textproduct: Jackson

KEY MESSAGES

- Widespread showers and a few storms can be expected through Thursday morning, bringing beneficial rainfall to the area.

- Cooler, below normal, temperatures settle in Thursday through Friday. Temperatures Thursday night drop into the mid to upper 30s in valleys, bringing the potential for fog and localized patchy frost.

- Periodic chances for showers return for the upcoming weekend into early next week.

UPDATE

Issued at 1140 PM EDT TUE MAY 5 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 as well as a tweaking of the PoPs per the current radar and CAMs guidance. These minor adjustments have been sent to the NDFD and web servers along with a freshening of the SAFs and zones.

UPDATE Issued at 730 PM EDT TUE MAY 5 2026

23Z sfc analysis shows a wavy cold front just northwest of the JKL CWA this evening. A large area of mainly showers is a associated with this boundary and is starting to brush into northwest parts of the area. Expect this to encroach more and overtake eastern Kentucky through the night with some thunder chances, as well. In the meantime, currently, temperatures are running in the lower 60s northwest with that rain to the low 70s in the southeast. Meanwhile, amid southerly winds of 5 to 10 mph, dewpoints vary from the low 50s west to the mid 40s east. Have updated the forecast mainly to add in the latest obs and trends for the T/Td/Sky grids as well as to fine tune the PoPs and thunder chances through the night per radar and CAMs guidance. These minor adjustments have been sent to the NDFD and web servers along with a freshening of the HWO, SAFs, and zones.

LONG TERM

(Thursday night through Tuesday) Issued at 224 AM EDT WED MAY 6 2026

The long term forecast period opens on the backside of the shortwave troughing responsible for the active weather described above. As that feature ejects east, subtle midlevel height rises and a building surface high pressure system suggest that a clearing trend will emerge on Thursday evening. A shift to more northwesterly winds aloft will advect a drier, continental airmass into the region, but surface winds will be light and variable given the weak pressure gradient. Collectively, this suggests that Thursday night's sensible weather will be driven by localized topographic effects.

Assuming that clearing trend comes to fruition, ridge-valley temperature splits are expected to emerge after sunset on Thursday evening. Sheltered and shaded hollows will see the most efficient radiational cooling and thus the coolest overnights. Temperatures in the mid 30s there could pose a risk for patchy frost development by Friday morning. In the main stem river valleys, the presence of additional moisture should insulate MinTs in the upper 30s/lower 40s. Given that similar post-frontal set-ups have recently produced patchy valley fog, fog was added to the grids along the Cumberland, Kentucky, Red, Licking, and Levisa/Tug Fork Rivers with tonight's forecast package. Greater fog coverage may be needed in future forecast updates, especially if grounds are wet by any additional rainfall on Thursday. The risk for frost/fog lowers as elevation increases, and ridgetop locales are the most likely to remain in the mid 40s on Thursday night.

Thursday night's surface high is forecast to quickly pass through the forecast area on Friday. Its proximity allows Friday's daytime hours to stay dry and mild, but southwesterly surface flow emerges on its backside by Friday afternoon. These winds will advect a relatively warmer airmass into the region for the end of the week. Highs rebound into the upper 60s/lower 70s on Friday afternoon, and lows stay near the 50 degree mark on Friday night amidst increasing cloud cover. A midlevel disturbance arriving around midnight on Saturday morning will work with the warmer air to produce some AM showers and storms, but misalignment with the diurnal instability cycle and the shallow nature of the antecedent moisture return will limit the intensity ceiling of this convection. LREF mean PWATS peak at a piddly 0.80 inches in the Bluegrass on Saturday morning, then decrease the further one goes into the higher terrain of SE KY on Saturday afternoon. The better forcing with this system is also contained to northern portions of the forecast area, as the parent disturbance aloft looks to eject NE and abandon the surface boundary on Saturday afternoon. Any early-day activity along the I-64 corridor should accordingly weaken as it moves deeper into the CWA after sunrise, and Saturday's PoPs accordingly follow a North-South gradient. Rain chances above 40% are limited to locations north of the Mountain Parkway, and the Cumberland River Basin may stay dry.

The above boundary becomes diffuse across the forecast area on Saturday night, resulting in seasonably mild and calm conditions. Another night of ridge-valley splits is possible, but with less concern for frost and fog. Given the lack of post-frontal cold air advection, temperatures are generally forecast to remain above the 50 degree mark on Saturday night. This gives Sunday's temperatures a head start and sets the stage for more widespread showers and storms on Sunday afternoon/evening. Sunday's setup features more vertically stacked southwesterly flow and thus a more effective warm air advection/moisture return regime. Breezy southwesterly flow will yield highs in the upper half of the 70s and dewpoints in the upper 50s/lower 60s on Sunday afternoon. LREF mean PWATs climb to around 1.15 inches in this same time frame, which suggests that Sunday's showers and storms will be more meaningful than Saturday's. The risk for severe weather does not currently appear particularly high, but the currently-available ML/AI/analog guidance collectively resolves marginal-esque probabilities in Southern Kentucky with this setup. It is possible that those pieces of guidance are picking up on the potential for a more favorable strong storm environment to emerge on the warm side of the previous day's stalled out boundary. The LREF joint probabilities for marginally favorable convective parameter spacing (>500 J/kg CAPE, <-25 J/kg CIN, and > 30 knots effective bulk shear) are in the 30-40% range south of the Mountain Parkway. While the higher probabilities are confined to the south in the Tennessee Valley, the progression of Saturday's boundary and the related convective model trends on Sunday are worth watching.

Broader longwave troughing digs into the Greater Ohio River Valley on Monday, setting up a postfrontal northwesterly flow regime from the surface to the midlevels. Expect a cooler and drier airmass to move into the commonwealth for the start of the next work week as a result. After skies clear from west to east on Monday, drier weather persists on the backside of that trough through Tuesday. The progressive nature of the overarching synoptic pattern means that the aforementioned trough is likely to lift into New England by mid week though. Quasi-zonal flow should emerge over the forecast area in its wake, but forecast models diverge from there. There is significant disagreement surrounding the timing and evolution of a potential system at the very end of the period, but there is a stronger signal for a warming trend out ahead of it. The CPC Days 8- 14 Temperature Outlook, which begins at the end of the period on Wednesday, May 13th, suggests that temperatures are trending above- normal for mid-May in Eastern Kentucky. This is good news for our frost-sensitive interests, but they are encouraged to pay close attention to Thursday night's frost forecast in the mean time.

AVIATION

(For the 06Z TAFS through 06Z Wednesday night) ISSUED AT 154 AM EDT WED MAY 6 2026

Scattered showers are over eastern Kentucky at the 06Z TAF issuance but more widespread showers and isolated thunderstorms are approaching from Central Kentucky with an approaching cold front. With this activity, conditions (VFR at the start of the period) will deteriorate to MVFR/IFR from northwest to southeast through daybreak. Shower activity should become more confined to areas near and southeast of an SJS-JKL-SME line by 15Z as the cold front sags through the forecast area. A weak wave riding the boundary may push shower activity back to the north for several hours toward the end of the TAF period but substantive rainfall should still remain southeast of I-64. Winds will generally be variable to southerly at 5 to 10 kts early this morning but a strong LLJ will cause LLWS for most of the pre-dawn timeframe. Sfc winds will eventually shift to a more northwesterly direction as the front starts to move in after 10Z.

JKL WATCHES/WARNINGS/ADVISORIES

None.