512 FXUS61 KILN 210733 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 333 AM EDT Tue May 21 2024 .SYNOPSIS... Much above normal temperatures continue about the region through midweek, with episodic showers and storms expected Wednesday into the upcoming weekend. Although slightly cooler temperatures may return for the end of the week, temperatures will likely stay above normal for the foreseeable future with an unsettled pattern persisting into early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Tranquil conditions have evolved locally as some cirrus due to convective blowoff continues to spill into the area. Temps will dip into the low/mid 60s by daybreak, still about 10 degrees above seasonal norms before rebounding once again this afternoon into the upper 80s. The main item of interest for the near term period is going to be the small chance for a spotty SHRA/TSRA from time-to-time, especially near the Tri-State/SE IN/N KY/S OH where the best SB instby should develop by mid afternoon. There is a subtle midlevel disturbance or remnant MCV (seen on satellite imagery over srn IN this morning) that will move through srn parts of the area into early afternoon, which may provide /just/ enough of a kick for some very spotty activity in these areas. So the potential for a few rogue downpours is certainly higher today than has been the case the past few days. But confidence in this occurring is still fairly low at this juncture. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... The short term period will turn a bit more active than has been the case the past several days. And it will start with a weakening MCS that should move into the local area during the predawn hours Wednesday morning. This bowing/linear structure, emanating from IA/IL, should outrun its source forcing/lift and encounter an increasingly unfavorable (more stable) environment with eastward extent. This being said, due to the organization of the convection, often times the storms are able to survive and maintain a bit longer than perhaps some guidance suggests. So the inclination is that at least /some/ structure of the convection will be maintained into the ILN FA during the predawn hours, likely providing a few rumbles and perhaps some brief gusty winds. This being said, the overall LL thermodynamic environment shouldn't be terribly favorable for strong/gusty winds to be maintained in a widespread sense. Any gusty wind potential would likely occur coincident with any N-S oriented segment that is able to be maintained with eastward extent, especially near the Tri-State between about 09z-12z Wednesday. At the very least, some patches of light rain and extensive cloud cover will overspread parts of the local area Wednesday morning, continuing to wane with SE extent. Subsidence and a stable environment should develop in the immediate wake of this feature, delaying the best destabilization efforts toward mid afternoon. While significant destabilization should eventually evolve, especially for locales near/W of I-71 by mid/late afternoon, there remain some questions regarding coverage of redevelopment during the afternoon itself as the LL southwesterly flow is largely parallel to the front/boundary, with very little in the way of pronounced LL convergence. This is not to say at all that there won't be a few storms that redevelop amidst the strongly unstable environment during mid/late afternoon, but the real impetus for redevelopment is likely going to be better S/W energy coming in from the srn Great Lakes, with additional S/W energy (perhaps an MCV remnant) drifting to the NE into the SW OH Vly, near/after sunset. This slightly better forcing, amidst strong instability, should allow for better blossoming of storm activity toward/beyond sunset, initially to the W of the immediate local area. For Wednesday evening/night, while confidence in storms occurring is high, confidence in severe potential or coverage of severe storms, is somewhat lower. The greatest severe potential locally may end up being during the evening hours itself as there should be sufficient overlap of good deep-layer shear and strong instby (owing to impressively-steep midlevel lapse rates). This suggests that, pending sufficient CI, there could be some storm organization posing a damaging wind and large hail threat. But, pushing aside questions of afternoon/early evening coverage, as we progress later into the evening and into the overnight, the thermodynamic environment should become a bit less favorable for maintenance of strong/severe storms, despite the potential maintenance of quite a bit of storm coverage. There is little doubt that there will be rumbles persisting through parts of the area through the nighttime into early Thursday morning, but do think the best severe potential, with robust updrafts, would likely manifest itself during the evening, particularly near the Tri-State/along I-71. As we progress later into Wednesday night, the main concern may shift to a localized heavy rain/flooding threat, especially if convection trains over the same areas. The anomalously-high PWATs combined with the largely boundary-parallel flow suggests that repeated storms/heavy rain over the same areas is very-much in play into early Thursday morning, particularly near/S of I-70. Will add mention of heavy rain/flooding to the HWO for awareness purposes. && .LONG TERM /THURSDAY THROUGH MONDAY/... The extended period begins Thursday with showers and storms exiting the middle Ohio Valley as a surface wave of low pressure shifts off to the east. In its wake, the overall pattern will consist of positive height anomalies over the southern Plains and negative height anomalies across the northern tier of the United States. This sets the stage for multiple disturbances moving east in zonal flow through our local area. Temperatures will continue at above normal levels without a source of cooler drier air through the period. The first disturbance arrives Friday, with showers and a few storms likely, particularly during the afternoon hours. PoPs will be highest near and south of the Ohio River. The next major disturbance arrives on Sunday with widespread showers and a few storms. To close the period on Monday, we get our first signs of a pending pattern shift as a sharp mid-level trough is kicked east from the northern Rockies heading toward the Great Lakes and Ohio Valley. This will cause showers ahead of the trough on Monday. Details on severe threat aren't clear at this time. However, from a broad perspective, we will need to watch for hydro impacts depending on where the heaviest rainfall is focused through the extended period. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... SCT/BKN convective blowoff cirrus continues to spill into the region, with a few patches of 6-8kft clouds also percolating about the area. Aside from some BR leading to MVFR, or even brief IFR, VSBYs at KLUK in the several hour period around sunrise, VFR conditions will prevail through daybreak and beyond. Some diurnally-driven VFR Cu will sprout about again around 15-16z, with a bit more coverage expected today owing to better LL moisture content. Cannot completely rule out a spotty SHRA/TSRA during the peak heating hours between 18z-23z, especially near KCVG/KLUK/KILN, but coverage should remain fairly limited and did not yet have the confidence to include even a VC at these sites. The better chance for more widespread SHRA/TSRA (albeit still somewhat low) will arrive after 06z Wednesday in the form of a weakening MCS that should move into the ILN FA toward the end of the KCVG 30-hr TAF. Light southerly flow at 5kts or less will increase to 10-12kts and become more southwesterly by/past 15z. Could even see a few gusts in the 15-20kt range before gustiness subsides once again toward/beyond sunset. OUTLOOK...Thunderstorms likely at times Wednesday into Thursday morning. MVFR CIGs possible Wednesday into Thursday. Additional chances for thunderstorms will return Friday and Saturday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...KC NEAR TERM...KC SHORT TERM...KC LONG TERM... AVIATION...KC