656
FXUS63 KJKL 101154
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
754 AM EDT Sun Aug 10 2025

.KEY MESSAGES...

-Hot and mainly dry weather today will give way to increasing
 chances for showers and thunderstorms on Monday as humidity
 rises.

-Scattered showers and thunderstorms will return on Tuesday as an
 active and wetter pattern settles in for the rest of the week.

-Locally heavy rainfall is the main hazard this week and could
 lead to isolated flash flooding, with the greatest potential on
 Wednesday.

-Daily chances for thunderstorms will persist through the end of
 the week, helping keep temperatures from becoming excessively
 hot.

&&

.UPDATE...
Issued at 655 AM EDT SUN AUG 10 2025

The latest observations have been blended into the forecast to
capture the latest hourly trends but no substantive changes are
needed at this time. Valley fog should lift and dissipate in most
locations by 9 to 10 AM.

&&

.SHORT TERM...(Today through Monday)
Issued at 359 AM EDT SUN AUG 10 2025

Satellite imagery shows fog developing and expanding through the
mainstem river valleys and larger tributaries early this morning
under clear skies. Thermometers are at seasonable levels, ranging
in the mid and upper 60s for all of the area, except for the
highest summits near the Virginia-Kentucky border. The fair
weather is courtesy of a ~1024 hPa high, extending from the
Canadian Maritimes southwestward along the Atlantic Seaboard to
the Outer Banks and then westward into the Tennessee Valley. The
parent upper-level ridge extends from the Mid-Mississippi Valley
northeastward through the St. Lawrence Valley. A subtle east-west
oriented surface trough is noted from southeast Missouri eastward
through the Bluegrass to near Charleston, WV. Further upstream, a
substantial 500hPa trough supports a cold front extending from low
pressure over eastern Manitoba southward into Kansas and then
southwestward into New Mexico.

The high pressure in our vicinity, as well as weak height rises
aloft, will keep deep convection negligible today over the vast
majority of eastern Kentucky -- just a decent cumulus field at
most locations. However, some guidance hints at the subtle west-
to-east oriented surface trough lingering near/north of Muldraugh
Hill to its transitional intersection with the Pottsville
Escarpment (in the Rockcastle/Jackson/Estill/Madison county area).
In this area, where some of the highest elevations of the
Pottsville Escarpment exist, most of the 10/00z HREF CAMs suggest
one or more pin-prick showers blossoming this afternoon in a weak
instability, weak shear environment. Some of the model guidance
supports an isolated shower threat extending further south to the
vicinity of Lake Cumberland and also up toward the Red River
Gorge. Thus a slight chance (15 to 24%) of showers has been added
to the forecast in these areas. Some of the guidance also hints
at convective initiation occurring over/adjacent to Big Black
Mountain but mentionable PoPs were not included in the forecast
for that area at this time as instability will be very meager.
Mid-level capping and dry air will almost certainly limit cloud
depth and inhibit any threat of lightning with convection this
afternoon. After any convection dissipates this evening with the
loss of diurnal heating, the upper-level ridging slowly shifts
overnight, allowing for minute height falls over the Commonwealth.
The latest guidance suggests that heights aloft may rise again
slightly on Monday as upper level ridging consolidates south of
Bermuda and retrogrades westward. Increasingly southerly to
southwesterly low- level return flow on the back side of the high
will begin advecting a higher PWAT air mass back across the
Eastern Kentucky Coalfields through the day. This will contribute
to rising instability levels, but forcing will be limited to
differential heating and perhaps weak 500hPa positive vorticity
closer to the Tennessee border ahead of a weak vorticity maximum.
In general, the highest chances for any shower or thunderstorm
activity appear to be near/south of the Hal Rogers Pkwy/KY-80
corridor, though some isolated activity could develop/sneak
further north, especially over and west of the Pottsville
Escarpment.

In sensible terms, look for a hot and mostly dry Sunday after any
valley fog dissipates by mid-morning. High temperatures are
forecast to range in the upper 80s to lower 90s. The only
potential fly in the ointment is a possible brief shower or
sprinkle (generally ~20 percent chance or lower). This nuisance
shower activity is most favored to occur over Jackson and adjacent
counties, though a brief shower or sprinkle cannot be entirely
ruled out further north along the Pottsville Escarpment to the Red
River Gorge area and also south toward the Tennessee border.
Another fair mid-August night follows Sunday night with fog
formation likely again in the favored river valley locales. It
will be seasonably mild with lows in the middle to upper 60s.
Looking ahead to Monday, temperatures are forecast to reach
similar levels, but rising humidity levels will make it feel
hotter, with maximum apparent temperatures reaching the mid 90s at
most locations. Scattered showers and thunderstorms are also
possible, especially south of the Hal Rogers Parkway/KY-80
corridor, though more isolated activity cannot be ruled out
further north, especially over and west of the Pottsville
Escarpment.

.LONG TERM...(Monday night through Saturday)
Issued at 448 AM EDT SUN AUG 10 2025

he beginning of the long term forecast period is marked by the
breakdown of the atmospheric ridging pattern that kept conditions
mostly dry across eastern Kentucky this weekend. Through Tuesday,
the upper level ridge previously positioned over the Appalachians
will shift eastward as troughing begins to dig deeper into the
Upper Midwest. In this same time frame, ridging begins to build
back over the Southeastern and South-Central CONUS. Collectively,
these features will place Eastern Kentucky in a persistent regime
of quasi-zonal flow aloft through the remainder of the new week.
As shortwave features navigate through this flow, an active
weather pattern will set up over the area through the end of the
forecast period.

After convection subsides with the sunset, expect ridge-valley
temperature splits Monday Night (ridge MinTs near 70 and valley
MinTs in the upper 60s). The synoptics at play support nocturnal
valley fog formation, especially in the river valleys and in
locations with wet grounds. Precipitation chances spread across
the entirety of Eastern Kentucky on Tuesday and then increase
further headed into Wednesday. This increase in convective
coverage is largely due to the persistence and amplification of
southwesterly-to-westerly flow throughout the atmospheric column.
The orientation of this flow favors persistent Gulf moisture
advection into the region, and LREF mean PWATs surge to near 1.75
inches across the forecast area by Tuesday afternoon and then to
above 1.8 inches on Wednesday afternoon. Tuesdays convective
activity is likely to remain diurnally-driven, although guidance
continues to show a more well-defined disturbance in the vicinity
of the forecast area on Wednesday.

Severe thunderstorm parameter spacing remains unimpressive for
the duration of the forecast period, although increasing amounts
of SBCAPE and the aforementioned PWAT values suggest that isolated
wet downbursts cannot be entirely ruled out on Tuesday and
Wednesday. It is more likely that these storms will be efficient
rainmakers, especially once the more vigorous shortwave
disturbance arrives on Wednesday. Some of the available 10/00z
modeled forecast soundings for Wednesday at KJKL show PWAT values
approaching 2 inches, with long/skinny CAPE profiles, low LCLs,
and a thick warm cloud layer present. If multiple rounds of
convection are able to pass over any given location in an
environment like that, localized flash flooding would be possible.
WPC has maintained a Marginal (Level 1/4) Excessive Rainfall
Outlook for the entire forecast area on Wednesday in response to
this signal, although the evolution of mesoscale factors such as
antecedent/upstream convective activity remain uncertain at this
temporal range. At the current moment, there is not a signal for
widespread flooding impact in any of the probabilistic river
forecast guidance, which gives credence to the idea that
Wednesdays flood risk will be confined to any locales that see
multiple rounds of heavy rain or a particularly persistent
downpour. Interests are encouraged to monitor future forecast
updates as higher-resolution data becomes available and the
mesoscale details of Wednesdays forecast become more clear.

The increasing rain chances and cloud coverage on Tuesday and
Wednesday should suppress any heat impacts related to the
increasing humidity. Forecast highs have trended a little bit
cooler for this mid-week time frame, and the latest forecast grids
reflect highs in the mid to upper 80s. If an AM round of
convection comes to fruition on Wednesday and skies remain
cloudier, the NBM-sourced forecast highs could be too warm.
Confidence was not high enough to deviate from this baseline data
with this forecast package issuance, but these cooler temperatures
could further mitigate the severe weather potential.

In the wake of Wednesday`s shortwave trough, high temperatures
are expected to linger in the mid to upper 80s on Thursday. The
Commonwealth is likely to remain in quasi-zonal flow through the
end of the week, although a shortwave ridge should lead to some
atmospheric drying/warming late in the day on Thursday and into
Friday. Highs on Friday correspondingly tick back up towards 90
degrees, but the pattern remains favorable for diurnally-forced
convection. PoPs remain in the forecast through the end of the
period, and heat-related impacts are not expected. Likewise,
expect overnight lows near/above 70 on ridgetops and in the upper
60s in the valleys. Valley fog grids have been added to the
baseline NBM grids each night through the long term forecast
period, although it is noted that any leftover cloud decks from
Tuesday and Wednesdays precipitation chances could mitigate fog
formation on those nights.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 754 AM EDT SUN AUG 10 2025

Surface and upper level ridging will dominate through the period.
This will lead to VFR at TAF sites. Fog in the mainstem river
valleys should dissipate between 13-14Z. Otherwise, some
diurnally-driven cumulus in the VFR range should develop across
portions of the area after ~15Z; but, with the area more under
the center of the upper ridge, shower coverage will be even more
limited than Saturday. Fog formation is likely in the valleys
again tonight but impacts are not expected at the TAF sites. Winds
will remain light and variable under 5 kts.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...GEERTSON
SHORT TERM...GEERTSON
LONG TERM...MARCUS/GEERTSON
AVIATION...GEERTSON