744
FXUS63 KJKL 200526
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
126 AM EDT Thu Jun 20 2024

.KEY MESSAGES...

- Hot and mainly dry weather will occur through the weekend.
  Afternoon heat indices will peak near 100 at some locations.

- The upper level high/ridge bringing our heat wave will weaken
  during the weekend and eventually allow a cold front to at least
  approach the area, with the PoPs peaking in the 40-50% range
  Sunday night ahead of the front.

- Uncertainty now exists concerning the progress of the cold front
  next week and whether or not a substantially drier air mass will
  arrive. A small PoP is maintained into next week due to this
  uncertainty.

&&

.UPDATE...
Issued at 1130 PM EDT WED JUN 19 2024

No significant changes to the forecast with just the inclusion of
the latest obs and trends for the T/Td/Sky grids with this update.
Did also tinker a bit with the low temperatures into Thursday
morning. These minor adjustments have been sent to the NDFD and
web servers along with a freshening of the zones and SAFs.

UPDATE Issued at 740 PM EDT WED JUN 19 2024

23Z sfc analysis shows a moderately strong area of high pressure
centered east of Kentucky. This has helped to maintain the very
warm and dry weather in place over this part of the state.
However, ample clouds of varying thickness kept the highs in
check this past afternoon and likewise prevented the heat indices
from reaching their potential. The clouds will gradually thin and
clear out through the night allowing for a decent ridge to valley
temperature split to develop along with some, mainly river valley,
fog. Currently, temperatures are running in the low 80s most
places - though some upper 70s are noted in a few of the valleys.
Meanwhile, amid light and variable winds, dewpoints have backed
off just a tad and are now running generally in the mid to upper
60s. Have updated the forecast primarily to tweak the sky cover
and fog threat through the night but also to include the latest
obs and trends for the T/Td grids. These minor adjustments have
been sent to the NDFD and web servers.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 350 PM EDT WED JUN 19 2024

The models were in good agreement regarding the large scale flow
pattern aloft in the short term. A strong ridge of high pressure
will be in place across most of the eastern third of the CONUS to
begin the period, and will be the dominant weather feature for
eastern Kentucky. Persistent, fairly widespread high clouds, along
with scattered low clouds, will steadily dissipate this evening and
tonight, and should give way to mostly clear skies overnight. A
couple of models did try to push a weak disturbance aloft through
the region, sparking isolated showers and storms over portions of
the area on Thursday, especially during the afternoon. However,
confidence in this scenario unfolding is quite low at this time, due
to the strength of the ridge that will be in place and the amount of
dry air that is expected to be in place through out the low levels
of the atmosphere. For those reasons, we kept precip chances well
below 15% for tomorrow, but still within tolerance with our
neighbors to the north and west. An increase in cloud cover is now
included on Thursday to account for the potential passage of the
weak disturbance aloft over the surface ridge during the afternoon.
That all being said, it still appears that Thursday will be dry.

As for tonight, with ridging in place nearly overhead, very light
winds, and steadily decreasing cloud cover, the stage will be set
for at least a modest ridge valley temperature split. Fog will also
possible again tonight for the same reasons the temperature
differences are possible. With much less cloud cover in the forecast
for tomorrow than what we saw today, and with ridging still in
place, we should see temperatures warming into the lower 90s around
the area. Heat index values in the low to mid 90s will be possible
as well.

.LONG TERM...(Friday through Wednesday)
Issued at 350 PM EDT WED JUN 19 2024

A broad upper level high centered over the Tennessee and lower Ohio
valleys at the start of the period will be weakening and dropping
further south as we move into the weekend. This process will be
helped along by a couple of shortwave troughs traversing through the
prevailing westerlies aloft to our north. They will lead to a larger
low/trough developing and tracking eastward through the Great Lakes
and northeast CONUS region Saturday into Tuesday. This will send the
southern edge of the faster flow aloft southward over the eastern
CONUS, with initially west and then northwest flow occurring over
our area.

The evolution of the upper level pattern will allow a cold front to
at least approach our area at the start of the new week. A rather
amorphous surface pattern with little air flow over our area at the
beginning of the period will give way to southwesterly winds ahead
of the cold front by Sunday. This should bring a flow of warm, moist
air over the region ahead of the front. Along with gradual cooling
aloft as geopotential heights fall, it could allow for some limited
deep convection Saturday and Sunday. This is shown in the GFS, but
not the ECMWF. However, the low level moisture in the ECMWF seems
too limited (surface dew points only in the upper 50s to near 60),
and have decided to make a mention of a slight chance of precip.

There is growing disagreement in the models regarding the eventual
progress of the cold front. The GFS is becoming less aggressive
and has the front stalling and dying without any meaningful change
in our air mass. This allows periodic convective precip through
Wednesday. Meanwhile, the ECMWF as of its 00Z run still had a
definitive cold fropa on Monday, with a much drier air mass
arriving behind it. Either model supports at least a modest
increase in POP to chance category Sunday night. The question is
what happens after that. Given the trend of the GFS and the
forecast uncertainties, a low POP mention is being included
through Wednesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
ISSUED AT 126 AM EDT THU JUN 20 2024

00z statistical guidance has trended more aggressive with fog
formation at most if not all terminals between 06z and 12z-13z
this morning. Have thus included either a TEMPO or prevailing
groups for fog formation. Many TAF sites are reporting near or at
100 percent humidity, which lends a bit more confidence that fog
formation at at least some of the terminals will occur. Otherwise,
VFR conditions are expected through the TAF period. Winds will
average between southerly and easterly at less than 5 kts through
the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GREIF
SHORT TERM...AR
LONG TERM...HAL
AVIATION...CMC