886
FXUS63 KJKL 180553
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
153 AM EDT Fri Sep 18 2026

.KEY MESSAGES...

- Well-above normal temperatures persist into the weekend, with
  near-record heat observed this afternoon.

- The heat and humidity could fuel isolated thunderstorms across
  the area at various times over the next several days.

- Rain chances increase early next week as the persistent upper
  level ridge starts to weaken and then retreat to the southwest.

&&

.UPDATE...
Issued at 1121 PM EDT THU SEP 17 2026

As of 03Z, fog can be seen forming on nighttime microphysics RGB
satellite imagery. Fog will continue to develop overnight, mainly
in valley locations. The latest observational and model data have
been ingested into the forecast. No major changes were made, with
the forecast remaining on track.

UPDATE Issued at 753 PM EDT THU SEP 17 2026

The forecast was updated to curb or remove some PoPs through
02Z this evening. Shower and storm activity has ceased across
the area. Minor adjustments were made to the weather and sky
grids to reflect the PoP revisions. Latest observational data
was also incorporated into the T/Td grids. The forecast
remains on track for fog to develop, mainly in valley locations
late this evening and overnight before mixing out early Friday.
Morning showers will work into the area from the north ahead of a
decaying cold front before additional afternoon showers and
thunderstorms develop.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 244 PM EDT THU SEP 17 2026

Weak north to northwesterly upper flow can be expected as the
area resides on the northeast side of a strong high that will be
centered over the Arklatex region. Meanwhile, at the surface, a
cold front will move south into the area Friday morning but then
quickly decay/dissipate as any upper support for southward
movement falls apart.

Hot and humid conditions will provide the fuel for isolated to
scattered shower and thunderstorm development both for the remainder
of this afternoon, and then again Friday morning through Friday
evening with more widespread scattered coverage. Lift will be
provided by subtle shortwave disturbances inducing upstream
convection focused near/along the cold front, with additional shower
and thunderstorm activity forming along differential heating
boundaries and localized terrain effects Friday afternoon before
largely dissipating Friday evening.

The arrival of the cold front and potential convection from the
north Friday may provide some relief from the scorching conditions,
though the trend has been upwards with forecast temperatures in the
last 24 hours across the north. South of the Mountain Parkway,
however, it will be another hot day with temperatures reaching the
lower to mid 90s for highs, with heat indices reaching 100 degrees
or slightly higher in the greater Lake Cumberland area.

The typical valley fog can be expected tonight, and may be locally
dense where rain occurs this afternoon and/or evening, with fairly
low ridge-valley splits of no more than 3 to 6 degrees in the deeper
valleys. More widespread fog is possible Friday night behind
scattered shower and thunderstorm activity along with very weak cold
advection in the wake of the dissipating cold front.

.LONG TERM...(Saturday through Thursday)
Issued at 420 PM EDT Thu Sep 17 2026

The ridging feature that dominated Eastern Kentucky`s sensible
weather during the short term forecast period is expected to erode
as the long term period progresses. A series of shortwave
impulses navigating around the ridge`s northeastern periphery and
a closed upper level low pushing west across the Floridian
Peninsula will work in tandem to suppress the ridge this weekend.
It is progged to weaken to a loosely-organized, sub-590 decameter
ridge over the Ozarks by Monday, a far cry from its peak intensity
as a well-defined 600+ decameter "heat dome." As this weakening
process occurs, the forecast area will be positioned in somewhat
of a split flow regime. The stronger westerlies associated with
the jet stream will remain displaced well to the north of the Ohio
River through early next week, and as the ridge loses its
definition, the winds aloft will weaken and become more quasi-
zonal. So, this weekend`s sensible weather forecast will largely
be governed by smaller scale features and processes.

Some of those mesoscale forecast ingredients are hard to predict at
the current temporal range. Machine learning and AI-enhanced
probabilistic models are beginning to resolve a corridor of low-end
severe storm potential along the NE periphery of the decaying ridge.
This will need to be investigated further as convection-allowing,
higher-resolution models enter the forecast guidance suite. The weak
nature of the flow aloft will limit the magnitude of the shear
available for any storms developing within our CWA this weekend, but
if a self-sustaining MCS develops somewhere upstream, we will need
to monitor its progress. This would cause the forecast to deviate
from current expectations, which are more scattered, pulse-type
convection during peak diurnal heating hours. Any MCS could also
throw a wrench in the temperature forecast, which currently calls
for highs in the upper 80s/lower 90s on both Saturday and Sunday. A
few isolated hydro impacts cannot be entirely ruled out where
multiple rounds of activity occur this weekend, and WPC has
accordingly outlined Marginal Excessive Rainfall Outlooks that clip
the northern Licking and northeastern Big Sandy River Basins.

There is still a notable increase in model spread within the NBM
ensemble across multiple sensible weather forecast parameters for
Monday and beyond. This is likely due to differing model solutions
surrounding a deeper trough ejecting out of the Plains. Significant
variations in this feature`s modeled amplitude, orientation,
phasing, and forward progression speed continue to preclude the
discussion of specific precipitation forecast details, but models
generally agree that a deeper, vertically-stacked trough will
move through the Midwest and the Greater Ohio River Valley by
midweek. It would take a trough like this to finally drag a
meaningful cold front through the CWA. So, despite the model
spread, there is a noticeable downward trend in the mean NBM
forecast temperatures. Highs could dip down into the low/mid 80s
by Tuesday, and then the 70s on Wednesday and Thursday. Northern
and Northeastern portions of the forecast area are the most likely
to reap the benefits of this cool- down, and the cooler air will
also reach them first. Thus, the gradual demise of the ridge could
give our area a taste of more fall- esque temperatures by the
middle of the next work week. Fingers crossed, as this would be
welcome relief from the record high temperature observed at our
office while this discussion was being typed.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 153 AM EDT FRI SEP 18 2026

VFR conditions were observed over the TAF sites at the 06Z
issuance. Valley fog is likely overnight but impacts at the TAF
sites outside of KSME appear unlikely. Any fog should dissipate
rapidly after sunrise. Showers are then possible as early as
12-15Z across northeastern TAF sites such as KSYM, KIOB, and KSJS
ahead of a weakening cold front pushing south out of the Ohio
Valley. Thunderstorm chances pick up around 18Z at all terminals
except KLOZ and KSME, where chances begin more toward 20-22Z,
later tapering off after sunset. Showers and storms could lead to
MVFR or lower reductions and PROB30s have been included in the
TAF sites during the periods of greatest concern. Winds will
remain light and variable through daybreak before increasing to
around 5 kts from the northwest to northeast. Locally stronger
and erratic winds are possible near convection.

&&

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

&&

$$

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