Isolated severe thunderstorms developed ahead of a weak upper level disturbance. 5 inches, which produced some flooding.
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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 ILN wrote it up.
Isolated severe thunderstorms developed ahead of a weak upper level disturbance. The storms produced heavy rain between 1.5 and 3.5 inches, which produced some flooding.
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 Wilmington, OH wrote its last area forecast discussion before the first event at Aug 4, 2:18 PM EST, 2 hours 5 minutes earlier.
Area Forecast Discussion National Weather Service Wilmington OH 318 PM EDT Sat Aug 4 2018 .SYNOPSIS... Isolated showers and storms will continue amidst a warm and humid airmass this afternoon and Sunday afternoon, but most areas will remain dry. Early next week several weak disturbances and a cold front will begin moving toward the area with a better chance of more widespread showers and storms, with cooler weather expected by the middle of next week in the wake of this system. && .NEAR TERM /UNTIL 9 PM THIS EVENING/... GOES-East water vapor loops and and RAP model analyses clearly indicated a weakening positive tilt mid-level shortwave trough across southern OH/northern KY. Underneath and immediately in the wake of this weak disturbance, a very baggy/weak surface pressure pattern was present where sheltering/shallowing of the boundary layer in comparison to areas further north/east had allowed dewpoints to fail to mix out - holding in the lower to middle 70s over southern ILN CWA. In this airmass, MLCAPE has approached and even exceeded 2000 J/KG amidst very weak tropospheric flow, with effective shear values < 10kts, and cloud-layer mean winds of only ~10kts as well. The 04.12Z KILN sounding sampled this weaker flow aloft, which has weakened further as the trough continues to lose amplitude and be cutoff/swallowed up by larger scale/background height rises downstream of deeper troughing to our west. Isolated storms this afternoon have behaved according to their forcing regime - very low predictability of initiation and a rapid increase/decrease of updraft magnitude over the course of an hour. Numerous weak downdraft signatures have been seen via WSR- 88D/TDWR, with outflows quickly becoming apparent after thunderstorm mass reaches a maximum. Anvil level winds blowing exhausted thunderstorm mass to the southwest back over the updrafts have also kept the thunderstorm lifecycle brief owing to efficient seeder/feeder processes and quick water loading of the downdraft. Expect the chaotic/low predictability formation, and thus the rapid increase/decrease of this storm lifecycle to continue through about 21Z after which skies should clear as the boundary layer decouples. .SHORT TERM /9 PM THIS EVENING THROUGH MONDAY NIGHT/... Expect shallow fog to be possible across many areas tonight as is typical for humid August nights in the Ohio Valley. The valley fog may be locally thick for a few hours overnight especially in the tributaries feeding into the Ohio River and main channel itself. On Sunday, a very similar scenario to today is expected albeit with the following exceptions 1) forcing for ascent will be even weaker in the absence of the weak shortwave trough across the area and 2)a modest reduction in instability with slightly lower dewpoints. Despite these unsupportive changes for the chance of afternoon storms, moderate destabilization will again take place in the boundary layer by 15Z. Diurnally forced cumulus will lead to more isolated airmass-type showers and thunderstorms during the peak of the diurnal cycle, and while the CAM signal for location is chaotic as can be expected given weak background forcing, there is a relative maximum over the ILN CWA from Columbus back down toward Wilmington, and this is where the rain chances were inserted into the forecast. On Monday, while large scale forcing is still mostly absent from the area, the warm/muggy boundary layer will remain and will be gently impinged by a slight increase in westerly flow and glancing shortwave trough energy to our northwest, and some hint of energy also impinging from the south. It's not much to hang a forecast on, but think the afternoon once again will see isolated/scattered showers and storms with better chances across nrn KY/wrn OH/ern IN but this is not an overly strong/confident signal in the data. && .LONG TERM /TUESDAY THROUGH SATURDAY/... An area of low pressure and associated frontal boundary will approach the region on Tuesday bringing with it showers and thunderstorms. Temperatures on Tuesday will be warmer across southeastern portions of the region where it will take longer for precipitation and cloud cover to work into the area. The frontal boundary lays out across the region for Wednesday before pushing out of the region Wednesday night. On Wednesday there is better upper support than on Tuesday and therefore increased precipitation chances from superblend on Wednesday. The frontal boundary in the vicinity and associated cloud cover will keep temperatures cooler and around 80 degrees. There are some model differences and run to run variability for Thursday and Friday with any precipitation possibilities. Due to this variability decided to go with a dry forecast for now, however cannot rule out some isolated activity during these two days. There is more continuity with a disturbance moving through on Saturday and therefore have a chance of thunderstorms in during that time. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... Diurnal cumulus has developed schedule and enough instability is present for isolated showers/storms which have developed in humid airmass characterized by very weak deep layer flow. Coverage of these will peak through 21Z before onset of boundary layer cooling will cause rapid decrease in coverage. Included a VCSH initially at KDAY for radar trends but in reality may need to add VCSH to KILN/KLUK/KCVG this afternoon - all of which lie in area of greater instability in comparison to KCMH. If one of these small showers/storms impacts an airfield - expect brief MVFR/IFR visibilities in the core of the downpour with up to 30kts of wind. But expect threat to be too isolated for inclusion in most TAFs. Skies becoming partly cloudy to clear overnight as cumulus dissipates and winds decouple to calm or light/variable at worst. Fog could again be a problem at KLUK near so have continued a tempo group to IFR visibility there. Outside of that, expect some potential reduction to MVFR visibility at other sites especially 08Z-12Z timeframe. Confidence is not high in this - only hinting at this via 5-6SM visibilities in most TAFs. Later tomorrow morning into Sunday afternoon, expect more towering cumulus to develop with isolated showers/storms, with the best signal from the Columbus terminals southwest back to KILN. These also expected to be quite isolated in nature, thus no inclusion at this time. OUTLOOK...Thunderstorms possible Monday and Wednesday, and likely on Tuesday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && SYNOPSIS...Binau NEAR TERM...Binau SHORT TERM...Binau LONG TERM...Novak AVIATION...Binau
Hazardous Weather Outlook National Weather Service Wilmington OH 333 AM EDT Sat Aug 4 2018 INZ050-058-059-066-073>075-080-KYZ089>100-OHZ026-034-035-042>046- 051>056-060>065-070>074-077>082-088-050745- Wayne-Fayette IN-Union IN-Franklin IN-Ripley-Dearborn-Ohio- Switzerland-Carroll-Gallatin-Boone-Kenton-Campbell-Owen-Grant- Pendleton-Bracken-Robertson-Mason-Lewis-Hardin-Mercer-Auglaize-Darke- Shelby-Logan-Union OH-Delaware-Miami-Champaign-Clark-Madison- Franklin OH-Licking-Preble-Montgomery-Greene-Fayette OH-Pickaway- Fairfield-Butler-Warren-Clinton-Ross-Hocking-Hamilton-Clermont-Brown- Highland-Adams-Pike-Scioto- 333 AM EDT Sat Aug 4 2018 This Hazardous Weather Outlook is for East Central Indiana, Southeast Indiana, Northeast Kentucky, Northern Kentucky, Central Ohio, South Central Ohio, Southwest Ohio and West Central Ohio. .DAY ONE...Today and Tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Sunday through Friday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE WILMINGTON OH
516 PM EDT SAT AUG 4 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0501 PM TSTM WND GST KLUK LUNKEN AIRPORT 39.10N 84.42W
08/04/2018 M47 MPH HAMILTON OH ASOS
28041KTS
&&
JEGThe Cincinnati radar (KILN), 64 km away, was scanning. The volume nearest the first event began at 21:23 UTC.
4 thunderstorm wind, 3 flood. Local standard time, as filed.
High water was reported on Columbia Parkway near Dead Man's Curve.
A large tree was knocked down on Reeves Golf Course.
Tree branches were reported knocked down everywhere on Red Bank Rd near I-71.
Several trees were knocked down on Old Five Mile Road and Forest Road.
High water was reported on Airport Road.
The southbound lane of Wilmer Avenue was closed due to high water.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Ohio in 2018Every state in 2018This day in weather historyWarnings in Ohio, August 2018
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: 763385, 763393, 763388, 763389, 763391, 763386, 763387.