTM WND DMG	4 Ene Sergeant Bluff, IA	DAMAGE TO BUILDING.
Dec 15, 4:25 PM CST	TSTM WND DMG	3 Se Sioux City, IA	POWER POLES LEARNING. REPORT RECEIVED VIA SOCIAL MEDIA. TIME ESTIMATED FROM RADAR.
Dec 15, 4:31 PM CST	TSTM WND DMG	2 E Lawton, IA	POWER LINES DOWN ACROSS HWY 20. TIME ESTIMATED FROM RADAR.
Dec 15, 4:31 PM CST	TSTM WND DMG	2 Ene Lawton, IA	POLE SHED ROOF OFF WITH DEBRIS BLOWN INTO FIELD. TIME ESTIMATED FROM RADAR.
Dec 15, 4:33 PM CST	TORNADO	3 Ene Lawton, IA	REPORT OF POWER FLASHES FROM POWER LINES.

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, 9.4 hours before the alert went out and 134 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.

329 
WUUS53 KFSD 152123
SVRFSD
IAC149-193-NEC043-051-SDC127-152230-
/O.NEW.KFSD.SV.W.0171.211215T2123Z-211215T2230Z/

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

The National Weather Service in Sioux Falls has issued a

* Severe Thunderstorm Warning for...
  Western Woodbury County in west central Iowa...
  Southwestern Plymouth County in northwestern Iowa...
  Dakota County in northeastern Nebraska...
  Dixon County in northeastern Nebraska...
  Southern Union County in southeastern South Dakota...

* Until 430 PM CST.

* At 322 PM CST, severe thunderstorms were located along a line
  extending from Hadar to 6 miles south of Pilger to 6 miles south of
  Dodge, moving northeast at 65 mph.

  HAZARD...70 mph wind gusts and penny size hail.

  SOURCE...Radar indicated.

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

* Severe thunderstorms will be near...
  Emerson, Concord and Dixon In Dixon County around 350 PM CST.
  Allen around 355 PM CST.
  Homer, Hubbard and Martinsburg around 400 PM CST.
  Ponca, Dakota City, Salix and Newcastle around 405 PM CST.
  Sioux City, South Sioux City, Sergeant Bluff and Ponca State Park 
  around 410 PM CST.
  Elk Point, Sloan, Lawton, Jefferson and Hornick around 415 PM CST.
  Moville around 420 PM CST.

Other locations impacted by these severe thunderstorms include
Bronson and Waterbury.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4225 9633 4228 9635 4228 9672 4227 9673
      4226 9702 4273 9702 4275 9700 4275 9696
      4272 9696 4273 9690 4271 9682 4271 9680
      4274 9680 4270 9607 4221 9602 4222 9634
TIME...MOT...LOC 2122Z 226DEG 57KT 4212 9745 4192 9707 4162 9690 

TORNADO...POSSIBLE
THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

Weisser

1 follow-up statement

877 
WWUS53 KFSD 152144
SVSFSD

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

IAC149-193-NEC043-051-SDC127-152230-
/O.CON.KFSD.SV.W.0171.000000T0000Z-211215T2230Z/
Woodbury IA-Plymouth IA-Dakota NE-Dixon NE-Union SD-
344 PM CST Wed Dec 15 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 430 PM CST
FOR WESTERN WOODBURY...SOUTHWESTERN PLYMOUTH...DAKOTA...DIXON AND
SOUTHERN UNION COUNTIES...

At 343 PM CST, severe thunderstorms were located along a line
extending from near Wayne to near Pender to near Uehling, moving
northeast at 70 mph.

HAZARD...70 mph wind gusts and penny size hail.

SOURCE...Radar indicated.

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

These severe storms will be near...
  Allen around 355 PM CST.
  Homer and Martinsburg around 400 PM CST.
  Sioux City metro and Salix around 405 PM CST.
  Elk Point, Jefferson and Ponca State Park around 410 PM CST.
  Lawton around 415 PM CST.
  Moville and Hornick around 420 PM CST.

Other locations impacted by these severe thunderstorms include
Bronson and Waterbury.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 800 PM CST for northwestern
and west central Iowa...northeastern Nebraska...and southeastern
South Dakota.
 
&&

LAT...LON 4225 9633 4228 9635 4228 9672 4227 9673
      4226 9702 4273 9702 4275 9700 4275 9696
      4272 9696 4273 9690 4271 9682 4271 9680
      4274 9680 4270 9607 4221 9602 4222 9634
TIME...MOT...LOC 2143Z 221DEG 62KT 4231 9706 4208 9662 4172 9655 

TORNADO...POSSIBLE
THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

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, 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, 4:51 PM CST	Severe Thunderstorm Warning Considerable damage threat	FSD	O'Brien, Sioux	39 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
Dec 15, 3:59 PM CST	Tornado Warning	FSD	Dakota, Dixon	31 min
Dec 15, 9:01 AM CST	Dense Fog Advisory	FSD	Beadle, Brookings, Davison, Hanson, Kingsbury, Lake and 4 more	119 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.