Alert archive / Iowa / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 55, NWS Sioux Falls, SD

May 11, 2011Union County, South Dakota; Dakota County, Nebraska; Plymouth County, Woodbury County, Iowa

NWS Sioux Falls, SD issued this severe thunderstorm warning at May 11, 2011, 4:55 PM CDT for Union County, South Dakota; Dakota County, Nebraska; Plymouth County, Woodbury County, Iowa. It was in force for 50 min. 3 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: May 11, 2011, 4:55 PM CDT (21:55 UTC)
Expired: May 11, 2011, 5:45 PM CDT
In force: 50 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Plymouth County, IA, Woodbury County, IA, Dakota County, NE, Union County, SD

The radar

The Omaha radar (KOAX), 114 km from the middle of the area, began a volume at 21:55 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
May 11, 5:10 PM CDT	HAIL 0.88	10 E Salix, IA
May 11, 5:13 PM CDT	HAIL 1.75	Salix, IA
May 11, 5:15 PM CDT	TSTM WND DMG	South Sioux City, NE	LIGHT POLE KNOCKED OVER

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 12:00Z, 9.9 hours before the alert went out and 114 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: 909 J/kg
Mixed-layer CIN: -95 J/kg
Mixed-layer LCL: 1123 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 55 m²/s²
0-3 km storm-relative helicity: 177 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.2

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

120 
WUUS53 KFSD 112155
SVRFSD
IAC149-193-NEC043-SDC127-112245-
/O.NEW.KFSD.SV.W.0055.110511T2155Z-110511T2245Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
455 PM CDT WED MAY 11 2011

THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  SOUTHERN PLYMOUTH COUNTY IN NORTHWEST IOWA...
  WOODBURY COUNTY IN NORTHWEST IOWA...
  EASTERN DAKOTA COUNTY IN NORTHEAST NEBRASKA...
  SOUTHEASTERN UNION COUNTY IN SOUTHEAST SOUTH DAKOTA...

* UNTIL 545 PM CDT

* AT 455 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS WERE
  TRACKING A SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE
  HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS
  LOCATED NEAR SLOAN...OR 22 MILES SOUTHEAST OF SIOUX CITY...AND
  MOVING NORTH AT 35 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  SALIX AROUND 505 PM CDT...
  SERGEANT BLUFF AND MOVILLE AROUND 515 PM CDT...
  DAKOTA CITY AND LAWTON AROUND 520 PM CDT...
  SOUTH SIOUX CITY AROUND 525 PM CDT...
  SIOUX CITY AROUND 530 PM CDT...
  STONE STATE PARK AND NORTH SIOUX CITY AROUND 535 PM CDT...
  HINTON AROUND 540 PM CDT...

OTHER LOCATIONS IMPACTED BY THIS SEVERE THUNDERSTORM INCLUDE BRONSON.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS STORM HAS A HISTORY OF PRODUCING DAMAGING WIND. THIS IS AN
EXTREMELY DANGEROUS SITUATION. SEEK SHELTER NOW INSIDE A STURDY
STRUCTURE AND STAY AWAY FROM WINDOWS.

&&

LAT...LON 4227 9634 4228 9642 4267 9659 4264 9602
      4221 9584 4220 9595 4221 9636
TIME...MOT...LOC 2155Z 160DEG 30KT 4226 9622
WIND...HAIL 60MPH 1.00IN

$$

CHAPMAN

2 follow-up statements

380 
WWUS53 KFSD 112215
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
515 PM CDT WED MAY 11 2011

IAC149-193-NEC043-SDC127-112245-
/O.CON.KFSD.SV.W.0055.000000T0000Z-110511T2245Z/
PLYMOUTH IA-WOODBURY IA-DAKOTA NE-UNION SD-
515 PM CDT WED MAY 11 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT FOR SOUTHEASTERN
UNION...EASTERN DAKOTA...WOODBURY AND SOUTHWESTERN PLYMOUTH COUNTIES
UNTIL 545 PM CDT...

AT 514 PM CDT...A SEVERE THUNDERSTORM WAS REPORTED...PRODUCING  GOLF
BALL SIZE HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM
WAS LOCATED NEAR SALIX...OR 14 MILES SOUTHEAST OF SIOUX CITY...MOVING
NORTHWEST AT 25 MPH.  ANOTHER SEVERE THUNDERSTORM WAS LOCATED 5 MILES
SOUTHEAST OF BRONSON...MOVING NORTHWEST AT 30 MPH.

THE SEVERE THUNDERSTORM WILL BE NEAR...
  MOVILLE AROUND 525 PM CDT...
  SERGEANT BLUFF AND LAWTON AROUND 530 PM CDT...
  DAKOTA CITY AROUND 535 PM CDT...
  SOUTH SIOUX CITY AROUND 540 PM CDT...
  SIOUX CITY...STONE STATE PARK AND NORTH SIOUX CITY AROUND 545 PM
  CDT...

AT 511 PM CDT...A TRAINED SPOTTER REPORTED GOLF BALL SIZE HAIL IN 
SALIX.

OTHER LOCATIONS IMPACTED BY THIS SEVERE THUNDERSTORM INCLUDE BRONSON.

LAT...LON 4227 9634 4228 9642 4267 9659 4264 9602
      4221 9584 4220 9595 4221 9636
TIME...MOT...LOC 2214Z 155DEG 22KT 4233 9628
WIND...HAIL 60MPH 1.75IN

$$

CHAPMAN

448 
WWUS53 KFSD 112228
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
528 PM CDT WED MAY 11 2011

IAC149-193-NEC043-SDC127-112245-
/O.CON.KFSD.SV.W.0055.000000T0000Z-110511T2245Z/
PLYMOUTH IA-WOODBURY IA-DAKOTA NE-UNION SD-
528 PM CDT WED MAY 11 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT FOR SOUTHEASTERN
UNION...EASTERN DAKOTA...WESTERN WOODBURY AND SOUTHWESTERN PLYMOUTH
COUNTIES UNTIL 545 PM CDT...

AT 528 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS WERE TRACKING
A SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS LOCATED NEAR
SERGEANT BLUFF...OR 8 MILES SOUTHEAST OF SIOUX CITY...MOVING 
NORTHWEST AT 35 MPH. ANOTHER STORM WAS LOCATED NEAR MOVILLE...MOVING 
NORTH AT 35 MPH.

THE SEVERE THUNDERSTORM WILL BE NEAR...
  SIOUX CITY AND SOUTH SIOUX CITY AROUND 530 PM CDT...
  STONE STATE PARK...NORTH SIOUX CITY AND HINTON AROUND 540 PM CDT...
  RURAL AREAS WEST OF KINGSLEY BY 540 PM CDT...

AT 510 PM CDT...WINDS OF 49 MPH WERE REPORTED AT SIOUX GATEWAY 
AIRPORT.  GOLF BALL SIZE HAIL WAS REPORTED AT SALIX AT 511 PM CDT.

LAT...LON 4236 9591 4227 9605 4227 9634 4228 9642
      4267 9659 4264 9602
TIME...MOT...LOC 2225Z 154DEG 32KT 4244 9635
WIND...HAIL 60MPH 1.00IN

$$
CHAPMAN

The office that day

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

Issued	Product	Office	Counties	Lasted
May 11, 4:51 PM CDT	Severe Thunderstorm Warning	FSD	Union	39 min
May 11, 5:37 PM CDT	Severe Thunderstorm Warning	FSD	Clay, Union, Yankton	38 min
May 11, 5:42 PM CDT	Severe Thunderstorm Warning	FSD	Union	48 min
May 11, 5:48 PM CDT	Severe Thunderstorm Warning	FSD	Lincoln	42 min
May 11, 6:06 PM CDT	Severe Thunderstorm Warning	FSD	Lincoln	24 min
May 11, 6:13 PM CDT	Tornado Warning	FSD	Lincoln, Union	32 min
May 11, 6:29 PM CDT	Severe Thunderstorm Warning	FSD	Lincoln, Turner, Union	31 min
May 11, 6:49 PM CDT	Severe Thunderstorm Warning	FSD	Lincoln, Minnehaha, Turner	41 min
May 11, 6:37 PM CDT	Tornado Warning	FSD	Lyon, Sioux	23 min
May 11, 6:58 PM CDT	Tornado Warning	FSD	Dickinson, Lyon, O'Brien, Osceola	32 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2011 Severe Thunderstorm Warnings in South Dakota, 2011 Severe Thunderstorm Warnings in Nebraska, 2011 Every severe thunderstorm warning in 2011

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.