JKL issues Area Forecast Discussion (AFD) at Sep 15, 2:05 PM EDT887
FXUS63 KJKL 151805
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
205 PM EDT Tue Sep 15 2026
.KEY MESSAGES...
- Above normal temperatures return for today through Saturday.
- Near-record heat is possible Thursday with high temperatures
expected around 90 degrees in many locations.
- Isolated to scattered showers and storms re-enter the forecast
on Thursday afternoon, then persist through the weekend. Most of
this activity will be limited to the afternoon/evening hours.
&&
.UPDATE...
Issued at 720 AM EDT TUE SEP 15 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.
These minor adjustments have been sent to the NDFD and web servers
along with a freshening of the zones.
&&
.SHORT TERM...(Today through Wednesday)
Issued at 430 AM EDT TUE SEP 15 2026
08Z sfc analysis shows high pressure northeast of the state
controlling the weather for eastern Kentucky. This has resulted in
a cooler night than we have seen in quite some time with clear
skies and areas of fog in the river valleys - locally dense in the
east. Meanwhile, amid light winds, temperatures range from the
the upper 50s north (and in the mid 50s for many of the sheltered
valleys) to the lower 60s over much of the south. Dewpoints
likewise varied from the mid 50s north to the lower 60s in the
south.
The models, and their individual ensemble suites, still continue
to be in close alignment aloft through the short term portion of
the forecast. They all depict an anomalously very strong 5h ridge
over the region holding firm through Wednesday evening with its
core pushing a rare 600 decameters over the heart of the Tennessee
Valley by that afternoon. This will keep all mid level activity
well to the north of the state and the full effect of the ridges
suppression will be in place over eastern Kentucky. Again
considering the very small model spread, much of the forecast
grids came from unadjusted NBM data this morning. However with the
lower dewpoint air in place today did include more terrain
distinction again tonight for the temperatures and lows tonight
while also drying out each afternoon's dewpoints to account for
deeper mixing and more dry air intrusion that allows. As for
PoPs, again saw no reason not to keep them at the NBM's near zero
values through the period while high pressure holds at the sfc
from the east and a front stays stuck well to the north.
Sensible weather will feature a decent amount of fog in the river
valleys - thickest in the southeast ones where dewpoint
depressions were smaller. Plenty of sunshine and warm air aloft
will send temperatures soaring across Kentucky today with similar
values anticipated for Wednesday. Both days will see Heat Indices
approach 100 degrees for a few spots in the west, but most of the
area will see values well away from Heat Advisory levels thanks to
drier afternoon humidity levels. For tonight, we can expect more
in the way of radiational cooling and a ridge to valley
temperature split favoring the MOS values for lows in the
sheltered low spots along with more in the way of late night river
valley fog.
The main changes to the NBM starting point were made to
temperatures and dewpoints - adjusted the T grids tonight for more
enhanced terrain details and the dewpoints lower during each
afternoon owing to a mixdown drier air. As for PoPs, they were
kept minimal and pretty much just as populated from the NBM -
again reasonable given the strong ridging holding aloft through
the breadth of the short term forecast period.
.LONG TERM...(Wednesday night through Monday)
Issued at 400 AM EDT TUE SEP 15 2026
The extended portion of the forecast remains on track with the
idea of a large 5h ridge weakening and drifting southwest a bit
through the rest of the week and into next weekend. This could
perhaps include the eastern Gulf or coastal southeast region
becoming more active late in the period - not necessarily a
recipe for helping to clear a 5h ridge to the north. The net
result will continue to mean temperatures staying unseasonable
warm and a limiting factor to the potential for widespread rain
for much of the time.
The previous long term discussion follows:
Ridging remains the dominant synoptic-scale weather feature across
the Eastern Kentucky for the duration of the long term forecast
period. When the period opens on Wednesday morning, a nearly 600
decameter ridge will be centered over the Tennessee River Valley, or
just to the south of the forecast area. The strength of this ridge
is quite impressive. These modeled geopotential heights rank among
the upper echelon of model climatology for this time of year. In
fact, mean LREF heights of 600 dm sit at the 100th percentile of
the dataset. This signal has been present in the data for multiple
runs in a row, which bolsters forecast confidence. The proximity
of this anomalously strong mid/upper atmospheric ridging should
accordingly yield mostly dry and unseasonably warm sensible
weather conditions across Eastern Kentucky. On Wednesday, expect
high temperatures in the lower 90s, mostly sunny skies, efficient
diurnal mixing processes, and overnight ridge-valley temperature
splits. Valley lows in the mid/upper 60s should be sufficient for
patchy fog formation near sources of water, while ridgetops and
the more exposed western locales could stay closer to the 70
degree mark.
Confidence in these dry/hot conditions is highest on Wednesday, as
the parent ridging will be closest to the JKL CWA in this time
frame. Large-scale subsidence and antecedent dry air throughout the
column will largely limit the potential for meaningful convection in
the initial stages of the period. The dry air (and mixed afternoon
dewpoints) should also prevent Eastern Kentucky from reaching heat
advisory criteria. Apparent temperatures peak in the upper 90s, but
remain largely below the triple digit mark. The heat continues into
Thursday, with similar forecast highs in the lower 90s and heat
indices in the upper 90s. While this may be enough to break the
record high at the Jackson climate site, this is only because the
previous record is a "weak" 90 degrees. The pattern actually looks
to shift a little bit on Thursday, and that shift will eventually
culminate in relief from the heat.
As the ridge retrogrades west a little bit, return flow around its
northern periphery will advect a plume of modified Gulf moisture
towards the CWA on Thursday. The presence of this moisture will
likely make it feel a couple of degrees warmer outside in the
western third of the CWA. Those western counties will remain closer
to the center of the ridge and thus under more of its influence.
Locales situated in the Bluegrass and near Lake Cumberland could
flirt with triple digit heat indices on Thursday, but this is
unlikely in counties further to the east. Isolated to scattered
general thunderstorm chances re-enter the forecast on Thursday
afternoon for locations along and east of the Pottsville Escarpment.
Similar, sub-50% PoPs remain in the grids through the weekend,
largely modulated by the diurnal instability cycle. These could
provide some localized pockets of relief from the heat before a more
robust pattern shift emerges early next week. The forecast guidance
suite continues to disagree on how exactly that pattern change
unfolds, but there is a notable increase in the spread between the
25th and 75th NBM temperature quartiles on Sunday and Monday. This
affirms the notion that the increased rain chances correspond with
increased forecast uncertainty surrounding the heat in the latter
stages of the period. However, there is a better-defined downward
trend in the temperatures early next week, with more compact model
spread and median values back in the upper 70s/near 80 degrees.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 158 PM EDT TUE SEP 15 2026
VFR conditions prevail at all TAF sites throughout the 18z
issuance period. Diurnal cumulus development has been observed in
this afternoon's satellite imagery, mostly across Southern
Kentucky. This cu field is not particularly robust due to the
presence of strong midlevel ridging and dry air throughout the
atmospheric column, but it has been included in the TAFs for KLOZ
and KSME. These two terminals are in closer proximity to the
existing and expanding cu field. Light and variable winds are
forecast at all terminals this afternoon. Isolated gusts up to 15
knots cannot be ruled out in locales that experience deeper
diurnal mixing. Once the sun goes down and the diurnal cu/mixing
processes subside, fog will eventually develop in the typical
river valley locales. That fog is not currently forecast to impact
any TAF sites though, and the terminals should remain above P6SM
VFR vsby criteria through tomorrow morning.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...GREIF
SHORT TERM...GREIF
LONG TERM...MARCUS/GREIF
AVIATION...MARCUS
Source:
JKL issues Area Forecast Discussion (AFD) at Sep 15, 2:05 PM EDT---------------
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