A upper level impulse, abundant moisture and a south-southwesterly flow combined to allow for the development of thunderstorms. While several produced small hail and locally gusty winds, the main effect was torrential rainfall, on the order of 1 to 3 inches per hour.
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 IWX wrote it up.
A upper level impulse, abundant moisture and a south-southwesterly flow combined to allow for the development of thunderstorms. While several produced small hail and locally gusty winds, the main effect was torrential rainfall, on the order of 1 to 3 inches per hour. This resulted in flash flooding in several locations across western Defiance county.
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 Northern Indiana wrote its last area forecast discussion before the first event at May 21, 2:59 PM EST, 1 hour 45 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 359 PM EDT FRI MAY 21 2010 .SHORT TERM... TONIGHT THROUGH SATURDAY NIGHT...THE MAIN CONCERN IS THE POTENTIAL FOR SEVERE STORMS...BUT ALSO FOR FLOODING. SOME TRAINING OF STORMS ON THE LATEST RADAR SCANS INDICATE THE POTENTIAL FOR HEAVY RAIN... SO GIVEN REPORTS OF SOME FLOODING IN ELKHART AND RADAR/SFC REPORTS OF HEAVY RAIN...WILL CONTINUE TO MENTION THE POTENTIAL FOR HEAVY RAIN. SPC MESO ANALYSIS INDICATES CAPE VALUES HAVE RISEN OVER 1000 J/KG OVER SOUTHEAST AREAS WHERE STORMS HAVE YET TO OCCUR. ONGOING CONVECTION AHEAD OF THE APPROACHING FRONT WILL LIKELY MAKE IT HARDER FOR STORMS TO BECOME SEVERE OVER WEST AREAS AHEAD OF THE FRONT...HOWEVER...GIVEN CELL MERGERS ON RADAR AND SOME EARLIER REPORTS OF WIND DAMAGE IN ELKHART AND THREE RIVERS...THE POTENTIAL FOR STORMS TO BECOME SEVERE CONTINUES THIS AFTERNOON. OTHERWISE... THE UPPER LOW WAS OVER NE IL AND WILL CONTINUE TO LIFT NORTHEAST AS A LARGE TROF DIGS DOWNSTREAM. PRECIPITATION SHOULD END FROM WEST TO EAST LATE TONIGHT AND EARLY SATURDAY. HAVE ADDED SOME DRIZZLE OVERNIGHT GIVEN UPPER AIR PROFILES. OTHERWISE...CONDITIONS SHOULD DRY OUT SATURDAY. && .LONG TERM... SUNDAY THROUGH FRIDAY. LITTLE CHNG TO ONGOING CONSISTENT AND WARM LONG TERM PD. 12 UTC GUIDANCE SUITES TRENDING TOWARD GENERAL CONSENSUS...WITH HIR CONFIDENCE FOR WARM/DRY FCST ESPCLY DYS3-6. ERN CONSENSUS REX BLOCK AT START OF LONG TERM WITH INCRSGLY STRONG UPSTREAM MIDLVL RIDGING FM SRN MS RVR VLY INTO CNTL GRTLKS...WITH MID LVL ANTICYCLONE REACHING CRESCENDO ACRS ERN/CTNL GRTLKS BY 00 UTC WED. LOW LEVEL THERMAL RIDGE TO ANCHOR FM SRN MO INTO WRN GRTLKS BY SUN AFTN AS WRN CONUS TROF SHARPENS COURTESY FUJIWHARA BTWN ALB/SASK WAVE AND STRONGLY TROP FOLDED ENERGY NOW ONTO WA/OR COAST. STRONG DOWNSTERAM RIDGE BLOCK TO HOLD ERLY/MIDWEEK CONVECTION WELL WEST OF CWA...FOCUSED IN HIR 1000-859MB THETA-E STREAM. SOME CONCERN FOR FRONTAL SYSTEM LAYING OUT E-W ACRS NRN GRTLKS DY6-7 TIMEFRAME AS IT BEGINS TO SAG SWD...POTNLY SPARKING SHRA/TSRA ACTIVITY. HOWEVER AS FURTHER UPSTREAM/INTERNATIONAL DATELINE SHORTWAVE PROGGED TO REDIG WRN TROF DEEPER AND FURTHER WEST BY END OF FCST PD...HAVE SOME RESERVATIONS ON FRONTS IMPACT WRT SENSIBLE WEATHER AS WARM MIDLVL CAPPING INVERSION SHOULD HAVE TIME TO REACH FULL MATURATION AND WITH BEST SFC FNTL CONVERGENCE AND MIDLVL COLD POOL VERY WELL COULD REMAIN ACRS CAN INTO NEW ENGLAND/LOWR GRTLKS FOR DY7...AND WL KEEP ENTIRE EXTND WARM/DRY FOR NOW AND AWAIT A MORE COHERENT PRECIP SIGNAL. && .AVIATION... HAVE ADJUSTED THE TIMING OF SHWRS/STORMS INTO THE SBN AND FWA TERMINALS EARLY IN THE PERIODS. AN UPPER LOW WAS OVER CENTRAL IL AND WAS LIFTING NORTH. SHWRS AND STORMS SHOULD CONTINUE TO DEVELOP THIS AFTERNOON WITH DAYTIME HEATING AND AS A SFC FRONT APPROACH. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && SHORT TERM...SKIPPER LONG TERM...MURPHY AVIATION...SKIPPER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE NORTHERN INDIANA 320 AM EDT FRI MAY 21 2010 INZ003>009-012-014-016>018-025>027-033-034-LMZ043-046-MIZ077>081- OHZ001-002-004-005-015-016-024-025-220730- LA PORTE-ST. JOSEPH IN-ELKHART-LAGRANGE-STEUBEN-NOBLE-DE KALB-STARKE- MARSHALL-KOSCIUSKO-WHITLEY-ALLEN IN-HUNTINGTON-WELLS-ADAMS-BLACKFORD- JAY-NEW BUFFALO MI TO ST JOSEPH MI- MICHIGAN CITY IN TO NEW BUFFALO MI-BERRIEN-CASS MI-ST. JOSEPH MI- BRANCH-HILLSDALE-WILLIAMS-FULTON OH-DEFIANCE-HENRY-PAULDING-PUTNAM- VAN WERT-ALLEN OH- INCLUDING THE CITIES OF...MICHIGAN CITY...LA PORTE...SOUTH BEND... MISHAWAKA...ELKHART...GOSHEN...LAGRANGE...TOPEKA...ANGOLA... KENDALLVILLE...LIGONIER...AUBURN...GARRETT...KNOX...NORTH JUDSON... PLYMOUTH...BREMEN...WARSAW...WINONA LAKE...COLUMBIA CITY... SOUTH WHITLEY...FORT WAYNE...HUNTINGTON...BLUFFTON...OSSIAN... DECATUR...BERNE...HARTFORD CITY...MONTPELIER...PORTLAND...NILES... BENTON HARBOR...ST. JOSEPH...BUCHANAN...DOWAGIAC...CASSOPOLIS... STURGIS...THREE RIVERS...COLDWATER...HILLSDALE...BRYAN...WAUSEON... ARCHBOLD...DEFIANCE...NAPOLEON...PAULDING...ANTWERP...OTTAWA... PANDORA...VAN WERT...DELPHOS...LIMA 320 AM EDT FRI MAY 21 2010 /220 AM CDT FRI MAY 21 2010/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST OHIO... SOUTHWEST LOWER MICHIGAN...NORTHERN INDIANA AND THE NEARSHORE WATERS OF SOUTHEASTERN LAKE MICHIGAN. .DAY ONE...TODAY AND TONIGHT THERE IS A CHANCE FOR THUNDERSTORMS TODAY AND TONIGHT. WHILE WIDESPREAD SEVERE WEATHER IS NOT EXPECTED...A FEW STORMS MAY PRODUCE SMALL HAIL AND GUSTY WINDS. IN ADDITION...LOCALLY HEAVY RAINFALL IS POSSIBLE TODAY WITH PONDING OF WATER ON AREA ROADWAYS AND RISES ON AREA STREAMS AND RIVERS. MINOR FLOODING OF A FEW RIVER POINTS IS POSSIBLE HEADING INTO THIS WEEKEND. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED. && STAY TUNED TO NOAA WEATHER RADIO FOR FURTHER DETAILS OR UPDATES...OR CHECK OUR WEB SITE AT WEATHER.GOV/IWX INZ013-015-020-022>024-032-220730- PULASKI-FULTON IN-WHITE-CASS IN-MIAMI-WABASH-GRANT- INCLUDING THE CITIES OF...WINAMAC...FRANCESVILLE...ROCHESTER... MONTICELLO...BROOKSTON...LOGANSPORT...PERU...WABASH... NORTH MANCHESTER...MARION 320 AM EDT FRI MAY 21 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHERN INDIANA. .DAY ONE...TODAY AND TONIGHT THERE IS A CHANCE FOR THUNDERSTORMS TODAY AND TONIGHT. THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON WITH LARGE HAIL AND DAMAGING WINDS BEING THE GREATEST THREATS. IN ADDITION...LOCALLY HEAVY RAINFALL IS POSSIBLE TODAY WITH PONDING OF WATER ON AREA ROADWAYS AND RISES ON AREA STREAMS AND RIVERS. MINOR FLOODING OF A FEW RIVER POINTS IS POSSIBLE HEADING INTO THIS WEEKEND. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS POSSIBLE THIS AFTERNOON. && STAY TUNED TO NOAA WEATHER RADIO FOR FURTHER DETAILS OR UPDATES...OR CHECK OUR WEB SITE AT WEATHER.GOV/IWX ARNOTT
PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE NORTHERN INDIANA
433 PM EDT FRI MAY 21 2010
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0410 PM TSTM WND DMG COLON 41.96N 85.32W
05/21/2010 ST. JOSEPH MI EMERGENCY MNGR
BARN DAMAGE AND UPROOTED TREES NEAR LONG STREET.
NUMEROUS TREES OF 1 TO 2 FOOT DIAMETER UPROOTED.
&&
CORRECTED REMARKS
EVENT NUMBER IWX1000542
MSLPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTHERN INDIANA
437 PM EDT FRI MAY 21 2010
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0340 PM TSTM WND DMG THREE RIVERS 41.94N 85.63W
05/21/2010 ST. JOSEPH MI TRAINED SPOTTER
POWER LINES DOWN. REPORTED ON ELM STREET AND PORTAGE
AVE.
&&
EVENT NUMBER IWX1000545
SAWPRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE NORTHERN INDIANA
438 PM EDT FRI MAY 21 2010
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0340 PM TSTM WND DMG THREE RIVERS 41.94N 85.63W
05/21/2010 ST. JOSEPH MI EMERGENCY MNGR
LARGE TREES DOWN AND REPORTED TO BE ACROSS THE STREETS.
&&
CORRECTED EVENT TIME
EVENT NUMBER IWX1000537
SAWPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTHERN INDIANA
439 PM EDT FRI MAY 21 2010
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0438 PM HAIL FREMONT 41.73N 84.93W
05/21/2010 M0.25 INCH STEUBEN IN AMATEUR RADIO
&&
EVENT NUMBER IWX1000546
MSLPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTHERN INDIANA
515 PM EDT FRI MAY 21 2010
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0514 PM HAIL 3 NNE AUBURN 41.41N 85.04W
05/21/2010 M0.25 INCH DE KALB IN TRAINED SPOTTER
PEA SIZE HAIL AND HEAVY RAINFALL. 0.6 INCHES IN 15
MINUTES.
&&
EVENT NUMBER IWX1000547
SAWPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTHERN INDIANA
532 PM EDT FRI MAY 21 2010
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0526 PM HAIL 3 ENE ROLLING HILLS 41.04N 85.22W
05/21/2010 E0.25 INCH ALLEN IN TRAINED SPOTTER
PEA SIZE HAIL AND HEAVY RAINFALL
&&
EVENT NUMBER IWX1000548
SAWThe Northern Indiana radar (KIWX), 107 km away, was scanning. The volume nearest the first event began at 21:42 UTC.
1 flash flood. Local standard time, as filed.
Emergency management officials reported numerous roads flooded across the western part of the county, including near the intersection of US 12 and Sand Lake Road. One to three inches of rain fell across portions of this area in roughly two hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Michigan in 2010Every state in 2010This day in weather historyWarnings in Michigan, May 2010
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: 257300.