Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 160759 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 359 AM EDT Tue Jul 16 2019 .SYNOPSIS... What remains of the decayed Tropical Depression Barry will move through the Ohio Valley tonight and Wednesday, bringing an increase in showers and a few thunderstorms, primarily tonight into Wednesday. It will remain muggy through the entire week with very warm and humid conditions expected Thursday through the weekend as a large dome of heat develops over much of the eastern half of the United States. Outside of rain chances tonight and Wednesday, much of the rest of the week and into the weekend will remain dry. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... What remains of the former Tropical Depression Barry is still spinning slowly northeast over Missouri per radar mosaics and GOES water vapor imagery. Per WSR-88D and TDWR VWPs, a belt of modestly enhanced low-mid level flow still exists on the eastern semi-circle of the circulation with belt of deeper moisture extending northeast from the Ark-La-Tex into the lower Ohio Valley. The 16.00Z KILN RAOB sampled some of this moisture /1.75" PWAT/ although the sounding had convective debris enhancing moisture just a bit. At 08Z, a large shield of sprinkles/light rain was still developing and shifting northeast into IN and southwestern OH downstream of the stronger height falls/vorticity maximum with the remnants of Barry. There is good model agreement that this activity will shift northeast along the OH/IN border this morning with some light rain/sprinkles continuing esp our southeast IN counties up into west-central Ohio. In the wake of this activity, there is a decided lull in forcing as we wait for the primary shortwave trough/vort max to eject out of MO/AR into the Ohio Valley later this afternoon. So - once the arc of light rain showers/sprinkles moves northeast across our western areas this morning, expect most of the day to be dry and again quite humid as low level moisture is entrenched and being enhanced by the modest feed of tropical southwesterly winds tied to the approaching trough. Expect highs into the 80s all areas - warmest southeast /lower Scioto Valley and northeast Kentucky/ which will be furthest removed from deeper inbound moisture. Could see heat indices in this area approach the mid 90s by afternoon. Can`t completely rule out a random/weakly forced shower to pop up with diurnal destabilization especially west of I-71 this afternoon but forecast soundings reflect the lull in forcing as PWATs pull back a bit with some mid-level drying with somewhat of stability maximum over the ILN CWA in comparison to areas southwest/west which will destabilize far more readily through the day. So broad-brushed low PoPs in place this afternoon to cover the potential for a random storm or two. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Primary vort maximum and height falls attendant to the weakening remnants of Barry will push northeast into Indiana early this evening as it slowly accelerates and the magnitude/sharpness of the trough decays. Expect the arrival of this forcing to manifest in a large area of increasing showers/storms (still quite scattered in coverage initially) to move into Indiana/western Ohio as the night wears on. Attendant to the arrival of this forcing will be deeper moisture with PWATs surging toward 2.10" or so, and low level /1km/ flow increasing to 30kts. Thus, any updrafts will have the potential to produce torrential rainfall rates of 2"+ /primary concern/ and very isolated gusty winds/marginally severe threats /distant secondary concern/. Despite very low LCLs and 0-1km shear > 25kts suggesting a non-zero weak tornado threat, think there`s better chances for isolated impacts tonight from localized flash flooding or brief water-loaded downdrafts causing sporadic tree damage /SPC MRGL risk/. Model QPF footprints continue to be underwhelming and mostly < 1". In fact, an amalgam of CAM QPFs show numerous very narrow swaths of ~1" to 1.25" amounts suggesting that an absence of a defined low level focus/convergence maximum will keep convection from being widespread or focused/tied to a particular area which is vastly different from the QPF footprints we saw in past days to our southwest when Barry had much more defined low level features. Thus, while confidence is high that there will be rain in most areas overnight, have capped PoPs around 75% because there will likely be some areas that dodge these swaths of locally heavy rain due to expected mode being narrow/progressive bands of showers/shallow thunderstorms. Supporting this is shrinking of WPC SLGT risk in the ILN CWA tonight /focused in far west-central Ohio/ and in Scioto Valley of southeastern Ohio on Wednesday. All things considered from a forcing/moisture perspective, feel the most confident that heaviest /relative/ QPF from this system will focus west of I-71 and north of I-70 (mostly west-central Ohio) this evening. Have added heavy rain to the forecast in all areas tonight into Wednesday morning to cover the potential for torrential rainfall rates with any convectively enhanced activity. On Wednesday, axis of very deep moisture with bands of showers and shallow thunderstorms will progress steadily through the ILN CWA, especially through the morning. By afternoon, the mid level trough axis will be shifting out with mid level flow turning westerly and a gradual loss of larger scale forcing. This should tend to allow activity to become more scattered into the afternoon. Temperatures with plenty of clouds will be tempered - mainly in the lower 80s but still very humid with dewpoints remaining in the 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Moisture and forcing associated with Barry remnants will be pushing east of the area Wednesday night, bringing an end to most showers and thunderstorms by Thursday morning. Isolated thunderstorms may still develop on Thursday afternoon, before a cap under a broad upper ridge keeps convection from forming on Friday and Saturday, resulting in sunny skies. Upper ridge is forecast to begin breaking down on Sunday, signaling the start of a change in the pattern. Lowering geopotential heights and somewhat cooler air aloft will produce an increase in instability, allowing scattered thunderstorms to form Sunday and Monday, aided by convergence and enhanced wind fields associated with a surface cold front. Hot temperatures and heat indices will the main story for this period. Highs in the low 90s Thursday will increase to the mid and upper 90s Friday and Saturday. Combined with a very humid airmass, heat indices will rise over 100, requiring heat headlines. As geopotential heights drop, and clouds, precip and modest cold advection arrive with the cold front, readings will transition slowly down to about 90 by Monday. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... At 05Z, VFR conditions across the TAF sites except for ILN where some shallow MVFR visibilities had developed thanks to evening storms and a brief period of clearing. Think most sites will be susceptible to a brief period of MVFR visibility through sunrise if some clearing can develop and persist for an hour or two, but looking at latest GOES imagery shows most of the pockets of clearing are quite small, so expect mostly cloudy skies /mid clouds/ to persist through sunrise. After sunrise, there may be a few showers that develop toward CVG/LUK/DAY on an arc of weak moisture transport but don`t expect much in the way of restrictions. Think sct/broken VFR clouds will persist across the sites through the day, and bulk of the day will be dry. Past 19Z or 20Z, expect scattered showers and a few storms to develop in random/scattered nature over the entire area as remnants of TD Barry approach as an opening shortwave trough, but a more focused/concentrated area of activity to the west over Indiana. This will move/develop toward KDAY/KCVG/KLUK by early to mid evening. Could be some brief MVFR or even IFR restrictions in torrential rainfall rates with this activity, but don`t have confidence in coverage/location to indicate anything more than prevailing showers /VFR/ right now. This axis of moisture/forcing will cross the TAF sites tonight but again - don`t have a good feeling for coverage and don`t think this will be a widespread/long event at any given TAF site - instead being bands of progressive showers and a few storms with very heavy rainfall rates for brief periods of time. Expect TAFs to be refined in later issuances in terms of timing of heaviest showers which may bring MVFR/IFR restrictions especially in the evening to early overnight. Late in the night could see a ceilings lower to MVFR categories as low level moisture peaks with the passage of the trough. OUTLOOK...MVFR/IFR ceilings possible Wednesday. Thunderstorms possible Wednesday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Binau NEAR TERM...Binau SHORT TERM...Binau LONG TERM...Coniglio AVIATION...Binau is the U.S. government's official web portal to all federal, state and local government web resources and services.