A small vorticity maximum moved from northwest Missouri into central Iowa during the afternoon and early evening of the 17th. CAPE values were around 2500 J/kg, with downdraft CAPE around 1200 J/kg.
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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 small vorticity maximum moved from northwest Missouri into central Iowa during the afternoon and early evening of the 17th. CAPE values were around 2500 J/kg, with downdraft CAPE around 1200 J/kg. Temperatures warmed into the low to mid 90s, with dewpoint readings in the upper 60s to low 70s. Isolated thunderstorms formed during the afternoon hours and weakened toward evening. One thunderstorm produced a downburst in Warren County at Lacona. Several trees were blown down. One three foot diameter tree fell on a 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 Jul 17, 5:32 PM CST, 23 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 632 PM CDT WED JUL 17 2013 .SHORT TERM.../TONIGHT /... ISSUED AT 229 PM CDT WED JUL 17 2013 SMALL VORT MAX MOVING INTO SWRN IA WILL PUSH INTO CENTRAL IA BY EARLY THIS EVENING. ONCE THE SUN STARTS TO GO DOWN...EXPECT TO SEE ISOLATED CONVECTION DWINDLE DOWN BY AROUND 01Z. THE REST OF THE NIGHT SHOULD BE QUIET WITH TEMPS RUNNING CLOSE TO WHAT WE HAD THIS MORNING. LIGHT SOUTH TO SOUTHWEST WINDS THROUGH THE NIGHT. .LONG TERM.../THURSDAY THROUGH WEDNESDAY/... ISSUED AT 229 PM CDT WED JUL 17 2013 IMPRESSIVE UPPER RIDGE OVER THE EASTERN HALF OF THE CONUS WILL GRADUALLY GIVE WAY INTO THE WEEKEND AS WESTERLIES DROP SOUTH INTO THE NORTHERN US. THURSDAY WILL BE CLOSE TO A CARBON COPY OF TODAY AND TUESDAY...ALTHOUGH WINDS WILL INCREASE AS PRESSURE GRADIENT TIGHTENS AS WESTERLIES DROP SOUTHWARD. SURFACE BOUNDARY IS FORECAST TO APPROACH NORTHERN IOWA LATE THURSDAY NIGHT. WINDS WILL REMAIN STRONGER ON THURSDAY NIGHT WITH TIGHTER GRADIENT AND WITH THERMAL RIDGE DROPPING INTO STATE...HAVE KEPT OVERNIGHT LOWS ON THE HIGH END OF GUIDANCE WITH READINGS IN THE MID TO UPPER 70S IN MOST LOCATIONS. BOUNDARY WILL CROSS THE STATE ON FRIDAY BUT CONVERGENCE IS RELATIVELY WEAK ALONG THE FRONT. MID LEVEL TEMPERATURES GENERALLY STAY QUITE WARM DURING THE DAY AS WELL AND IT APPEARS ANY CONVECTION WILL BE ISOLATED AND HAVE CUT BACK ON POPS. ALSO WORRIED ABOUT HIGHS ON FRIDAY AS THERMAL RIDGE PASSES THROUGH THE STATE. WITH DECENT SOUTHWEST TO WEST SURFACE FLOW AND AT LEAST PARTIAL SUNSHINE...READINGS MAY ACTUALLY APPROACH THE UPPER 90S IN PORTIONS OF CENTRAL AND SOUTHERN IOWA. REMAINDER OF THE FORECAST IS COOLER AS WESTERLIES WILL REMAIN FARTHER SOUTH INTO THE MIDDLE OF NEXT WEEK. BOTH GFS AND EURO BRING A SERIES OF SHORTWAVES THROUGH WNW FLOW DURING THE LATER HALF OF THE WEEKEND THROUGH THE MIDDLE OF NEXT WEEK. SURFACE BOUNDARY WILL ALSO BE NEARBY ALONG WITH MOISTURE TRANSPORT INTO THE MIDWEST. THEREFORE...THERE ARE CHANCES FOR THUNDERSTORMS DURING THIS PERIOD WITH TIMING BEING THE BIGGEST CHALLENGE AT THIS POINT. && .AVIATION...18/00Z ISSUED AT 632 PM CDT WED JUL 17 2013 SCATTERED THUNDERSTORMS IN VICINITY OF KMCW AND KDSM WILL DIMINISH WITH SUNSET THEN WIDESPREAD VFR AND LIGHT SOUTHERLY WINDS WILL BE IN PLACE. CUMULUS WILL DEVELOP AGAIN ON THURSDAY WITH SOUTH TO SOUTHWEST WINDS BECOMING A TOUCH MORE BREEZY. ANY LOCALIZED CIGS WILL BE BASED AROUND 4-5 KFT. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...MS JUL 13 LONG TERM...COGIL AVIATION...DONAVON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 128 PM CDT WED JUL 17 2013 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086- 092>097-181830- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN- WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE- BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER- POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION- CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE- DAVIS- 128 PM CDT WED JUL 17 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...THIS AFTERNOON AND TONIGHT HEAT INDICES MAY REACH THE LOW 100S FOR A FEW HOURS LATE THIS AFTERNOON MAINLY EAST OF INTERSTATE 35 AND SOUTH OF INTERSTATE 80. AN ISOLATED THUNDERSTORM IS POSSIBLE THIS AFTERNOON...HOWEVER NO SEVERE WEATHER IS EXPECTED. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THUNDERSTORM CHANCES WILL RETURN AT TIMES FROM THURSDAY NIGHT THROUGH TUESDAY. THE SEVERE THREAT REMAINS LOW AT THIS TIME BUT A FEW STRONGER STORMS ARE POSSIBLE NORTH LATE THURSDAY NIGHT AND SOUTH ON FRIDAY. HEAT INDICES WILL BE IN THE LOW 100S AT TIMES IN THE AFTERNOON MAINLY EAST OF INTERSTATE 35 THURSDAY AND SOUTH OF INTERSTATE 80 ON FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED.
The Des Moines radar (KDMX), 67 km away, was scanning. The volume nearest the first event began at 23:55 UTC.
1 thunderstorm wind. Local standard time, as filed.
Several trees and large branches down in town. A three foot diameter tree was blown over by downburst winds. One large tree landed on a car.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2013Every state in 2013This day in weather historyWarnings in Iowa, July 2013
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: 453602.