A weak cold frontal boundary that entered the state the previous day regained momentum and moved southeast of the state by the afternoon. In its wake was an environment of relatively steep low level lapse rates, lifted condensation levels around 1000 m or less, and a few hundred J/kg of SBCAPE.
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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 weak cold frontal boundary that entered the state the previous day regained momentum and moved southeast of the state by the afternoon. In its wake was an environment of relatively steep low level lapse rates, lifted condensation levels around 1000 m or less, and a few hundred J/kg of SBCAPE. In all, it ended up enough for a couple of weak updrafts to produce funnel clouds.
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 May 23, 11:57 AM CST, 1 hour 26 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 1257 PM CDT Tue May 23 2017 .SHORT TERM.../Today through Tonight/ Issued at 322 AM CDT Tue May 23 2017 A large mid/upper low pressure system currently centered over Minnesota will drop south across Iowa and Missouri today and tonight. The attendant surface trough has already made its way through most of our forecast area, and will exit our southeastern counties later this morning. Behind the trough and below the core of the mid/upper level trough, regional radar imagery depicts scattered light showers and it is expected that these will increase in coverage across Iowa this afternoon, coincident with the diurnal heating maximum and the low moving overhead. Have maintained generally 40 to 50 POPs this afternoon accordingly, and gone with coverage wording of showers. Presence of thunderstorms this afternoon is uncertain with little to no instability indicated by forecast and upstream profiles, but the core of the low moving overhead this afternoon. Have opted to remove thunder mention from about the northwest half of the area, but kept isolated in the east and southeast this afternoon. In any event no strong or severe storms are anticipated. Coverage and intensity of showers/storms should gradually diminish overnight tonight, but continued light showers are expected as the low will be slow to depart to the south, with fairly deep saturation remaining in its wake. .LONG TERM.../Wednesday through Monday/ Issued at 322 AM CDT Tue May 23 2017 Wednesday through Thursday Night: Confidence High Upper level low will track across the region Wednesday with residual showers advancing southeast and exiting the region by 00z Thursday. A gradual decrease in clouds is expected by Wednesday afternoon from west to east...with some sun over the west briefly helping with afternoon high recovery there. Quiet conditions and cool temperatures will move over the region for Wednesday night with generally clear to partly cloudy conditions. By Thursday an H500 ridge aloft will help increase temperatures as H850 temperatures recover during the afternoon hours. The Euro model is showing some light precipitation edging into the region by 18-00z due to warm air advection aloft...with a similar forecast with the GFS. Friday through Monday: Confidence Low Run to run and model to model consistency quickly drops heading into the weekend. The GFS continues to hold onto a deepening wave on Saturday across Iowa and the Great Lakes while the Euro shows no such amplification in the flow over Iowa but keeps any wave south of the state with rainfall generally confined to Missouri and areas south. The GFS appears to be suffering from convective feedback on Saturday with the amplifying short wave over Iowa and Wisconsin. With such large disparity between models...targets of opportunity to make any meaningful changes to extended are few and far between with such disparity between solutions. There is some consistency between models on Monday...with showers and potentially some thunderstorms as a cold front and stronger upper level trough swings southeast over the Northern and Central Plains. This would potentially lead to a cooler and more showery day Monday with temperatures falling into the 60s by Tuesday. Overall the period will be mixed with 60s/70s for highs and 40s/50s for lows. The warmest day appears to be Friday with gradually cooler temperatures into the weekend. Specifics will need to be parsed out over the next few days. Overall...there should be sufficient breaks in any rain chances to enjoy the period but still some confidence issues with timing and strength of potential systems tracking our way. && .AVIATION.../For the 18Z TAFS through 18Z Wednesday afternoon/ Issued at 1257 PM CDT Tue May 23 2017 Broad cyclonic circulation will continue across Iowa for much of the forecast period with lower status and diurnally driven precipitation. While conditions will be mainly VFR this afternoon, MVFR conditions will exist in and around showers. Tonight, ceiling will lower to MVFR across much of the forecast area continuing into Wednesday morning. Surface winds will be from the northwest today becoming northerly overnight as cold advection persists. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...Lee LONG TERM...REV AVIATION...Cogil
Hazardous Weather Outlook National Weather Service Des Moines IA 435 AM CDT Tue May 23 2017 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-240945- 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- 435 AM CDT Tue May 23 2017 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Showers and isolated non severe thunderstorms will be possible this afternoon and early evening mainly east of a line from Butler to Ringgold Counties. Flood Warnings remain in effect on a few area rivers. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Thunderstorm chances will return at times from Friday through Monday. The severe weather threat is low at this time. .SPOTTER INFORMATION STATEMENT... Spotters activation is not likely at this time. REV
The Des Moines radar (KDMX), 20 km away, was scanning. The volume nearest the first event began at 19:23 UTC.
2 funnel cloud. Local standard time, as filed.
Emergency manager relayed public report of a funnel cloud northwest of Slater that was present for several minutes.
Storm chaser reported a brief funnel cloud near Pleasantville, possibly between there and Melcher-Dallas.
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, May 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: 698569, 698568.