Area Forecast Discussion

KEY MESSAGES

- Mainly dry weather is expected through the rest of the weekend.

- Warmer temperatures and a greater potential for showers and thunderstorms return to start the new work week.

- These storms could be more organized and strong to severe on Monday afternoon into the night depending on thunderstorm complex development and evolution to the north of Kentucky.

- Drier weather returns for the second half of the upcoming work week.

SHORT TERM

(This evening through Monday night) Issued at 311 PM EDT SUN JUL 26 2026

It has been a challenging cloud forecast today as a stratus deck has been slow to erode, with moisture getting stuck underneath a healthy inversion aloft. This has slowly started to dissipate into some lower cumulus this afternoon. Given this the afternoon high temperatures have been a bit more depressed. These clouds will continue to scatter out through the remainder of the afternoon. Then we see one of several complicated convective evolutions take place later this evening into tonight. The CAMs are generally developing a complex of storms across northern Illinois and this will dive southward under the influence of the northwest flow pattern in place across the Ohio Valley. The vast majority of the CAMs want to take this complex mainly across parts of western and central Kentucky. However, there is some chance this convection sneaks into the Lake Cumberland and Cumberland Valley region region later tonight into early Monday morning. Given this have some PoPs in the 20 to 40 percent range, with highest chances west of I-75. The other hazard to contend with tonight will be fog formation, with the forecast sounding across the area suggesting more of fog scenario. That said, for now have mostly limited this to the river valleys and portions of the Lake Cumberland region given the potential for overnight convection.

This leads into what should be a mostly dry day for Monday, but some uncertainty does exist with this idea. This as left over boundary and northwest flow aloft could lead to some kind of isolated convection. However, this looks fairly isolated at this point given the lack of better triggers for convection and the relatively drier airmass noted in the PWAT values in the 1.2 to 1.4 range. This as a weak quai-stationary boundary will slide into the Tennessee Valley and weak high pressure will remain nearby. The bigger potential difference will be the much warmer day of late depending on the convective evolution, with highs climbing into the upper 80s to lower 90s.

Monday night is looking more interesting for a MCS like structure possibly diving southward across parts of Kentucky. There still remains a fair amount of uncertainty on timing and evolution of this complex of storms. However, there are many of the CAMs showing a storm complex moving out of southern Michigan and diving southward toward the Lower Ohio Valley. There is also decent signals showing up in the various deterministic and ensemble synoptic guidance, with even some of the machine learning and AI guidance showing signal for stronger storms. There will be ample MUCAPE in the 1000-2000 J/kg range and effective shear in the 30-40 knot range for keeping this complex organized. Even the derecho composite parameter remains elevated, which can be a decent signal for more organized severe wind potential. Therefore, the primary risk will be severe wind gusts, but some of the ML guidance would indicate a small risk for a weak spinup.

LONG TERM

(Tuesday through Sunday) Issued at 258 PM EDT SUN JUL 26 2026

The long-term period opens Tuesday morning with a pronounced ~596 dam high over the Southern Rockies with a ridge axis extending northward into Central Canada. Meanwhile, troughing extends southward from an around 540 dam low over northern Quebec to along the Mid-Atlantic Coast. An embedded shortwave trough is present over the Lower Great Lakes. This will be mirrored at the surface by a 997 mb surface low over Lake Erie. A warm front extends southward from that low to over the Southern Appalachians while a cold front arcs southwest from the surface low over southern Indiana and Illinois and then beyond to over the High Plains of Montana. This will leave eastern Kentucky in the low's warm sector at daybreak Tuesday morning with a seasonably moist air mass (PWATs around 1.8 inches).

The surface low will shift eastward along the PA/NY Twin Tiers through the day and evening on Tuesday, dropping the cold front across the Commonwealth. Substantial uncertainty remains as to instability recovery ahead of this boundary given the likelihood for convection early in the day, and especially prior to sunrise with a potential MCS. If the frontal arrival is slower and greater destabilization occurs, unseasonably strong northwesterly flow aloft would support robust shear and organized convection. Conversely, a quicker frontal passage would tend to favor keeping any stronger organized convection confined to far southeastern Kentucky or perhaps entirely southeast of our CWA. In addition to the convective potential, Tuesday does appear breezy with some momentum transfer mixing to the surface from a low-level jet (30+ kt at 850 hPa). The high PWATs could also favor some isolated heavy rainfall. Any hydro problems would probably occur where substantial rainfall occurred during the last 12 hours of the short-term period; by Tuesday, the strong flow aloft should keep cell motions quite progressive.

Once the front clears the area, cooler and drier air will filter in on Tuesday night and Wednesday, with LREF mean precipitable water values dropping to between 0.75 and 1.00 inch, or near the 10th percentile relative to climatology. Aloft, ridging will remain over the West while troughing lingers over Eastern Canada and much of the Eastern CONUS. Surface high pressure drifting south from Ontario and Quebec will ensure dry conditions through Friday. Another shortwave trough drops into the broader trough during the upcoming weekend. This will foster another surface low developing over the Plains and drifting toward the Tennessee Valley vicinity, bringing back higher PWATs and the renewed threat of convection for Saturday and Sunday.

In sensible weather terms, look for a high chance of showers and thunderstorms (PoPs of 60 to 90 percent, highest in far eastern and southeastern Kentucky) on Tuesday. If substantial sunshine materializes, some of the storms could be strong to severe and also produce heavy downpours. It will be warm and humid with highs in the 80s. Fair weather follows for Tuesday night through Friday with highs in the low to mid 80s and lows mostly from 60 to 65F. As the threat of showers and thunderstorms returns for Saturday and Sunday, daily high temperatures will remain at similar levels, but nighttime lows will moderate to between 65 and 70F with higher humidity levels.

AVIATION

(For the 18Z TAFS through 18Z Monday afternoon) ISSUED AT 143 PM EDT SUN JUL 26 2026

We have seen some pesky stratus that has plagued much of the area this morning and now into the afternoon. We are seeing this slowly scatter out through the afternoon hours. However, did keep a few sites (JKL, SYM, and IOB) in the MVFR range for Cigs this afternoon for at least another hour. Outside this we will see most sites return to VFR through the afternoon into the evening. The forecast soundings then favor fog potential tonight. The extent of this fog is still uncertain especially at SME. This is because a complex of storms will move across mainly portions of western and central Kentucky, but given the uncertainty did add in a Prob30 for a few hours late tonight into early Monday morning for rain showers and resulting vis restrictions. Outside this, added a combination of fog/low stratus in the MVFR to IFR range with fog being the primary concern. Winds will be light and variable at or below 5 knots through the period.

JKL WATCHES / WARNINGS / ADVISORIES

None.