textproduct: Jackson

KEY MESSAGES

- Dry weather with mild days and cool nights holds through the end of the work week.

- Breezy and rainy conditions are possible this weekend as a strong system, including the remnants of Tropical Storm Isaias (currently in the Gulf), moves northeast across the region.

- There is still considerable uncertainty with this system and potential impacts, and forecasts will become better refined as the event nears.

UPDATE

Issued at 833 PM EDT WED OCT 7 2026

As of 8 PM EDT, sfc high pressure was centered over the Southern Appalachians, while a cold front extended from an area of low pressure in Canada across the Great Lakes into the mid MS Valley to the Plains. This boundary has limited moisture on its southern extent and a few clouds in the 7 to 8kft agl range were reported near and in advance of it. Locally, valleys decoupled prior to sunset and dropped off a bit more quickly this evening than the current forecast. With this update, trended hourly T based on current observations. With the front crossing the region overnight, the areal extent and/or temporal duration of valley fog as well as hourly temperatures in valley locations later tonight are somewhat uncertain. However, based on higher observed afternoon dewpoints and lower current dewpoint depressions, valley locations generally near and south of the Mtn Parkway and east of I-75 have the best chance for experiencing fog tonight. With the front passing across the region tonight and although many valleys in the southeast are around 10 degrees colder than nearby ridges, the ridge/valley split magnitude for overnight lows should be less than what was observed last night. The current forecast lows are on track, so no changes were made to those at this time.

LONG TERM

(Friday through Wednesday) Issued at 420 PM EDT WED OCT 7 2026

Fair weather can be expected to open up the extended period on Friday. Surface high pressure previously over the area begins shifting toward the Mid-Atlantic and Northeast. Dry weather will remain through Friday, with unseasonably warm afternoon high temperatures reaching the upper 70s to low 80s. The area will remain in downslope east to southeast flow through Saturday. This could lead to warmer temperatures and drier dew points. Dew points were lowered below the NBM deterministic using raw model guidance to account for the downslope flow through Saturday. Clear skies and light winds will favor ridge-valley temperature splits, with lows dropping into the lower 50s in the coldest, sheltered valleys, while remaining in the mid to upper 50s elsewhere.

A significant pattern shift unfolds over the weekend as an anomalous upper-level ridge amplifies across the Eastern US, raising 500 mb heights over the Commonwealth toward 584-588 dam by Friday night to early Saturday. Some of the more recent model runs had sped up the northward progression of Tropical Storm Isaias. However, the latest runs have maintained the systems speed following that initial acceleration. Forecast uncertainty remains regarding timing and track, though the most recent guidance tracks the system west of the area, keeping much of the heavier rain west of I-75. Strong east to southeasterly downslope flow will also aid in cutting into forecasted rainfall, with drier dew points. Another area of uncertainty lies in the high temperatures for Saturday. Ensembles range from highs in the upper 60s to the mid 80s for Saturday, dependent on when this tropical system arrives. A quicker arrival will lead to cloudy skies and suppressed high temperatures, while a slower track north could allow for a period of sunshine ahead of Isaias, leading to warmer temperatures. Additionally, the aforementioned downslope winds will favor warmer temperatures under these conditions. A blend of raw model data was used to go slightly under NBM guidance, leading to forecasted highs in the upper 70s. Highs in the mid to upper 70s fall near the 75th percentile of ensemble guidance. As low- level flow turns southerly around the departing high, deep moisture associated with Isaias will begin creeping northward. PWATs will climb toward 1.00-1.25 inches near the Tennessee border by Saturday morning, bringing shower and thunderstorm chances from the south. While timing confidence remains low at present, shower and thunderstorm chances will increase through the day and into the overnight. With current guidance placing the heaviest rain Saturday into Sunday along and west of I-75, WPC has placed that portion of eastern Kentucky in a Marginal Risk for Excessive Rainfall.

Saturday evening and overnight, southeasterly winds could become breezy to gusty, with strong winds aloft associated with Isaias impacting the higher terrain along the TN, VA, and WV borders. Both the GFS and ECMWF indicate 50-65 kt winds at 850 mb. 13Z NBM ensemble guidance indicates a 20-65% probability of surface wind gusts meeting or exceeding 40 mph overnight Saturday into Monday. Ensemble probabilities have increased over the last three model runs in both the NBM and LREF ensembles. This trend will be closely monitored in subsequent model runs.

As the system lifts northeast through the Lower Mississippi and Tennessee Valleys, rain is likely across eastern Kentucky through Sunday morning, along with isolated to scattered thunderstorms. Rainfall amounts remain highly uncertain given model spread regarding system strength and positioning, as well as its interaction with an approaching surface cold front driven by northern stream energy passing through the Great Lakes. Broad southwesterly flow aloft between the Atlantic ridge and western troughing will help channel the tropical moisture plume from the Gulf low into the Ohio Valley. This will surge PWAT values across the JKL CWA Sunday morning into early Sunday afternoon, with forecasted PWATs currently falling within the 90th percentile of climatology. The latest 12Z GFS guidance has trended slightly higher with rainfall across the area. PWATs drop off noticeably Monday into Tuesday as the primary moisture plume axis shifts east of the region. As a cold front sags slowly into the region, shower chances will linger into early next week, though decreasing moisture will mitigate the threat for heavy rainfall after Sunday. Daytime highs will range through the low to mid 70s Sunday through Tuesday. Heights lower briefly Wednesday, allowing temperatures to cool slightly into the upper 60s to low 70s. Overnight lows remain mild through Monday night in the mid to upper 50s, with upper 40s returning Tuesday and Wednesday night.

AVIATION

(For the 00Z TAFS through 00Z Thursday evening) ISSUED AT 820 PM EDT WED OCT 7 2026

High pressure centered over the Southern Appalachians was leading to VFR and light winds at issuance time. A cold front will approach the region from the northwest tonight, crossing the area between about 06Z and 15Z. Despite that, at least a period of patchy valley fog, with MVFR or lower reductions is anticipated to develop by around 04Z, mainly for valleys near and south/ southeast of a KSJS to KJKL to KLOZ line. This fog is still not expected to affect the TAF sites and the passing front may lead to a shorter period of valley fog than what has occurred the past couple of nights. Winds will be light and variable or south to west through 08Z in all areas, before becoming northwest to north through 15Z as the front passes. Northwest to north winds at less than 10kt should then prevail for most of the rest of the period, with winds slackening toward sunset/23Z.

JKL WATCHES/WARNINGS/ADVISORIES

None.