Tornado and Flash Flood in Iowa, June 20, 2011

Name: Tornado and Flash Flood in Iowa, June 20, 2011
Start: 2011-06-20T20:04
End: 2011-06-20T22:30
Location: Iowa

June 20, 2011 · NWS FSD · 15 events in 6 counties and zones

Thunderstorms produced flash flooding and damaging winds at several locations in northwest Iowa on the evening of June 20th. There was also one tornado reported.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 2
Property damage: $245,000
Crop damage: None recorded
Events: 15

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS FSD wrote it up.

Thunderstorms produced flash flooding and damaging winds at several locations in northwest Iowa on the evening of June 20th. There was also one tornado reported.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Sioux Falls, SD wrote its last area forecast discussion before the first event at Jun 20, 2:35 PM CST, 5 hours 29 minutes earlier.

Area forecast discussion, Jun 20, 2:35 PM CST, 5 hours 29 minutes before

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
335 PM CDT MON JUN 20 2011

.DISCUSSION...
THE 18Z SURFACE ANALYSIS HAD LOW PRESSURE CENTERED OVER NORTH
CENTRAL KANSAS WITH A WARM FRONT EXTENDING EAST INTO SOUTHEAST
NEBRASKA AND SOUTHERN IOWA. WATER VAPOR LOOP HAD A VERY STRONG WAVE
ROTATING NORTH INTO SOUTHWEST NEBRASKA THIS AFTERNOON WHICH SHOULD
BEGIN TO INTERACT WITH AN INCREASINGLY UNSTABLE AIR MASS IN THE LOW
LEVELS. EXPECT THUNDERSTORMS TO DEVELOP OVER CENTRAL NEBRASKA...THEN
PROPAGATE NORTHEAST THIS EVENING. DEEP LAYER SHEAR VERY SUPPORTIVE
OF SEVERE THUNDERSTORMS AND WITH A VERY STRONG UNIDIRECTIONAL SOUTH
WIND FROM ABOUT 3KM ON UP...SOME CONCERN THAT A NORTHWARD MOVING BOW
ECHO COULD DEVELOP EARLY THIS EVENING . THE MOST IMPRESSIVE CAPE
VALUES CURRENTLY BOTTLED UP FROM ABOUT INTERSTATE 80 SOUTH...SO SOME
OF THE LARGEST HAIL POTENTIAL LIKELY TO BE CONFINED TO THAT
AREA...ALTHOUGH THE WARM FRONT COULD BEGIN TO SURGE NORTH A BIT NOW
THAT THE WAVE IS LIFTING NORTH WHICH WOULD STILL PLACE THE FAR
SOUTHERN CWA UNDER RISK FOR VERY LARGE HAIL...STRONG WINDS AND
TORNADOES...ESPECIALLY WITH 0KM TO 1KM BULK SHEAR NEAR THE BOUNDARY
OF ABOUT 25 KNOTS. EXPECT THUNDERSTORMS TO MERGE WEST INTO THE
INVERTED TROUGH AND BRING A VERY GOOD CHANCE FOR HEAVY RAINFALL. IN
FACT...ADDED A FEW COUNTIES TO THE FLASH FLOOD WATCH IN NORTHEAST
NEBRASKA...NORTHWEST IOWA AND SOUTHWEST MINNESOTA AS THE RAIN THIS
EVENING COULD ALSO BE PRETTY HEAVY.

THE UPPER LEVEL LOW WILL TRACK OUT OF EASTERN NEBRASKA AND INTO OUR
ZONES ON TUESDAY...WITH ASSOCIATED MIDLEVEL TROWAL LIKE FEATURE AND
INVERTED SURFACE TROUGH PUSHING FROM WEST TO EAST ACROSS THE COUNTY
WARNING AREA THROUGH TUESDAY NIGHT. WITH THIS...WILL HAVE WIDESPREAD
SHOWERS/ISOLATED THUNDERSTORMS THROUGH THE PERIOD. COULD HAVE HEAVY
RAIN ON TUESDAY WITH PRECIPITABLE WATER VALUES RUNNING BETWEEN 1.5
TO 2 INCHES...AND IN LIGHT OF THAT...CONTINUED WITH FLASH FLOOD
WATCH THROUGH TOMORROW AND EXPANDED IT FARTHER TO THE EAST. COOLER
AIR WILL BE FILTERING INTO THE REGION WITH THE LOW PRESSURE...AND
HIGHS ON TUESDAY WILL BE IN THE MID 60S WEST TO MID 70S EAST.
SHOWERS WILL TAPER OFF SLOWLY ON WEDNESDAY...AND IT WILL BE VERY
COOL  UNDER THE DEPARTING LOW PRESSURE...WITH HIGHS BARELY TOPPING
60 DEGREES IN OUR NORTHEASTERN AREAS WHERE CLOUDS/SHOWERS WILL
REMAIN THE LONGEST. FARTHER TO THE WEST...WHERE SUN WILL BE POSSIBLE
IN THE AFTERNOON...HIGHS WILL CLIMB TO NEAR 70.

KEPT A SMALL CHANCE OF SHOWERS IN OUR FAR NORTHEAST ON THURSDAY WITH
A LINGERING UPPER LEVEL VORTICITY FILAMENT STREAMING ACROSS THE
AREA. HIGHS WILL BE A LITTLE WARMER...THOUGH STILL BELOW NORMAL...IN
THE UPPER 60S TO MID 70S. UPPER LEVEL RIDGING BUILDS INTO THE REGION
FOR THE REMAINDER OF THE WEEK INTO THE WEEKEND...WITH A WARMING
TREND THROUGH THE PERIOD. CANNOT COMPLETELY RULE OUT A
SHOWER/THUNDERSTORM FOR THE TIME PERIOD FRIDAY INTO SUNDAY...BUT NO
REAL MODEL CONSENSUS ON WEAK WAVES TOPPING THE UPPER LEVEL
RIDGE...BUT KEPT SMALL POPS ALMOST EVERYDAY.  /JM

&&

.HYDROLOGY...
EXPANDED THE FLASH FLOOD WATCH EASTWARD A FEW COUNTIES. AN AREA OF
HEAVY RAINFALL IS EXPECTED TO DEVELOP TONIGHT WITH THE HIGHEST
THREAT FOR EXCESSIVE RAINFALL ACROSS SOUTH DAKOTA. THE MAIN THREAT
FOR THIS HEAVY RAIN WILL BE FROM 600 PM THROUGH MIDNIGHT WHERE 2 TO
4 INCHES WILL BE POSSIBLE AS THUNDERSTORMS DEVELOP AND MOVE NORTH
FROM NEBRASKA. THE POTENTIAL FOR ADDITIONAL POCKETS OF HEAVY RAIN
WILL CONTINUE INTO TUESDAY AS THE STRONG LOW PRESSURE IS VERY SLOW
TO EXIT. /08

&&

.AVIATION...
MAINLY VFR THROUGH ABOUT 1Z THIS EVENING...THEN OCCASIONAL SHOWERS
AND THUNDERSTORMS ALONG WITH CEILINGS LIKELY DROPPING BACK TO MVFR
THROUGH 18Z TUESDAY.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...

IA...NONE.
MN...NONE.
NE...NONE.
SD...FLASH FLOOD WATCH THROUGH TUESDAY EVENING FOR SDZ038>040-050-
     052>066-068-069.

&&

Hazardous weather outlook, Jun 20, 6:32 PM CST, 1 hour 32 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
732 PM CDT MON JUN 20 2011

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-
IAZ001>003-012>014-020>022-031-032-NEZ013-014-211200-
AURORA-BEADLE-BON HOMME-BROOKINGS-BRULE-BUENA VISTA IA-
CHARLES MIX-CHEROKEE IA-CLAY-CLAY IA-COTTONWOOD MN-DAKOTA NE-
DAVISON-DICKINSON IA-DIXON NE-DOUGLAS-GREGORY-HANSON-HUTCHINSON-
IDA IA-JACKSON MN-JERAULD-KINGSBURY-LAKE-LINCOLN-LINCOLN MN-
LYON IA-LYON MN-MCCOOK-MINER-MINNEHAHA-MOODY-MURRAY MN-NOBLES MN-
OBRIEN IA-OSCEOLA IA-PIPESTONE MN-PLYMOUTH IA-ROCK MN-SANBORN-
SIOUX IA-TURNER-UNION-WOODBURY IA-YANKTON-
732 PM CDT MON JUN 20 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA...
SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS...
SEVERE THUNDERSTORMS ARE EXPECTED THIS EVENING...ESPECIALLY NEAR
THE MISSOURI RIVER IN FAR SOUTHEAST SOUTH DAKOTA AND NORTHWEST
IOWA. HAIL TO THE SIZE OF GOLF BALLS...WIND GUSTS TO 80 MPH AND
ISOLATED TORNADOES. ACROSS EAST CENTRAL AND SOUTH CENTRAL SOUTH
DAKOTA WIND GUSTS TO 70 MPH AND HAIL TO THE SIZE OF QUARTERS WILL
BE THE MAIN THREATS.

FLOODING...
HEAVY RAIN AND SLOW THUNDERSTORM MOTION ACROSS SOUTH CENTRAL
SOUTH DAKOTA THROUGH TUESDAY EVENING WILL CREATE THE POTENTIAL
FOR 2 TO 4 INCHES OF RAINFALL ACROSS MUCH OF SOUTHEAST SOUTH
DAKOTA. THESE AREAS ARE ALREADY SATURATED FROM RAINFALL LAST WEEK
AS WELL AS ONGOING RIVER FLOODING...AND ARE THEREFORE VERY PRONE
TO FLASH FLOODING WITH THIS AMOUNT OF RAINFALL. WHILE THE
HEAVIEST RAIN SHOULD BE IN SOUTH DAKOTA LOCATIONS ACROSS
SOUTHWEST MINNESOTA AND NORTHWEST IOWA WILL ALSO SEE A THREAT FOR
HEAVY RAINFALL...ESPECIALLY THIS EVENING.

RECORD HIGH RELEASES ARE OCCURRING FROM THE MISSOURI RIVER
RESERVOIRS AND WILL CONTINUE INTO MID SUMMER. HIGH WATER LEVELS
WILL CAUSE SIGNIFICANT IMPACTS BETWEEN CHAMBERLAIN AND SIOUX
CITY.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

SHOWERS AND NON-SEVERE THUNDERSTORMS WILL BE ONGOING ACROSS
CENTRAL AND EASTERN SOUTH DAKOTA ON TUESDAY...WHICH WILL LIKELY
DECREASE IN INTENSITY AND COVERAGE BY THE EVENING. SLOW MOVING
SHOWERS AND STORMS ARE EXPECTED TO PRODUCE HEAVY RAINFALL AT
TIMES ON TUESDAY... ESPECIALLY ACROSS SOUTH DAKOTA AND SOUTHWEST
MINNESOTA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE NEEDED TONIGHT.

&&

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.

In the hours before

Local storm report, Jun 20, 6:28 PM CST, 1 hour 36 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
728 PM CDT MON JUN 20 2011

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0720 PM     FLASH FLOOD      10 WNW PLATTE           43.44N 99.03W
06/20/2011                   CHARLES MIX        SD   LAW ENFORCEMENT

            WATER OVER ROAD ON HIGHWAY 50

&&

MFUHS

Local storm report, Jun 20, 7:33 PM CST, 31 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
833 PM CDT MON JUN 20 2011

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0825 PM     TSTM WND DMG     YANKTON                 42.89N 97.39W
06/20/2011                   YANKTON            SD   LAW ENFORCEMENT

            POWER LINES DOWN. LARGE TREE LIMBS DOWN THAT REQUIRED
            STREET DEPARTMENT REMOVAL.

&&

LS

Local storm report, Jun 20, 7:35 PM CST, 29 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
835 PM CDT MON JUN 20 2011

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0827 PM     FLASH FLOOD      10 NW PLATTE            43.49N 98.99W
06/20/2011                   CHARLES MIX        SD   EMERGENCY MNGR

            HIGHWAY 50 EAST OF ACADEMY WAS COVERED WITH WATER.

&&

MDB

The radar

The Omaha radar (KOAX), 114 km away, was scanning. The volume nearest the first event began at 02:02 UTC.

Open the radar archive at this moment

Event by event

13 thunderstorm wind, 1 tornado, 1 flash flood. Local standard time, as filed.

Thunderstorm Wind, Woodbury

When: June 20, 8:04 PM CST
Where: Woodbury County, 1.47 mi NNW of Salix
Measured: 61 kt (70 mph) estimated gust
Reported by: Public
Coordinates: 42.340, -96.290

Thunderstorm winds blew down several large branches.

Thunderstorm Wind, Woodbury

When: June 20, 8:12 PM CST
Where: Woodbury County, 0.51 mi E of Oto
Measured: 52 kt (60 mph) estimated gust
Reported by: Fire Department/Rescue
Coordinates: 42.280, -95.890

Thunderstorm winds caused tree damage, including several branches blown down.

Thunderstorm Wind, Woodbury

When: June 20, 8:20 PM CST
Where: Woodbury County, 0.69 mi S of Moville
Measured: 70 kt (81 mph) estimated gust
Injuries: 2 direct, 0 indirect
Property damage: $150,000
Reported by: Trained Spotter
Coordinates: 42.490, -96.070

Thunderstorm winds tore roofs off 3 homes and damaged the roofs of at least 40 other homes. The winds also caused widespread tree damage and overturned four campers. There were 2 people injured in the overturned campers.

Thunderstorm Wind, Ida

When: June 20, 8:30 PM CST
Where: Ida County, Battle Creek
Measured: 61 kt (70 mph) estimated gust
Property damage: $5,000
Reported by: Trained Spotter
Coordinates: 42.320, -95.600

Thunderstorm winds blew down large branches and power lines, with a resulting power outage.

Thunderstorm Wind, Ida

When: June 20, 8:30 PM CST
Where: Ida County, 0.86 mi NE of Holstein
Measured: 61 kt (70 mph) estimated gust
Reported by: COOP Observer
Coordinates: 42.490, -95.540

Thunderstorm winds caused tree damage, including up to 12 inch diameter branches blown down. Some roads were closed by tree debris.

Tornado, Plymouth

When: June 20, 8:40 PM CST to 8:42 PM CST
Where: Plymouth County, 2.46 mi SSW of O Leary to 1.87 mi S of O Leary
Rating: EF0
Path length: 0.91 mi
Path width: 100 yd
Property damage: $20,000
Reported by: Fire Department/Rescue
Coordinates: 42.667, -96.088

A tornado damaged several farm buildings and grain bins.

Thunderstorm Wind, Plymouth

When: June 20, 9:00 PM CST
Where: Plymouth County, 0.51 mi W of Craig
Measured: 61 kt (70 mph) estimated gust
Property damage: $30,000
Reported by: COOP Observer
Coordinates: 42.900, -96.310

Thunderstorm winds caused tree damage, including up to 3 foot diameter trees blown down. Some vehicles were damaged by falling trees.

Thunderstorm Wind, O'Brien

When: June 20, 9:10 PM CST
Where: O'Brien County, Sutherland
Measured: 61 kt (70 mph) estimated gust
Reported by: Emergency Manager
Coordinates: 42.970, -95.500

Thunderstorm winds caused tree damage, including large trees blown down.

Thunderstorm Wind, O'Brien

When: June 20, 9:15 PM CST
Where: O'Brien County, 0.69 mi N of Primghar
Measured: 52 kt (60 mph) estimated gust
Reported by: Emergency Manager
Coordinates: 43.090, -95.630

Thunderstorm winds caused tree damage, including several trees blown down.

Flash Flood, Plymouth

When: June 20, 9:21 PM CST to 10:30 PM CST
Where: Plymouth County, 0.51 mi E of Merrill to 0.41 mi SE of Merrill
Cause: Heavy Rain
Reported by: Other Federal Agency
Coordinates: 42.720, -96.240

Heavy rain from thunderstorms caused flash flooding of Perry Creek.

Thunderstorm Wind, O'Brien

When: June 20, 9:25 PM CST
Where: O'Brien County, 3.49 mi S of Hartley Muni Arpt
Measured: 52 kt (60 mph) estimated gust
Property damage: $5,000
Reported by: Emergency Manager
Coordinates: 43.120, -95.480

Thunderstorm winds damaged the roofs of two hog confinement structures.

Thunderstorm Wind, O'Brien

When: June 20, 9:30 PM CST
Where: O'Brien County, 0.69 mi N of Hartley
Measured: 52 kt (60 mph) estimated gust
Property damage: $5,000
Reported by: Emergency Manager
Coordinates: 43.190, -95.480

Thunderstorm winds blew off part of the roof of a machine shed.

Thunderstorm Wind, Clay

When: June 20, 9:42 PM CST
Where: Clay County, 1.38 mi N of Spencer
Measured: 52 kt (60 mph) measured gust
Reported by: Broadcast Media
Coordinates: 43.170, -95.150

Thunderstorm winds caused tree damage, including large branches and a few trees blown down.

Thunderstorm Wind, Osceola

When: June 20, 9:45 PM CST
Where: Osceola County, 2.56 mi SE of May City
Measured: 61 kt (70 mph) estimated gust
Property damage: $20,000
Reported by: Fire Department/Rescue
Coordinates: 43.290, -95.450

Thunderstorm winds damaged the roof of a machine shed and caused tree damage. Some trees were blown down on houses and across roads.

Thunderstorm Wind, Osceola

When: June 20, 9:50 PM CST
Where: Osceola County, 1 mi W of Harris
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Reported by: Emergency Manager
Coordinates: 43.450, -95.470

Thunderstorm winds blew a 3 stall garage off its foundation.

What these are

Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Tornado: A violently rotating column of air in contact with the ground and extending from a thunderstorm, filed with its path, width and Fujita or Enhanced Fujita rating from the damage survey.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Iowa in 2011 Every state in 2011 This day in weather history The tornado archive for Iowa, 2011 Warnings in Iowa, June 2011

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 323626, 323651, 323655, 323656, 323659, 325085, 325088, 325091, 325093, 325100, 325109, 325113, 325117, 325119, 325122.