085 FXUS63 KJKL 291815 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 215 PM EDT Mon Jun 29 2026 .KEY MESSAGES... - Just a small chance for a stray shower or thunderstorm each day for most of the week. - Heat and humidity build today - likely becoming quite oppressive by mid-week. && .UPDATE... Issued at 158 PM EDT MON JUN 29 2026 Some adjustments were made to the pops/weather based on where some very isolated showers were shooting up in far eastern KY. These should be pretty benign, but can't rule out a rumble of thunder at their peak. A good chunk of the mid-morning was spent collaborating with other offices and looking at the latest model data/forecasts to expand our heat products. While we won't meet the Heat Warning criteria any single day, the accumulation of days with Heat Advisory criteria spawned several offices (including our western CWA) to upgrade to the Excessive Heat Warning. The remaining CWA is in an advisory through Thursday. That being said, there isn't a large difference in temperatures or heat indices between the watch and the advisory - so based on how things trend the advisory could remain an advisory or also be upgraded in the future. Loaded in the latest observations a couple different times to make sure the near-term forecast was on track with the current conditions. This resulted in only very minor changes. All updates have been published and sent to NDFD/web. UPDATE Issued at 740 AM EDT MON JUN 29 2026 No significant changes were made to the forecast with mainly just the inclusion of the latest obs and trends for the T/Td/Sky grids. These minor adjustments have been sent to the NDFD and web servers along with a freshening of the zones. && .SHORT TERM...(Today through Tuesday) Issued at 450 AM EDT MON JUN 29 2026 08Z sfc analysis shows a wavy warm front just northeast of the area while ridging is building aloft. This has mostly brought an end to the convective activity through the area this night, though a few light returns are noted stretched out from northwest to southeast through the western parts of the Cumberland Valley. Amid partly cloudy skies, some radiational cooling down to the quite high dewpoints are leading to the formation of fog that has become locally dense in the valleys as evidenced by some of the obs, web cams, and the microphysics channel from satellite. On account of this, an SPS urging caution with the patches of low visibility has been issued through 9 am. Meanwhile, in this very humid environment, temperatures and dewpoints are similar and currently running in the muggy lower 70s, amid light and variable winds. The models, and their individual ensemble suites, are still in good agreement aloft through the short term portion of the forecast. They all depict a fairly strong and expanding 5h ridge pushing northeast and deeper into Kentucky today through Tuesday afternoon - when it will be right overtop the JKl CWA. Broad subsidence from this will limit vertical motion through the period while the ridge keeps any mid-level impulses well to the north and east of the state. Given the continued strong agreement among the models, the NBM was used as the starting point for the grids with some adjustment needed from a touch of the higher resolution CAMs guidance incorporated into the PoPs grids through evening. In addition, some minor terrain details were included for the temperature grids tonight, along with a bit of extra drying both afternoons. Sensible weather features a much drier day for the area with only a very limited threat for showers and storms through the afternoon. While we get a chance to effectively dry out, the heat and humidity will build today and especially on Tuesday. A heat advisory is in effect for the western parts of the area for peak heating today with additional heat headlines likely to be issued in the days ahead. Similar to this night, expect valley fog tonight along with mild temperatures exhibiting a small ridge to valley difference. Sunnier conditions and a warmer starting point to the day, Tuesday, should yield high temperatures for the majority of the area topping 90 degrees. The main adjustments to the NBM starting point were to fine tune the PoPs today per the latest consensus CAM guidance. Did also adjust the NBM temps for terrain distinction tonight and not quite so high on maximum temps today and Tuesday. In addition, have also tweaked dewpoints a bit lower than the outlier NBM values each afternoon. .LONG TERM...(Tuesday night through Sunday) Issued at 300 AM EDT MON JUN 29 2026 The long-term period opens Tuesday evening with an ~597 dam high situated directly over the Commonwealth. At the surface, corresponding high pressure centered off the Delmarva Peninsula will exert its influence across the Southeastern US. A very hot air mass will be found under the upper-level high with 850 hPa temperatures over the eastern Kentucky Coalfields around 22C. Upstream, a 500 hPa trough will be stationed over the Western CONUS. The upper-level high will very slowly drift eastward through midweek to a position over Virginia by Thursday evening, at which point, 850 hPa temperatures over the JKL CWA will reach the zenith of the forecast period at 23 to 24C. Dew points will also be in the 70s on both days, allowing for moderate to strong destabilization on both Wednesday and Thursday, but a mid-level cap should keep a lid on most deep convection. Only isolated PoPs are found across portions of the area through Thursday. Heat indices will continue to climb each afternoon, with the hottest readings on Thursday afternoon in the 100 to 110 degree range for most areas. Relief at night will be limited, with low temperatures generally ranging in the 70s. Heading into Friday and the Independence Day weekend, the upper- level ridging will gradually break down as troughing ejects eastward. As this occurs, difficult-to-time perturbations will lead to renewed threats for more widespread, diurnally modulated convection amidst weaker capping. Model soundings suggest that continued weak shear combined with high PWATs could lead to a threat of downburst winds from stronger pulse storms. The heat will also gradually subside. While heat indices could still rise to near or above 100F through Sunday, there will have been an overall slow cooling trend as the ridge dissipates. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 212 PM EDT MON JUN 29 2026 As high pressure continues to set up across the region, subsidence is increasing. That being said, there is still enough lingering moisture and mixing this afternoon to spawn some fair-weather CU across much of eastern KY. A few small showers are also possible near the KSJS TAF in far eastern KY, but should not cause any issues other than a temporary visibility reduction. All CU and any lingering shower chances should dissipate heading into the evening hours with the loss of mixing. This will give way to mostly clear skies overnight, and the potential for some valley fog development. Did not include any fog impacts at the TAF sites at this time. Winds are also light at the TAF issuance, and should remain light through the remainder of the TAF period as well, less than 5 kts. && .JKL WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning until 8 PM EDT Thursday for KYZ044-050>052- 058>060-068-069-079-080-083>086. Heat Advisory until 8 PM EDT Thursday for KYZ087-088-104-106>120. && $$ UPDATE...JMW SHORT TERM...GREIF LONG TERM...GEERTSON AVIATION...JMW