textproduct: Jackson

KEY MESSAGES

- Well above normal temperatures persist into the weekend, with near-record heat this afternoon.

- The heat and humidity could fuel isolated thunderstorms across the area at various times over the next several days.

- Rain chances increase early next week as the persistent upper level ridge starts to weaken and then retreat to the southwest.

UPDATE

Issued at 1041 AM EDT THU SEP 17 2026

Updated PoPs and Sky grids through Friday, especially as new 12z CAMS guidance is coming in. The general trend is to go a little more aggressive than previous forecasts. Another fine-tuning of PoPs will come with the early afternoon package as additional 12z guidance arrives in addition to the 13z NBM.

UPDATE Issued at 725 AM EDT THU SEP 17 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. These minor adjustments have been sent to the NDFD and web servers along with a freshening of the zones.

LONG TERM

(Friday night through Wednesday) Issued at 400 AM EDT THU SEP 17 2026

The extended portion of the forecast looks to still be on track with the idea of the large 5h ridge weakening further, drifting southwest and out of the region enough through the weekend for more intrusions of energy at mid levels. This should keep mainly unorganized convection as part of the forecast into the new work week even as we remain unseasonable warm.

The previous long term discussion follows:

A pattern change is in store for Eastern Kentucky during the long term forecast period, and it should bring some relief from the recent heat with it. The previously-dominant ridging over the Tennessee Valley is progged to retrograde west towards the Ozarks this weekend. At the same time, a closed upper level low will move over the Floridian Peninsula and set up a Rex-esque blocking feature for a few days. Models collectively resolve both of these features sitting in place through Sunday morning, although the ridging will be in a weakening state. A series of troughing disturbances ejecting around the ridge's northern periphery will work in tandem with this closed low to suppress the ridge by early next week. While the initial two disturbances will yield minor sensible weather impacts across the forecast area, a deeper trough is expected to eject out of the Rockies early next week. While models disagree on its exact evolution, they do agree that it will be the final nail in the coffin for the antecedent ridging pattern. Between Friday morning and Monday afternoon, the ridge is poised to weaken from its peak "heat dome" intensity of 600+ decameters to a looser-organized ridge of sub-590 decameter heights. Therefore, this late-period troughing disturbance is more likely to bring noticeable heat relief to all of Eastern Kentucky than its predecessors.

The first disturbance is expected to pass well to the north of the Ohio River Valley on Friday, with weak northwesterly flow and minuscule midlevel height falls modeled across the forecast area. While a surface frontal boundary is resolved in the vicinity of the forecast area in this time frame, there will be little to no syntopic-scale airmass modification associated with it. Temperatures in the northeastern half of the CWA will be a few degrees cooler than they were in the short term forecast period, but this moreso a byproduct of the cloud cover from the convective activity associated with the boundary. Given the lack of dynamic support aloft, any showers/storms on Friday will be well below severe limits. The lack of forcing should also limit the heavy rainfall potential. So, the greatest sensible weather effects from this activity will come in the form of a SW->NE temperature gradient. There could be a 10 degree difference in highs on Friday between NE KY and areas west of I-75 that are closer to the influence of the ridge. The latest data blend accordingly depicts highs in the mid 80s in the Big Sandy/Licking River Basin, whereas places closer to the Cumberland River will experience yet another day of temperatures in the 90s. Any rain that does fall on Friday could help bolster the areal coverage of fog on Friday night, when temperatures should cool into the 60s area wide.

Given the blocking to the south and the quasi-zonal flow aloft, the boundary responsible for Friday's activity is expected to hang around into Saturday. Models resolve low-level flow adopting more of a southerly directional component on Saturday and Sunday, this is associated with the boundary nudging back north of the Ohio River in this time frame. The resultant warm air advection will bump temperatures back into the upper 80s/lower 90s area-wide on both days. Isolated summertime showers/storms cannot be ruled out during peak diurnal heating hours on Saturday, but there could be greater convective coverage late Saturday night into Sunday. The second ridge-riding impulse is expected to arrive in the latter stages of the weekend, with relatively greater shortwave support aloft than Friday's. WPC has outlined a Marginal Excessive Rainfall outlook in the vicinity of the forecast area for late Saturday night and then again on Sunday, but this appears contingent on the evolution of upstream activity on Saturday night. A few isolated hydro impacts cannot be ruled out where multiple rounds of activity occur in the vicinity of the increasingly stationary boundary, but this is most likely to be north and northeast of the JKL CWA.

There is a notable increase in model spread within the NBM ensemble across multiple sensible weather forecast parameters for Sunday and beyond. This is likely due to differing model solutions surrounding the third trough ejecting out of the Rockies. Significant variations in this feature's modeled amplitude, orientation, phasing, and forward progression speed preclude the discussion of specific forecast details at the present moment, but models generally agree that a deeper, vertically-stacked trough will move through the Midwest and the Greater Ohio River Valley by midweek. It would take a trough like this to finally drag a meaningful cold front through the CWA, and despite the model spread, there is a noticeable downward trend in the mean forecast MaxTs and MinTs for Tuesday and Wednesday. Highs dip down into the low/mid 80s by Wednesday alongside widespread lows in the 60s (not accounting for smaller-scale enhanced radiational cooling in the valleys). Such values are technically still above climatological norms for Mid- September in Eastern Kentucky, but we will cling onto the glimmer of hope that is some type of relief from this week's near-record heat.

AVIATION

(For the 12Z TAFS through 12Z Friday morning) ISSUED AT 745 AM EDT THU SEP 17 2026

VFR conditions will prevail through much of the TAF period. Valley fog will mix out around 14Z this morning. Localized MVFR to IFR conditions will remain possible, though fog largely will only affect some of the TAF sites briefly. Later this afternoon, showers and thunderstorms will be possible again - mainly east of I-75. Thunder probabilities were sub-30% for all sites except KSJS and possibly KSYM, therefore a PROB30 was included at those terminals from 18Z through 24Z. Winds away from any storms will be light and variable today into tonight.

JKL WATCHES/WARNINGS/ADVISORIES

None.