Showers and thunderstorms developed during the morning hours along a warm front situated across the Ohio Valley.
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The episode as NWS ILN wrote it up.
Showers and thunderstorms developed during the morning hours along a warm front situated across the Ohio Valley.
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 May 17, 5:50 AM EST, 1 hour 10 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Wilmington OH 650 AM EDT Mon May 17 2021 .SYNOPSIS... A few rounds of showers are expected today and Tuesday, as a warm front slowly moves north through the area. Drier and warmer conditions are expected for the second half of the week, with temperatures well above normal from Thursday through Saturday. && .NEAR TERM /THROUGH TONIGHT/... Current surface analysis indicates high pressure located over the mid-Atlantic, low pressure over the southern plains, and generally southerly deep-layer flow over the Ohio Valley and other in-between regions. Surface flow remains somewhat backed, as the stronger warm advection just off the surface (particularly from 850mb-700mb) has yet to really translate to the boundary layer. The elevated theta-e advection has resulted in an increase of mid-level clouds, and precipitation is soon to follow. A cluster of elevated convection has moved from Illinois into Indiana, and will encroach on the southwestern quarter of the ILN CWA in the next few hours. SPC HREF and SPC mesoanalysis plots do not suggest that the elevated instability is much to speak of, and should continue to weaken as the cluster moves east. Although the instability will weaken, the overall forcing over the area will become stronger. This suggests the development of widespread showers with a few embedded storms, largely along a WNW-to-ESE oriented band that will slowly move northeast through the forecast area through the morning and afternoon. With poor alignment between the elevated frontal forcing and any weak instability that builds into the southern sections of the CWA, chances for additional thunderstorm development this afternoon appear quite limited. What the persistent clouds and rain may do, however, is keep temperatures limited as well. This max temp forecast is several degrees lower than the previous forecast, with only mid 60s across the heart of the ILN forecast area. Warmer conditions (lower 70s) appear likely in northern Kentucky and parts of southeast Indiana. && .SHORT TERM /TUESDAY/... Largely meridional 850mb flow will remain in place west of the ILN forecast area tonight into Tuesday morning. A wave in this flow, moving south to north, will lead to a compaction in the height contours over the lower Ohio Valley tonight -- and a resulting increase in southerly 850mb flow and theta-e advection over the middle Ohio Valley. This should serve as a focus for additional shower development early Tuesday morning, particularly for the southwestern sections of the ILN CWA. Continued cloudy conditions will keep min temps mild, ranging from the middle to upper 50s. On Tuesday, the elevated warm front will finally have undergone some kind of combination of washing out and moving north of the area, leaving a more uniform theta-e profile across the region. In fact, by Tuesday afternoon, the boundary layer should finally become a little more mixed as well -- with surface winds taking more of a southerly component. Weak forcing will remain a limiting factor in terms of precipitation chances on Tuesday, with no real features in the boundary layer. With some general theta-e advection in the lowest 1-2km, and some influence from a 500mb wave (which will mostly remain west of the area), isolated to scattered storms may develop in the heat of the afternoon. With storm coverage looking questionable, this is not worth anything more than a 30-50 percent chance as of now, and neither instability or shear parameters suggest much of a threat for anything strong. Greater chances for precipitation, and cloudier conditions in general, are likely to be found in the western half of the ILN CWA on Tuesday. Max temps will likely be warmest (upper 70s) near and east of the US-23 corridor, where the first signs of the upcoming warming trend will begin to take effect. Lower to middle 70s are expected elsewhere. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A weakening mid level short wave will lift up the back side of an upper level ridge building up into the upper Ohio Valley Tuesday night. With this, we could see a few lingering showers persist into Tuesday night, especially across western/northwest portions of our area. The upper level ridge will continue to build up into our area through Wednesday afternoon with temperatures pushing up into the upper 70s to lower 80s for highs. Some weak destabilization could lead to isolated shower/thunderstorm development during the afternoon, with the best chance for this again being across northwest portions of our area, along the northwest edge of the ridge. The upper level ridge will build across the eastern CONUS Thursday into Friday with rising heights, centered over the Tennessee and Ohio Valleys. GFS/EC ensemble means are showing the strongest heights across our area on Friday, before the ridge begins to retrograde back the the southwest and begin to weaken somewhat through the weekend. With the ridge overhead, will maintain a dry forecast Thursday and Friday and go a few degrees warmer than model blends, with highs by Friday into the upper 80s. As the ridge begins to weaken through the weekend, we will see an increasing chance for some isolated, diurnally driven, thunderstorm development each day through the remainder of the long term period. High temperatures will also begin to back off a bit heading into early next week, but will continue to nudge up guidance with highs still well into the 80s. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... An area of showers and thunderstorms has moved into the KCVG/KLUK area, with MVFR to possibly IFR conditions expected for the next few hours. Lighter rain will move into the other TAF sites in the next few hours, perhaps producing some brief MVFR conditions, but prevailing VFR conditions are expected. Any MVFR ceilings should lift by mid to late afternoon, resulting in VFR conditions from evening onward. Chances for additional showers and storms this afternoon are somewhat limited, but most likely to occur near Cincinnati. A VCSH was introduced for KCVG/KLUK. Additional rain, and possibly some lower ceilings, may impact KCVG/KLUK/KDAY overnight. Winds through the TAF period are likely to remain under 10 knots, and generally out of the ESE. .OUTLOOK...No significant weather expected. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && SYNOPSIS...Hatzos NEAR TERM...Hatzos SHORT TERM...Hatzos LONG TERM...JGL AVIATION...Hatzos
Hazardous Weather Outlook National Weather Service Wilmington OH 427 AM EDT Mon May 17 2021 INZ050-058-059-066-073>075-080-KYZ089>100-OHZ026-034-035-042>046- 051>056-060>065-070>074-077>082-088-180830- 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- 427 AM EDT Mon May 17 2021 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...Tuesday through Sunday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. HATZOS
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
High water was reported across County Road 750 N between 600 E and Old Milan Road.
High water was reported on County Road 800 N between 500 E and 600 E.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Indiana in 2021Every state in 2021This day in weather historyWarnings in Indiana, May 2021
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: 948981, 948982.