textproduct: Jackson

KEY MESSAGES

- The potential for showers and thunderstorms will persist through Monday.

- Some of the storms could arrive as organized clusters with a possibility for strong to damaging wind gusts. - Excessive rainfall may occur where storms are most persistent, or train, leading to flash flooding.

- Heat indices will flirt with Heat Advisory levels (~105F) through early this evening.

UPDATE

Issued at 1252 PM EDT SUN AUG 16 2026

As of midday, temperatures had mostly climbed to the mid 80s to around 90. Dewpoints are mainly in the low to mid 70s. Some cumulus has begun to form nearer to the VA border while debris clouds and likely subtle shortwave was moving from IN into OH and across northern sections of KY. An associated outflow boundary/ windshift from earlier upstream convection was working into areas near and north of I-64 attm. Recent mid level lapse rates were analyzed in the 5.5 to 6C/km range with low level lapse rates around or in excess of 7C/km. 16Z MLCAPE was around 1000 J/kg west to 1500 east and southeast. Effective shear remained lower end, generally west at 20KT or less and best nearer to the WV border. Over the next 2 to 6 hours, SPC Mesoanalysis based on the RAP has effective shear climbing to roughly 20 to 25KT areawide through 20Z to 22Z. At the same time, mid level lapse rates should be near 6/km or less while low level lapse rates remain near 7C/km or greater and MLCAPE peaks in the 1500 to 3000 J/kg range toward evening, 22Z, with the higher values generally in the northwest and east while inhibition in the north and northwest erodes in the next 1 to 2 hours. This should result in continued cumulus development through mid afternoon and the possibility of isolated to scattered convection in the north and/or east by mid to late afternoon. Given the generally moderate instability and moderate shear, if anything develops is could produce some strong to locally damaging wind gusts given DCAPE roughly 800 to 1200 J/kg in those areas. PW remains a bit elevated in the 1.6 to 1.9 inch range from south to north and per 12Z HREF and should remain at 1.8 inches or higher (90th percentile or greater) in the north and east through the evening. Any convection should produce heavy downpours and if any training occurs locally heavy rain is possible. If this were to coincide with where heavier rain has fallen over the past couple of days, flash flooding would be possible.

Hourly grids have been updated for recent CAM and observation trends.

LONG TERM

(Tuesday through Sunday) Issued at 353 PM EDT SUN AUG 16 2026

At the onset of the long term period, a strong closed upper level low will sit over Manitoba, with general troughing over the northern CONUS, especially in the vicinity of the Great Lakes. Meanwhile, a relatively flattened ridge will linger over the southern US, with eastern Kentucky finding itself in a region of zonal to slightly northwesterly flow aloft, depending on the orientation of ridging. At the surface, the previous frontal system will be south of the forecast area, having fully moved through, and surface high pressure will be building near the Middle Mississippi Valley. Behind the surface high, a secondary cold front associated with the relatively vertically stacked Canadian low will extend southward into the Upper Midwest. As these features travel eastward, building high pressure over the forecast area will keep eastern Kentucky largely dry on Tuesday. Temperatures will be fairly seasonable as well, with highs ranging from the mid to upper 80s across the forecast area. Clear skies overnight may allow a very modest ridge/valley temperature split to develop, with the limiting factor being lingering moisture. MOS guidance is rather aggressive with these splits, but given expected moisture, valley minTs have been nudged down only modestly into the low 60s for now. Of note, fog formation on Wednesday morning appears likely for much of the forecast area, particularly in typical mainstem river valleys.

Dry weather will persist through much of Wednesday as surface high pressure continues to translate through the area. Meanwhile, the upper level trough will continue to dig towards the Commonwealth, with the aforementioned cold front pushing southeast. By Wednesday evening, the front will approach eastern Kentucky and rain chances will return to the area. Of note, some models depict an additional shortwave traversing the base of the trough (roughly centered over the Ohio Valley) around the time frontally forced convection approaches, or perhaps slightly before. This enhanced mid level flow may elevate shear somewhat, and depending on frontal timing, instability may also be adequate for stronger storms, although model spread remains quite high at this time. Any risk for severe weather (or lack thereof) remains dependent on how these ingredients line up, with overall risk looking quite low at this time. Meanwhile, a moist air mass will be in place ahead of the front, with LREF mean PW values generally in the range of 1.6-1.7 in (roughly 80th percentile or higher compared to climatology). This, in addition to potentially enhanced convective coverage if shortwave energy interacts with the front, could allow for at least isolated instances of flash flooding. Again, model variability remains very high at this stage, but WPC has already outlined the forecast area in a Day 4 Marginal (Level 1/4) Risk for Excessive Rainfall on Wednesday, and an additional Day 5 Marginal Risk on Thursday as the system sags south. Guidance does suggest the front will slow as it passes through the southern portion of our area and into Tennessee. Exactly how quickly this boundary progresses is still a source of uncertainty, but rain chances have been maintained through Thursday to account for this slowing motion. Any hydrological concerns will also be dependent on the speed of this frontal passage in addition to the extent of convective coverage.

Following the frontal passage, troughing will continue to amplify, eventually digging all the way into the Southeast as ridging retreats towards the Four Corners region. This will usher in cooler weather, with high temperatures as low as the upper 70s for some locations on Friday (and perhaps lower if convection can take hold). Additional impulses will keep at least scattered showers and storms in the forecast each day, with rain chances generally peaking in the afternoon/evening.

AVIATION

(For the 12Z TAFS through 12Z Monday morning) ISSUED AT 750 AM EDT SUN AUG 16 2026

Outside of localized fog in sheltered river valley locations, VFR conditions are noted across eastern Kentucky terminals at the 12Z TAF issuance. The valley fog will lift and dissipate by 13-14Z, leaving behind a cumulus field with cloud bases near 5-7kft AGL. Although a stray shower or storm cannot be ruled out today, greater convective coverage should hold off until the evening and nighttime hours as a cold front sags into the area. Winds will generally be southwesterly at 10KT or less, except locally stronger and erratic near thunderstorms.

JKL WATCHES/WARNINGS/ADVISORIES

None.