Thunderstorms produced heavy rain which caused flash flooding in the Sioux City area during the early evening of September 6th. The thunderstorms also produced golf ball size hail near LeMars.
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The episode as NWS FSD wrote it up.
Thunderstorms produced heavy rain which caused flash flooding in the Sioux City area during the early evening of September 6th. The thunderstorms also produced golf ball size hail near LeMars.
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 Sep 6, 2:20 PM CST, 3 hours 28 minutes earlier.
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 320 PM CDT THU SEP 6 2007 .DISCUSSION... CDFNT BASICALLY HUNG UP ATTM FM NR BKX TO JUST W OF YKN AND SHOULD BE THE LOCUS OF THE FOCUS FOR SOME SFC BASED CONVECTION YET LATE THIS AFTN AND EARLY EVE. POST FRONTAL MID LVL BAND OF TSTMS NOW MOVG SLOWLY EWD THRU JAMES VALLEY WITH MORE SCT DVLPMT EXPCD TO THE WEST WITH APPROACHING UPR LOW FM ERN WY. THIS UPR WAVE SHOULD KEEP THE DVLPMT GOING FM I29 CORRIDOR AND EAST THRU MIDN OR SO. SVR STORMS NOT AS LIKELY DUE TO LACK OF HEATING WITH LWR CLDS THIS AFTN...BUT WITH ANY MORE DESTABILIZATION WITH BREAKS IN CLDS AND MID LVL COOLING THERE COULD BE A FEW SVR YET ALG AND EAST OF I29. HEAVY RAINS STILL QUITE PSBL MAINLY I29 CORRIDOR AND EAST THRU THE EVE. DVLPG SFC TROF TAKES OFF TO EAST OF AREA AFT MIDN AS UPR LOW MOVES EWD...BRINGING IN BRISK NWLY FLOW OF COOLER AND MORE STABLE AIR...AND TAKING MOST OF THE PRECIP EAST OF CWA BY LATE TNGT...BUT LWR CLDS SHOULD LINGER THRU EARLY MRNG. DRY WITH A LOT OF SUNSHINE TOMORROW AND BREEZY UNDER COOL NW FLOW. THE PASSAGE OF ANOTHER COLD FRONT ON SAT WILL BRING THE NEXT CHANCE PRECIPITATION. HOWEVER...UPPER FORCING MAINLY CONFINDED TO THE MAIN S/WV OVER ND...MAKING IT TOUGH TO GET CONVECTION TO DEVELOP. KEPT 20 TO 30 POPS AS FROPA STILL MAY BE ENOUGH TO POP A FEW STORMS. BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS WILL BE LATE SUN THROUGH SUN NIGHT AS A STRONGER DISTURBANCE MOVES ACROSS A MID LEVEL BNDRY. NEARLY A CERTAINTY FOR PRECIPITATION WITH THIS DISTURBANCE...ONLY UNCERTAINTY IS WHERE MID LEVEL BNDRY WILL SET UP. MODLES HAVE BEEN TRENDING N WITH BNDRY POSITION. ALSO...WILL BE VERY COOL BEHIND THE SFC FRONT ON SUN AND IF SHOWERS BREAK OUT IN THE AFTERNOON... TEMPERATURES MAY BE STUCK IN THE 50S NEAR BKX AND HON. MONDAY THROUGH FRIDAY...CONTINUED COOL. EARLY NEXT WEEK TROUGH OVER THE CNTRL CONUS BEGINS TO MOVE EAST ALONG WITH A STRONG S/WV... ENDING THE MAIN THREAT FOR PRECIPITATION IN THE ERN SWA DURING THE MORNING...BUT WITH VERY COLD AIR ALOFT...COULD POSSIBLY SEE A FEW CONVECTIVE AFTERNOON SHOWERS REDEVELOP. DROPPED TEMPERATURES BELOW GUIDANCE THROUGH THE PERIOD...ESPECIALLY EARLY IN THE WEEK. EXTENDED MODELS INCLUDING ENSEMBLES INDICATE 850 TEMPS IN THE SINGLE DIGITS CELSIUS...WHICH SEEMS REASONABLE GIVEN SFC TEMPS OVER A LARGE PORTION OF WRN CANADA IS CURRENTLY IN THE 40S AND 50...WITH 30S FARTHER NORTH. AIR WILL MODIFY AS IS COMES SOUTH AND THE MODELS MAY BE A TAD TOO COOL...BUT EVEN FULLY MIXED...MAY NOT GET OUT OF THE 50S IN SOME PLACES. FOR NOW HAVE 60S FOR HIGHS ON MONDAY...BUT WILL NEED TO TREND DOWN FURTHER IF FUTURE MODEL RUNS CONTINUE COLD. S/WV RIDGE TRIES TO BUILD IN DURING THE MIDDLE OF THE WEEK BUT TEMPERATURES WILL LIKELY REMAIN BELOW NORMAL...THEN ANOTHER SHOT OF COLD AIR EXPECTED LATE IN THE WEEK. && .AVIATION... MVFR CIGS WILL BE THE RULE THRU TNGT WITH CONSIDERABLE LWR LVL MOISTURE. BANDS OF TSTMS WILL MOVE EAST THRU THE CWA...ESP EAST OF JAMES RIVER THRU MIDN WITH SOME IFR VSBYS AND CIGS AT TIMES. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && RYRHOLM/LIEBL
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SIOUX FALLS SD 1126 AM CDT THU SEP 06 2007 SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098- IAZ001>003-012>014-020>022-031-032-NEZ013-014-071200- 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- 1126 AM CDT THU SEP 06 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA... SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS... A COLD FRONT WILL PUSH EAST ACROSS THE AREA THIS AFTERNOON AND TONIGHT. THUNDERSTORMS ARE EXPECTED TO DEVELOP NEAR THE FRONT WEST OF INTERSTATE 29 BY MID AFTERNOON...THEN MOVE EAST OVER SOUTHWEST MINNESOTA AND NORTHWEST IOWA THIS EVENING. THE POTENTIAL EXISTS FOR A SEVERE WEATHER OUTBREAK DURING THE AFTERNOON AND EVENING HOURS. THE MAIN THREAT WILL BE LARGE HAIL TO THE SIZE OF HALF DOLLARS AND WINDS GUSTS TO 70 MPH. TORNADOES WILL ALSO BE POSSIBLE ACROSS PORTIONS OF SOUTHEAST SOUTH DAKOTA INTO NORTHWEST IOWA...SOUTHWEST MINNESOTA AND NORTHEAST NEBRASKA...LATE THIS AFTERNOON AND EVENING. FLOODING... HEAVY RAINS OF 1 TO 3 INCHES WILL BE POSSIBLE WITH THE HEAVIER THUNDERSTORMS THIS EVENING...FROM SOUTHEAST SOUTH DAKOTA TO SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND FAR NORTHEAST NEBRASKA. SOME URBAN FLOODING AND PONDING OF WATER WILL BE POSSIBLE. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THERE WILL BE ANOTHER CHANCE OF THUNDERSTORMS ON SATURDAY. AT THE PRESENT FORECAST TIME...THESE STORMS ARE NOT EXPECTED TO BE SEVERE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL BE LIKELY AFTER 3 PM ALONG AND WEST OF INTERSTATE 29...AND IN SOUTHWEST MINNESOTA AND NORTHWEST IOWA AFTER 6 PM. && FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WWW.CRH.NOAA.GOV/FSD. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK. RSR
The Sioux Falls radar (KFSD), 124 km away, was scanning. The volume nearest the first event began at 23:50 UTC.
1 flash flood, 1 hail. Local standard time, as filed.
Heavy rainfall caused flash flooding of numerous roads, including up to four feet of water covering some main roads.
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, September 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: 59773, 59774.