FXUS63 KJKL 180650 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 250 AM 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...(Today through Tuesday) Issued at 249 AM EDT MON MAY 18 2026 Seasonably hot and dry weather is expected into Tuesday as the area resides on the western/northwestern periphery of a strong cut-off mid-level high situated over the Carolinas, a narrow westward extension of the Bermuda High. High temperatures are forecast to reach the upper 80s to lower 90s both days, with an increase in high clouds Tuesday as a cold front begins to move toward the area. Low-end PoPs are introduced Tuesday afternoon for some areas from the west, but a clear trigger for the marginal instability that is likely to exist at that time is not readily apparent giving the continued warm mid-level temperatures through early evening Tuesday. .LONG TERM...(Tuesday night through Sunday) Issued at 249 AM EDT MON MAY 18 2026 The long term forecast period opens on the precipice of a pattern change. A series of shortwave disturbances moving around the northwestern periphery of the previous days' amplified SE CONUS ridging will gradually work to break this ridge down. As this happens, flow in the lower half of the column adopts a more southwesterly orientation. This translates to increased moisture return and increasing sky cover into Tuesday night. A frontal boundary arrives from the northwest on Tuesday night, and its forcing should be sufficient to spark additional showers and storms. The question is - how does the thermodynamic environment look ahead of this feature? Given the boundary's nocturnal arrival in our portion of the Commonwealth, temperatures and instability *should* be at their diurnal cycle minimum. However, the persistence of SW low level flow and the antecedent warmth will leave Tuesday night's surface temperature insulated well above climatological averages. Expect lows to remain above the 60 degree mark, with some of the warmer ridgetops potentially hovering around 70. Depending on the amount of sky cover present around sunset, valley locales could thermally decouple and experience efficient radiational cooling. This could yield a scenario in which upstream convection becomes elevated above a more stable boundary layer in the valleys once it reaches our CWA's western escarpment. In other words, we are on QLCS graveyard watch for Tuesday night into Wednesday morning. Regardless of the strength of this convection, it will provide some highly beneficial widespread rainfall to eastern Kentucky. There is a 65-75% chance for at least a quarter of an inch of rain in the 24 hour period ending at 8pm Wednesday across the entire forecast area. The greatest chances and the greatest storm total QPF will fall across the Cumberland River Basin, which is also subsequently where some of the most impactful drought is also in place in the state - so any precipitation will be well received. While the boundary has trended a little bit more progressive with this morning's forecast guidance suite and storm total QPF has ticked a bit down, the boundary will struggle to fully push into the ridging in the SE CONUS. It is poised to stall out in the Tennessee Valley by midweek, and thus the southern half of the commonwealth will see repeated rain chances through the end of the period. Given these trends, Wednesday's Marginal (Level 1/4) Excessive Rainfall Outlook was trimmed down to just the Lake Cumberland region with the afternoon update. The entire Cumberland River Basin remains outlooked in a Marginal ERO for Thursday, as that boundary looks quite stubborn. Widespread, significant flash flooding is still not the most likely forecast solution, but areas where multiple rounds of thunderstorms persist for multiple days will need to be monitored closely as the ground progressively saturates. Again, this will likely be more beneficial than anything for the rain deficit in this region. On the north side of the boundary, post-frontal winds will work to advect a cooler and drier airmass into portions of the area. Northern portions of the forecast area should cool into the upper 70s on Wednesday, and more recent guidance suggests that Wednesday's MaxT grids could actually trend downward in future forecast packages. Temperatures then cool to the 70s area-wide on Thursday. Unfortunately this reset back to cooler weather is short-lived. The same boundary that stalled to our south will then lift back north as a warm front on Friday, leaving much of eastern KY in the warm and unstable sector through the weekend as another surface low passes across the Ohio Valley. In addition to more warm air advection, it will also advect moisture into the region, resulting in heightened rain chances from Friday through Sunday. This second, potentially more active pattern bears watching for agricultural and hydrological interests, though. The LREF Grand Ensemble resolves a 70-90% chance of at least 1 inch of precipitation across the entire CWA by Saturday night, with more expected on Sunday. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) ISSUED AT 120 AM EDT MON MAY 18 2026 A bit of valley fog will likely affect some locations with IFR or worse conditions late tonight and early Monday morning, but it is not expected to affect any of the TAF sites. Otherwise, VFR conditions will hold through the period along with winds less than 10 kts generally from the south through 12z-14z. However, LLWS likely impacting western sites will gradually diminish from south to north through the overnight. Southwest winds at 6 to 12 kts sustained develop between 14z-16z, with max gusts reaching as high as around 20 kts in the afternoon during peak heating, before diminishing significantly again toward sunset. Some models develop marginal south-southwesterly LLWS again briefly in the mid to late evening, but with low confidence, and with it appearing to be very transitory if it does occur, will opt to leave this out of TAFs for now. && .JKL WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CMC LONG TERM...JMW/MARCUS AVIATION...CMC