472 FXUS63 KLMK 310708 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 308 AM EDT Tue May 31 2022 .Short Term...(Today and tonight) Issued at 305 AM EDT Tue May 31 2022 Another dry and very warm day is in store as high pressure at the sfc and aloft remains parked over the southern Appalachians. Progged low-level thicknesses and H9/H8 temps suggest that we'll end up close to persistence for highs this afternoon, perhaps a degree warmer. Will trend tonight's lows up a degree or two from this morning to account for a little better mixing as a cold front slowly approaches from the NW. && .Long Term...(Wednesday through Monday) Issued at 250 AM EDT Tue May 31 2022 Wednesday through Thursday night... Mid- and upper-level ridging across the eastern CONUS is expected to break down as we head into Wednesday and the latter half of the week. A series of shortwave disturbances/vorticity lobes will swing along the southern periphery of a large upper low located near Hudson Bay, gradually but consistently shifting the mid- and upper- flow regime from ridging to troughing by Thursday night/Friday morning. The most highly-amplified shortwave will have an attendant surface cold front which is expected to extend SW-NE from the southern Plains, across IL/IN, and into southern ON Wednesday morning. Global model guidance is generally in good agreement with the evolution of the front, taking it slowly southeastward during the day on Wednesday, bringing it to near the Ohio River overnight Wednesday night before pushing it through central Kentucky during the day on Thursday. At present, the progression of the cold front is expected to be slow enough for all areas across southern Indiana and central Kentucky to once again surge into the mid-to-upper 80s to near 90 Wednesday afternoon. Current global and mesoscale model depictions suggest that the cold front should serve as the main initiating boundary for convection Wednesday afternoon through Thursday night. Forecast soundings contain more than sufficient instability in the pre-frontal environment Wednesday afternoon (MLCAPE 2000-3000 J/kg); however, vertical wind shear will be lackluster thanks in part to only 15-20 kt flow at both 850 and 700 mb. With forecast soundings also showing considerable low- and mid-level dry air, the potential exists for quite negatively-buoyant downdrafts in strong storms, which could create some damaging wind concerns Wednesday afternoon and evening. Unsurprisingly (given antecedent ridging), melting heights will be quite height Wednesday afternoon, and low/mid-level lapse rates will generally be in the 6.5-7 deg C/km range, so the environment is not particularly favorable for large hail. However, given the amount of instability, isolated severe hail cannot be ruled out in storms with the strongest updrafts. There should be a nocturnal lull in convection Wednesday night into Thursday morning as the near-surface layer stabilizes and overall instability decreases. However, with the front close by and increasing low- and mid-level moisture, expect shower chances (with a few embedded thunderstorms possible) to persist overnight Wednesday night. Lows Thursday morning will be mild, only falling into the mid-to-upper 60s. Another chance for scattered thunderstorms is expected Thursday afternoon, with a few strong-to- severe storms possible across central Kentucky as sufficient instability will combine with slightly better shear as the low- and mid-level trough will be in closer proximity to the region by this time. Temperatures will be cooler Thursday afternoon with the front and additional cloud cover overhead, with highs only expected to reach the upper 70s to near 80. The storm threat will subside as the front clears the area Thursday evening, bringing cooler and drier air with it for Friday morning. Friday and Saturday... High pressure will settle into the Ohio Valley for Friday into Saturday, combining with mid-level NW flow to usher in drier weather for the end of the week and the first half of the weekend. Highs on Friday should reach the upper 70s to near 80, with lows Friday night falling into the mid-to-upper 50s. Highs Saturday will be near normal, with maximums generally expected to reach the low 80s. With dewpoints in the upper 40s and lower 50s both afternoons, expect comfortable conditions both days. Lows Saturday night should fall into the upper 50s to lower 60s. Sunday into early next week... Beyond Saturday, model solutions begin to diverge as the remnants of Hurricane Agatha begin to interact with the mid-latitude wave pattern across the eastern half of the Northern Hemisphere. WPC cluster analysis reveals that 30/12Z GEFS solutions are generally wetter for this time period, in line with the 31/00Z GFS deterministic run, while the 30/12Z EPS solutions are generally drier, which is in line with the 31/00Z ECMWF deterministic member. Since confidence is extremely low in any one solution at this amount of lead time, will stick with NBM temps and PoPs, which blends in information from multiple different guidance suites. In general, expect the warming trend which should begin Saturday to continue through Sunday and into Monday, with highs returning to above-normal levels. PoP chances will also slowly increase as we head into Monday and Tuesday as low- and mid-level moisture return should allow for typical afternoon shower/storm chances. && .Aviation...(06Z TAF Issuance) Issued at 110 AM EDT Tue May 31 2022 Sfc and upper ridging over the southern Appalachians will maintain dry weather through the valid TAF period. Expect VFR conditions with just scattered diurnal Cu, and light south winds at night increasing and veering to more of a SSW direction during the mixy part of the day. Gradient looks a bit tighter as you go north and west away from the high center, so included gusts just short of 20 kt in SDF and HNB this afternoon. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Short Term...RAS Long Term...CSG Aviation...RAS