A very unstable airmass was over Iowa with the warmest weather of the season. Temperatures soared into the 90s with dew point readings in the mid 70s to mid 80s by early afternoon.
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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 very unstable airmass was over Iowa with the warmest weather of the season. Temperatures soared into the 90s with dew point readings in the mid 70s to mid 80s by early afternoon. CAPE values rose to near 8000 J/kg with lifted indices in the -12 to -14 C range. Downdraft CAPE was in the 1000 to 1500 J/kg range. Available CAPE in the -10 to -30 C layer of the atmosphere was quite high, between 1000 and 1300 J/kg by mid afternoon, however freezing levels were also very high and were in excess of 15,500 feet. The shear environment was favorable with 35 kts of effective shear. Moisture was high with precipitable water values of 1.6 to 2 inches. A line of thunderstorms formed during the late afternoon hours and moved across the state as a cold front entered northwest Iowa. The mode of severe weather with the storms was in the form of high winds. Little hail occurred due to the warm atmosphere. The line of storms weakened rather rapidly for the same reason. Temperatures aloft at the 700 mb level were in excess of 15 C, which hampered the storms. Winds of 60 to 70 MPH occurred with the line for a couple hours as it moved into western Iowa. Tree damage was reported with the high winds, along with some shed and crop damage on area farms.
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 14, 5:10 PM CST, 52 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DES MOINES IA 610 PM CDT WED JUL 14 2010 ...UPDATED AVIATION DISCUSSION... .SHORT TERM /TONIGHT/... HEAT INDICES WILL CONTINUE TO BE IN THE 105 TO 115 DEGREE RANGE ACROSS THE ENTIRE CWA...WITH VALUES DROPPING BELOW CRITERIA BY MID EVENING...SO WILL CONTINUE CURRENT TIMING OF THE HEAT ADVISORY. COLD FRONT NEARING CWA...WITH STRONG CAP EVIDENT ON KOAX MID DAY SOUNDING. RUC/NAM TRY TO ERODE CAP ACROSS NORTHERN CWA WITHIN THE NEXT FEW HOURS...BUT LOOKS LIKE MAIN ACTIVITY OF CONVECTION STILL EXPECTED WITH AS COLD FRONT MOVES THROUGH THE AREA. STRONG INSTABILITY...AND MODERATE SHEAR TO STILL ALLOW FOR GREATER CHANCES OF SEVERE WEATHER ESPECIALLY ACROSS NORTHERN HALF OF CWA. SHEAR STILL EXPECTED TO DECREASE LATER THIS EVENING...WITH THE SEVERE ACTIVITY DIMINISHING SOME BUT STILL A THREAT ACROSS ENTIRE CWA THIS EVENING. ABUNDANT MOISTURE...WILL ALLOW FOR LOCALLY HEAVY RAINFALL AS WELL...BUT ANY STORM SYSTEMS SHOULD BE PROGRESSIVE ENOUGH TO INHIBIT FLASH FLOODING FOR THE MOST PART. DEWPOINTS INTO THE 60S BEHIND THE FRONT...SO EXPECT RELATIVELY DRIER AIR ACROSS THE CWA BY LATE TONIGHT. .LONG TERM /THURSDAY THROUGH WEDNESDAY/... UPPER RIDGE OVER THE MIDWEST WILL RETROGRADE TOWARD THE DESERT SW THROUGH THE REMAINDER OF THE WEEK AS AN UPPER LOW PROGRESSES EAST ACROSS SRN CANADA. THE RESULT WILL BE NW TO ZONAL FLOW THROUGH THE WEEKEND. A FEW THUNDERSTORMS ARE POSSIBLE ON THURSDAY OVER THE SOUTHEAST AS THE SFC COLD FRONT CONTINUES TO DROP TO THE SOUTH. THE MAIN EFFECT OF THE BOUNDARY WILL BE LOWER DEWPOINTS AS TEMPERATURES WILL STILL BE IN THE UPPER 80S TO AROUND 90 INTO THE WEEKEND. THE NEXT BEST CHANCE FOR THUNDERSTORMS WILL ARRIVE SATURDAY NIGHT AS ANOTHER BOUNDARY AND SHORT WAVE SHIFTS THROUGH THE STATE. LONG WAVE TROUGH DIGGING INTO THE WRN CONUS EARLY NEXT WEEK WILL SHIFT THE UPPER RIDGE BACK INTO THE CENTRAL PLAINS. STILL UNCERTAIN IF THE RIDGE WILL BUILD BACK IN AS STRONG AS TODAY. THE ECMWF SUGGEST IT BEING WEAKER WITH IOWA MORE WET AND NEAR THE RING OF FIRE. && .AVIATION... 15/00Z...CONVECTION DEVELOPING ALONG AND AHEAD OF ADVANCING COLD FRONT IN WESTERN IOWA WILL PUSH INTO CENTRAL IOWA OVER THE NEXT 6 HOURS. HAVE TIMING OF CONVECTION HANDLED WITH TEMPO GROUP FOR ALL TAF SITES EXCEPT OTM. LOOKING AT POTENTIAL MVFR CONDITIONS WITH TSRA ACTIVITY ALONG WITH WIND SHIFT TO THE WEST/NORTHWEST AS COLD FRONT PUSHES THROUGH. && .DMX WATCHES/WARNINGS/ADVISORIES... SEVERE THUNDERSTORM WATCH UNTIL 10 PM CDT THIS EVENING FOR WEST CENTRAL TO NORTHERN SECTIONS OF CWA. HEAT ADVISORY UNTIL TO 8 PM CDT THIS EVENING FOR ENTIRE CWA. && SHORT TERM...BEERENDS LONG TERM...DONAVON AVIATION...PODRAZIK
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 141 PM CDT WED JUL 14 2010 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086- 092>097-151000- 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- 141 PM CDT WED JUL 14 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...THIS AFTERNOON AND TONIGHT HEAT INDEX READINGS WILL REACH THE 105 TO AROUND 115 DEGREE RANGE ACROSS THE AREA THIS AFTERNOON INTO THE EARLY EVENING HOURS. A HEAT ADVISORY IS IN EFFECT FOR CENTRAL IOWA. PLEASE REFER TO THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES FOR FURTHER DETAILS. THUNDERSTORMS ARE EXPECTED BY LATE AFTERNOON...AND MOST LIKELY BETWEEN 3 PM AND 9 PM. SEVERE STORMS ARE POSSIBLE WITH GOLF BALL SIZE HAIL...DAMAGING WINDS AND POSSIBLY TORNADOES. LOCALLY HEAVY RAINFALL IS ALSO LIKELY. RIVER FLOOD WARNINGS REMAIN IN EFFECT FOR PORTIONS OF SOUTH CENTRAL IOWA. PLEASE REFER TO THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES FOR FURTHER DETAILS. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THERE IS A CHANCE OF THUNDERSTORMS SATURDAY NIGHT AND SUNDAY...WITH SLIGHT CHANCES OF THUNDERSTORMS AT TIMES MONDAY AND TUESDAY. THE SEVERE THREAT CANNOT BE DETERMINED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED LATE THIS AFTERNOON AND TONIGHT. MJB
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 624 PM CDT WED JUL 14 2010 IAZ004-005-015-023-024-033-034-044-045-150100- EMMET-KOSSUTH-PALO ALTO-POCAHONTAS-HUMBOLDT-SAC-CALHOUN-CRAWFORD- CARROLL- INCLUDING THE CITIES OF...ESTHERVILLE...ALGONA...EMMETSBURG... POCAHONTAS...HUMBOLDT...SAC CITY...ROCKWELL CITY...DENISON... CARROLL 624 PM CDT WED JUL 14 2010 ...POTENTIAL FOR SEVERE STORM DEVELOPMENT... A LINE OF STRONG TO SEVERE THUNDERSTORMS EXTENDS FROM NEAR GRAETINGER SOUTHWEST TO THE IOWA AND NEBRASKA BORDER. THIS LINE OF STORMS WILL MOVE EASTWARD OVER THE NEXT HOUR AND LIKELY AFFECT AREAS IN AND AROUND DENISON...TO SAC CITY...POCAHOTAS AND EMMETSBURG. LARGE HAIL AND DAMAGING WINDS MAY ACCOMPANY THESE STORMS THROUGH 800 PM CDT. LOCALLY HEAVY RAIN IS ALSO EXPECTED. KLP
The Omaha radar (KOAX), 100 km away, was scanning. The volume nearest the first event began at 00:03 UTC.
7 thunderstorm wind. Local standard time, as filed.
Winds estimated over 60 MPH bent crops over at a 45 degree angle along highway 30 just northeast of Dow City.
A shed was blown over in Dow City.
Trees were blown over.
Trained spotter reported winds estimated at 70 MPH. A horse feeder was blown over.
Trees were blown over.
Tree limbs and branches were downed. Some were large. One power line was blown down.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2010Every state in 2010This day in weather historyWarnings in Iowa, July 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: 232523, 232521, 232522, 232524, 232525, 232526, 232527.