Thunderstorms caused another heavy rainfall and flash flooding event in Storm Lake on the evening of August 4th, after a similar event on the morning of the same day.
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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.
The episode as NWS FSD wrote it up.
Thunderstorms caused another heavy rainfall and flash flooding event in Storm Lake on the evening of August 4th, after a similar event on the morning of the same 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 Aug 4, 2:59 PM CST, 6 hours 26 minutes earlier.
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 359 PM CDT SAT AUG 4 2007 .DISCUSSION... LOW LYING STATUS CONTINUES TO OOZE SOUTHWARD INTO CWA THIS EVENING. HAVE ADDED THE MENTION OF FOG CWA WIDE...AND DENSE FOG IN PORTIONS OF SOUTHWEST MINNESOTA AND FAR EASTERN SOUTH DAKOTA WHERE MOISTURE IS QUITE ABUNDANT. && .PREV DISCUSSION... MAIN FCST IN THE SHORT TERM IS CONVECTIVE REDEVELOPMENT ALONG THE NEARLY STNRY FRONTAL BOUNDARY. AT 19Z...SFC ANALYSIS SHOWED WELL DEFINED LOW PRES IN EXTREME NERN NEB...WITH THE SFC BOUNDARY EXTENDING EWD TO ALONG THE MN/IA BORDER. THIS LOW WL TRACK ALONG THE SFC BOUNDARY THIS EVENING. WINDS HAVE ALREADY COME AROUND TO THE N AND NW IN OUR WRN FA ON THE NW QUAD OF THIS LOW...WITH OUR ERN FA EVENTUALLY COMING AROUND TO THE N AS THE OVERNIGHT HRS PROGRESS. QUITE A FEW DYNAMICAL PARAMETERS ARE SHOWING A GOOD POTENTIAL FOR REDEVELOPING TSRA ON THE FRONTAL BOUNDARY LATE THIS AFTN AND EVENING...ESP IN NW IA. BUT ALSO DID NOT WANT TO RULE OUT ACTIVITY CLOSE TO THE BOUNDARY IN EXTREME NE NEB...EXTREME SE SD...AND SOME DYNAMICS EXTENDING NWD TOWARD WINDOM. SPC MESOANALYSIS PWATS ARE CURRENTLY IN THE 2.0 TO 2.1 INCH RANGE IN THE SE QUAD OF THE FSD FA. SO IF TS DOES DEVELOP ON THE CONVERGENCE AXIS...SOME HEAVY RAINFALL IS LIKELY. FOR SVR POTENTIAL...ELEVATED CAPES GREATER THAN 1500 J/KG ABOUND WITH LITTLE IN THE WAY OF CIN. BUT ADMITTEDLY THE WIND SHEAR COULD BE BETTER AFTER LOOKING AT THE NLG PROFILER AND PROGGED RUC/NAM SNDGS IN NW IA THIS EVENING. SO A SLGT RISK IS WARRANTED WITH THE INSTABILITY AND STRONG SFC HEATING GOING ON ATTM FROM YANKTON TO STORM LAKE. DIFFERENTIAL HEATING IS OBVIOUSLY QUITE INTENSE MOVG NWD FM THAT AREA WHICH SHOULD AID IN TS DEVELOPMENT. FOR LOWS...LIKE LAST NIGHT...WENT WITH THE COOLER GUIDANCE READINGS AS TEMPS ARE ONLY 65 TO 70 ACROSS OUR N IN THE CLOUD COVER...AND THERE COULD BE SOME RAIN COOLED AIR AROUND KSUX AND KSLB TO HELP LOWER LOWS IN THAT AREA TO READINGS SIMILAR TO LAST NIGHT. READ THE BLO AVIATION DISCUSSION FOR STRATUS POTENTIAL CONTINUING. SUNDAY SHOULD BE QUIET FROM A SENSIBLE WX PERSPECTIVE IN WAKE OF DEPARTING WAVE. EXPECT THAT THE CONTINUED CAA WITH DRYING ALFT WL HELP TO ERODE LOWER CLDS THRU MIDDAY AND EARLY AFTN...BUT WL HANDLE WITH A MUCH SLOWER THAN DIURNAL WARMUP. SFC RIDGE SLIDING THRU SW MN AND LINGERING IN NWRN IA INTO EVENING...WITH RETURN FLOW STARTING TO INCREASE GRADUALLY DURING THE EVENING. SOME ELEVATED INSTABILITY PRESENT...WHILE MOISTURE TRANSPORT AND CONVERGENCE WITHIN LIFT AREA INCREASES. ENOUGH TO ADD IN LOW CHC THREAT FOR SRN/WRN AREAS AFTER MIDNIGHT. RETREATING WARM FRONT LKLY TO GET MUCH MORE ACTIVE BY MON AFTN/EVNG AS WAVE STRONGLY INTERACTS WITH FRONT...WHICH WL HAVE TIME TO SET UP QUITE AN INSTABILITY GRADIENT. MAIN FOCUS FOR PRECIP THREAT LOOKS TO BE SPREADING INTO NW IA AND SW MN BY EVENING WITH DEEPER CONVERGENCE AND FOCUS FOR MOISTURE TRANSPORT VECTORS. DEGREE OF PWAT SUGGESTS THAT WL AGAIN PROVIDE THREAT FOR HEAVY RAINFALL. BNDRY IN NO REAL HURRY SWRD AS Q VECTORS SUPPORT A SLOWER THAN GFS MOTION...BUT OVERALL LIKE THE LOOK OF GFS DYNAMICS BETTER...AND WL SIMPLY SLOW UP 3-6H. THIS WL MEAN BNDRY WL BE SITTING ACRS SERN CWA DURING AFTN WITH GREATEST DESTABILIZATION. THE EXTENDED RANGE CONTINUES TO INDICATE A CLASSIC RIDGE RIDER PATTERN WITH A VARIETY OF IMPULSES COMING AROUND THE RIDGE CENTER AND ALONG THE SRN EDGE OF THE MAIN WLY FLOW TO INDUCE CONVECTION ACROSS THE NORTHERN PLAINS. THESE WAVES HAVE BEEN A BIT JUMPY IN TIMING...AND NOT SURE HOW MUCH CONFIDENCE TO PUT IN ANY PARTICULAR CONVECTIVE BLOB OVER ANOTHER. STILL LOOKS TO HAVE A WAVE IN AND AROUND WED NIGHT INCREASING LLJ AND MOISTURE TRANSPORT ACRS SFC BNDRY STALLED TO S. THERE IS SURE TO BE SOME EXCESSIVE PCPN AMOUNTS DURING THE PD MUCH LIKE LAST NIGHT...BUT EXACTLY WHERE AND WHEN IS WELL BEYOND DETAIL FOR THIS FCST. MODEST POPS ARE ABOUT AS HIGH AS CONFIDENCE ALLOWS AT THIS TIME. MOST SLNS...AND MORE CLEARLY IN THE 1-5 WAVE FIELDS...SHOW A TENDENCY FOR THE RIDGE TO RETROGRADE TOWARD DAY 7 BACK INTO THE PLAINS AFTER FLATTENING OUT EARLY TO MID WEEK OVR ERN AREAS. THIS MIGHT CUT OFF SOME OF THE MORE SUBTROPICAL WAVE INFLUENCE OVR IMMEDIATE AREA BY SAT...AND LEAVE MORE UP TO WLYS TO BRING PCPN THREAT TO AREA. TEMPWISE...DID NOT STRAY TOO FAR FROM GUIDANCE AND KEPT THINGS MORE RESTRAINED ON MAXES WITH MOISTURE AROUND...AND POTENTIAL FOR CONVECTIVE DEVELOPMENT TO LEAVE CLDS ARND AS WELL AS WORK NIGHTTIME AIR MASS OVER TO LOWER DWPTS...ESPLY WHEN RIDING N OF E/W BNDRY. && .AVIATION... THUNDERSTORMS CONTINUE TO DEVELOP ALONG A FRONTAL BOUNDARY THAT IS SAGGING SLOWLY OFF TO THE SOUTHEAST THIS EVENING. MVFR TO IFR CONDITIONS WILL DEVELOP OVERNIGHT AS LOW LYING STRATUS DEVELOPS ACROSS THE EASTERN DAKOTAS...MINNESOTA AND NORTHWEST IOWA. THE BEST CHANCES FOR DENSE FOG APPEAR TO BE EAST OF THE JAMES RIVER VALLEY...AFFECTING THE KFSD TAF SITE. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && MJF/CHAPMAN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SIOUX FALLS SD 1148 AM CDT SAT AUG 04 2007 SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098- IAZ001>003-012>014-020>022-031-032-NEZ013-014-051200- 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- 1148 AM CDT SAT AUG 04 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA... SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS... THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS DEVELOPING THIS AFTERNOON OR EARLY EVENING...MAINLY ALONG AND SOUTH OF A TYNDALL SOUTH DAKOTA TO JACKSON MINNESOTA LINE. THIS INCLUDES ALL OF NORTHWEST IOWA...EXTREME NORTHEAST NEBRASKA AND EXTREME SOUTHEAST SOUTH DAKOTA. HAIL UP TO THE SIZE OF QUARTERS AND BRIEF WET MICROBURST WINDS TO AROUND 60 MPH ARE POSSIBLE...ESPECIALLY IN NORTHWEST IOWA AND EXTREME NORTHEAST NEBRASKA. FLOODING... SOME HEAVY RAINFALL IS POSSIBLE WITH ANY THUNDERSTORM DEVELOPMENT THIS AFTERNOON AND EARLY EVENING ALONG A FRONTAL BOUNDARY. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY THERE IS A CHANCE OF THUNDERSTORMS OVER MUCH OF THE AREA FROM LATE MONDAY AFTERNOON INTO MONDAY NIGHT. SOME OF THESE STORMS COULD BECOME SEVERE PRODUCING LARGE HAIL AND DAMAGING WINDS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL BE POSSIBLE FROM 3 PM TO 8 PM IN THE ABOVE MENTIONED SLIGHT RISK AREA. && FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WWW.CRH.NOAA.GOV/FSD. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK.
The Des Moines radar (KDMX), 159 km away, was scanning. The volume nearest the first event began at 03:27 UTC.
1 flash flood. Local standard time, as filed.
Thunderstorms caused heavy rain which caused flooding of streets and yards in Storm Lake on the evening of August 4th. The flash flood was the second one in town on the same day; the first being during the morning.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2007Every state in 2007This day in weather historyWarnings in Iowa, August 2007
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: 54021.