


Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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588 FXUS63 KJKL 230459 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1259 AM EDT Mon Jun 23 2025 .KEY MESSAGES... - Areas of fog, locally dense in some locales, will affect the river valleys through mid-morning. - Heat builds this week. Heat indices peaking in the 100 to 105 degree range are forecast for many locations through Saturday. && .UPDATE... Issued at 1259 AM EDT MON JUN 23 2025 Satellite imagery already shows tendrils of fog developing through the deeper southeastern/southcentral Kentucky valleys, especially where rainfall occurred yesterday afternoon and evening. Look for this fog to continue expanding in coverage through the remainder of the overnight and become locally dense. It will be muggy overnight with low temperatures only in the upper 60s to lower 70s at most locations. Looking ahead to Monday, a slight chance of shower and thunderstorms was added to the forecast across most of eastern Kentucky during the afternoon hours. While convective coverage is likely to be less than today, strong differential heating under an uncapped atmosphere has the potential to support isolated popup showers and thunderstorms. The most likely areas for convective initiation will be over the higher ridges along the Kentucky/ Virginia and Kentucky/Tennessee borders as well as near/along the Pottsville Escarpment. Any shower/storm that does develop could produce a downpour and gusty winds. UPDATE Issued at 919 PM EDT SUN JUN 22 2025 Leftover deep convection has dissipated with the loss of daytime heating. Forecasts and HWO have been updated to remove mention of showers/thunderstorms through the remainder of tonight. UPDATE Issued at 755 PM EDT SUN JUN 22 2025 Isolated to scattered showers and thunderstorms, mostly over the Cumberland River Basin near/west of I-75, have begun to diminish as the sun prepares to set. Expect this trend to continue with all locations likely rain-free within a couple of hours. Fog is likely to develop again overnight and is favored to become locally dense as the combination of clear skies and light low-level winds allow for efficient radiational cooling in an increasingly muggy air mass (afternoon dew points were roughly 5 to 8 degrees higher than yesterday`s). At least patchy fog is possible outside of the river valleys, and especially in locations which experienced rainfall this afternoon and evening. && .SHORT TERM...(This evening through Monday night) Issued at 455 PM EDT SUN JUN 22 2025 20Z sfc analysis shows high pressure off to the southeast of the state. This, combined with a building ridge aloft, is keeping convection somewhat limited through the area though the Cumberland Valley is seeing some activity, mainly in the form of showers and sprinkles. Otherwise, it is quite a hot day with heat indices approaching 105 degrees in the Bluegrass area. For that reason we have started the Heat Advisories for those counties this afternoon and both northwest and northeast potions of the CWA for Monday and Tuesday with a potential to expand in time and areal coverage into midweek. Currently, readings are generally in the upper 80s to lower 90s while sticky dewpoints are running in the upper 60s and lower 70s. The models, and their individual ensemble suites, are still in excellent agreement aloft through the short term portion of the forecast. They all depict strong 5h ridging building over the region - holding in place through Tuesday morning and beyond. This will keep the mid level impulses far away from Kentucky with weak flow overhead. However, it seems that this ridge is not capable of completely shutting down convection lacking a warm capping layer of temperatures aloft. The very small model spread through Monday night supported using the NBM as the starting point for the forecast grids with minimal adjustments needed - mainly just to add some limited terrain details for temperatures each night - though capped by high dewpoints. Sensible weather features the heatwave starting in earnest today with the first 90s of the season for many locations. This warmth continues into the nights with only a slight extra drop off in temps for the valleys compared to the ridges. Again we will also see some locally dense fog in the valleys and near bodies of water each night. Similar conditions to today will be in place for Monday with highs again in the low 90s most places along with a chance for a stray shower or storm in the southern parts of the CWA during the afternoon into early evening. The changes to the NBM starting point were primarily focused on temperatures each night for some slight terrain differences. PoPs and Wx were too quiet in the NBM so incorporated the CAMs guidance for a stray threat of convection in the afternoon and early evening on Monday. .LONG TERM...(Tuesday through Sunday) Issued at 400 PM EDT SUN JUN 22 2025 The period is expected to begin with a 597 dm+ 500 mb ridge centered in the Southern Appalachians/western VA/western NC to WV area, though it is expected to be flattening at that point as multiple shortwaves move from an upper level trough extending from over the western Conus to Northern Plains/Upper MS Valley to the Great Lakes and Northeast. Additionally, shortwaves are expected to move near the US/Canadian border as well. At the surface, an area of low pressure associated with an upper trough moving across eastern portions of Canada is anticipated to be initial centered over Quebec with a cold front/frontal zone trailing to Lake Huron and MI to the Central Plains with much of the southern and eastern COnus in the warm sector with a ridge of sfc high pressure centered in the Southern Appalachians/Tri Cities of VA and TN vicinity. Tuesday to Wednesday night, guidance generally has trended toward the center of the ridge retrograding west and southwest to the Lower OH Valley to TN Vally to mid to lower MS Valley regions Tue to Wed and weakening and becoming more east to west oriented and extending from parts of the Atlantic across the mid Atlantic states to Central Appalachians to OH Valley. This will occur as multiple systems move near the US/Canadian border and across portions of eastern Canada and the Great Lakes to the Northeast and Maritimes and an upper level low/trough develops between Bermuda and the Bahamas and then moves west to near the Bahamas to perhaps as far west as the FL peninsula by late Wednesday night. At the surface, a ridge of sfc high pressure should remain in place from the central to southern Appalachians to the Lower MS Valley/much of the Southeast weakening a couple of mb gradually while the frontal zone to the north eventually sags across the Northeast to the mid Atlantic states to the Southern Great Lakes to Central Plains. Across eastern KY heat will have already been building in the short term period and as we enter this timeframe overnight recovery is expected to become increasingly poorer with low generally in the 70s. Meanwhile the airmass should warm into the 90s, generally mid 90s with some upper 90s possible in the deeper valleys/lower elevation communities in the Big Sandy and KY river valleys. At the same time, even during peak convective mixing, dewpoints near the time of the Max T per the guidance consensus in the upper 60s to mid 70s range. This should result in heat indices peaking in the around 100 to around 105 degree F range both days with temperatures in some places falling below 75 degree F only briefly. This should get some portions of the region very close to Heat Advisory Some pop up convection cannot be completely ruled out by Wednesday particularly nearer to the VA and TN borders where differential heating over the Cumberland Plateau or Cumberland Mtns or perhaps an outflow from convection that develops nearer to or northwest of the crest of the Appalachians nearing the region becoming a trigger as the upper ridge becomes weaker with capping perhaps be a bit less robust by that point. At this point, opted to mostly maintain the NBM PPI06 for pops which were under 15 percent in most areas. However, given guidance trends and in collaboration with surrounding WFOs included a 15 percent pop in small portions of Pike to Harlan Counties for both Tuesday and Wednesday afternoons near Pine and Black Mtns near the VA border. As these days approach guidance should help fine tune whether or not slight chance pops may be warranted for more portions of the area. ECMWF, ENS based EFI has Max T for Tuesday and Wednesday above the 80th percentile climatologically for the 5 week period centered around this week for much of the JKL CWA with eastern portions of the area above the 90th percentile. Overall, the heat likely peaks Tuesday to Wednesday and it is probable that an areal and temporal extension of the ongoing heat advisories to be needed, though if pop up storms were to form lower peak heat indices would be possible. The current forecast is for 94 at JKL and 95 at LOZ for Tuesday the 24th and Wednesday the 25th. For the 24th, that would break the record at JKL of 92 from the warm summer of 1988 while at LOZ the current forecast would break the record of 94 set in 1988 and tied in 2012. For the 25th record highs are more robust. Thursday into Friday night, guidance varies with the positions and strength of upper level ridging as the upper low initially over or near FL moves into the Southeast. The recent operational ECMWF runs have a weakness or weak troughing from the Southeast into parts of the Central to Southern Appalachians on Friday, while recent GFS runs have lower heights/weak upper low over the Gulf into the Southeast and higher heights across the entire Commonwealth, Appalachians into the mid Atlantic States with upper level ridging from the eastern Atlantic west toward eastern KY generally stronger through Friday and Friday night. Further north and west, stronger westerlies are forecast to remain from the Northwest Conus near or North of the US/Canadian border into eastern Canada and the Northeastern Conus with weak trough into lingering over parts of the western Conus though the guidance consensus is for that troughing to be weaker overall by late Friday into Friday night with heights rising over the Southern Rockies/Four Corners to Southwest Conus areas. one more notable shortwave trough is generally progged to move from the Northern Plains/Dakotas to parts of the Great Lakes during this time. At the surface, a ridge of sfc high pressure should remain in place from the Southern Appalachians to parts of the Southeast while the frontal zone that will be nearly stalled out from the mid Atlantic states into the Great Lakes should make little southward progress while further west it lifts north toward the upper MS Valley as a warm front in response to a surface low tracking across parts of Canada in advance of a shortwave tracking also near the northern US border area. During this timeframe, with the high anticipated to weaken, and a moist airmass remaining in place, diurnal heating should be sufficient for greater coverage of afternoon to evening convection as compared to Tuesday and Wednesday with isolated to scattered coverage forecast for Thursday with more in the way of scattered development for Friday. If less convective development occurs both days, peak heat indices currently forecast in the 100 to 105 degree rang for some areas could be at the upper end of that range. Next weekend, recent operational ECMWF runs have lower heights across eastern KY/weak troughing from the Southeast into parts of the Appalachians while the GFS continues into Saturday with a trend of higher heights from the mid Atlantic coast to the Central Conus to Southwest Conus. There is run to run variability with troughing from western Canada into the Northwest Conus to Northern Rockies vicinity that gradually is progged to shift east into Central portions of Canada into the Northern Plains to upper MS Valley with a trend to height rises across parts of the Great Basin toward the Northwest Conus toward the end of the period. The recent GFS runs maintain slightly higher heights over the Commonwealth during this time as compared to the ECMWF runs while a shortwave trough is progged to move from the Central Great Lakes to the eastern Great Lakes to Northeast to end the period. There remains quite a bit of spread in guidance as far as heights and the possible timing of weaker shortwaves that could be a trigger for convection. With generally less capping than earlier in the week, diurnal development could be more substantial into the high chance to likely range for both Saturday and Sunday afternoons Guidance generally agrees that the heat relaxes/high temperatures will not be quite as warm as earlier in the week. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) ISSUED AT 1259 AM EDT MON JUN 23 2025 At TAF discussion issuance time, very poor flying conditions due to FG were noted at SME but the remaining TAF terminals were still VFR. Through the remainder of tonight, FG/BR coverage will increase through the valleys and should eventually deepen up to the adjacent ridgetops. While the worst impacts are expected at SME, FG/BR is expected to eventually spread into and affect the remaining TAF sites closer to sunrise. The FG/BR will lift/ dissipate after sunrise Monday. Winds will generally be variable under 5 kts. && .JKL WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM EDT Tuesday for KYZ044-050>052-058>060. Heat Advisory from 11 AM this morning to 8 PM EDT Tuesday for KYZ104-107-110-119-120. && $$ UPDATE...GEERTSON SHORT TERM...GREIF LONG TERM...JP AVIATION...GEERTSON