588
FXUS63 KJKL 230459
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1259 AM EDT Mon Jun 23 2025

.KEY MESSAGES...

- Areas of fog, locally dense in some locales, will affect the
  river valleys through mid-morning.

- Heat builds this week. Heat indices peaking in the 100 to 105
  degree range are forecast for many locations through Saturday.

&&

.UPDATE...
Issued at 1259 AM EDT MON JUN 23 2025

Satellite imagery already shows tendrils of fog developing through
the deeper southeastern/southcentral Kentucky valleys, especially
where rainfall occurred yesterday afternoon and evening. Look for
this fog to continue expanding in coverage through the remainder
of the overnight and become locally dense. It will be muggy
overnight with low temperatures only in the upper 60s to lower 70s
at most locations.

Looking ahead to Monday, a slight chance of shower and
thunderstorms was added to the forecast across most of eastern
Kentucky during the afternoon hours. While convective coverage is
likely to be less than today, strong differential heating under an
uncapped atmosphere has the potential to support isolated popup
showers and thunderstorms. The most likely areas for convective
initiation will be over the higher ridges along the Kentucky/
Virginia and Kentucky/Tennessee borders as well as near/along the
Pottsville Escarpment. Any shower/storm that does develop could
produce a downpour and gusty winds.

UPDATE Issued at 919 PM EDT SUN JUN 22 2025

Leftover deep convection has dissipated with the loss of daytime
heating. Forecasts and HWO have been updated to remove mention of
showers/thunderstorms through the remainder of tonight.

UPDATE Issued at 755 PM EDT SUN JUN 22 2025

Isolated to scattered showers and thunderstorms, mostly over the
Cumberland River Basin near/west of I-75, have begun to diminish
as the sun prepares to set. Expect this trend to continue with all
locations likely rain-free within a couple of hours. Fog is
likely to develop again overnight and is favored to become locally
dense as the combination of clear skies and light low-level winds
allow for efficient radiational cooling in an increasingly muggy
air mass (afternoon dew points were roughly 5 to 8 degrees higher
than yesterday`s). At least patchy fog is possible outside of the
river valleys, and especially in locations which experienced
rainfall this afternoon and evening.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 455 PM EDT SUN JUN 22 2025

20Z sfc analysis shows high pressure off to the southeast of the
state. This, combined with a building ridge aloft, is keeping
convection somewhat limited through the area though the Cumberland
Valley is seeing some activity, mainly in the form of showers and
sprinkles. Otherwise, it is quite a hot day with heat indices
approaching 105 degrees in the Bluegrass area. For that reason we
have started the Heat Advisories for those counties this
afternoon and both northwest and northeast potions of the CWA for
Monday and Tuesday with a potential to expand in time and areal
coverage into midweek. Currently, readings are generally in the
upper 80s to lower 90s while sticky dewpoints are running in the
upper 60s and lower 70s.

The models, and their individual ensemble suites, are still in
excellent agreement aloft through the short term portion of the
forecast. They all depict strong 5h ridging building over the
region - holding in place through Tuesday morning and beyond.
This will keep the mid level impulses far away from Kentucky with
weak flow overhead. However, it seems that this ridge is not
capable of completely shutting down convection lacking a warm
capping layer of temperatures aloft. The very small model spread
through Monday night supported using the NBM as the starting point
for the forecast grids with minimal adjustments needed - mainly
just to add some limited terrain details for temperatures each
night - though capped by high dewpoints.

Sensible weather features the heatwave starting in earnest today
with the first 90s of the season for many locations. This warmth
continues into the nights with only a slight extra drop off in
temps for the valleys compared to the ridges. Again we will also
see some locally dense fog in the valleys and near bodies of water
each night. Similar conditions to today will be in place for
Monday with highs again in the low 90s most places along with a
chance for a stray shower or storm in the southern parts of the
CWA during the afternoon into early evening.

The changes to the NBM starting point were primarily focused on
temperatures each night for some slight terrain differences. PoPs
and Wx were too quiet in the NBM so incorporated the CAMs guidance
for a stray threat of convection in the afternoon and early
evening on Monday.

.LONG TERM...(Tuesday through Sunday)
Issued at 400 PM EDT SUN JUN 22 2025

The period is expected to begin with a 597 dm+ 500 mb ridge
centered in the Southern Appalachians/western VA/western NC to WV
area, though it is expected to be flattening at that point as
multiple shortwaves move from an upper level trough extending from
over the western Conus to Northern Plains/Upper MS Valley to the
Great Lakes and Northeast. Additionally, shortwaves are expected
to move near the US/Canadian border as well. At the surface, an
area of low pressure associated with an upper trough moving
across eastern portions of Canada is anticipated to be initial
centered over Quebec with a cold front/frontal zone trailing to
Lake Huron and MI to the Central Plains with much of the southern
and eastern COnus in the warm sector with a ridge of sfc high
pressure centered in the Southern Appalachians/Tri Cities of VA
and TN vicinity.

Tuesday to Wednesday night, guidance generally has trended toward
the center of the ridge retrograding west and southwest to the Lower
OH Valley to TN Vally to mid to lower MS Valley regions Tue to Wed
and weakening and becoming more east to west oriented and extending
from parts of the Atlantic across the mid Atlantic states to Central
Appalachians to OH Valley. This will occur as multiple systems
move near the US/Canadian border and across portions of eastern
Canada and the Great Lakes to the Northeast and Maritimes and an
upper level low/trough develops between Bermuda and the Bahamas
and then moves west to near the Bahamas to perhaps as far west as
the FL peninsula by late Wednesday night. At the surface, a ridge
of sfc high pressure should remain in place from the central to
southern Appalachians to the Lower MS Valley/much of the Southeast
weakening a couple of mb gradually while the frontal zone to the
north eventually sags across the Northeast to the mid Atlantic
states to the Southern Great Lakes to Central Plains.

Across eastern KY heat will have already been building in the short
term period and as we enter this timeframe overnight recovery is
expected to become increasingly poorer with low generally in the
70s. Meanwhile the airmass should warm into the 90s, generally mid
90s with some upper 90s possible in the deeper valleys/lower
elevation communities in the Big Sandy and KY river valleys. At
the same time, even during peak convective mixing, dewpoints near
the time of the Max T per the guidance consensus in the upper 60s
to mid 70s range. This should result in heat indices peaking in
the around 100 to around 105 degree F range both days with
temperatures in some places falling below 75 degree F only
briefly. This should get some portions of the region very close to
Heat Advisory Some pop up convection cannot be completely ruled
out by Wednesday particularly nearer to the VA and TN borders
where differential heating over the Cumberland Plateau or
Cumberland Mtns or perhaps an outflow from convection that
develops nearer to or northwest of the crest of the Appalachians
nearing the region becoming a trigger as the upper ridge becomes
weaker with capping perhaps be a bit less robust by that point. At
this point, opted to mostly maintain the NBM PPI06 for pops which
were under 15 percent in most areas. However, given guidance
trends and in collaboration with surrounding WFOs included a 15
percent pop in small portions of Pike to Harlan Counties for both
Tuesday and Wednesday afternoons near Pine and Black Mtns near
the VA border. As these days approach guidance should help fine
tune whether or not slight chance pops may be warranted for more
portions of the area. ECMWF, ENS based EFI has Max T for Tuesday
and Wednesday above the 80th percentile climatologically for the
5 week period centered around this week for much of the JKL CWA
with eastern portions of the area above the 90th percentile.
Overall, the heat likely peaks Tuesday to Wednesday and it is
probable that an areal and temporal extension of the ongoing heat
advisories to be needed, though if pop up storms were to form
lower peak heat indices would be possible. The current forecast
is for 94 at JKL and 95 at LOZ for Tuesday the 24th and Wednesday
the 25th. For the 24th, that would break the record at JKL of 92
from the warm summer of 1988 while at LOZ the current forecast
would break the record of 94 set in 1988 and tied in 2012. For
the 25th record highs are more robust.

Thursday into Friday night, guidance varies with the positions and
strength of upper level ridging as the upper low initially over
or near FL moves into the Southeast. The recent operational ECMWF
runs have a weakness or weak troughing from the Southeast into
parts of the Central to Southern Appalachians on Friday, while
recent GFS runs have lower heights/weak upper low over the Gulf
into the Southeast and higher heights across the entire
Commonwealth, Appalachians into the mid Atlantic States with
upper level ridging from the eastern Atlantic west toward eastern
KY generally stronger through Friday and Friday night. Further
north and west, stronger westerlies are forecast to remain from
the Northwest Conus near or North of the US/Canadian border into
eastern Canada and the Northeastern Conus with weak trough into
lingering over parts of the western Conus though the guidance
consensus is for that troughing to be weaker overall by late
Friday into Friday night with heights rising over the Southern
Rockies/Four Corners to Southwest Conus areas. one more notable
shortwave trough is generally progged to move from the Northern
Plains/Dakotas to parts of the Great Lakes during this time. At
the surface, a ridge of sfc high pressure should remain in place
from the Southern Appalachians to parts of the Southeast while the
frontal zone that will be nearly stalled out from the mid
Atlantic states into the Great Lakes should make little southward
progress while further west it lifts north toward the upper MS
Valley as a warm front in response to a surface low tracking
across parts of Canada in advance of a shortwave tracking also
near the northern US border area. During this timeframe, with the
high anticipated to weaken, and a moist airmass remaining in
place, diurnal heating should be sufficient for greater coverage
of afternoon to evening convection as compared to Tuesday and
Wednesday with isolated to scattered coverage forecast for
Thursday with more in the way of scattered development for Friday.
If less convective development occurs both days, peak heat
indices currently forecast in the 100 to 105 degree rang for some
areas could be at the upper end of that range.

Next weekend, recent operational ECMWF runs have lower heights
across eastern KY/weak troughing from the Southeast into parts of
the Appalachians while the GFS continues into Saturday with a
trend of higher heights from the mid Atlantic coast to the
Central Conus to Southwest Conus. There is run to run variability
with troughing from western Canada into the Northwest Conus to
Northern Rockies vicinity that gradually is progged to shift east
into Central portions of Canada into the Northern Plains to upper
MS Valley with a trend to height rises across parts of the Great
Basin toward the Northwest Conus toward the end of the period. The
recent GFS runs maintain slightly higher heights over the
Commonwealth during this time as compared to the ECMWF runs while
a shortwave trough is progged to move from the Central Great Lakes
to the eastern Great Lakes to Northeast to end the period. There
remains quite a bit of spread in guidance as far as heights and
the possible timing of weaker shortwaves that could be a trigger
for convection. With generally less capping than earlier in the
week, diurnal development could be more substantial into the high
chance to likely range for both Saturday and Sunday afternoons
Guidance generally agrees that the heat relaxes/high temperatures
will not be quite as warm as earlier in the week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1259 AM EDT MON JUN 23 2025

At TAF discussion issuance time, very poor flying conditions due
to FG were noted at SME but the remaining TAF terminals were
still VFR. Through the remainder of tonight, FG/BR coverage will
increase through the valleys and should eventually deepen up to
the adjacent ridgetops. While the worst impacts are expected at
SME, FG/BR is expected to eventually spread into and affect the
remaining TAF sites closer to sunrise. The FG/BR will lift/
dissipate after sunrise Monday. Winds will generally be variable
under 5 kts.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Tuesday for KYZ044-050>052-058>060.

Heat Advisory from 11 AM this morning to 8 PM EDT Tuesday for
KYZ104-107-110-119-120.


&&

$$

UPDATE...GEERTSON
SHORT TERM...GREIF
LONG TERM...JP
AVIATION...GEERTSON