The Missouri River, which had been near flood stage in many areas, began a significant rise near the end of the month in response to widespread upstream heavy rain which fell after unusually large upstream snowmelt. Flooding reached the moderate category by the end of May with the river on the way up across its length.
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.
The Missouri River, which had been near flood stage in many areas, began a significant rise near the end of the month in response to widespread upstream heavy rain which fell after unusually large upstream snowmelt. Flooding reached the moderate category by the end of May with the river on the way up across its length.
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 May 20, 3:03 AM CST, 2 hours 57 minutes earlier.
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 403 AM CDT FRI MAY 20 2011 .DISCUSSION... UPPER TROUGH WHICH SPANS THE WESTERN HALF OF THE CONUS WILL CONTINUE ITS SLOW EASTWARD MOVEMENT THE NEXT SEVERAL DAYS. THIS MEANS CHANCES OF PRECIPITATION THROUGH THE WEEKEND ALTHOUGH THE MAIN PERIOD OF WET WEATHER WILL BE TONIGHT AS MAIN UPPER LOW SHIFTS INTO THE AREA. STRONG UPPER LEVEL JET ACCOMPANIED BY MOIST LOW LEVEL FLOW AND ISENTROPIC FORCING WILL BE SUFFICIENT FOR SHOWERS AND THUNDERSTORMS TO REDEVELOP LATE THIS AFTERNOON AND LIFT NE ACROSS THE AREA TONIGHT. POTENTIAL FOR FLASH FLOODING ON THE LOW SIDE WITH THESE SHOWERS AND THUNDERSTORM. 3 HR FLASH FLOOD GUIDANCE CURRENTLY IN THE 2 TO 4 INCH WILL LIKELY COME DOWN A BIT WITH THE THU NIGHT CONVECTION ADDING SOME MOISTURE TO THE SOILS. STILL IT HAS BEEN DRY THE LAST WEEK OR SO...SUCH THAT THE GROUND SHOULD BE ABLE TO HANDEL A DECENT AMOUNT OF MOISTURE. MODELS HAVE BACKED OFF ON QPF AMOUNTS AND FOR GOOD REASON. LOW LEVEL MOISTURE FLOW FROM THE GULF OF MEXICO CURRENTLY BEING DISRUPTED BY A NEAR CONTINUOUS LINE OF THUNDERSTORMS FROM NEBRASKA TO NORTHERN TEXAS. AS THE UPPER TROUGH SWINGS EAST TODAY...THESE THUNDERSTORMS SHOULD CONTINUE MOVING EAST INTO THE MISSISSIPPI VALLEY. EXPECT THIS TO IMPACT HOW MUCH MOISTURE CAN ACTUALLY REACH THE FORECAST AREA. REGARDLESS THERE WILL BE SHOWER AND THUNDERSTORM ACTIVITY TONIGHT AND DO EXPECT POCKETS OF HEAVY RAIN WITH SOME THUNDERSTORMS. MAINLY EXPECTING ADDITIONAL RAINFALL TODAY AND TONIGHT IN THE HALF INCH TO ONE INCH RANGE EAST OF THE JAMES VALLEY...ALTHOUGH MAY SEE LOCALIZED 2 INCH AMOUNTS WHERE THUNDERSTORMS ARE MORE PERSISTENT. CERTAINLY COULD SEE SOME SOUTH TO NORTH TRAINING OF THUNDERSTORMS...BUT SHOULD MOVE EAST FAST ENOUGH AS TO NOT CAUSE FLASH FLOODING PROBLEMS. CHANCES FOR SHOWERS AND THUNDERSTORMS CONTINUE ON SAT. OTHER THAN SOME LINGERING SHOWERS IN THE EASTERN CWA...SHOULD START THE DAY ON THE DRY SIDE AS A WEDGE OF DRYER AIR PUNCHES IN FROM THE SOUTHWEST. EXPECTING CLOUDS TO CLEAR OUT FOR A TIME WITH THE DRYER MID LEVEL AIR...BUT THIS WILL ALLOW FOR THE ATMOSPHERE TO DESTABILIZE IN THE AFTERNOON. STEEP LAPSE RATES AND LITTLE TO NO CONVECTIVE INHIBITION SHOULD ALLOW SHOWERS AND THUNDERSTORMS TO POP. CONVECTION SHOULD BE FIGHTING SOME SUBSIDENCE UPSTAIRS...BUT DOUBT IT WILL BE ENOUGH TO SHUT DOWN DEVELOPMENT. CONVECTION SHOULD DIE OFF IN THE EVENING BUT COULD SEE SHOWERS MOVING INTO THE WESTERN CWA LATE SAT NIGHT AS UPPER LEVEL LOW IS PROGGED TO SLIDE EAST ACROSS SOUTH DAKOTA. NOT CONFIDENT ON THE EXACT TRACK OF THE LOW...BUT DO EXPECT SHOWERS WITH IT. CHANCES WITH THE UPPER LOW WILL CONTINUE INTO SUN...WITH THE BEST CHANCES IN THE NORTHERN CWA. UPPER LOW TO MOVE EAST OF THE AREA SUNDAY NIGHT. A COLD FRONT WILL PUSH ACROSS THE AREA ON MONDAY... WITH ANOTHER SHOT OF SHOWERS AND THUNDERSTORMS. COOLER MORE STABLE AIR IS EXPECTED TO MOVE SOUTH ACROSS THE ARE MONDAY NIGHT...WHICH SHOULD SHUT DOWN THE CHANCE FOR PRECIPITATION...ALTHOUGH THAT DEPENDS HOW FAR SOUTH THE COLD FRONT MAKES IT BEFORE STALLING OUT. /97 && .AVIATION... WIDESPREAD MVFR CEILINGS AND VISIBILITIES CAN BE EXPECTED ACROSS THE AREA THROUGH 06Z SATURDAY WITH OCCASIONAL IFR CEILINGS. SHOWERS AND SCATTERED THUNDERSTORMS WILL BE FAIRLY WIDESPREAD ACROSS THE REGION THROUGH TONIGHT. && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SIOUX FALLS SD 421 AM CDT FRI MAY 20 2011 SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098- IAZ001>003-012>014-020>022-031-032-NEZ013-014-211200- 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- 421 AM CDT FRI MAY 20 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA... SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS... SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ACROSS THE AREA TODAY...ALTHOUGH THE BULK OF THE SHOWER AND THUNDERSTORM ACTIVITY WILL BE LATE THIS AFTERNOON AND INTO THE OVERNIGHT. MOST SHOWERS AND THUNDERSTORMS WILL BE FOUND EAST OF THE JAMES VALLEY...ESPECIALLY FROM AROUND INTERSTATE 29 AND EASTWARD INTO SOUTHWEST MINNESOTA AND NORTHWEST IOWA TONIGHT. SEVERE THUNDERSTORMS ARE NOT EXPECTED... HOWEVER...SMALL HAIL AND HEAVY RAIN WILL BE POSSIBLE WITH SOME OF THE STRONGER THUNDERSTORMS. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY CHANCES FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE ON SATURDAY AND SUNDAY. SEVERE THUNDERSTORMS ARE NOT EXPECTED. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED TODAY OR TONIGHT. && FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK.
The national radar mosaic for the moment the first event began.
6 flood. Local standard time, as filed.
Flooding along the Missouri River developed and then increased in late May as runoff from excessive upstream snowmelt and rain reached the area. Lowlands flooded included camping and other recreational facilities, as well as some roads.
Flooding along the Missouri River developed and then increased in late May as runoff from excessive upstream snowmelt and rain reached the area. Lowlands flooded included camping and other recreational facilities, as well as some roads. The river reached its highest May stage at 3.2 feet above flood stage near Greenwood at the end of the month.
Flooding along the Missouri River developed and then increased in late May as runoff from excessive upstream snowmelt and rain reached the area. Lowlands flooded included camping and other recreational facilities including marinas next to Springfield. Roads flooded included some outlying Springfield streets. The river reached its highest May stage at about 3 feet above flood stage near Springfield and near Niobrara, Nebraska at the end of the month.
Flooding along the Missouri River developed and then increased in late May as runoff from excessive upstream snowmelt and rain reached the area. Lowlands flooded included some roads near the River away from Lewis and Clark Lake. The river reached its highest May levels at the end of the month.
Flooding along the Missouri River developed and then increased in late May as runoff from excessive upstream snowmelt and rain reached the area. Lowlands flooded included a few roads near the River. The river reached its highest May levels at the end of the month.
Flooding along the Missouri River developed and then increased in late May as runoff from excessive upstream snowmelt and rain reached the area. Lowlands flooded included some roads and recreational facilities near the river, including part of a golf course at Dakota Dunes. The river reached its highest May levels at the end of the month, including a peak stage 2.5 feet above flood stage at Ponca, Nebraska.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2011Every state in 2011This day in weather historyWarnings in South Dakota, May 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: 316503, 316510, 316512, 316514, 316516, 316518.