366 FXUS63 KLMK 241503 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1103 AM EDT Tue Aug 24 2021 .Forecast Update... Issued at 1055 AM EDT Tue Aug 24 2021 Rinse and repeat forecast today with persistent sfc and upper ridging. Currently looking at oppressive dewpoints in the lower/mid 70s with the late morning spike, but continued boundary-layer growth will mix those down to around 70 this afternoon. Max temps in the lower/mid 90s for most, while upper 90s in the Louisville heat island will likely result in a better mixdown with dewpoints into the upper 60s. The end result will be heat indices just either side of 100 for most, but approaching 105 under the strongest influences of the heat island, or in southern Indiana, strong evapotranspiration in cornfields. Will continue to highlight the heat via Special Weather Statements as almost the entire area will stay out of Heat Advisory territory. && .Short Term...(Today and tonight) Issued at 300 AM EDT Tue Aug 24 2021 Surface high pressure continues to keep winds light over our portion of the Ohio Valley. Ridge aloft also will reinforce dry conditions as well as heat. We are starting the early morning with some upper clouds as a weak wave moves within that ridge aloft. Those clouds are showing signs of thinning out though, and by this afternoon expect similar lower-level scattered cloud development to what Monday brought. Will be watching through daybreak for patches of fog to form. Eastern KY valleys already have good coverage, per latest satellite data, but the clouds here have slowed development down. Expect highs today to be equal to if not a little warmer than Monday. NBM 10-90th percentile range for SDF today is from 93 to 98, with the median at 96. Given Monday's 97, will lean towards the upper end of that spread. Heat indices likely will top out around 100 for most locations east of a line from Shelbyville to Tompkinsville in KY, whereas points west will see 100-105. Tonight under more clear skies, will watch again for patches of fog, but the persistence of drying soils slowly should erode the chances for fog development until we reach our next cool down. On this date in weather history, back in 1992, category 5 Hurricane Andrew made landfall just south of Miami, FL. .Long Term...(Wednesday night through Monday) Issued at 314 AM EDT Tue Aug 24 2021 On Wednesday, the long term begins with more of the same. Upper high pressure remains centered over Oklahoma and extends towards the northeast over the Lower Ohio Valley. The main flow of the jet stream will continue to cut from northern California northeast towards eastern Canada, remaining well north of our area. At the surface, high pressure is expected to be centered over Ohio. This should keep skies over the CWA mostly clear, winds light, and temperatures high. Highs are expected to climb into the 90s in the CWA. Those west of Interstate 65 will likely see the mid 90s, farther east the low 90s, and Louisville, the area sauna, will likely be knocking on the door to 100. Dew points in the low 70s will push heat indices over 100, possibly in the 102-104 range along and west of Interstate-65. On Thursday, a surging upper trough will help to push the high, over Oklahoma, east towards an Atlantic high parked off the coast of North Carolina. At the same time, a surface high will strengthen over South Carolina as it drifts to the northwest. This will begin to act as a east to west moving warm front pulling in deeper moisture over the CWA increasing precipitation chances. No shear and modest summer CAPE values are expected to keep things garden variety. Precipitable water values are just under 2", so heavy rainfall and lightning will likely be the greatest hazards. To start the weekend with high pressure and upper riding overhead, mostly dry conditions are expected. Temperatures will remain hot in the upper 80s to mid 90s through Sunday. && .Aviation...(12Z TAF Issuance) Issued at 615 AM EDT Tue Aug 24 2021 High pressure at the surface and aloft will continue to keep our weather dry with fairly light winds this TAF period. High clouds earlier this morning have thinned out, and so far HNB and BWG have gone to MVFR. As we get into the late morning and early afternoon, expect a cloud field to develop in the 5-6 kft range and then skies should clear out again this evening. Best potential for early Wednesday morning reduced vsby looks to be at BWG. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...RAS Short Term...RJS Long Term...KDW Aviation...RJS