Alert archive / Iowa / Tornado Warnings in 2011
Tornado Warning 21, NWS Sioux Falls, SD
NWS Sioux Falls, SD issued this tornado warning at May 11, 2011, 6:58 PM CDT for 4 counties in Iowa; Rock County, Minnesota. It was in force for 32 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
- May 11, 2011, 6:58 PM CDT (23:58 UTC)
- Expired
- May 11, 2011, 7:30 PM CDT
- In force
- 32 min
- Issued by
- NWS Sioux Falls, SD
- Area
- Storm-based polygon
Counties Dickinson County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Rock County, MN
The radar
The Sioux Falls radar (KFSD), 84 km from the middle of the area, began a volume at 00:02 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, 7:07 PM CDT | TORNADO | Ashton, IA |
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, 12.0 hours before the alert went out and 229 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.
- 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
The text
As transmitted, in the capitals the NWS used until 2016.
395
WFUS53 KFSD 112358
TORFSD
IAC059-119-141-143-MNC133-120030-
/O.NEW.KFSD.TO.W.0021.110511T2358Z-110512T0030Z/
BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
658 PM CDT WED MAY 11 2011
THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A
* TORNADO WARNING FOR...
SOUTHWESTERN DICKINSON COUNTY IN NORTHWEST IOWA...
EASTERN LYON COUNTY IN NORTHWEST IOWA...
NORTHERN O'BRIEN COUNTY IN NORTHWEST IOWA...
OSCEOLA COUNTY IN NORTHWEST IOWA...
SOUTHEASTERN ROCK COUNTY IN SOUTHWEST MINNESOTA...
* UNTIL 730 PM CDT
* AT 657 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO NEAR
GEORGE. DOPPLER RADAR SHOWED A LINE OF THUNDERSTORMS CAPABLE OF
PRODUCING BRIEF TORNADOES MOVING NORTHEAST AT 25 MPH.
* THE TORNADO WILL BE NEAR...
GEORGE AROUND 705 PM CDT...
ASHTON AND SANBORN AROUND 720 PM CDT...
LITTLE ROCK AROUND 725 PM CDT...
SIBLEY AROUND 730 PM CDT...
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR
OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.
&&
LAT...LON 4325 9535 4325 9540 4321 9540 4309 9553
4321 9587 4326 9587 4326 9602 4335 9628
4356 9614 4354 9606 4350 9606 4350 9594
4331 9529
TIME...MOT...LOC 2357Z 227DEG 20KT 4330 9603
$$
LAFLIN2 follow-up statements
371
WWUS53 KFSD 120009
SVSFSD
SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
709 PM CDT WED MAY 11 2011
IAC059-119-141-143-MNC133-120030-
/O.CON.KFSD.TO.W.0021.000000T0000Z-110512T0030Z/
DICKINSON IA-OSCEOLA IA-LYON IA-O'BRIEN IA-ROCK MN-
709 PM CDT WED MAY 11 2011
...A TORNADO WARNING REMAINS IN EFFECT FOR SOUTHEASTERN ROCK...
NORTHERN O'BRIEN...EASTERN LYON...OSCEOLA AND SOUTHWESTERN DICKINSON
COUNTIES UNTIL 730 PM CDT...
AT 709 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO. THIS
TORNADO WAS LOCATED NEAR ASHTON...MOVING NORTHEAST AT 25 MPH.
THE TORNADO WILL BE NEAR...
ASHTON AND SANBORN AROUND 720 PM CDT...
LITTLE ROCK AND SIBLEY AROUND 730 PM CDT...
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TO REPEAT...A TORNADO IS ON THE GROUND. TAKE COVER NOW. MOVE TO AN
INTERIOR ROOM ON THE LOWEST FLOOR OF A STURDY BUILDING. AVOID
WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR OUTDOORS...MOVE TO THE
CLOSEST SUBSTANTIAL SHELTER AND PROTECT YOURSELF FROM FLYING DEBRIS.
&&
LAT...LON 4325 9535 4325 9540 4321 9540 4309 9553
4321 9587 4326 9587 4326 9602 4335 9628
4356 9614 4354 9606 4350 9606 4350 9594
4331 9529
TIME...MOT...LOC 0009Z 227DEG 20KT 4335 9596
$$
LAFLIN164
WWUS53 KFSD 120023
SVSFSD
SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
723 PM CDT WED MAY 11 2011
IAC059-119-141-143-MNC133-120033-
/O.EXP.KFSD.TO.W.0021.000000T0000Z-110512T0030Z/
DICKINSON IA-OSCEOLA IA-LYON IA-O'BRIEN IA-ROCK MN-
723 PM CDT WED MAY 11 2011
...THE TORNADO WARNING FOR SOUTHEASTERN ROCK...NORTHERN O'BRIEN...
EASTERN LYON...OSCEOLA AND SOUTHWESTERN DICKINSON COUNTIES WILL
EXPIRE AT 730 PM CDT...
THE STORM WHICH PROMPTED THE WARNING HAS WEAKENED AND MOVED OUT OF
THE WARNED AREA.
LAT...LON 4325 9535 4325 9540 4321 9540 4309 9553
4321 9587 4326 9587 4326 9602 4335 9628
4356 9614 4354 9606 4350 9606 4350 9594
4331 9529
TIME...MOT...LOC 0023Z 227DEG 20KT 4340 9588
$$
LAFLINThe office that day
Everything else NWS Sioux Falls, SD issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 11, 4:55 PM CDT | Severe Thunderstorm Warning | FSD | Plymouth, Woodbury | 50 min |
| May 11, 5:37 PM CDT | Severe Thunderstorm Warning | FSD | Plymouth | 38 min |
| May 11, 5:42 PM CDT | Severe Thunderstorm Warning | FSD | Plymouth, Sioux, Woodbury | 48 min |
| May 11, 5:48 PM CDT | Severe Thunderstorm Warning | FSD | Lyon, Sioux | 42 min |
| May 11, 6:37 PM CDT | Tornado Warning | FSD | Lyon, Sioux | 23 min |
| May 11, 6:49 PM CDT | Severe Thunderstorm Warning | FSD | Lyon, Sioux | 41 min |
Nearby
Tornado Warnings in Iowa, 2011Tornado Warnings in Minnesota, 2011Every tornado warning in 2011Tornadoes 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.