Elevated storms were the name of the game in the morning of the 14th before surface based convection later in the day. A surface low pressure center slowly made its way out of South Dakota and into parts of western and central Iowa.
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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.
Elevated storms were the name of the game in the morning of the 14th before surface based convection later in the day. A surface low pressure center slowly made its way out of South Dakota and into parts of western and central Iowa. The morning round of elevated storms were strongest across northern Iowa within an environment of 500-1000 J/kg MUCAPE and effective bulk shear values around 30 to 40 kts. While most storms were sub-severe, a couple were able to produce damaging winds and hail. By the afternoon, much of the state found itself within the weak warm sector and was able to experience some weak surface based convection. As a result, no noteworthy storms developed, but a pair of funnel cloud reports were received.
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 14, 3:11 AM CST, 34 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 411 AM CDT Mon Aug 14 2017 .SHORT TERM.../Today through Tonight/ Issued at 405 AM CDT Mon Aug 14 2017 Thunderstorms are currently ongoing over north central Iowa mainly along and north of Highway 20. These storms are ahead of a surface boundary that has moved into northwest Iowa and are supported by strong theta-e advection along the nose of a veering low level jet that is pointing into the state. Forcing is further enhanced by a strong short wave that is morning into southern Minnesota. The boundary will gradually settle southeast today. Much drier mid- level air will filter into the state in the wake of the boundary with the aid of subsidence behind the short wave. The thunderstorms will settle southeast and should be mostly out of the forecast area by 15z. Modest instability does return this afternoon as the mid-level moisture recovers some but it will be difficult to activate the instability. Any chances for precipitation should remain south of the boundary and over southern Iowa though no overly enthused about chances across that region. Severe weather chances will be low though an isolated severe storms is possible across the south. Low thunderstorm chances will remain over southern Iowa tonight. Have reduced pops through this period and suspect that much of the state will have little to no rainfall overnight. Other concern will be fog potential tonight across northern Iowa. Light winds, recent precipitation and the potential for good radiational conditions will enhance the fog potential. Similar to Sunday, high temperatures today will be dependent on amount of sunshine but generally highs will be in the mid 70s to mid 80s. .LONG TERM.../Tuesday through Sunday/ Issued at 405 AM CDT Mon Aug 14 2017 The main focus of the extended period was on rain chances Tuesday and Wednesday. Leaned toward a blend of the ECMWF/NAM Tuesday into Wednesday and then closer to the ECMWF through the rest of the forecast package. Tuesday into Wednesday...GFS seems to be the outlier on Tuesday's convection as it develops convection along the stalled boundary over southern Iowa early Tuesday morning and lingers across the southern two-thirds of the forecast area to around 18z. NAM and ECMWF delay the convection associated with an upper level shortwave until the afternoon and leaned toward trimming off pops across the eastern and northern sections of the forecast area Tuesday morning to coincide with this solution. Plenty of dry air to contend with from the surface high pressure remaining planted over the Great Lakes before decent theta-e advection pushes across the forecast area past 18z Tuesday. The parent surface low remains on track to move across the state late Tuesday night into Wednesday. A fair amount of isentropic upglide and moisture transport along the 305-315K isentropic surface into the state b/t 03z to 18z Wednesday. The GFS suggest forecast soundings across central Iowa become deeply saturated by around 12z Wednesday, while the NAM/ECMWF are a bit slower to saturate the column until around 18-21z. The GFS/ECMWF show a secondary 500mb shortwave trough trailing behind the surface low Wednesday evening providing additional lift for rain through 06z Thursday. The best potential for long duration rainfall across the forecast area looks to be from past 09z to 21z Wednesday. Precipitable water values around 2.0 inches and warm layer cloud depths range from 4000-4500 meters during the aforementioned time frame. Although growing confidence in widespread and potentially long-duration rainfall Wednesday, certainly not a drought buster for the drought stricken locations in Iowa. The QPF amounts of 0.25 to over an inch widespread are possible by Wednesday evening. Thursday through Sunday...Surface high pressure builds into the region Thursday and Friday providing some clear skies and dry conditions. This high pressure looks to dominate the weather pattern through the weekend with the GFS and ECMWF suggestions a couple very weak shortwaves to try and penetrate the surface high, but higher confidence to go dry for much of the weekend with a significant amount dry air in place. && .AVIATION.../For the 06Z TAFS through 06Z Monday night/ Issued at 1126 PM CDT Sun Aug 13 2017 Have tried to fine tune timing for showers/possible thunderstorms at KMCW and KFOD overnight. Still possibility the line of storms may hold together into KALO and KDSM, but uncertainty is high and therefore have left dry for now. Otherwise winds to become more southwesterly into Monday. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...Donavon LONG TERM...Podrazik AVIATION...Beerends
Hazardous Weather Outlook National Weather Service Des Moines IA 158 PM CDT Sun Aug 13 2017 IAZ004>007-015>017-023>028-033>037-044>048-057>059-070>072-081- 082-092-141100- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Crawford-Carroll-Greene-Boone-Story- Audubon-Guthrie-Dallas-Cass-Adair-Madison-Adams-Union-Taylor- 158 PM CDT Sun Aug 13 2017 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight Scattered thunderstorms are forecast at times this afternoon and overnight. Severe weather appears unlikely, but a few storms could produce small hail and gusty winds, mainly across northern Iowa. .DAYS TWO THROUGH SEVEN...Monday through Saturday Additional thunderstorms are forecast at intervals from Monday through Wednesday night, then again around Friday. The highest chances will come from late Tuesday night into Wednesday. The severe weather threat appears low at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. IAZ038-039-049-050-060>062-073>075-083>086-093>097-141100- Grundy-Black Hawk-Marshall-Tama-Polk-Jasper-Poweshiek-Warren- Marion-Mahaska-Clarke-Lucas-Monroe-Wapello-Ringgold-Decatur-Wayne- Appanoose-Davis- 158 PM CDT Sun Aug 13 2017 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Monday through Saturday Thunderstorms are forecast at intervals from Monday through Wednesday night, then again around Friday. The highest chances will come from late Tuesday night into Wednesday. The severe weather threat appears low at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. Lee
The Des Moines radar (KDMX), 131 km away, was scanning. The volume nearest the first event began at 09:47 UTC.
1 thunderstorm wind, 1 hail. Local standard time, as filed.
Emergency manager reported a large machine shed partially destroyed, partial roof damage, a hog building with door damage and tin ripped up, and grain storage bins with damage to 2 doors. This is a delayed report and time estimated from radar.
Trained spotter reported brief pea to quarter sized hail between Nevada and Colo on Highway 30.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2017Every state in 2017This day in weather historyWarnings in Iowa, August 2017
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: 714605, 714606.