734
FXUS63 KJKL 170007
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
807 PM EDT Wed Sep 16 2026

.KEY MESSAGES...

- Above normal temperatures persist into the weekend, with near-
  record heat possible on Thursday.

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

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

&&

.UPDATE...
Issued at 807 PM EDT WED SEP 16 2026

Refreshed the forecast to incorporate the latest observational and
model data from across the area. Earlier showers and storms continue
to dissipate heading into the evening. Valley fog is expected to
develop, mainly in the favored river valley locations. No major
changes were made to the forecast.

UPDATE Issued at 358 PM EDT WED SEP 16 2026

Isolated showers have started to develop across the area, so have
introduced broad 15 PoPs to account for this up until around 00z
this evening. A stray thunderstorm or two cannot be ruled out
toward the I-64 corridor. The vast majority of areas will remain
dry.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 222 PM EDT WED SEP 16 2026

An exceptionally strong 600-dm upper high over the Upper
Tennessee Valley this afternoon will retrograde to the Mid-South
region tonight, then continue west and southwest through the
Arklatex region Thursday into Thursday night while slowly
weakening (yet remaining quite strong). A strong ridge axis from
this upper high situated across eastern Kentucky today will subtly
slide south into the Cumberland and Upper Tennessee Valley
Thursday before briefly redeveloping back over eastern Kentucky Thursday
night in the wake of a subtle shortwave .

The primary concern through the short-term period is the unusually
strong heat for mid-September, with a secondary concern coming with
any potential shower and thunderstorm development as weak
disturbances move around the periphery of the upper high.

As for the heat, highs both today and Thursday will be quite
similar, with perhaps a touch more humidity Thursday than today
resulting in perhaps a few more heat indices reaching the 100 to 105
degree range.

Convection potential will be quite limited this afternoon given
the strength of the upper high, but the ridge axis shifting south
Thursday will allow for a bit more moisture and instability in the
afternoon accompanied by very weak synoptic-scale lift with a
subtle shortwave. Convection should be limited in coverage and
favor northern through eastern Kentucky Thursday where the best
moisture and topography may align to produce isolated to widely
scattered showers and a few storms.

Ridge-valley temperature splits will continue to lessen each night
as the cumulative effects of the building heat and increasing
humidity begin to exert more of an influence on overnight
temperatures. Widespread valley fog can also be expected, and may be
locally dense especially where any rain occurs the afternoon or
evening before.

.LONG TERM...(Friday through Wednesday)
Issued at 455 PM EDT Wed Sep 16 2026

A pattern change is in store for Eastern Kentucky during the long
term forecast period, and it should bring some relief from the
recent heat with it. The previously-dominant ridging over the
Tennessee Valley is progged to retrograde west towards the Ozarks
this weekend. At the same time, a closed upper level low will move
over the Floridian Peninsula and set up a Rex-esque blocking feature
for a few days. Models collectively resolve both of these features
sitting in place through Sunday morning, although the ridging will
be in a weakening state. A series of troughing disturbances ejecting
around the ridge`s northern periphery will work in tandem with this
closed low to suppress the ridge by early next week. While the
initial two disturbances will yield minor sensible weather impacts
across the forecast area, a deeper trough is expected to eject out
of the Rockies early next week. While models disagree on its exact
evolution, they do agree that it will be the final nail in the
coffin for the antecedent ridging pattern. Between Friday morning
and Monday afternoon, the ridge is poised to weaken from its peak
"heat dome" intensity of 600+ decameters to a looser-organized ridge
of sub-590 decameter heights. Therefore, this late-period troughing
disturbance is more likely to bring noticeable heat relief to all of
Eastern Kentucky than its predecessors.

The first disturbance is expected to pass well to the north of the
Ohio River Valley on Friday, with weak northwesterly flow and
minuscule midlevel height falls modeled across the forecast area.
While a surface frontal boundary is resolved in the vicinity of the
forecast area in this time frame, there will be little to no
syntopic-scale airmass modification associated with it. Temperatures
in the northeastern half of the CWA will be a few degrees cooler
than they were in the short term forecast period, but this moreso a
byproduct of the cloud cover from the convective activity associated
with the boundary. Given the lack of dynamic support aloft, any
showers/storms on Friday will be well below severe limits. The lack
of forcing should also limit the heavy rainfall potential. So, the
greatest sensible weather effects from this activity will come in
the form of a SW->NE temperature gradient. There could be a 10
degree difference in highs on Friday between NE KY and areas west of
I-75 that are closer to the influence of the ridge. The latest data
blend accordingly depicts highs in the mid 80s in the Big
Sandy/Licking River Basin, whereas places closer to the Cumberland
River will experience yet another day of temperatures in the 90s.
Any rain that does fall on Friday could help bolster the areal
coverage of fog on Friday night, when temperatures should cool into
the 60s area wide.

Given the blocking to the south and the quasi-zonal flow aloft, the
boundary responsible for Friday`s activity is expected to hang
around into Saturday. Models resolve low-level flow adopting more of
a southerly directional component on Saturday and Sunday, this is
associated with the boundary nudging back north of the Ohio River in
this time frame. The resultant warm air advection will bump
temperatures back into the upper 80s/lower 90s area-wide on both
days. Isolated summertime showers/storms cannot be ruled out during
peak diurnal heating hours on Saturday, but there could be greater
convective coverage late Saturday night into Sunday. The second
ridge-riding impulse is expected to arrive in the latter stages of
the weekend, with relatively greater shortwave support aloft than
Friday`s. WPC has outlined a Marginal Excessive Rainfall outlook in
the vicinity of the forecast area for late Saturday night and then
again on Sunday, but this appears contingent on the evolution of
upstream activity on Saturday night. A few isolated hydro impacts
cannot be ruled out where multiple rounds of activity occur in the
vicinity of the increasingly stationary boundary, but this is
most likely to be north and northeast of the JKL CWA.

There is a notable increase in model spread within the NBM ensemble
across multiple sensible weather forecast parameters for Sunday and
beyond. This is likely due to differing model solutions
surrounding the third trough ejecting out of the Rockies.
Significant variations in this feature`s modeled amplitude,
orientation, phasing, and forward progression speed preclude the
discussion of specific forecast details at the present moment, 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, and despite the model spread,
there is a noticeable downward trend in the mean forecast MaxTs and
MinTs for Tuesday and Wednesday. Highs dip down into the low/mid 80s
by Wednesday alongside widespread lows in the 60s (not accounting
for smaller-scale enhanced radiational cooling in the valleys). Such
values are technically still above climatological norms for Mid-
September in Eastern Kentucky, but we will cling onto the glimmer of
hope that is some type of relief from this week`s near-record
heat.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 807 PM EDT WED SEP 16 2026

Isolated showers continue to taper off over the next hour or so,
with mainly VFR conditions prevailing through much of the TAF
period. Valley fog is expected to develop late tonight, beginning
around 06Z before mixing out around 14Z Thursday morning.
Localized MVFR to IFR conditions will remain possible, though fog
largely shouldn`t impact TAF sites. An MVFR reduction was thrown
into KIOB for possible fog from 07Z through 13Z as rainfall
earlier this evening may aid in localized development.

Thursday afternoon, showers and thunderstorms will be possible again
mainly east of I-75. Thunder probabilities were sub-30% for all
sites except KSJS, therefore a PROB30 was introduced for KSJS
from 18Z through 24Z. Elsewhere, showers remain possible
anytime after 18Z, such as at KSYM.

&&

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

&&

$$

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