Thunderstorms produced damaging winds in the Sioux City area on the morning of August 28th.
Every event with a place to put it. Tap one for its entry below.
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 produced damaging winds in the Sioux City area on the morning of August 28th.
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 28, 3:56 AM CST, 5 hours 25 minutes earlier.
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 455 AM CDT SAT AUG 27 2011 .DISCUSSION... OVERALL CONDITIONS ACROSS THE MUCH OF THE CENTRAL AND WESTERN U.S. HAVE CHANGED FAIRLY LITTLE OVER THE LAST 24 HOURS...WITH RIDGE BACKING JUST A BIT FARTHER WESTWARD...A LITTLE MORE ESTABLISHED SUBTROPICAL FLOW UP THE BACK SIDE...AND STRONGER NORTHWEST FLOW ESTABLISHED ACROSS THE IMMEDIATE AREA. EVENING RAOBS EXHIBIT A FAIRLY STRONG SHEAR IN PLACE IN LAYER ABOVE 2KM...THANKS TO A 55-60 KT MID LEVEL FLOW. SURFACE RIDGE IN PLACE FROM MINNESOTA TO IOWA FEEDING DRIER AIR IN FROM THE EAST...BUT SLIGHTLY STRONGER RETURN FLOW BRINGING SOME MARGINAL MOISTURE THE LONG WAY THROUGH THE HIGH PLAINS. COMPLEX OF STORMS HAS DEVELOPED ACROSS NORTH DAKOTA HEADING SOUTHEAST...AND IN LAST HALF HOUR OR SO ISOLATED MID LEVEL STORMS HAVE POPPED WEST OF THE JAMES VALLEY. CHALLENGE TODAY IS AGAIN CONVECTIVE TIMING AND PLACEMENT. FOR THE SHORT TERM...CONVECTIVE MODE AT THE START WILL BE DOMINATED BY ISOLATED SUPERCELLS...AS STORMS ALREADY SHOWING GOOD ROTATING CORES AT QUICK EARLY DEVELOPMENT. 45 TO 55 KNOTS OF EFFECTIVE SHEAR INDICATED ON ANALYSIS...AND STEEP MID LEVEL LAPSE RATES WILL RESULT IN AVAILABLE CAPE OF 1000-1500 J/KG. THREAT WITH THESE STORMS WOULD SEEM TO BE MAINLY ISOLATED LARGE HAIL THROUGH THE EARLY MORNING HOURS. THIS AXIS OF ELEVATED INSTABILITY WILL PUSH SLOWLY EASTWARD FROM A HURON TO YANKTON LINE TOWARD DAYBREAK. AT THE SAME TIME... COMPLEX OF STORMS TO THE NORTH WILL CONTINUE TO DIVE SOUTHEAST PER ANY OF THE MYRIAD OF SHORT RANGE MODELS ALONG THE EDGE OF THE ELEVATED MIXED LAYER...AFFECTING AREAS GENERALLY FROM THE JAMES VALLEY EASTWARD THROUGH THE MORNING HOURS. AN INCREASINGLY BETTER ENVIRONMENT SHOULD RESULT IN SOME UPSCALE GROWTH AND INTENSIFICATION AT LEAST THROUGH MID MORNING...AND LOOK FOR STORMS ON THIS COMPLEX FLANK TO ALSO BE CAPABLE OF LARGE HAIL BEFORE WEAKENING OF COMPLEX BEGINS. WILL TIME THE FEATURES GENERALLY ALONG WITH THE SUBTLE UPPER WAVE IN ND AS IT MOVES TOWARD IA BY MIDDAY. BY AFTERNOON...LIKELY NOT A WHOLE LOT OF ACTION REMAINING IN SOUTHEASTERN CWA. THE EFFECT OF CONVECTION CLOUDS/PRECIPITATION WILL MAKE FOR A DIFFICULT TEMPERATURE FORECAST...AND HEDGED THINGS DOWN A BIT WITH THE POST CONVECTIVE DEBRIS/STABILIZATION LIKELY TO PUT DAMPER ON WARMING. HEADING INTO TONIGHT...WEAK HIGH PRESSURE UNDER CLEARING SKIES WILL LIKELY ALLOW FOR AT LEAST SOME PATCHY TO AREAS OF FOG TO DEVELOP LATER IN THE NIGHT. IF RAINFALL BECOMES MORE WIDESPREAD OR SIGNIFICANT...MAY GET SOME AREAS OF DENSE FOG FROM ERN SD INTO NW IA. BOUNDARY LOOKS NOW LIKE IT WILL DISSIPATE OUTSIDE OUT NORTHERN DOORSTEP LATER ON MONDAY...BUT NOT A LOT OF FOCUS FOR PRECIPITATION UNTIL AT LEAST LATER IN THE DAY...WHEN A FAIRLY DISTINCT UPPER WAVE MOVES ACROSS THE AREA LATER MONDAY AFTERNOON INTO MONDAY EVENING. AIRMASS AT LOWER LEVELS WILL REMAIN SOMEWHAT DRY OVER MOST OF AREA...AND TRIMMED BACK TO ONLY A SLIGHT CHANCE LATER IN AFTERNOON AROUND KHON/KBKX AREAS. GOING THROUGH MONDAY NIGHT AND INTO TUESDAY...AN ILL TIMED WAVE WILL MOVE THROUGH AS FLOW TRANSITIONS FROM NORTHWEST TO EVENTUAL SOUTHWEST. GOOD STRONG THETA E ADVECTION WITH STRENGTHENING LOW LEVEL JET...FOCUS FOR MONDAY NIGHT PRIMARILY FROM MID JAMES TO LOWER MISSOURI VALLEY...PUSHING NORTH AND EAST WITH BUILDING RIDGE THROUGH TUESDAY AND TUESDAY EVENING. OTHER THAN THREAT FOR A LINGERING SHOWER OR THUNDERSTORM IN THE FAR NORTHEAST AREAS VERY EARLY WEDNESDAY IN ELEVATED WARM ADVECTION ZONE...SHOULD THEREAFTER THROUGH THURSDAY END UP CAPPED OFF TO ANY MORE CONVECTIVE DEVELOPMENT. WILL SHAKE OFF ANY TENDENCY FOR LOW LEVEL DRYING...AND MAKE FOR A VERY WARM AND HUMID PERIOD. THURSDAY HAS POTENTIAL TO BE VERY WARM...AND MAY BE UNDERDOING TEMPERATURES GIVEN THE MINIMAL CHANCE FOR AN EAST OF SOUTH COMPONENT TO WINDS...LIKELY EVEN MORE SOUTHWEST IN THE PRE FRONTAL ENVIRONMENT. DID RAISE TEMPERATURE...BUT MAY NEED MORE AS A FEW SOLUTIONS INDICATE SHALLOW MIXING TOWARD 100 NOT OUT OF THE QUESTION IN THE LOWER JAMES/LOWER MISSOURI VALLEY. /CHAPMAN && .AVIATION... A THUNDERSTORM COMPLEX...NOW LOCATED IN CENTRAL ND...IS EXPECTED TO TRACK SOUTHEASTWARD ACROSS THE AREA LATE THIS MORNING. TIMING WOULD PLACE IT AT OUR NORTHERN BORDER AROUND 12Z...AND FINALLY REACHING THE KSUX AREA AROUND 15Z. POSSIBLE DEVELOPMENT AHEAD OF THE MAIN THUNDERSTORM COMPLEX COULD BRING A ROUND OF THUNDERSTORMS A FEW HOURS AHEAD OF SCHEDULE. A FEW STORMS WITH STRONG GUSTS AND MARGINAL HAIL IS POSSIBLE. STORMS WILL CLEAR OUT FROM NORTHWEST TO SOUTHEAST AFTER 18Z. LINGERING MOISTURE WILL BRING THE POTENTIAL FOR PATCHY FOG DEVELOPMENT LATE TONIGHT. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SIOUX FALLS SD 604 AM CDT SUN AUG 28 2011 SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098- IAZ001>003-012>014-020>022-031-032-NEZ013-014-291200- 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- 604 AM CDT SUN AUG 28 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA... SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS... SCATTERED THUNDERSTORMS EARLY THIS MORNING WILL BE CAPABLE OF HAIL FROM QUARTER TO GOLF BALL SIZE FROM THE LOWER JAMES VALLEY THROUGH THE MISSOURI RIVER CORRIDOR TOWARD SIOUX CITY. ADDITIONALLY...A COMPLEX OF THUNDERSTORMS ACROSS NORTH CENTRAL SOUTH DAKOTA WILL DROP SOUTHEAST AND AFFECT AREAS ALONG AND EAST OF THE JAMES VALLEY STARTING AFTER SUNRISE. THESE STORMS WILL PRODUCE HAIL TO WALNUT SIZE AND WIND GUSTS TO AROUND 60 MPH...TRACKING AS FAR EAST AS THE INTERSTATE 29 CORRIDOR THROUGH MIDDAY. BY AROUND NOON...THE THREAT FOR SEVERE THUNDERSTORMS SHOULD DIMINISH...WITH A FEW LINGERING STORMS ACROSS MAINLY NORTHWEST IOWA IN THE EARLY AFTERNOON. FLOODING... MINOR TO MODERATE FLOODING ON PARTS OF THE JAMES RIVER WILL CONTINUE OVER THE NEXT COUPLE OF WEEKS...BUT RIVER LEVELS WILL SEE A SLOW BUT STEADY DROP. BARRING HEAVY RAINS...THE JAMES RIVER IS EXPECTED TO BE LARGELY BELOW FLOOD STAGE DURING THE FIRST HALF OF SEPTEMBER. FLOODING WILL CONTINUE ALONG THE MISSOURI RIVER BETWEEN FORT RANDALL DAM AND NEAR PONCA NEBRASKA...WITH RIVER LEVELS CONTINUING TO DROP VERY SLOWLY. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY SCATTERED THUNDERSTORMS WILL RETURN TO THE MISSOURI VALLEY ON MONDAY EVENING...WITH THE THREAT FOR STORMS GRADUALLY SPREADING NORTH AND EAST THROUGH TUESDAY. AT THIS TIME...SEVERE STORMS ARE NOT EXPECTED. THUNDERSTORMS WILL RETURN ON THURSDAY NIGHT AND FRIDAY...ALONG WITH THE RISK FOR AN ISOLATED SEVERE STORM. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL BE THROUGH NOON ALONG AND WEST OF INTERSTATE 29. && FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK. CHAPMAN
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
707 AM CDT SUN AUG 28 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0652 AM HAIL BRIDGEWATER 43.55N 97.50W
08/28/2011 M1.00 INCH MCCOOK SD TRAINED SPOTTER
0700 AM HAIL BRIDGEWATER 43.55N 97.50W
08/28/2011 M1.00 INCH MCCOOK SD TRAINED SPOTTER
CONTINUATION OF QUARTER SIZE HAIL.
&&
JCHAPMANPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
728 AM CDT SUN AUG 28 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0727 AM TSTM WND GST 3 W HURON 44.36N 98.28W
08/28/2011 E60 MPH BEADLE SD TRAINED SPOTTER
&&
JCHAPMANPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
749 AM CDT SUN AUG 28 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0731 AM HAIL FREEMAN 43.35N 97.43W
08/28/2011 E2.00 INCH HUTCHINSON SD TRAINED SPOTTER
0747 AM HAIL FREEMAN 43.35N 97.43W
08/28/2011 E0.50 INCH HUTCHINSON SD TRAINED SPOTTER
&&
MDBPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
824 AM CDT SUN AUG 28 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0820 AM HAIL 5 WSW TYNDALL 42.96N 97.96W
08/28/2011 E0.50 INCH BON HOMME SD TRAINED SPOTTER
VERY HEAVY RAIN.
&&
MDBPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
849 AM CDT SUN AUG 28 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0835 AM TSTM WND GST 3 S SALEM 43.68N 97.39W
08/28/2011 M42 MPH MCCOOK SD EMERGENCY MNGR
0845 AM HAIL 8 W CLAYTON 43.44N 97.82W
08/28/2011 E1.00 INCH HUTCHINSON SD TRAINED SPOTTER
&&
MDBPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1003 AM CDT SUN AUG 28 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0959 AM HAIL 1 S GAYVILLE 42.87N 97.17W
08/28/2011 E0.88 INCH YANKTON SD EMERGENCY MNGR
&&
MFUHSThe Sioux Falls radar (KFSD), 118 km away, was scanning. The volume nearest the first event began at 15:18 UTC.
3 thunderstorm wind. Local standard time, as filed.
Thunderstorm winds caused tree damage, including at least one tree blown down onto a power line.
Thunderstorm winds caused tree and power line damage.
Thunderstorm winds caused tree and power line damage.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2011Every state in 2011This day in weather historyWarnings in Iowa, August 2011
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: 341511, 341512, 341513.