Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 261835 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 235 PM EDT Tue Mar 26 2024 .SYNOPSIS...
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Deep and potent surface low pressure in Wisconsin will continue to move north into Lake Superior tonight as a cold front sweeps east into the Ohio Valley. This pattern will continue to bring gusty winds, showers and a few storms, and cooling temperatures into Wednesday. High pressure will build into the Mississippi and Ohio River Valleys on Wednesday and Thursday with dry weather. A warm front will begin to develop across Indiana and Ohio on Friday into Saturday as southerly flow transports moisture into the area, leading to the next chance of showers and thunderstorms.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Forecast thinking surrounding this evening`s rain chances and wind/thunderstorm threats/potential has not changed much over the last 4-6 hours. Clouds have been thick today, and winds very gusty to 40-45 mph at times, especially on the fringe of rain areas where evaporation of rain from the mid deck has augmented wind gusts. Low level jet core has worked north of the forecast area for the most part, but enough southward extension of 50kts /h85/ into the area to continue to foster the gust potential. Per HREF probabilities of 40 mph gusts, should see wind gusts begin to lose their `edge` from south to north after about 3 or 4 PM. Thus, have the southern/eastern segment of the Special Weather Statement expiring first at 4 PM, and holding onto to it through 7 PM for areas of wind-prone west-central Ohio where HREF probabilities and recent HRRR gust information suggests gusts will hang on longer. Winds should drop back more considerably after sunset as a cold front works across the area. Not much destabilization has taken place in the forecast area as of 1830Z, and this was expected with the stout cloud cover. We are starting to see breaks in the clouds to the west, with temperatures poking up some into the low 60s, and feel this will happen across the Tri-State area/I-75 corridor between 3PM and 6PM, adding a little instability, pushing MLCAPE toward 300 J/Kg as dewpoints hold in the lower 50s.Starting to see showers slowly deepen across central Indiana, though movement has been more north than east so far. As low level frontogenesis increases to our west in the later afternoon hours, the showers should conceal more into a north-south line or broken line of deeper updrafts /perhaps thunderstorms though that remains in question if lightning strikes will realized/. Either way - it won`t really matter on potential impacts due to strong/extreme low level wind fields. Despite the low level shear vector having a considerable line-parallel component, there could still be enough magnitude to vector to allow for shear-dominant line segments to develop and transport brief strong/severe wind gusts to the surface via weak/transient mesovortex development, or just downward momentum transfer and evaporative accelerations. While overall parameter space - and especially AI/ML guidance of severe wind/tornado...and HREF calibrated probabilities of thunder and accumulated 0-3km updraft helicity progs have all diminished from 00Z to 12Z...the combination of a line of storms in these very strong wind fields in and of itself suggests a non-zero severe weather threat. Primary concern would be brief wind gusts to 55 or 60 mph, and given persistent 0-1km curvature of the hodograph and effective SRH of ~150 m2/s2, a brief/weak tornado simply cannot be ruled out. Areas of west central Ohio are under the greatest relative threat, but a conditional threat extends southward into southeast Indiana and southwest Ohio for a few hours. Main window of threat overall is 5PM-8PM, before activity rapidly weakens.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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Post frontal low clouds should hang tough on Wednesday morning as westerly winds usher in colder temperatures, but through the day expect these clouds to scatter out to some degree with temperatures a few degrees either side of normal. Better clearing takes hold of the area on Wednesday night, with temperatures falling below freezing.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/...
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It`ll likely be a tale of two different weather patterns through the long term period -- a quiet one Thursday through Friday followed by a much more unsettled pattern Saturday through the beginning of next week, the latter of which will bring with it the potential for several rounds of rain and storms. For starters, the end of this workweek will close out on a relatively tranquil note as sfc high pressure builds into the TN Vly as the pronounced mid/upper level trof finally swings through the Great Lakes/OH Vly regions. This will set the stage for NW flow to become established, at least briefly, late Thursday/Thursday night, with sfc ridging nudging E into the OH Vly as we progress into Friday/Friday night. Several weak disturbances aloft will eject E through this flattening flow Thursday night through Friday night, bringing with it perhaps an increase in cloud cover. However, despite better moisture transport developing eastward into the area, LL moisture profiles should remain too meager to allow anything more than ISO measurable pcpn locally through Friday night. Near normal temps are on tap Thursday/Thursday night before slightly warmer air (5-15 degrees above normal) builds in Friday/Friday night. As we progress into the weekend, a somewhat unsettled weather pattern looks likely to evolve, with several rounds of rain and/or storms increasingly likely Saturday through at least Monday night. While the details of this pattern are still to be resolved, there is good deterministic and ensemble consensus on a wet pattern developing this weekend into early next week. Several disturbances should pivot about the nrn periphery of a midlevel ridge centered over the nrn Gulf, promoting the development of several weak low pressure waves/centers moving approximately W to E through the mid MS and OH Rvr Vlys. The first of these should develop as early as Saturday morning, with a corresponding enhanced LLJ allowing for better moisture/mass transport ENE from MO through IL/IN/OH. There will be a quasi-oscillating boundary that will become established within the region for the better part of ~3 days, which will serve as a focus for renewed/additional rounds of rain/storms each day Saturday, Sunday, and Monday. While ensemble guidance points toward higher probs of more widespread rain/storm activity Saturday near/N of I-70, PoPs have been broad-brushed at these time ranges to include a chance of precip just about everywhere. This initial wave, upon its departure Saturday night, may act to shift the aforementioned boundary S to closer to/S of the OH Rvr as drier air briefly builds in behind the first sfc wave Saturday night/early Sunday. However, renewed convective development is likely on Sunday as additional S/W energy pivots around the broad-scale ridge axis and into the OH Vly. This will coincide with more aggressive moisture transport back N into the region, with PWAT anomalies exceeding 150% of normal by Sunday night. This should allow for another round of rain/storms (with some low-end instby being shown on much of the prevailing guidance). We should see a northward pivot in the boundary once again Sunday night into Monday, with more of the local area becoming situated squarely in the warm sector of the eastward-moving system, which should eject through the central plains into the mid MS Rvr Vly by Monday afternoon. Renewed rain/storm chances will occur once again late Monday/Monday night with the better forcing and additional lift spreading E ahead of/along the front, with drier conditions finally returning by later Tuesday. There are several items to watch regarding the pattern this weekend into early next week -- most notably the repeated rounds of rain and whether the heaviest activity from each "round" moves over the same areas more than once. Still a bit too far out to isolate one specific favored area/corridor for heavy rain, but it is mentioned here for general awareness purposes, especially considering the cumulative effect as we progress into Monday/Monday night. The other item will be the potential for a few strong/severe storms late Monday/Monday night. The overall setup, from a pattern recognition perspective, certainly suggests that severe storms may develop in/near the local area if the necessary ingredients come together. And if a more wide-open warm sector is able to develop Monday afternoon/evening, allowing for a better LL thermodynamic setup, amidst seasonably strong deep-layer wind fields, a few strong to severe storms could evolve. However, even with this said, there are too many uncertainties in time and space at this juncture to include in the HWO.
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&& .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Plenty of aviation concerns with this TAF cycle as detailed below... 1) Surface winds - have been strong out of the SSE this morning with frequent gusts to around 35kts, locally higher. Short term model guidance suggests that - while in general winds will start to slowly decrease from south to north as the low level jet axis shifts north, it will still remain very windy through the afternoon as southerly winds continue 15 to 25kts, with gusts to 35kts at times. First to decrease will likely be CVG/LUK with gusts losing some magnitude by later this afternoon, and similarly ILN/LCK/CMH a few hours later. DAY may continue to gust strongly into early evening. After sunset, winds will diminish but still be gusty, turning southwest, and temporarily west behind the cold front crossing the area. Several hours after frontal passage, as winds weaken back < 10kts they will drift back to southwesterly and then increase to around 10kts after sunrise as they try to shift back to the west. 2) Low clouds - ceilings have been a mix of MVFR/VFR this morning and will stay that this afternoon. Some light rain moving north from Kentucky this afternoon may keep MVFR ceilings in play for ILN/LCK/CMH a little longer than points west, which should slowly ascend into VFR category through the night outside of showers/storms. However, in the wake of the cold front, cooling will lower cloud bases back into a mix of MVFR and VFR on Tuesday morning. 3) Thunderstorms - expect scattered showers to continue to slowly develop and congeal into a line or a broken line of showers (with isolated lightning strikes) as it crosses the terminals in the 23Z-03Z timeframe from west to east. While precipitation is rather certain as this line works west to east across the area, the presence of thunder is not owing to weak instability, and thus have kept predominant SHRA with VCTS for right now. 4) Visibilities - only in the heaviest part of the line of showers are visibilities expected to drop, but there is uncertainty right now on low it could go, so for right now have focused any /MVFR/ visibility restrictions on the northern TAF sites with the showers where they are more certain, and are more likely to be heavier. OUTLOOK...MVFR conditions are possible on Saturday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Binau NEAR TERM...Binau SHORT TERM...Binau LONG TERM...KC AVIATION...Binau

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