Flash Flooding in Iowa, August 2, 2001

Name: Flash Flooding in Iowa, August 2, 2001
Start: 2001-08-02T09:00
End: 2001-08-02T12:00
Location: Iowa

August 2, 2001 · NWS DMX · 2 events in 2 counties and zones

A nearly stationary front extended west-southwest to east-northeast across Iowa. Thunderstorms fired repeatedly along this front during the night of the 1st into the morning of the 2nd.

Where it happened

Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. 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: $150,000
Crop damage: $15,000
Events: 2

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.

A nearly stationary front extended west-southwest to east-northeast across Iowa. Thunderstorms fired repeatedly along this front during the night of the 1st into the morning of the 2nd. The first round of thunderstorms left around three inches of rain in the area as they passed. With conditions prior to the rain being relatively dry, flooding from this round was limited to urban and a few low lying areas. Another round of thunderstorms moved into the area during the morning on the 2nd, leaving another three to four inches of rain over much of northern Calhoun and southern Pocahontas Counties. With the previous rainfall only a few hours prior, the second round resulted in flash flooding. Water was reported over many roads and farm fields were flooded. Significant flooding took place in the Manson area of Calhoun County. Several roads in the area were under several feet of water during the late morning hours.

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 Aug 2, 1:25 AM CST, 7 hours 35 minutes earlier.

Area forecast discussion, Aug 2, 1:25 AM CST, 7 hours 35 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
225 AM CDT THU AUG 2 2001

FORECASTS KEEP GETTING TOUGHER - HEAT SOUTH AND POPS MAIN CHALLENGE
AGAIN TODAY.

SFC FRONT DRAPED ACROSS STATE...FROM TKE TO CCY AND MOVING LITTLE.
TSRA HAVE DEVELOPED IN NRN CWA JUST NORTH OF FRONT AT NOSE OF
WHOPPING 20-25KT SW LLJ. PLENTY OF JUICE AVAILABLE THOUGH WITH 2.12
INCHES AT 00Z FOR PWATS AT OAX AND MID 70S DEWPOINTS ALONG/S OF
FRONT. 88D OHP SHOWING PRETTY GOOD RAINS...THOUGH NOT WIDESPREAD.
SVN SPOTTER JUST CALLED IN WITH INCH PER HOUR RATES.  CORFIDI
VECTORS WOULD PULL THIS STUFF EVER SO SLOWLY SOUTHWARD NEXT FEW
HOURS. 50H RIDGE RETROGRADES NEXT FEW DAYS...EVENTUALLY PUTTING CWA
IN NW FLOW. VORT MAX IN MONSOONAL FLO OVR NM/CO BORDER WILL PROVIDE
FOCUS JUST TO OUR WEST TONIGHT.

ETA CONTINUES TO PUSH FRONT AND PRECIP TOO FAR SOUTH. ITS NOT
BAD...JUST TOO FAR SOUTH.  ADJUSTED NORTH A HUNDRED MILES OR SO AND
IT LOOKS A LOT LIKE THE AVN - AND NEW HPC QPF.  WILL FOLLOW.

TODAY...COLD POOL FROM CONVECTION TO THE NORTH WILL PUSH TO I80 WEST
OF I35 THIS AFTERNOON...BUT NOT BEFORE HEAT INDICES PUSH UP TO
DANGEROUS LEVELS AGAIN.  BLOW OFF FROM CONVECTION MAY INHIBIT ALO
HI'S BETTER TODAY THAN YESTERDAY.  WILL NO LONGER SPLIT DSM METRO
THOUGH AND HAVE INCLUDED DALLAS CO. IN NPW.  EXPECT PRECIP POTENTIAL
TO END THIS MORNING FAR NORTH. WILL HAVE TO RUN WDLY SCT...HEAVY
POTENTIAL...CENTRAL THIRD OF CWA...AND GO WITH AFTERNOON SMALL POPS
FAR SOUTH.  TEMPS...WARMEST GUID IN NPW AREA/LOWER MID 80S IN NORTH
HALF.

TONIGHT...INFLOW INTO WHATS LEFT OF BOUNDARY IS MINIMAL AT BEST
ALONG I-80 CORRIDOR THIS EVENING. ALREADY HAVE POPS IN WC CWA...AND
WILL LEAVE ALONG.  ALONG I-80 AND E OF 35...TOUGHER TO FIGURE OUT
WHATS TO DO...BUT A SMALL POP MAY BE THE WAY TO GO.  LATER IN WC
INTO SW...EXPECT A SMALL COMPLEX OF TSRA INDUCED BY AFOREMENTIONED
NM/CO VORT MAX TO PERHAPS BRUSH DNS TO CSQ LINE. LLJ AGAIN NOT GREAT
SO DON'T EXPECT TOO MUCH.  WILL HANDLE THAT WITH POPS TOO.  DRY
NORTH AND NE.  GUID TEMPS AND GOING FCST CLOSE ON TEMPS - NO REASON
TO DEVIATE.

FRI INTO FRI NIGHT...SEE LITTLE CHC FOAR RAIN AT THIS POINT.  GOING
'CAST ON TRACK.

.DSM...HEAT ADVY OVRNGT ROUGHLY ALG AND S OF A AIO TO DSM TO MIW
LINE LINE.
IAZ049-050-059>062-070>075-081>086-092>097-

In the hours before

Special weather statement, Aug 2, 4:35 AM CST, 4 hours 25 minutes before

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
535 AM CDT THU AUG 2 2001

A WEAK COLD FRONT EXTENDING FROM NORTHEAST IOWA INTO WEST CENTRAL
SECTIONS OF THE STATE WILL PROVIDE A FOCUS FOR THUNDERSTORM
DEVELOPMENT ON AND OFF TODAY.  ABUNDANT MOISTURE REMAINS ACROSS THE
REGION WHICH WILL HELP FUEL ANY THUNDERSTORMS THAT DEVELOP.  WHILE
INSTABILITY IS MODERATELY HIGH...WIND SHEAR IS QUITE WEAK AS IS
INFLOW INTO AND OVER THE FRONT.  WARM TEMPERATURES ALOFT WILL
INHIBIT MOST THUNDERSTORMS FROM PRODUCING LARGE HAIL...HOWEVER SOME
DAMAGING WIND GUSTS MAY OCCUR. ADDITIONALLY LOCALLY HEAVY RAINFALL
MAY OCCUR DUE TO THE SLOW MOVEMENT OF THE STORMS AND DEEP MOISTURE.

SEE SITE SPECIFIC DETAILS BELOW FOR MORE INFORMATION.

IAZ004>007-015>017-031100-
CERRO GORDO-EMMET-HANCOCK-KOSSUTH-PALO ALTO-WINNEBAGO-WORTH-
INCLUDING THE CITIES OF...ALGONA...ESTHERVILLE AND MASON CITY
529 AM CDT THU AUG 2 2001

* EVENT TIMING... THROUGH NOON.

* THREAT CATEGORIES...
     TORNADO.......... NONE.
     DAMAGING WINDS... LOW.
     LARGE HAIL....... NONE.
     FLASH FLOODING... LOW.

* SPOTTER ACTIVATION OUTLOOK... LOW.

IAZ023>028-033>039-044>050-057>062-070>074-031100-
ADAIR-AUDUBON-BLACK
HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-CASS-CRAWFORD-DALLAS-
FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HARDIN-HUMBOLDT-JASPER-
MADISON-MARION-MARSHALL-POCAHONTAS-POLK-POWESHIEK-SAC-STORY-TAMA-
WARREN-WEBSTER-WRIGHT-
INCLUDING THE CITIES OF...AMES...ATLANTIC...BOONE...CARROLL...
DENISON...DES MOINES...FORT DODGE...GRINNELL...INDIANOLA...IOWA
FALLS...KNOXVILLE...MARSHALLTOWN...NEWTON...PELLA...PERRY...
WATERLOO...WAVERLY AND WEBSTER CITY
529 AM CDT THU AUG 2 2001

* EVENT TIMING... MAINLY THROUGH NOON.

* THREAT CATEGORIES...
     TORNADO.......... NONE.
     DAMAGING WINDS... LOW.
     LARGE HAIL....... NONE.
     FLASH FLOODING... LOW.

* SPOTTER ACTIVATION OUTLOOK... LOW.

IAZ075-081>086-092>097-031100-
ADAMS-APPANOOSE-CLARKE-DAVIS-DECATUR-LUCAS-MAHASKA-MONROE-RINGGOLD-
TAYLOR-UNION-WAPELLO-WAYNE-
INCLUDING THE CITIES OF...CENTERVILLE...CHARITON...CRESTON...
LAMONI...OSKALOOSA AND OTTUMWA
529 AM CDT THU AUG 2 2001

* EVENT TIMING... THROUGH 5 PM.

* THREAT CATEGORIES...
     TORNADO.......... NONE.
     DAMAGING WINDS... LOW.
     LARGE HAIL....... NONE.
     FLASH FLOODING... LOW.

* SPOTTER ACTIVATION OUTLOOK... LOW.

SEARCY

-------------------------------------------------------------------

THREAT KEY:
    TORNADO.......... ANY TORNADO OCCURRENCE
    DAMAGING WINDS... WINDS >= 58 MPH
    LARGE HAIL....... HAIL >= 3/4 INCH DIAMETER
    FLASH FLOODING... FLOODING CAUSED BY HEAVY RAINS WITHIN 6 HOURS
                      OF RAIN EVENT. POSES THREAT TO LIFE OR
                      PROPERTY.

THREAT CATEGORY KEY:  PROBABILITY OF THREAT OCCURRING WITHIN 25
                      MILES OF POINT WITHIN FORECAST AREA
    NONE....... NOT EXPECTED.  LESS THAN 5% ( 2% FOR TORNADOES)
    LOW........ 5-15% (2-15% FOR TORNADOES)
    MODERATE... 25-35%
    HIGH....... 45% OR GREATER

SPOTTER ACTIVATION OUTLOOK KEY:
    NOT EXPECTED
    LOW........ ACTIVATION POSSIBLE BUT NOT LIKELY
    MODERATE... POSSIBILITIES ABOUT 50-50
    HIGH....... ACTIVATION LIKELY

FOR MORE INFORMATION ON PROBABILISTIC SEVERE WEATHER OUTLOOKS...GO
TO THE STORM PREDICTION CENTER WEBSITE AT
WWW.SPC.NOAA.GOV/PRODUCTS/OUTLOOK/PROBINFO.HTML .

Local storm report, Aug 2, 8:17 AM CST, 43 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
917 AM CDT THU AUG 02 2001

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0910 AM    SCHALLER                  IA   60 MPH TSTM GUST
08/02/01   SAC                            REPORTED BY STORM
                                          SPOTTER.

Local storm report, Aug 2, 8:45 AM CST, 15 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
945 AM CDT THU AUG 02 2001

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0942 AM    1 NW JOLLEY               IA   60 MPH TSTM GUST
08/02/01   CALHOUN                        REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL.

The radar

The Des Moines radar (KDMX), 105 km away, was scanning. The volume nearest the first event began at 14:59 UTC.

Open the radar archive at this moment

Event by event

2 flash flood. Local standard time, as filed.

Flash Flood, Calhoun

When: August 2, 9:00 AM CST to 12:00 PM CST
Where: Calhoun County, North Portion
Property damage: $100,000
Crop damage: $10,000
Reported by: NEWSPAPER
Coordinates: 42.385, -94.640 (the zone’s center; the record gives no point)

Flash Flood, Pocahontas

When: August 2, 9:00 AM CST to 12:00 PM CST
Where: Pocahontas County, South Portion
Property damage: $50,000
Crop damage: $5,000
Reported by: NEWSPAPER
Coordinates: 42.734, -94.679 (the zone’s center; the record gives no point)

What these are

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 2001 Every state in 2001 This day in weather history Warnings in Iowa, August 2001

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: 5260970, 5260971.