Area Forecast Discussion

KEY MESSAGES

- Well-above normal temperatures persist this weekend with near record values both days over the Cumberland River Basin. - The heat, humidity, and a nearby frontal boundary could foster isolated to scattered thunderstorms across the area at various times over the next several days.

- Rain chances increase early next week as the persistent upper level ridging breaks down.

UPDATE

Issued at 1119 AM EDT SAT SEP 19 2026

Isolated showers and thunderstorms have developed amidst weak elevated instability as a warm frontal boundary slowly drifts northeast toward the Eastern Kentucky Coalfields. Low end PoPs have been added into the forecast to account for this. More widespread PoPs are expected to hold off until late afternoon/ evening when convection, potentially associated with an upstream outflow northwest of Indianapolis, approaches/develops.

SHORT TERM

(Today through Sunday) Issued at 519 AM EDT SAT SEP 19 2026

The unseasonably warm and muggy pattern of late continues across eastern Kentucky, with temperatures settling back into the upper 60s to lower 70s this morning--more typical of mid-summer than mid-late September. A mixture of fog and low stratus is found in most places following yesterday's hit-and-miss shower and thunderstorm activity. The latest surface analysis shows a poorly defined frontal boundary draped across the region from the Carolinas through much of Tennessee and then northwest to a weak surface low over Iowa. Looking aloft, an ~594 dam upper-level ridge is centered over northeast Texas while eastern Kentucky remains on its northeastern periphery.

This will place eastern Kentucky under deep-layer northwesterly to westerly flow as the aforementioned frontal boundary wavers back to the north over the next couple of days. Multiple weak disturbances moving through the flow could spark a few showers and thunderstorms, most likely during the afternoon or evening, coincident with peak heating and destabilization. Many HREF/REF members hint at a more substantial MCS developing over Indiana and portions of Ohio this afternoon, dropping southeast this evening and weakening, potentially brushing portions of northeastern Kentucky. Some of the guidance also suggests isolated activity bubbling up farther south. The best instability is favored to be upstream of our area while the better shear remains farther north, but any storms that do develop or move in from the northwest will have access to a moderate 1000 to 2000 J/kg of SBCAPE and DCAPE values near 1000 J/kg, bringing the potential to produce strong to isolated damaging wind gusts. Therefore, SPC has maintained a Marginal Risk (1/5) of severe weather for today. The story appears similar for tomorrow, including a Marginal Risk SWODY2, but there is little model agreement on timing for any particular round of convection as upper-level disturbances remain weak.

In sensible weather terms, fog and low stratus will gradually lift this morning. This will leave behind mostly to partly sunny skies for this afternoon, and similar skies will follow on Sunday. Both weekend days will also remain quite hot for this time of year, with temperatures ranging from the mid 80s in the northeastern hills to the lower 90s over the Cumberland River Basin. There will also be a threat of showers and thunderstorms, isolated to scattered in coverage during the afternoon and evening, though a rogue shower or thunderstorm cannot be ruled out at another time. Meanwhile, Saturday night will remain warm and muggy, with lows mainly in the mid 60s to around 70F along with the typical favored river valley fog.

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.