FXUS63 KJKL 182050 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 450 PM EDT Mon May 18 2026 .KEY MESSAGES... - Very warm and mainly dry weather will persist through Tuesday afternoon. - Showers and thunderstorms enter the forecast late Tuesday into Tuesday night, then persist through next weekend. - The switch to a wetter pattern yields temperatures closer to normal readings and produces a highly-beneficial, widespread wetting rainfall. && .SHORT TERM...(This evening through Tuesday night) Issued at 435 PM EDT MON MAY 18 2026 Late this afternoon an upper level ridge extended from the Southern Appalachians across the Carolinas to near Bermuda and another upper ridge was centered in the Gulf. Meanwhile an upper trough extended from Central Canada across Alberta and Saskatchewan to the Four Corners vicinity to the Southwest Conus. A couple of shortwaves were moving around the ridging and across sections of the mid MS Valley and the Lower OH Valley while a more substantial shortwave was working across sections of the Central Plains. At the surface, a ridge of high pressure extended from the Atlantic into parts of the Southeast and Southern Appalachians while a wavy frontal zone extended from the Northeast across sections of Quebec and Ontario to the northern and western Great Lakes to the Central Plains to Southwest Conus. Cumulus have developed during the heat of the day and temperatures are mild averaging between 10 and 15 degrees above normal highs for this time of year. Tonight and Tuesday, upper level ridging is expected to remain in place from near or north of Bermuda across the Southeast and into the Gulf. At the same time, a shortwave trough is expected to move across sections of the Central an Northern Plains and into the western Great Lakes through Tuesday morning and then to the Central Great Lakes through the remainder of the day. A general trend of rising 500 mb heights is expected through tonight with near neutral tendencies on Tuesday morning and then some height rises for the afternoon to early evening. Further 500 mb height falls are anticipated to end the period as the upstream shortwave moves to the eastern Great Lakes to Lower OH Valley. At the surface, the high pressure ridge will build into the Southern Plains tonight, before shifting to the south and southeast to end the period. As this occurs a sfc low tracks from the Plains across the Great Lakes and eventually to Ontario and Quebec while the trailing cold front will move into the Northeast and sag across sections of the OH Valley and into eastern KY. Dry weather should prevail through at least midday on Tuesday with the pattern favoring a modest ridge/valley split and temperatures in the coldest locations could fall a couple of degrees below the current forecast based on trends from last night and some mixed dewpoints near the 60 degree mark versus the lower 60s. Valley fog along the larger creeks, rivers, and lakes should form around or near midnight and then dissipate toward 9 AM EDT. With height falls on Tuesday afternoon, some convection cannot be completely ruled out during peak heating in the northwest half of the CWA and it is possible a larger areal extent of slight chance pops may ultimately be needed. Any stronger storm could produce gusty winds as there are some stronger gusts in the 18Z HRRR with some of the activity near peak heating. Better chances arrive later Tuesday evening and especially Tuesday night as the height falls continue and the front nears eastern KY. .LONG TERM...(Wednesday through Monday) Issued at 343 PM EDT MON MAY 18 2026 If the long term period could be summarized with just one word, it would be wet. The period will open with broad ridging over the southeastern US and troughing over the HudsonBay. This will leave Kentucky in a regime of generally southwesterly flow aloft at the onset of the long term period. At the surface, a cold front will extend through the CONUS from a surface low centered over Quebec and push into eastern Kentucky on Wednesday, although the exact timing of the frontal passage remains dependent the upstream evolution of this system. The environment ahead of the front will be moist (owing to prefrontal southwesterly winds), but instability will be dependent on whether the timing of the frontal passage can align with maximal daytime heating. Accordingly, LREF guidance still shows a wide range of MUCAPE values, but the most likely outcome at this time is that instability should be sufficient for a few thunderstorms. Given that wind shear is expected to be meager, widespread organized severe weather appears unlikely. A few machine learning sources have introduced very low-end probabilities for gusty winds Wednesday afternoon, but this threat remaining highly conditional on favorable frontal timing, and thus confidence remains very low in this outcome. Regardless of storm strength, this system will bring much-needed rain to eastern Kentucky, which currently remains in drought (ranging from D1 conditions in our eastern forecast area to D2 and a pocket of D3 conditions in the western portion of forecast area). With broad ridging over the southeastern CONUS, the aforementioned cold front will struggle to push through into the Atlantic coast states and likely stall over the periphery of the ridge going into Thursday (TN area) before lifting into Kentucky again as a warm front on Friday. This pattern will bring multiple rounds of rain to the forecast area. As such, WPC has introduced multiple Marginal (Level 1 of 4) Excessive Rainfall Outlooks for the forecast area; one for our entire area on Wednesday, another for the Lake Cumberland area on Thursday, and a third for our entire forecast area again on Friday. QPF does not look overly impressive on any given day; LREF guidance shows that the chance of exceeding 0.5 of rain on any given day is low to moderate (maxing out at around 50% on Wednesday). However, this does not account for enhanced rain rates in any thunderstorms that do develop. If storms track over the same area for multiple days in a row, isolated instances of nuisance flooding cannot be ruled out. This is especially true closer to the KY/TN border, which will feel the greatest impacts of the stalling front. However, these details will need to be refined in the short term when convective rain rates can be better accounted for. Thursday looks to be the coolest day of the period. Following the frontal passage, CAA via postfrontal winds will keep maxTs generally below normal, with a defined thermal gradient over our forecast area as the front stalls. Currently, the NBM is outputting highs in the 80s for the southern portion of our forecast area; however, this appears to be an outlier compared to other guidance, so maxTs were bumped down a few degrees on Thursday afternoon to better account for the frontal passage. After the front lifts northward again, flow will become more southerly, and temperatures will be warmer than on Thursday. The NBMs highs in the upper 70s and low 80s may be slightly overdone given that rain is likely going into Friday afternoon (80-90% chance), but highs do represent an expected warming trend as the warm front lifts northward. Unfortunately (for outdoor activities) or fortunately (for drought relief), this weekend also looks to be quite wet even as the original front exits our area. A slow- moving upper level trough over the central CONUS, in addition to potential embedded impulses, will allow for rain chances every day through the weekend and into the end of the period. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 235 PM EDT MON MAY 18 2026 VFR conditions are expected to prevail through the period. The one caveat will be valley fog between 04Z and 13Z with some MVFR and IFR reductions that is not expected to affect the TAF sites. Otherwise, diurnal mixing will lead to continued cumulus during the first few hours of the period in the 4.5 to 6kft agl range. South to southwest winds will average 6 to 12KT with gusts to near 20KT. However, the winds should slacken and gusts subside toward 00Z and the cumulus should also dissipate. Light and variable winds will prevail overnight, before becoming south to southwest at 5 to 12KT with some gusts up to 20KT. By the end of the period some cumulus may again develop between 4 and 6kft agl. && .JKL WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...JP LONG TERM...JMW/MARCUS AVIATION...JP