A warm front was positioned west-northwest to east-southeast to the south of Iowa. An upper level disturbance moved into the area as the low level jet increased during the early morning hours of the 20th.
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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 DMX wrote it up.
A warm front was positioned west-northwest to east-southeast to the south of Iowa. An upper level disturbance moved into the area as the low level jet increased during the early morning hours of the 20th. During the pre-dawn hours, the low level jet increased to 35 to 40 kts. The airmass was unstable with about 2000 J/kg of elevated CAPE available. CAPE in the -10 to -30 C layer of the atmosphere was near 600 J/kg. Thunderstorms formed north of the warm front. A few of them became severe and produced large hail. Quarter to golf ball size hail fell in Dallas and Polk Counties. The largest hail fell in De Soto in Dallas County where golf ball size hail was reported. A car was struck by lightning as a man was driving to work on Iowa Highway 5. The man was not injured, but about $15,000 in damage occurred to the car.
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 Des Moines, IA wrote its last area forecast discussion before the first event at Aug 20, 3:09 AM CST, 9 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 409 AM CDT WED AUG 20 2014 .SHORT TERM /TODAY/... ISSUED AT 405 AM CDT WED AUG 20 2014 AS ANTICIPATED ELEVATED THUNDERSTORMS HAVE FORMED IN A BROKEN BAND ACROSS SOUTHERN/SOUTHWESTERN IOWA EARLY THIS MORNING...ALONG THE NOSE OF THE VEERING LOW LEVEL JET AND WITHIN A REGION OF THETA E ADVECTION ALOFT. A FEW STORMS WILL LIKELY PRODUCE SOME HAIL BUT NO ORGANIZED SEVERE WEATHER IS EXPECTED. THIS ACTIVITY WILL PERSIST FOR THE NEXT SEVERAL HOURS AS IT SLOWLY DRIFTS NORTHEAST TOWARD CENTRAL IOWA...THEN GRADUALLY FADE LATER THIS MORNING WITH MOSTLY DRY CONDITIONS ANTICIPATED BY THE AFTERNOON. CONCURRENTLY...AN EFFECTIVE WARM FRONT IN THE FORM OF A SURGE OF WARMER AND MORE MOIST AIR WILL MOVE IN FROM THE SOUTHWEST TODAY...RESULTING IN SULTRY CONDITIONS ACROSS MUCH OF OUR AREA BY LATER TODAY. HEAT INDEX VALUES WILL TOP OUT NEAR 100 DEGREES FROM AROUND THE I-80 CORRIDOR SOUTHWARD THUS NO ADVISORY IS WARRANTED AT THIS TIME. .LONG TERM /TONIGHT THROUGH TUESDAY/... ISSUED AT 405 AM CDT WED AUG 20 2014 PRECIP TRENDS WILL BE THE PRIMARY FORECAST CONCERN RIGHT ON INTO NEXT WEEK...BUT UNFORTUNATELY DETAILS WILL BE HARD TO COME BY. GENERAL PATTERN CHANGES LITTLE WITH PERSISTENT WRN CONUS TROUGH/ERN RIDGE SCENARIO AS PNA INDEX CONTINUES TO LOWER. THIS LEAVES IA IN PROLONGED SW FLOW ALOFT WITH SURFACE FEATURES REACHING THE STATE LATER THIS WEEK AND MOVING LITTLE INTO NEXT WEEK. CONVECTION FOR THE NEXT FEW DAYS WILL MAINLY BE NOCTURNAL WITH LITTLE CONVERGENCE OR LARGER SCALE FORCING. WARM/THETA-E ADVECTION SURGE WILL PUSH THROUGH TONIGHT WITH WEAKER THERMODYNAMIC FORCING THU NIGHT. WITH BAROCLINIC ZONE ADVANCING NE...THIS WILL LEAVE IA IN A VERY WARM AND HUMID AIRMASS WITH HIGHS IN THE UPPER 80S/LOWER 90S. PEAK HEAT INDICES WILL BE PUSHING ADVISORY CRITERIA...JUST OVER 100F...BUT NOT QUITE THERE SO WILL CONTINUE MENTION IN THE HWO. BY THE WEEKEND AND EARLY NEXT WEEK SURFACE BOUNDARY SHOULD ADVANCE MORE SOUTH AND EAST INCREASING THE POTENTIAL FOR PEAK HEATING/SURFACE BASED CONVECTION. SURFACE FEATURES SHOULD LINGER THROUGH THE END OF THE VALID PERIOD WITH A PROLONGED MENTION OF POPS. BETTER SYNOPTIC FORCING WITH WRN TROUGH FINALLY ADVANCES FAR ENOUGH EAST TO INCREASE POPS AND PRECIP COVERAGE BY TUE...BUT BEST SENSIBLE WEATHER REFLECTION SEEMS JUST BEYOND THE CURRENT VALID PERIOD TUE NIGHT INTO WED. THE AIRMASS WILL BE FAVORABLE FOR LOCALLY HEAVY RAINS THROUGH THE ENTIRE PERIOD WITH QUITE FAVORABLE ELEVATED K INDICES...WARM CLOUD DEPTHS AND PWS. HAVE STARTED WITH HEAVY RAIN MENTION NORTH TONIGHT...BUT ADDITIONAL WORDING MAY NEED TO BE ADDED WITH LATER PACKAGES. NE HALF OF THE FORECAST AREA REMAINS QUITE DRY...SO NO HEADLINES FOR NOW UNTIL CONFIDENCE OF HEAVY RAIN LOCATIONS AND MORE FAVORABLE ANTECEDENT MOISTURE CONDITIONS BECOME BETTER PHASED. SEVERE POTENTIAL WILL REMAIN ELEVATED AS WELL DUE TO THE DEGREE OF INSTABILITY AND AT LEAST MARGINAL EFFECT SHEAR...BUT THERE DOES NOT APPEAR TO BE ANY PARTICULAR PERIOD TO FOCUS ON BESIDE MARGINAL INCREASE FROM THE WEEKEND ON DUE TO BOUNDARY INTERACTIONS. WILL KEEP BROAD MENTION OF BOTH THREATS GOING IN THE HWO. && .AVIATION...20/06Z ISSUED AT 1134 PM CDT TUE AUG 19 2014 BOUNDARY WILL LIFT ACROSS IOWA THROUGH WEDNESDAY...THIS WILL BRING CHANCES FOR SHRA/TSRA TO SITES...PRIMARILY SOUTHERN SITES THROUGHOUT THE PERIOD. BEST CHANCES WILL COME BEFORE 12Z...BEFORE DECREASING. HAVE INCLUDED VC MENTION AT KFOD/KDSM/KOTM. NORTHERN SITES WILL LIKELY SEE BR/FG NEAR 12Z GIVEN AMPLE LOW LEVEL MOISTURE. MVFR...IFR OR LOWER CEILINGS AND VISIBILITIES WILL BE POSSIBLE AT TIMES AT SITES THROUGH 12Z BEFORE IMPROVING QUICKLY AFTER 12Z. WINDS WILL BECOME SOUTHERLY AND CONDITIONS WILL REMAIN VFR THROUGH REMAINDER OF PERIOD. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...LEE LONG TERM...SMALL AVIATION...AWB
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 327 PM CDT TUE AUG 19 2014 IAZ004>007-015>017-023>028-035>039-049-050-062-202030- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-WEBSTER- HAMILTON-HARDIN-GRUNDY-BLACK HAWK-MARSHALL-TAMA-POWESHIEK- 327 PM CDT TUE AUG 19 2014 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TONIGHT AREAS OF FOG ARE LIKELY TO DEVELOP TONIGHT. THE FOG MAY BECOME LOCALLY DENSE WITH VISIBILITIES LESS THAN ONE QUARTER MILE AT TIMES. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY PERIODIC THUNDERSTORMS ARE ANTICIPATED WEDNESDAY THROUGH MONDAY. LOCALLY HEAVY RAINFALL IS POSSIBLE. THE PROBABILITY OF SEVERE WEATHER IS LOW...HOWEVER THE BEST CHANCES WILL BE WEDNESDAY NIGHT AND AGAIN OVER THE WEEKEND. LOCALLY HEAVY RAINFALL IS POSSIBLE WITH AN OF THE THUNDERSTORMS. HEAT INDICES WILL RISE INTO THE LOW TO MID 90S TUESDAY...WEDNESDAY...AND THURSDAY AFTERNOON. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED. IAZ033-034-044>048-057>061-070>075-081>086-092>097-202030- SAC-CALHOUN-CRAWFORD-CARROLL-GREENE-BOONE-STORY-AUDUBON-GUTHRIE- DALLAS-POLK-JASPER-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS- UNION-CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE- APPANOOSE-DAVIS- 327 PM CDT TUE AUG 19 2014 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TONIGHT SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP OVERNIGHT TONIGHT. AN ISOLATED SEVERE STORM WITH QUARTER SIZED HAIL IS POSSIBLE. LOCALLY HEAVY RAINFALL MAY OCCUR AS WELL. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY PERIODIC THUNDERSTORMS ARE ANTICIPATED WEDNESDAY THROUGH MONDAY. LOCALLY HEAVY RAINFALL IS POSSIBLE. THE PROBABILITY OF SEVERE WEATHER IS LOW...HOWERVER THE BEST CHANCES WILL BE WEDNESDAY NIGHT AND AGAIN OVER THE WEEKEND. LOCALLY HEAVY RAINFALL IS POSSIBLE WITH AN OF THE THUNDERSTORMS. HEAT INDICES WILL RISE INTO THE UPPER 90S TO JUST OVER 100 DEGREES TUESDAY...WEDNESDAY...AND THURSDAY AFTERNOON. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 335 AM CDT WED AUG 20 2014 IAZ057>059-070>072-082-083-201000- AUDUBON-GUTHRIE-DALLAS-CASS-ADAIR-MADISON-UNION-CLARKE- INCLUDING THE CITIES OF...AUDUBON...EXIRA...GUTHRIE CENTER... PANORA...BAYARD...CASEY...PERRY...WAUKEE...ADEL...ATLANTIC... GREENFIELD...STUART...ADAIR...FONTANELLE...WINTERSET...EARLHAM... CRESTON...OSCEOLA 335 AM CDT WED AUG 20 2014 ...SCATTERED THUNDERSTORMS PRODUCING HEAVY RAIN AND HAIL... SCATTERED THUNDERSTORMS HAVE DEVELOPED EARLY THIS MORNING AND WILL PERSIST THROUGH SUNRISE. A FEW OF THESE STORMS WILL PRODUCE PENNY TO NICKEL SIZED HAIL...ALONG WITH LOCALLY HEAVY RAIN THAT COULD RESULT IN PONDING OF WATER AND MINOR FLOODING OF LOW LYING AREAS. LEE
The Des Moines radar (KDMX), 33 km away, was scanning. The volume nearest the first event began at 09:15 UTC.
3 hail, 1 lightning. Local standard time, as filed.
Golf ball size hail reported by a KCWI Television viewer.
Report from the Des Moines Airport COOP observer.
A car was struck by lightning as the occupant was driving to work.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2014Every state in 2014This day in weather historyWarnings in Iowa, August 2014
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: 528555, 528556, 528557, 529061.