883
FXUS63 KJKL 200732
AFDJKL

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

.KEY MESSAGES...

- Areas of locally dense fog in some valley locations may cause
  sharply reduced visibility early this morning.

- 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 to 60 percent
  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. For this package, Monday night through Tuesday afternoon
  were left dry, but with precipitation and thunderstorm chances
  returning late Tuesday night and continuing through Wednesday
  night.

&&

.SHORT TERM...(Today through Friday)
Issued at 329 AM EDT THU JUN 20 2024

Statistical guidance late last evening trended more aggressive
with fog potential for the early morning hours, and this has
materialized as fog has been more widespread and more dense than
in previous early morning periods recently. Have included mention
of this in the HWO product, but will withhold any other products
at this time. The fog will burn off by 9 AM this morning.

The models are in good agreement regarding the large scale flow
pattern aloft in the short term. A strong ridge of high pressure
remains 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 through Friday. A couple of models still try to
push a weak disturbance aloft through the region, sparking isolated
showers and storms over portions of the area later today, 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% today still. An
increase in cloud cover is now included today 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 today will be dry.

With overall less cloud cover today, expect high temperatures to
rebound back into the 90s for many locations, through with more
cloud cover forecasted than initially expected in the northwest
part of the CWA, highs may trend nearer to 90 degrees with perhaps
a few upper 80s.

For tonight, expect mostly clear to partly cloudy skies with the
typical fog forming in the river valleys. Lows in some of the
typically cooler sheltered valleys have remained elevated by a few
degrees from expectation the last couple of nights, especially in
the Upper Kentucky River Basin, so this will need to be watched in
case lows need to be raised back a couple of degrees. Nevertheless,
the current forecast calls for lows in the mid 60s to lower 70s
tonight.

PoPs rise somewhat Friday afternoon but still remain below the 15
percent threshold for mention in the forecasts and grids. This is
due to a disturbance moving southeast from the Midwest toward the
Carolinas, which is likely to also bring some increase in cloud
cover. This will do little to keep highs from once again reaching
the 90s, with heat indices once again approaching 100 degrees.


.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.
&&

$$

SHORT TERM...CMC
LONG TERM...HAL
AVIATION...CMC