textproduct: Jackson

KEY MESSAGES

- Very warm and mainly dry weather will persist into Tuesday.

- 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.

UPDATE

Issued at 735 PM EDT SUN MAY 17 2026

23Z sfc analysis shows high pressure east of the state in control of the weather over eastern Kentucky. This is working to settle the winds and keep skies mostly clear. Currently, temperatures are unseasonably warm - running in the low to mid 80s. Meanwhile, amid southerly winds of 5 to 10 mph, dewpoints are generally in the upper 50s to lower 60s. Have updated the forecast mainly to add in 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.

LONG TERM

(Tuesday through Sunday) Issued at 505 PM EDT Sun May 17 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 results in one last day of unseasonable heat. While the increased moisture will result in relatively greater sky cover and thus MaxTs a couple degrees cooler than they were on Monday, it will also bolster heat indices. Expect it to feel similarly hot outside on Tuesday afternoon, with widespread apparent temperatures in the upper 80s and lower 90s.

The greatest moisture return will occur within our western counties, and isolated to scattered thunderstorms reenter the forecast for the northwestern half of the CWA on Tuesday afternoon. This initial round of activity will likely be diurnally driven, as the better frontal forcing will lag well to the west of the CWA at this time. Convective temperature guidance will need to be monitored in the coming days to bolster confidence in the spatial coverage of Tuesday afternoon's storms, but the parameter spacing is mediocre. There is sufficient CAPE in place for generic thunderstorms; the LREF mean data resolves a SE->NW gradient of 500 to 1000 J/kg of CAPE. Southeastern counties will be closer to the core of the antecedent ridging, and models accordingly resolve greater convective inhibition down there. Thus, there are sub-mentionable PoPs in the grids for counties bordering West Virginia and Virginia for this time frame. Further to the northwest, bulk wind shear values are generally below the marginally-favorable 30 knot threshold. The strongest storm cores across the Bluegrass may produce frequent lightning, gusty winds, and small hail, but Tuesday daytime convective setup looks rather pulsy.

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, where chances will persist through the of the forecast period. 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 Day 5 (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.

On the north side of the boundary, post-frontal winds will work to advect a cooler and drier airmass into the area. Northern portions of the forecast area should cool into the 70s on Wednesday, and more recent guidance suggests that Wednesday's MaxT grids could actually trend downward in future forecast packages. Temperatures cool to the 70s area-wide on Thursday before moderating into the next weekend. Unfortunately, rain chances ramp back up across the entire area around the same time. A disturbance passing through the mean west- southwesterly flow aloft will drag the stalled boundary back to the north by then. This allows the active weather to persist through the end of the period, and it marks a significant departure from the hot and dry pattern observed at the beginning of the forecast period. The newer, 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 the end of the forecast period on Saturday night. The actual accumulation footprints will be streaky and spatially variable, but since most of the area is currently outlined in Moderate to Severe Drought and the most severe drought is situated down in the Cumberland Basin, this forecast's rainfall should prove highly beneficial.

AVIATION

(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 750 PM EDT SUN MAY 17 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. However, just off the sfc the southwestern TAF terminals may see a period of LLWS from the south at up to 45 kts late this evening and into the first part of the overnight.

JKL WATCHES/WARNINGS/ADVISORIES

None.