Flooding in Iowa, May 22 to 31, 2011

Name: Flooding in Iowa, May 22 to 31, 2011
Start: 2011-05-22T13:45
End: 2011-05-31T23:59
Location: Iowa

May 22 to 31, 2011 · NWS DMX · 9 events in 9 counties and zones

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: 0
Property damage: $525,000
Crop damage: None recorded
Events: 9

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 DMX wrote it up.

As has been the case in recent months, Iowa saw many large variations in temperature. The first six days of the month were much cooler than usual with temperatures falling to 20 at Sibley and Spencer on the 3rd. A lower May minimum temperature has been recorded only four times in the past 100 years (most recently in 2005). The second six days of the month were unusually warm with the temperature soaring to 100 at Jefferson on the 10th. This was Iowa’s earliest triple digit temperature since April 22, 1980 and the first time that 100 has been reached during the month since May 15, 2001. The heat was followed by another six days of below normal temperatures (13th-18th) with scattered freezes reported on the mornings of the 16th and 17th. Another six day period of unusual warmth followed on the 19th through the 24th. The alternating six day temperature cycle was cut short by one day with below normal temperatures from the 25th through the 29th with Elkader reporting a low of 35 on the 27th. Finally, the last two days of the month brought very warm weather with Spencer and Sheldon reaching 91 on the 30th. The month began with a very welcome period of mostly dry weather with a statewide average of only 0.21 inches of rain for the first ten days of the month. This helped to finally end the flooding along the upper Des Moines River. Spring planting, which was far behind the normal pace in April, managed to surge ahead of the typical progress in early May with 84% of the corn and 47% of the soybeans planted during the first two weeks of the month according to Iowa Agricultural Statistics. Rain became increasingly frequent for the remainder of the month, particularly on the 24th-25th when an average of 1.63 inches fell over Iowa. The initial round of heavy rainfall brushed northern Iowa and fell in the upper portions of the Des Moines River basin in southern Minnesota that lead to flooding beginning by the 22nd in the Estherville area. Rainfall was especially heavy over south central Iowa where Osceola reported 10.86 inches for the month. This was the second highest ever total for rainfall in the month of May among 80 years of records in Osceola with May 1996 reporting 11.65 inches of rain. Meanwhile, a small area of east central Iowa experienced a drier than normal May with only 2.17 inches of rain recorded at Manchester for their driest May since 1992. Flooding during the 3rd week of the month moved down the Des Moines River basin. For the most part the flooding was relatively minor, not causing a great deal of damage.

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 Des Moines, IA wrote its last area forecast discussion before the first event at May 22, 12:12 PM CST, 1 hour 33 minutes earlier.

Area forecast discussion, May 22, 12:12 PM CST, 1 hour 33 minutes before

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE DES MOINES IA
112 PM CDT SUN MAY 22 2011

.SHORT TERM /TODAY/...
FORECAST CHALLENGE THIS MORNING IS THUNDERSTORM CHANCES TODAY.
SHORTWAVE ROTATING AROUND UPPER LOW OVER SD WILL MOVE EAST REACHING
SOUTHERN MN BY 18Z. VERY STRONG WSW FLOW ALOFT WITH WIND SPEEDS FROM
50-60 KNOTS ABOVE 700 MB.  AT THE SURFACE...OUTFLOW BOUNDARY FROM
SATURDAY EVENING/S STORMS WAS ACROSS NORTHERN MO AT 08Z. PACIFIC
COLD FRONT SOUTH OF LOW PRESSURE CENTER IN SD EXTENDED SOUTH ACROSS
NEBRASKA. MODIFIED AIR OVER CENTRAL IA THIS MORNING SHOULD RECOVER
THIS MORNING AS SOUTHWEST LOW-LEVEL FLOW ADVECTS MID 60 DEW POINTS
INTO EASTERN IA BY 18Z. ONE ISSUE THIS MORNING IS THE POSSIBILITY OF
THUNDERSTORMS DEVELOPING ALONG OUTFLOW BOUNDARY JUST TO THE SOUTH.
THE 00Z AND 06Z NAM BOTH DEVELOP THUNDERSTORMS IN THIS AREA THIS
MORNING. FORECAST A SMALL POP FOR THIS POTENTIAL. IF STORMS DO NOT
DEVELOP...DON/T SEE ANYTHING TO PREVENT AIRMASS RECOVERY ACROSS
EASTERN IOWA. CURRENT FORECAST CALLS FOR THUNDERSTORMS DEVELOPING
EAST OF COLD FRONT IN UNSTABLE AIRMASS.  SHEAR VALUES LOOKS
IMPRESSIVE AND SEVERE WEATHER POSSIBLE AND WORDED FORECAST
ACCORDINGLY.  A NEGATIVE IS SOUTHWEST FLOW AHEAD OF COLD FRONT WHICH
WILL MINIMIZE CONVERGENCE.  IF BOUNDARY LAYER FLOW BACKS...POTENTIAL
WOULD BE GREATER.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
PRIMARY FORCING SHOULD HAVE REACHED THE FAR EAST TO SOUTHEAST OF THE
COUNTY WARNING AREA BY 00Z THIS EVENING THEN PUSH OUT OF THE AREA
TOWARD 03Z. MID LEVEL CLOUDINESS MAY LINGER THROUGH DRYING WILL
COMMENCE AFTER 06Z. THE UPPER LOW WILL BE ENGULFED BY THE CYCLONIC
FLOW OVER EASTERN CANADA ON MONDAY AND DEPART QUICKLY. A WEAK
FRONTAL BOUNDARY WILL DROP SLOWLY SOUTH THROUGH THE STATE DURING THE
AFTERNOON. MID LEVEL WARMING AND DRYING DURING THE DAY WILL LIMIT
OVERALL INSTABILITIES HOWEVER A FEW SHOWERS AND THUNDERSTORMS MAY
DEVELOP ALONG THE BOUNDARY. THE GREATER PORTION OF THE DAY WILL
REMAIN DRY THOUGH. THE NEXT IN THE SERIES OF STRONG UPPER LEVEL LOWS
WILL ENTER THE MIDWEST TUESDAY INTO WEDNESDAY. GENERAL TRENDS WILL
THIS SYSTEM HAVE BEEN FARTHER NORTH AND MORE WET FOR CENTRAL IOWA
THOUGH THE STATE WOULD REMAIN ON THE COOL SIDE OF THE SFC BOUNDARY.
HAVE FOLLOWED A ECMWF/UKMET/GEM BLEND WITH THIS FEATURE WHICH SHIFTS
PRECIPITATION FARTHER NORTH AND LINGERS A BIT LONGER THROUGH
WEDNESDAY NIGHT. THIS SCENARIO WOULD PROMOTE A COOL AND WET
WEDNESDAY WITH WIDESPREAD SHOWERS AND THUNDERSTORMS. THURSDAY AND
THURSDAY NIGHT SHOULD BE MOSTLY DRY. THE NEXT UPPER LEVEL WAVE
REMAINS ON TRACK FOR A FRIDAY ARRIVAL ALONG WITH ADDITIONAL
PRECIPITATION CHANCES. THIS SYSTEM IS EXPECTED TO PASS TO THE EAST
THEN DEEPEN AND STALL OVER THE OHIO VALLEY WITH ANOTHER PATTERN
BLOCK DEVELOPING. THIS SYSTEM COULD HAVE IMPLICATIONS INTO THE
MEMORIAL DAY WEEKEND IF IT BECOMES STRONG ENOUGH TO INDUCE COOL
CYCLONIC FLOW OVER THE STATE.

&&

.AVIATION...22/18Z
CDFNT/DRYLINE FROM EAST OF KAXA TO NEAR KDSM TO WEST OF KLWD WILL
MOVE TO ERN IA BY THIS EVE.  STRONG CONVECTION EXPECTED TO DVLP
ALONG AND AHD OF THE DRYLINE.  SCT MVFR CONDS REMAIN EARLY THIS AFTN
OVR NERN IA IN STRATUS...OTRW VFR CONDS WIL PREVAIL THIS TAF PD
OUTSIDE OF TSRA.  TSRA THREAT WILL END BFR MIDN WITH WSWLY TO WLY
FLOW.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

SHORT TERM...MS MAY 11
LONG TERM...DONAVON
AVIATION...MS MAY 11

Hazardous weather outlook, May 22, 4:24 AM CST, 9 hours 21 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
524 AM CDT SUN MAY 22 2011

IAZ004-005-015-023-033-034-044-045-057-231030-
EMMET-KOSSUTH-PALO ALTO-POCAHONTAS-SAC-CALHOUN-CRAWFORD-CARROLL-
AUDUBON-
524 AM CDT SUN MAY 22 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST AND
WEST CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TODAY. A SEVERE STORM IS
POSSIBLE WITH QUARTER SIZED HAIL AND 60 MPH WINDS THROUGH 2 PM.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

ISOLATED THUNDERSTORMS ARE POSSIBLE THROUGHOUT THE WORK WEEK. THE
POTENTIAL FOR SEVERE WEATHER IS LOW DURING THE PERIOD.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED.

IAZ006-007-016-017-024>027-035>037-046>048-058>060-070>073-081>084-
092>095-231030-
WINNEBAGO-WORTH-HANCOCK-CERRO GORDO-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-
WEBSTER-HAMILTON-HARDIN-GREENE-BOONE-STORY-GUTHRIE-DALLAS-POLK-CASS-
ADAIR-MADISON-WARREN-ADAMS-UNION-CLARKE-LUCAS-TAYLOR-RINGGOLD-
DECATUR-WAYNE-
524 AM CDT SUN MAY 22 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA
INCLUDING THE MASON CITY...AMES AND DES MOINES METRO AREAS.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON. THESE STORMS
WILL HAVE THE POTENTIAL TO BECOME SEVERE WITH GOLF BALL SIZE
HAIL...DAMAGING WINDS AND A FEW TORNADOES POSSIBLE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A FEW THUNDERSTORMS ARE POSSIBLE THROUGHOUT THE WORK WEEK WITH THE
GREATEST POTENTIAL ON WEDNESDAY. THE POTENTIAL FOR SEVERE WEATHER
IS LOW DURING THE PERIOD.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED BETWEEN 1 PM AND 6 PM TODAY.

IAZ028-038-039-049-050-061-062-074-075-085-086-096-097-231030-
BREMER-GRUNDY-BLACK HAWK-MARSHALL-TAMA-JASPER-POWESHIEK-MARION-
MAHASKA-MONROE-WAPELLO-APPANOOSE-DAVIS-
524 AM CDT SUN MAY 22 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA
MAINLY EAST OF A WATERLOO TO NEWTON TO CENTERVILLE LINE.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON. THESE STORMS
ARE EXPECTED TO BECOME SEVERE WITH GOLF BALL SIZE HAIL...DAMAGING
WINDS AND TORNADOES POSSIBLE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A FEW THUNDERSTORMS ARE POSSIBLE THROUGHOUT THE WORK WEEK WITH THE
GREATEST POTENTIAL ON WEDNESDAY. THE POTENTIAL FOR SEVERE WEATHER
IS LOW DURING THE PERIOD.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED BETWEEN 2 PM AND 8 PM TODAY.

DONAVON

In the hours before

Local storm report, May 22, 1:21 PM CST, 24 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
221 PM CDT SUN MAY 22 2011

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

0210 PM     HAIL             BARNES CITY             41.51N 92.47W
05/22/2011  E1.75 INCH       MAHASKA            IA   TRAINED SPOTTER

            TRAINED SPOTTER REPORTED GOLF BALL HAIL IN BARNES CITY.

&&

FBOKSA

Local storm report, May 22, 1:22 PM CST, 23 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
222 PM CDT SUN MAY 22 2011

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

0209 PM     HAIL             3 SSW BARNES CITY       41.46N 92.48W
05/22/2011  E1.00 INCH       MAHASKA            IA   TRAINED SPOTTER

            QUARTER SIZE HAIL NEARLY COVERING GROUND...

&&

JB

Local storm report, May 22, 1:23 PM CST, 22 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
223 PM CDT SUN MAY 22 2011

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

0210 PM     HAIL             1 W BROOKLYN            41.73N 92.46W
05/22/2011  E0.75 INCH       POWESHIEK          IA   TRAINED SPOTTER

0210 PM     HAIL             4 SW BROOKLYN           41.69N 92.52W
05/22/2011  E1.00 INCH       POWESHIEK          IA   TRAINED SPOTTER

&&

SKOW

Local storm report, May 22, 1:37 PM CST, 8 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
237 PM CDT SUN MAY 22 2011

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

0215 PM     HAIL             4 E BROOKLYN            41.73N 92.37W
05/22/2011  E1.75 INCH       POWESHIEK          IA   TRAINED SPOTTER

&&

SKOW

Local storm report, May 22, 1:41 PM CST, 4 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
241 PM CDT SUN MAY 22 2011

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

0240 PM     HAIL             3 S JANESVILLE          42.60N 92.46W
05/22/2011  E1.00 INCH       BLACK HAWK         IA   TRAINED SPOTTER

&&

SKOW

Local storm report, May 22, 1:42 PM CST, 3 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
242 PM CDT SUN MAY 22 2011

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

0238 PM     HAIL             5 NW WATERLOO AIRPORT   42.60N 92.48W
05/22/2011  E0.88 INCH       BLACK HAWK         IA   TRAINED SPOTTER

            OBLONG HAIL STONES NICKEL SIZE

&&

KJ

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

9 flood. Local standard time, as filed.

Flood, Emmet

When: May 22, 1:45 PM CST to May 31, 11:59 PM CST
Where: Emmet County, 5.64 mi W of Huntington to 2.53 mi SW of Wallingford
Cause: Heavy Rain
Property damage: $100,000
Reported by: Official NWS Observations
Coordinates: 43.501, -94.912

Flood, Kossuth

When: May 23, 6:45 AM CST to May 31, 11:59 PM CST
Where: Kossuth County, 4.37 mi ENE of Burt to 2.3 mi SW of Lu Verne
Cause: Heavy Rain
Property damage: $50,000
Reported by: Official NWS Observations
Coordinates: 43.224, -94.140

Flood, Wapello

When: May 25, 6:13 AM CST to May 26, 4:20 AM CST
Where: Wapello County, 3.11 mi S of Eddyville to 1.4 mi WSW of Eldon
Cause: Heavy Rain
Property damage: $50,000
Reported by: Official NWS Observations
Coordinates: 41.125, -92.637

Flood, Marion

When: May 25, 6:13 AM CST to May 26, 4:20 AM CST
Where: Marion County, 1.83 mi WNW of Bussey to 1.41 mi SW of Tracy
Cause: Heavy Rain
Property damage: $25,000
Reported by: Official NWS Observations
Coordinates: 41.211, -92.932

Flood, Wayne

When: May 25, 6:41 AM CST to May 26, 11:11 AM CST
Where: Wayne County, 2.03 mi SSE of Confidence to 1.36 mi ENE of Promise City
Cause: Heavy Rain
Property damage: $50,000
Reported by: Official NWS Observations
Coordinates: 40.844, -93.113

Flood, Warren

When: May 25, 6:52 AM CST to May 26, 1:05 AM CST
Where: Warren County, 2.2 mi ENE of Hartford to 1.21 mi SSE of Summerset
Cause: Heavy Rain
Property damage: $100,000
Reported by: Official NWS Observations
Coordinates: 41.485, -93.383

Flood, Humboldt

When: May 25, 9:21 AM CST to May 31, 11:59 PM CST
Where: Humboldt County, 0.53 mi S of Humboldt Muni Arpt to 1.07 mi S of Dakota City
Cause: Heavy Rain
Property damage: $75,000
Reported by: Official NWS Observations
Coordinates: 42.722, -94.249

Flood, Decatur

When: May 25, 3:17 PM CST to May 27, 6:15 AM CST
Where: Decatur County, 0.99 mi N of Grand River to 3.35 mi W of Pleasanton
Cause: Heavy Rain
Property damage: $50,000
Reported by: Official NWS Observations
Coordinates: 40.834, -93.953

Flood, Webster

When: May 26, 6:55 AM CST to May 31, 11:59 PM CST
Where: Webster County, 6.88 mi ESE of Lehigh to 4.38 mi SSE of Dayton
Cause: Heavy Rain
Property damage: $25,000
Reported by: Official NWS Observations
Coordinates: 42.320, -93.934

What these are

Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.

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 Warnings in Iowa, May 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: 300877, 300875, 300891, 300896, 300909, 300904, 300880, 300901, 300886.