Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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912 FXUS63 KLMK 180146 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 946 PM EDT Fri May 17 2024 .KEY MESSAGES... * Widespread showers and scattered storms today and Saturday, with locally heavy downpours possible. * Drier Sunday with hot temperatures Monday and Tuesday. * Showers and storms return Tuesday with increasing potential of strong to severe storms on Wednesday. && .UPDATE... Issued at 945 PM EDT Fri May 17 2024 Light rain has exited the region to the east and skies are beginning to thin. In the overnight hours, calm-light winds, clearing skies, and recent rain will allow for low stratus and fog to develop in the early morning. Ceilings and visibilities will continue to deteriorate until sunrise. In some areas, fog may become dense and drivers should use caution. An SPS has been issued for patchy dense fog. && .SHORT TERM /THROUGH SATURDAY/... Issued at 344 PM EDT Fri May 17 2024 Rain shield across the lower Ohio Valley is diminishing in coverage as an upper impulse departs, leaving behind weak lapse rates and not much in the way of lifting mechanisms. Main upper trof still hanging back across the Red River Valley, and expected to move slowly eastward into the Tennessee Valley by Saturday evening. As we lose lifting and then heating late this afternoon and this evening, expect the diminishing trend in precip to continue. Thunder chances will remain low, but not diminish as quickly especially if we get breaks in the clouds. The overall theme will be intermittent rain eventually tapering off completely. Humid and stagnant air mass overnight will be favorable for fog, though enough cloud cover is expected to persist to mitigate the fog potential. Still could easily have a stratus build-down, so we`ll mention fog but will not go as far as dense fog. Any dense fog should remain confined to the most sheltered valleys and typical fog- prone locations. Saturday will be on the muggy side with seasonable temperatures. Confidence in the precip forecast is much lower. Recent trend is to suppress most of the moisture feed in the Tennessee Valley as any southerly flow is fairly weak. However upper trofiness over a humid and relatively uncapped air mass will yield at least isolated showers over southern Indiana, with better chances along and south of the Parkways in Kentucky. Poor lapse rates will limit rainfall intensity and storm severity, though we can`t rule out a rumble of thunder. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 344 PM EDT Fri May 17 2024 Saturday Night through Sunday Night... The upper low which is bringing the unsettled weather to the region today and tomorrow will begin to pull out of the region Saturday night. Any showers and thunderstorms which are ongoing Saturday evening would be expected to dissipate with the loss of daytime heating, with most of the overnight hours expected to be dry. There is an enhanced potential for fog across the region late Saturday night into Sunday morning given the expected combination of moist soils, light winds, and clearing skies. Sunday should be the first in a stretch of two or three relatively quiet days as mid- and upper-level ridging builds from the southern Plains northeastward into the Ohio Valley. A diffuse area of sfc high pressure will move across the region, resulting in weak winds speeds. Low level moisture will remain in place, with dewpoints Sunday afternoon still in the low-to-mid 60s. However, warmer temperatures aloft, especially in the 850-700 mb layer, and the lack of any large-scale forcing should curtail precipitation chances. Warm, muggy conditions should continue into Sunday night, with another possibility for areas of fog Monday morning, depending on how much mixing and drying there is during the day on Sunday. Monday through Tuesday... Warm and humid conditions are expected to continue into the first few days of next week as upper ridging builds downstream of an amplifying trough over the western CONUS. There is elevated confidence in dry weather Monday and Tuesday, because while there will be some instability present and steep low-level lapse rates, any triggering mechanism in the form of a sfc cold front or upper level forcing should remain well to the north and west of the region. The main focus during this time period will be on above normal temperatures, with highs progressively warming through Tuesday as SW flow increases ahead of an incoming trough. NBM probabilities of highs 90 degrees or above range from 20-30% along and west of I-65 on Monday, increasing to 30-50% on Tuesday. Recent rainfall and saturated soils will limit the top end potential for temperatures, so expect most locations to remain in the mid-to-upper 80s. Tuesday Night through Thursday Night... The next period of unsettled weather looks to arrive Tuesday night into Wednesday as an upper trough and attendant sfc cold front cuts into the ridge in place over the eastern CONUS. Increasing moisture and forcing ahead of this system, along with falling mid- and upper- level heights will re-introduce the potential for showers and thunderstorms across the region. While machine learning and analog severe prediction tools show elevated potential for strong to severe storms Wednesday into Thursday, it continues to look like the best combination of instability and shear should remain west and north of the region at this time. Also, while susceptibility to flooding should decrease somewhat given expected dry weather Sunday through Tuesday, heavy rainfall could once again lead to localized flooding issues during this time period. Heading into the end of next week, model guidance diverges and forecast confidence decreases. In general, ensembles suggest a return to a more zonal pattern, though some of this is due to the averaging of differing solutions. && .AVIATION /00Z TAFS THROUGH 06Z MONDAY/... Issued at 756 PM EDT Fri May 17 2024 Light rain is exiting to the east of the region in the next hour. The remainder of the evening will consist of calm-light winds and lowering ceilings. In the early morning, CIGs will lower to low-end MVFR and IFR conditions. Visibilities will decrease over the region as low stratus and fog develops. Low stratus and fog will begin to break up with sunrise. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...SRM SHORT TERM...RAS LONG TERM...CSG AVIATION...SRM