JKL issues Area Forecast Discussion (AFD) at Aug 31, 7:50 AM EDT
491
FXUS63 KJKL 311150 AAA
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
750 AM EDT Mon Aug 31 2026
.KEY MESSAGES...
- Mainly dry weather is expected through mid week, along with a
strong warming trend. Afternoon heat indices will top 100
degrees in many locations from Tuesday through Friday with
Wednesday and Thursday likely the hottest days.
- Showers and thunderstorms are possible at times from Thursday
through the weekend.
&&
.UPDATE...
Issued at 725 AM EDT MON AUG 31 2026
No significant changes were made to the forecast with mainly just
the inclusion of the latest obs and trends for the T/Td/Sky grids
along with some near term small PoPs in the north per the current
radar returns. These minor adjustments have been sent to the NDFD
and web servers along with a freshening of the SAFs and zones.
&&
.SHORT TERM...(Today through Tuesday)
Issued at 445 AM EDT MON AUG 31 2026
08Z sfc analysis shows high pressure just southeast of Kentucky
holding in place and still controlling the weather over the
central Appalachians. Yet again, this has meant light to calm
winds, mostly clear skies, and the typical of late river valley
fog development for the JKL CWA. Also, radiational cooling
allowed a small ridge to valley temperature difference to set up
over the area again this night with readings ranging from the
upper 60s in the lower sheltered spots to the lower 70s on the
hilltops. Meanwhile, dewpoints are generally in the upper 60s to
lower 70s.
The models, and their individual ensemble suites, remain in very
good agreement aloft through the short term portion of the
forecast. They all depict a 5h ridge centered over western
Kentucky at the start of the period. This dome of heat will work
east through the start of the work week with its subsidence
covering eastern Kentucky through at least Wednesday evening.
Meanwhile, the mid level northwest flow will shift further off to
the northeast and away from the state but not before a diffuse
impulse passes by the area this morning - responsible for the
passing mid and high level clouds. After that perturbation moves
on past, any influence from activity aloft will be minimal until
later in the week. On account of the very small model spread,
mainly unadjusted NBM data was used for the forecast grids.
However, some enhancements were made to highlight terrain details
in temperatures tonight along with slightly lower afternoon
dewpoints and maximum temperatures each day. Meanwhile, in
conjunction with the most current consensus of the CAMs, PoPs
were kept near zero through 00Z Thursday.
Sensible weather will feature areas of valley fog, locally dense
near the rivers and lakes, again clearing out shortly after
sunrise and not interfering too much with the expected mostly
sunny skies today. Plenty of sunshine and milder starting points
will continue to build warmer temperatures day by day with low
90s common place this afternoon and some mid 90s likely showing up
for a few spots on Tuesday afternoon under dry conditions. We
will see more humidity for Tuesday, as well, pushing heat indices
over 100 degrees for several locations during the afternoon.
Before then, you can again look for a near repeat of the night-
time conditions pf this past night with readings being a few
degrees warmer while more river valley fog develops towards
midnight and lasts until just past dawn.
The main adjustments to the NBM starting point once again included
specific terrain details in the upcoming overnight temperatures,
lower afternoon dewpoints, and a capping of the hottest modeled
temperature in certain spots across the CWA. As for PoPs - kept
them in the low single digits to zero through the period thanks to
the nearby sfc high and building heights aloft - ruling our
neighborhood through at least mid-week.
.LONG TERM...(Tuesday night through Sunday)
Issued at 400 AM EDT MON AUG 31 2026
Again the most current model data supports the forecast of an
unseasonably hot period into the latter part of the week with mid
90s expected for highs at its peak on Wednesday and Thursday. In
the earlier model runs disagreement it seems trends are favoring
the drier and somewhat warmer ECMWF through Thursday. We still
see the potential for convection in a good number of the model
solutions across forecast area later Thursday and into the
weekend. This occurs as the 5h ridge weakens a bit and the mid
level northwest flow pattern to the northeast starts to get
increasingly active - perhaps close enough to brush into eastern
Kentucky with its periodic impulses as they pass through the
central Appalachians. Heat headlines may yet be warranted for at
least the western parts of the area at midweek - still dependent
on how effectively higher dewpoints can move east into this part
of the state.
The previous long term discussion follows:
The main story of the long term period will be heat. On Tuesday
morning, there is high confidence that an anomalously strong upper
level ridge will sit directly over Kentucky. LREF mean 500-mb
heights reach 595 dam across the forecast area, representing the
99th percentile when compared to climatology, with minimal spread
among ensemble solutions. Subsidence associated with this ridge
should suppress convection, keeping weather dry and PoPs near zero
through at least midweek. Meanwhile, at the surface, high pressure
over the Southern Appalachians will keep winds out of the southwest
across the forecast area, maintaining a moist air mass across
eastern Kentucky. There is still some uncertainty regarding how high
dewpoints will climb, owing to model disagreement regarding the
exact positioning of the surface high (and associated wind pattern);
however, ensemble guidance indicates dewpoints in the mid to upper
60s are likely, with raw NBM output even suggesting widespread
dewpoints in the 70s (with the highest dewpoints in our southwestern
counties). Given that both ensemble and deterministic guidance favor
a drier solution, these NBM dewpoints are likely overdone, and
forecast dewpoints were nudged down a few degrees to better match
model consensus at this time. Should this hold, we will narrowly
avoid hitting heat advisory criteria, though apparent temperatures
could reach the triple digits. Regardless, expect hot and humid
weather on Tuesday and Wednesday. High temperatures will generally
range from the mid to upper 90s, with the hottest temperatures
closer to the I-64 corridor. Overnight, limited relief is expected;
lows on Tuesday and Wednesday nights will range from the upper 60s
in sheltered valley locations to the low 70s on ridges, with typical
valley fog formation likely.
A pattern change is expected on Thursday as upper level troughing
over the Northeast digs southward, flattening and weakening the
ridge over Kentucky. There is still some disagreement over how
quickly this ridging will break down over us; however, high
temperatures should cool from Thursday onward, and rain chances look
to increase through the end of the period. With a trend toward
northwesterly flow, pattern recognition suggests that this setup
could open the door for multiple shortwave impulses to ride the
periphery of the ridge. In fact, deterministic guidance shows a
signal for MCS type activity to develop in the Midwest and progress
southeastward with time, potentially into our area. That being said,
the track of any convective complexes would depend on the position
and strength of upper level ridging. Unfortunately, models disagree
significantly on these details on Thursday and Friday; the ECMWF
favors a more quasi-zonal pattern aloft during this time, while the
GFS keeps flow more northwesterly, with a much more amplified ridge
to the west over the Mississippi Valley. In both scenarios, some
scattered showers and storms would be possible on Friday, but
confidence in any further forecast details remains very low at this
time.
By the weekend, models come into better agreement regarding a more
robust northwest flow pattern aloft as ridging continues to amplify
over the Plains. Meanwhile, at the surface, a weak cold front will
sag south into the forecast area, providing additional forcing for
more focused shower and storm chances, although details again remain
quite uncertain at this stage in the forecast. Thankfully,
temperatures will fall closer to normal around this time, bringing
an end to any heat concerns.
&&
.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 750 AM EDT MON AUG 31 2026
High pressure in place across the region will result in valley
fog through 13Z. This is not expected to affect any of the TAF
sites and VFR should return to all locations by 14Z. Through then
we may also see some sprinkles fall over the northern terminals
but no impact to aviation operations is anticipated. Thereafter,
diurnally driven cumulus clouds in the 3 to 5 kft agl range are
expected to develop by the 16Z to 18Z timeframe though these
should remain in the VFR range. Winds will be light through the
period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...GREIF
SHORT TERM...GREIF
LONG TERM...FAGAN/GREIF
AVIATION...GREIF
Source: JKL issues Area Forecast Discussion (AFD) at Aug 31, 7:50 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202608311150-KJKL-FXUS63-AFDJKL-AAA)
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