A vertically stacked low pressure system tracked into western North Dakota. Meanwhile, at the surface, an occluded front curved out to the east and south from near Minot to Fargo (ND) to Morris (MN).
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 FGF wrote it up.
A vertically stacked low pressure system tracked into western North Dakota. Meanwhile, at the surface, an occluded front curved out to the east and south from near Minot to Fargo (ND) to Morris (MN). Some afternoon sun over portions of northern South Dakota helped spawn scattered late afternoon and early evening thunderstorms.
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 Grand Forks, ND wrote its last area forecast discussion before the first event at May 21, 1:29 PM CST, 6 hours 16 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND FORKS ND 229 PM CDT SAT MAY 21 2011 .SHORT TERM... THE MAIN CHALLENGE WILL BE PRECIP CHANCES THROUGH SUNDAY...AND TEMPS. A SLOW MOVING AND POTENT UPPER LEVEL LOW CONTINUES TO SPIN IN THE NORTHERN PLAINS. THE MOST ORGANIZED BAND OF SHOWERS TODAY IS IN THE EAST AND NORTHERN AREAS...WITH CLEARING TRYING TO MOVE INTO NORTHERN SD/SOUTHERN ND. MODELS ARE IN GOOD OVERALL AGREEMENT...WITH NO REAL PREFERENCE TODAY. FOR LATE THIS AFTERNOON AND EVENING...IF CLEARING CAN MOVE INTO SOUTHEAST ND...THEN THUNDERSTORMS MAY DEVELOP. THERE WILL BE ABOUT 1000 J/KG OF SFC BASED CAPE...AND LI/S TO -4C. THERE WILL BE MINIMAL DEEP LAYERED SHEAR THOUGH...BUT COULD BE A FEW PULSE STORMS CAPABLE OF SMALL HAIL AND BRIEF GUSTY WINDS. OTHERWISE...EXPECT MAINLY SHOWERS SLOWLY SHIFTING NORTH AND DISSIPATING THROUGH THE OVERNIGHT. ON SUNDAY...THERE COULD BE A FEW BREAKS OF SUNSHINE DURING THE MORNING AS THE STACKED UPPER LOW DRIFTS INTO THE SOUTHERN FORECASTS AREA. THERE WILL BE CAPES TO AROUND 500 J/KG IN THE NORTH AND NEAR 1500 J/KG IN THE SOUTH. THIS WILL MEAN LIKELY THUNDERSTORM CHANCES BY AFTERNOON. THIS WILL HINGE LARGELY ON INSOLATION...BUT WITH LOW CONVECTIVE TEMPS IN THE UPPER 60S TO AROUND 70...EXPECT THUNDERSTORMS NEAR THE UPPER LOW. BY MONDAY...CLEARING AND DRYING WILL MOVE FROM NORTH TO SOUTH. EXPECT THINGS TO SLOWLY CLEAR THROUGH THE DAY WITH THE BEST THREAT FOR MAINLY MORNING SHOWERS IN THE SOUTH AND EAST. ON TUE...EXPECT DRY WEATHER WITH NW FLOW ALOFT AND A WEAK PRESSURE GRADIENT. TEMPS SHOULD BE NEAR TO SLIGHTLY BELOW NORMAL. .LONG TERM...TUESDAY NIGHT THROUGH SATURDAY GFS/ECMWF IN REASONABLE AGREEMENT THROUGH NEXT WEEK...BOTH SHOWING A WEAK UPPER RIDGE BUILDING ACROSS THE HIGH PLAINS WEDNESDAY AND INTO THE NORTHERN PLAINS BY THURSDAY. WITH UPPER LEVEL DYNAMIC FORCING WELL TO THE NORTH AND SOUTH AND SURFACE HIGH PRESSURE...FORECAST AREA SHOULD REMAIN DRY THROUGH THURSDAY WITH HIGHS IN THE UPPER 60S TO NEAR 70 DEGREES. SHORT-WAVE ENERGY EJECTS EASTWARD FROM EASTERN PACIFIC TROUGH THURSDAY NIGHT INTO FRIDAY BRINGING WITH IT THE THREAT THUNDERSTORMS. LATEST GFS IS STRONGER AND A BIT QUICKER WHEN COMPARED TO THE ECMWF...SO WILL KEEP POPS IN THE CHANCE CATEGORY FOR NOW. TEMPERATURES APPEAR TO GRADUALLY WARM INTO NEXT WEEKEND...BUT HIGHS SHOULD ONLY REACH INTO THE LOWER 70S. && .AVIATION... PREDOMINANT MVFR/IFR CEILINGS IN PERIODIC RAIN SHOWERS WILL SLOWLY GIVE WAY TO RISING CLOUD BASES LATE THIS AFTERNOON AND EVENING AS DRIER AIR MOVES INTO THE REGION FROM SOUTH TO NORTH. VISIBILITY MAY DROP TO 2 TO 3 SM IN HEAVIER SHOWERS. EAST-SOUTHEAST WIND WITH SOME GUSTS TO 20 KTS WILL CONTINUE THROUGH THE DAY. && .HYDROLOGY... MINOR FLOODING CONTINUES ON SIX POINTS IN THE HSA. RIVER LEVELS CONTINUE TO RECEDE AND GRAND FORKS HAS FALLEN BELOW FLOOD STAGE. RAINFALL THIS WEEKEND MAY CAUSE A FEW MINOR RISES ON SOME POINTS...BUT OVERALL MINIMAL IMPACTS ARE EXPECTED. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && DK/ROGERS/BH
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GRAND FORKS ND 700 AM CDT SAT MAY 21 2011 MNZ001>009-013>017-022>024-027>032-040-NDZ006>008-014>016-024- 026>030-038-039-049-052>054-221200- WEST POLK-NORMAN-CLAY-KITTSON-ROSEAU-LAKE OF THE WOODS- WEST MARSHALL-EAST MARSHALL-NORTH BELTRAMI-PENNINGTON-RED LAKE- EAST POLK-NORTH CLEARWATER-SOUTH BELTRAMI-MAHNOMEN- SOUTH CLEARWATER-HUBBARD-WEST BECKER-EAST BECKER-WILKIN- WEST OTTER TAIL-EAST OTTER TAIL-WADENA-GRANT-TOWNER-CAVALIER- PEMBINA-BENSON-RAMSEY-EASTERN WALSH-EDDY-NELSON-GRAND FORKS- GRIGGS-STEELE-TRAILL-BARNES-CASS-RANSOM-SARGENT-RICHLAND- WESTERN WALSH- 700 AM CDT SAT MAY 21 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN NORTH DAKOTA...WEST CENTRAL AND NORTHWEST MINNESOTA. .DAY ONE...TODAY AND TONIGHT BANDS OF RAIN WILL ROTATE NORTH AND WEST ACROSS THE AREA. CLEARING IS FORECAST TO MOVE INTO THE SOUTHERN RED RIVER VALLEY THIS AFTERNOON. HOWEVER AFTERNOON AND EVENING INSTABILITY SHOWERS CAN BE EXPECTED. NEARLY A HALF TO THREE QUARTERS OF AN INCH OF RAIN IS EXPECTED OVER NORTHEAST NORTH DAKOTA AND NORTHWEST MINNESOTA. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SHOWERS AND AN ISOLATED THUNDERSTORM WILL MOVE THROUGH SUNDAY. THUNDERSTORMS WOULD BE MOST LIKELY IN THE LATE AFTERNOON AND EARLY EVENING. THE STORMS ARE NOT EXPECTED TO BE SEVERE. ADDITIONAL LIGHT SHOWERS ARE EXPECTED MONDAY. AN ADDITIONAL QUARTER TO HALF AN INCH OF RAIN IS EXPECTED SUNDAY AND MONDAY MAINLY OVER THE NORTHERN RED RIVER VALLEY. THE TOPSOIL HAS DRIED OUT IN MOST AREAS AND SHOULD BE ABLE TO TAKE THIS RAIN. THERE COULD BE A SMALL RISE ON SOME RIVERS IN AREAS THAT DO GET THE HEAVIER AMOUNTS. BUT OVERALL RIVERS WILL CONTINUE TO RECEDE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED. HOPPES
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND 736 PM CDT SAT MAY 21 2011 NDZ052-053-220130- RICHLAND ND-SARGENT ND- 736 PM CDT SAT MAY 21 2011 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN RICHLAND AND EASTERN SARGENT COUNTIES UNTIL 830 PM CDT... AT 731 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A THUNDERSTORM 5 MILES NORTHWEST OF VEBLEN...OR 21 MILES NORTHEAST OF BRITTON...MOVING TO THE NORTH AT 25 MPH. HAIL UP TO THE SIZE OF PENNIES IS EXPECTED WITH THE STORM...ALONG WITH HEAVY RAIN. THE STORM WILL BE NEAR... CAYUGA...RUTLAND AND GENESEO AROUND 755 PM CDT. HAMLIN AROUND 810 PM CDT. WYNDMERE AROUND 820 PM CDT. MILNOR...GWINNER AND DE LAMERE AROUND 830 PM CDT. IF SEVERE WEATHER IS OBSERVED CONTACT YOUR LOCAL LAW ENFORCEMENT AND ASK THEM TO RELAY YOUR INFORMATION TO THE NATIONAL WEATHER SERVICE. RITTERLING
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND 750 PM CDT SAT MAY 21 2011 NDZ049-052-220145- RANSOM ND-SARGENT ND- 750 PM CDT SAT MAY 21 2011 ...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL SARGENT AND SOUTHERN RANSOM COUNTIES UNTIL 845 PM CDT... AT 745 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A THUNDERSTORM 5 MILES WEST OF FORMAN...OR 23 MILES NORTH OF BRITTON... MOVING TO THE NORTH AT 15 MPH. HAIL UP TO THE SIZE OF NICKELS IS EXPECTED WITH THE STORM...ALONG WITH HEAVY RAIN. THE STORM WILL BE NEAR... GWINNER AND STIRUM AROUND 815 PM CDT. IF SEVERE WEATHER IS OBSERVED CONTACT YOUR LOCAL LAW ENFORCEMENT AND ASK THEM TO RELAY YOUR INFORMATION TO THE NATIONAL WEATHER SERVICE. TORRENTIAL RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. RITTERLING
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
811 PM CDT SAT MAY 21 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 PM HAIL MCLEOD 46.39N 97.30W
05/21/2011 E0.50 INCH RANSOM ND CO-OP OBSERVER
&&
WBARRETTPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
812 PM CDT SAT MAY 21 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 PM HAIL GWINNER 46.22N 97.66W
05/21/2011 E0.25 INCH SARGENT ND PUBLIC
&&
WBARRETTThe Aberdeen radar (KABR), 96 km away, was scanning. The volume nearest the first event began at 01:45 UTC.
1 hail, 1 heavy rain. Local standard time, as filed.
Several quarter sized hailstones were embedded within a greater volume of pea sized hail.
Farm fields were flooded with water.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in North Dakota in 2011Every state in 2011This day in weather historyWarnings in North 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: 293557, 317921.