


Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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935 FXUS63 KLMK 200138 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 938 PM EDT Tue Aug 19 2025 .KEY MESSAGES... * Peak Heat index values around 105 are likely, mainly along and west of I-65 through early evening. * Scattered thunderstorms are expected for some this evening into the overnight. The strongest storms could produce locally gusty winds and heavy rainfall. * Drier and temperatures closer to normal for mid to late week. * Below normal temperatures expected for the second half of the weekend into next week. && .MESOSCALE... Issued at 938 PM EDT Tue Aug 19 2025 A cluster of thunderstorms extends from northern Butler to southern Spencer County at this hour, with convection trailing well behind its associated outflow boundary. As these storms continue to move to the southeast, a weakening trend has been noted in terms of lightning and peak wind gusts over the past 30 minutes to an hour. Earlier this evening, isolated instances of wind damage were observed, mainly in association with downburst/microburst signatures. Now that low-level lapse rates have decreased to around 6-6.5 degrees, less of the momentum aloft is translating to the ground. Additionally, decreasing instability overall and convection trailing well behind the initiating outflow has led to weaker updrafts and convective cores overall. While a few 30+ mph gusts will be possible over the next hour, expect mostly in the range of 20-30 mph gusts as the strongest storms move overhead. This cluster of storms should subside by around midnight, with showers possibly lingering into the overnight hours. Convection has been progressive enough to stave off major flooding concerns, and would expect this to continue as rain rates decrease over coming hours. Outside of the line of showers and storms, the cold front will continue to sink through the area overnight, with light northerly winds and lower dewpoints working in behind the front. Toward daybreak Wednesday, low stratus and some patchy fog will be possible in the vicinity of the front. Temperatures should fall into the upper 60s and lower 70s across the area Wednesday morning. Issued at 551 PM EDT Tue Aug 19 2025 While the radar and satellite imagery is clear over much of the CWA at this time, there are numerous showers and storms to the immediate north and west of the area. The most organized area of convection is a line of thunderstorms roughly along US 50 at this time, which is pushing toward our southern Indiana counties at around 20-25 mph. This activity has fired along the surface cold front, and SPC mesoanalysis shows a band of enhanced llvl moisture convergence in the vicinity of where this activity is. While radar does show evidence that some of this activity is beginning to gust out, with 3500-4500 J/kg of SBCAPE ahead of this line and the aforementioned moisture convergence, would expect activity to continue into southern IN and toward the Ohio River over the next 2-3 hours. With deep-layer shear on the order of 5-10 kt, the front is serving as the main organizing feature for convection, with isolated pulse convection being observed along and south of the Ohio River so far this afternoon. On the other hand, for the next 1-3 hours, steep llvl lapse rates and DCAPE on the order of 1200-1400 J/kg will make isolated strong-to-severe wind gusts possible where the tallest cores develop. Further to this point, elevated values of microburst potential are also noted across southern IN on latest mesoanalysis. Farther to the south and west across western KY, storms have been less organized but still sufficiently tall to produce isolated strong to severe wind gusts. While this activity may try to creep into Ohio/Butler/Logan County over the next few hours, generally would expect sub-severe wind gusts and locally heavy rainfall with this activity (if it makes it into our CWA). The main change to the forecast at this time was to increase PoPs over the next 3 hours over southern Indiana. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 350 PM EDT Tue Aug 19 2025 A sfc cold front cuts NE to SW from Southeast Lower MI through central IN and southern IL this afternoon. Strong destabilization has taken place along and just south of the boundary with rich low- level moisture (mid 70s Tds) pooling in that area. Recent SPC mesoanalysis shows an axis of 3000+ J/kg MLCAPE from eastern MO northeast into west-central IN. MLCAPE of 2000-2500 J/kg extends in southern IN and west-central KY, with less instability further east. Scattered convection has developed along the boundary in central Indiana. The front is forecast to sink to near the Ohio River by 00Z this evening. Expect increasing chances for scattered showers and storms in southern IN and portions of central KY after 5-6 PM. Isolated strong to severe storms remain on the table, but the overall severe risk is Marginal/low-end. The primary storm hazards will be locally strong wind gusts, torrential rainfall, and frequent lightning. Storm intensity will diminish by 11 pm to Midnight due to waning instability. Weaker near sfc lapse rates should eliminate the marginal damaging wind threat by that time. However, spotty showers and storms will remain possible through much of the overnight period as the cold front pushes through the area. Sfc temperatures are currently running in the low to mid 90s. Heat Index values range from the mid/upper 90s in the Bluegrass Region to around 105 west of I-65. The Heat Advisory looks fairly well placed based on obs the past two hours, so will continue it through 8 PM with no changes. A slightly cooler, less humid airmass begins to move into the region Wednesday in the wake of the cold front. Morning lows will be in the upper 60s to lower 70s. Highs in the mid/upper 80s will be common Wednesday afternoon. A few showers and storms will be possible, mainly in southern KY closer to the boundary. Otherwise, most can expect a dry day with a steady north wind and partly to mostly cloudy skies. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Issued at 350 PM EDT Tue Aug 19 2025 Wednesday Night - Friday Night... Wednesday night looks quiet and dry. A light north wind continues with high pressure centered over the Great Lakes. Temperatures are forecast to fall into the mid and upper 60s by daybreak Thursday. Thursday and Friday continue to look mainly dry with a light NE wind continuing at the surface. High pressure centered off to our north gradually weakens with time as a fairly strong low pressure system barrels west to east across Canada. However, this system`s cold front won`t impact our weather until later this weekend. Look for highs in the low to mid 80s Thursday, with mid to upper 80s on Friday. Lows Friday morning could get down as low as the low to mid 60s. Saturday - Monday... The Canadian storm system continues to deepen across Ontario Friday into Saturday, pulling a trailing cold front southeast through the Great Lakes and Midwest. Moisture briefly deepens Saturday and Saturday night ahead of this front, which could bring some isolated showers and storms. Highs on Saturday will be fairly typical for this time of year in the mid 80s to around 90. Significantly cooler air arrives for the second half of the weekend, with a reinforcing shot of cool air from the northwest. Deep upper level troughing takes shape over the eastern CONUS, with deep NW flow locally. This refreshing pattern will bring notably lower dewpoints (50s) to the region. Expect lows in the low to mid 60s Sunday morning, with afternoon highs in the low to mid 80s. Lows in the mid 50s to around 60 will be possible for the commute to work and school Monday morning. && .AVIATION /00Z TAFS THROUGH 06Z THURSDAY/... Issued at 749 PM EDT Tue Aug 19 2025 A line of showers and thunderstorms associated with a cold front will move through SDF over the next hour, and may try to approach LEX, RGA, and BWG later this evening. The line will bring gusty NW winds, as well as brief IFR/LIFR visibilities as it passes, though it is expected to weaken over the next 1-2 hours. Once this line dissipates, winds should gradually veer to the north as the front sinks south across the region late tonight. Behind the front, there appears to be a window for MVFR, and possibly IFR stratus, particularly at LEX and SDF tomorrow morning. Flight categories should improve by early afternoon on Wednesday, with post-frontal stratus expected to mix up into a 3-5 kft stratocu field. Winds are expected to strengthen Wednesday afternoon out of the north, with 20 kt gusts possible at SDF, LEX, and HNB. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ MESOSCALE...CSG SHORT TERM...EBW LONG TERM...EBW AVIATION...CSG