Area Forecast Discussion

KEY MESSAGES

- Above normal heat and humidity will persist to start the new week. - A cold front will eventually make its way through the region, with an increasing potential for showers/thunderstorms through mid week.

- Cooler and drier air will arrive behind the cold front for late week.

SHORT TERM

(This evening through Sunday night) Issued at 642 PM EDT SAT SEP 19 2026

A strong upper level high is over east TX early this evening, with ridging extending eastward through the southeast CONUS. However, the ridging is weakening. Under the influence of the ridge, our local winds aloft are light, with the prevailing westerlies aloft being to our north and flow increasing north of the Ohio River. A surface front is stalled out near or just north of Kentucky's northern border near the southern edge of greater flow aloft, with a poorly defined portion of the front then extending south through extreme eastern Kentucky. Elevated convection occurred near this boundary over eastern Kentucky during the day, but has moved on. Clouds hindered destabilization for JKL's forecast area during the day, but western portions have managed to heat to convective temperatures and isolated surface based showers/thunderstorms have developed there early this evening. These may make their way east into the JKL forecast area this evening before dissipating with diurnal loss of instability. There is also a possibility that convection could develop to our north tonight, closer to the front, and move near our northeastern border. At this time, it looks like it would remain to our north, but this will need to be monitored for possible updated.

The portion of the front in eastern KY is expected to move east and place all of our area in the warm sector on Sunday. Stronger heating should occur on Sunday, but forecast soundings suggest warm air aloft and dry mid level air will make it difficult to initiate convection. While precip can't completely be ruled out, at this point the POP is being held below the threshold for precip to be in the forecast, with higher POPs being to our north and east.

Weak waves moving trough the mid-upper level flow will work to gradually drop the faster flow further south as the southeast CONUS ridge continues to weaken Sunday and Sunday night. This would allow the surface front to drop south into KY and support at least a small potential for showers/thunderstorms on Sunday night.

LONG TERM

(Monday through Saturday) Issued at 409 PM EDT SAT SEP 19 2026

At the start of the long term period, eastern Kentucky will find itself in a region of largely zonal flow aloft, with a broad trough over the northeastern CONUS and a closed upper level low to the northwest in the Northern Plains. At the surface, a cold front will push through the forecast area before losing momentum near the TN line. Although the timing of this front remains in question, a temperature gradient looks to set up across the forecast area; north of the boundary, northerly winds will keep weather cooler, with high temperatures remaining seasonable (upper 70s to low 80s), while south of the boundary, southerly to southwesterly flow will dominate. This will keep weather feeling more like summer, with highs in the upper 80s or perhaps low 90s in areas unaffected by convection. That being said, the aforementioned boundary, in addition to a shortwave trough embedded within flow aloft, will keep PoPs elevated, with at least scattered convection possible as early as Monday afternoon.

The pattern looks to be quite active from Monday evening onwards as the previously mentioned closed low progresses eastward and eastern Kentucky finds itself under the influence of amplifying troughing centered over the western Great Lakes. Each day, the environment will be moist (LREF mean PW values generally in the 70th percentile or higher compared to climatology). There will be ample forcing for convection as multiple embedded shortwaves traverse the base of this trough, and with a surface low and associated boundary lingering in the vicinity of the forecast area through at least Wednesday, rain chances should remain high through at least midweek. Ensemble guidance suggests moderate instability remains favored to build each afternoon, and with high freezing levels and a very saturated profile, any convection could yield efficient rainfall rates. Flow will remain fairly weak aloft, and thus minimal shear should preclude an organized severe weather risk; however, this unimpressive upper level flow will also keep storm motion quite slow (generally in the 10-15 kt range). Altogether, these factors indicate that the environment will be favorable for flash flooding, particularly in areas that receive multiple rounds of heavy rain. Given this, WPC has maintained Day 3, 4, and 5 Marginal Risks (Level 1/4) for Excessive Rainfall across most of eastern Kentucky, with the caveat that model spread remains high and a categorical upgrade could be needed if/when confidence in these details increases. On a positive note, this pattern should also provide some relief from the heat; highs will generally be in the 70s across the forecast area, near to below average for this time of year.

In the latter half of the week, ridging will build over the central CONUS, with troughing now displaced east of our area. With this more stagnant pattern in place, the trend will be towards less active weather, with only slight chance PoPs from Friday onwards. It will also feel more like fall; northerly flow should maintain cooler temperatures, with highs in the low to mid 70s!

AVIATION

(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 231 PM EDT SAT SEP 19 2026

A band of showers/thunderstorms extended from the vicinity of KJKL southward into VA and TN at the start of the period. This was due to elevated (non surface based) instability based around 6K ft AGL. It should be passed KJKL very shortly and it's unclear if this elevated activity will affect KSJS as it creeps eastward. As surface temperatures climb, surface based convection may result in a few additional surface based showers/thunderstorms late this afternoon and evening, but the the probability looks too low at any TAF site to explicitly address it. If it looks apparent that the threat is increasing, AMDs will be necessary.

Away from precip, VFR conditions are expected into tonight. Valley fog is likely to develop overnight and last into Sunday morning, especially in extreme eastern and southeastern KY. It could affect some TAF sites at times. Once fog dissipates on Sunday morning, VFR follows area wide again through the end of the period

JKL WATCHES / WARNINGS / ADVISORIES

None.