textproduct: Jackson

KEY MESSAGES

- Isolated instances of frost are possible late tonight into Tuesday morning in deeper rural valleys and hollows - mainly away from mainstem rivers.

- There is a greater concern for frost formation late Thursday night into Friday morning, especially in sheltered rural valleys and hollows away from mainstem rivers. - A cold front is expected to bring chances for showers and perhaps a few thunderstorms for Wednesday.

- Additional shower and thunderstorm chances arrive this weekend accompanied by a trend of increasingly warmer temperatures into early next week.

UPDATE

Issued at 731 PM EDT MON MAY 11 2026

Added the latest surface observations and interpolated through the rest of the evening. Grids have been saved and sent.

LONG TERM

(Wednesday through Monday) Issued at 339 PM EDT MON MAY 11 2026

The long-term period begins daybreak Wednesday with the next round of unsettled weather developing from the northwest with an approaching cold front. Aloft, a potent high amplitude 500 hPa trough axis will extend from Northern Ontario southward across the Ohio and Tennessee Valleys. Meanwhile, a similarly high amplitude ridge extends from New Mexico NNW along the Rocky Mountains all the way to over the Brooks Range of Alaska. In between this unusually strong upper level ridge and trough, surface high pressure resides from the Plains north and westward into the Canadian Arctic.

The aforementioned cold front seems to be moving through more quickly in recent guidance and should initially be on our northwestern doorstep mid-morning on Wednesday before quickly marching southeast across the forecast area and departing into southwestern Virginia by early to mid-afternoon. The early timing of the frontal passage will limit destabilization and overall thunderstorm potential, especially across the northwestern half of the CWA. Over the southeastern half of the CWA, the late morning and early afternoon frontal arrival may give sufficient time for more substantial destabilization (MLCAPE might reach 500 to 1000 J/kg). If sufficient destabilization occurs, effective shear should be greater than 30 kts and could favor some organization of the cells. However, the recent forecast trends for a quicker frontal passage leave some doubt on this potential. Overall PoPs for the frontal passage are highest over the Big Sandy Basin where 80 to 90 percent probabilities of measurable rainfall are common, but those quickly decrease with southwestward extent, only ranging in to the 10 to 30 percent probability range in the drought-stricken areas around Lake Cumberland. Rainfall amounts generally appear light, mainly under 0.10 inch outside of thunderstorms. Also, 850 hPa temperatures near 10C and good mixing should support temperatures on Wednesday at similar levels compared to Tuesday, ranging in the 70s.

Low-level CAA behind the front will send 850 hPa temperatures falling later in the day on Wednesday and throughout Wednesday night. The 11/00z LREF mean supported 850 hPa temperatures falling to 2 to 4C by 12Z Thursday, with the colder end of the guidance suite near 0C. The northwesterly flow through Wednesday night does diminish from 20 to 25 kts at 925 hPa in the evening to 10 to 20 kts by daybreak, but should keep low-level mixing going for most of the night and thus keep temperatures from radiating very efficiently. Thus, anticipate widespread lows in the 40s early Thursday morning. A dry, cool Canadian air mass will then reside over the Commonwealth for Thursday with minimal change in the overall air mass temperature. Given the 00z LREF mean 850 hPa temperatures of 3 to 5C, widespread highs in the lower to middle 60s seems reasonable for Thursday afternoon given deep mixing, but if the actual air mass is closer to the colder end of guidance, then many places could struggle to reach 60F. Given the spread in the guidance suite regarding the true dryness and modification of this air mass, there is currently moderate confidence in Thursday's high temperatures.

This will all be in place as high pressure shifts east and crests directly over eastern Kentucky Thursday night, providing nearly optimal conditions for radiative cooling. If dew points remain mainly above 32F on Thursday afternoon, there will likely be a competition between fog and frost Thursday night, especially in the sheltered valleys and hollows. Those locales prone to fog along the mainstem rivers and larger tributaries are likely to fog, whereas those hollows and rural valley/low-lying areas not prone to fog are more likely to pick up on a late season frost. COOP MOS suggests lows in the mid 30s by early Friday morning for the cooler hollows and valleys and in the upper 30s in those locations prone to fog. Those with cold-sensitive agricultural interests are encouraged to monitor later forecasts for the late Thursday night and early Friday morning timeframe, as a Frost Advisory may eventually be needed for some of our sheltered eastern valleys. For perspective, the 30-year normal lows (1991-2020 computational period) for May 15th range from 49F in the colder northeastern hollows to 56F in the vicinity of Lake Cumberland, while daytime highs range from 74F to 76F across the lower elevations. Furthermore, the average last frost dates (temperatures 36F or less) for the colder northeastern hollows generally fall in the May 5th to May 18th timeframe.

For the colder hollows, this could be the latest frost in 5 to 10 years. Most of the mainstem river valleys should fog and be protected from frost concerns. After this cold night, May 15th will mark the pivot to a significant pattern change heading into late May. Heights aloft will rapidly rebound as the upper level ridging presses eastward, replacing the troughing, though the ridge will be flattened by a Pacific trough that rides along the US and Canadian border late week. Locally, a mild southwesterly return flow develops behind the departing surface high while a cold front associated with the Pacific trough approaches the Ohio Valley. However, that front will lose its upper level forcing as a new upstream trough digs deeply into the western CONUS late week and early next week. Specific details on the overall rainfall threat with the approaching front remain obscure due to increased model spread, but agreement is good that rising heights and very warm temperatures aloft will send thermometers soaring past normal levels by Saturday and potentially nearing record highs (close to 90F) by Monday.

For area gardeners, the outlook for the remainder of the month, once we get past Friday morning's chill, does not favor any additional cold snaps sufficiently cool for frost, even in the colder sheltered hollows. However, a few cold fronts could still bring cool mornings (probably 40s to near 50F).

AVIATION

(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 731 PM EDT MON MAY 11 2026

VFR conditions are expected to prevail through the TAF period for KJKL, KSJS, KSYM and KIOB but MVFR to IFR conditions are possible as river valley fog is forecast to develop and impact KLOZ and KSME. Once the fog burns off, all sites will return to VFR and stay there. Light and variable winds are likely through the TAF window.

JKL WATCHES/WARNINGS/ADVISORIES

None.