668
FXUS63 KJKL 211123
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
723 AM EDT Fri Jun 21 2024

.KEY MESSAGES...

- Hot and mainly dry weather will continue 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 still 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.

&&

.UPDATE...
Issued at 720 AM EDT FRI JUN 21 2024

There are no changes with the early morning update. Fog has not
been as deep in the valleys as yesterday morning, which makes
sense given an extra day of drying. Hourly observations were
blended into the forecast for seamless transition and continuity.
With no changes, only the NDFD database is updated, but fresh
zone forecasts will be sent out once the fog has burned off.

&&

.SHORT TERM...(Today through Saturday)
Issued at 358 AM EDT FRI JUN 21 2024

Hot and humid weather continues under a gradually weakening (yet
still quite strong) upper level high/ridge. Main question mark
for both this afternoon and Saturday afternoon is whether we see a
stray shower or thunderstorm develop across the area. The most
likely area we would see such development in on the high terrain
near/along the Virginia border, such as Pine and/or Black
Mountains. For these areas, kept PoPs just under the 15 percent
threshold needed for inclusion in the official forecast.

After a couple of slightly cooler days, highs will rise about a
degree or two each day into the lower to mid 90s, with heat
indices in the upper 90s to a few locations in the lower 100s.

Lows tonight should be quite similar to previous nights, and fall
on the upper end of the NBM probabilistic range, especially on
ridges, with upper 60s to lower 70s. Expect the typical nighttime
and early morning fog in the sheltered river valleys.

.LONG TERM...(Saturday night through Thursday)
Issued at 314 AM EDT FRI JUN 21 2024

We finally transition out of a dominating upper level ridging
pattern by the extended portion of the forecast, though it does look
to make it`s way back into place by next weekend. As the ridge loses
control across the region, this opens us up to a more active weather
period. It also allows for a bit more temperature swings as frontal
systems near and move through.

The upper level ridge will suppress southwestward during the
weekend, giving way to lowering heights across the Ohio Valley by
Sunday. This will be amplified by a shortwave turned upper level
low, which will move through the Upper Great Lakes Sunday afternoon
and night, then the Lower Great Lakes on Monday. A surface low will
be associated with this system, and will provide a cold front
stretching to the SW. The front will sink southward into Kentucky by
Sunday night, spreading pops across the state during the day Sunday.
It will then pivot SEward, lingering pops across the far eastern
portion of the state (JKL CWA) through much of the day Monday.

By Monday night into Tuesday, the system will exit to the east,
leaving KY in a brief area of high pressure at the surface.
Unfortunately, in such a pattern without an upper level banked ridge
to keep it in place, these surface high pressure systems are short-
lived, as a shortwave begins to develop upstream in south-central
Canada by Tuesday morning. There is quite a bit of disagreement in
the models at this point, but they do at least both show precip
along a frontal boundary which will develop, connected to a surface
low pressure system co-located with the upper level low. This precip
and frontal boundary should move through the state during the day
Wednesday. Again, given the model disagreement by this point, will
stick with the NBM, which shows pops moving in ahead of this system
as early as Tuesday night, ramping up during the day Wednesday. Will
note that both the GFS and ECMWF try to develop a secondary
shortwave across Kentucky for Wednesday afternoon/night, which is
likely the reason for the amplified precip chances and QPF during
this time. This will be a slow moving system, so the front and
lingering precip could continue to impact the CWA through the day
Thursday as well before finally exiting to the east Thursday
evening.

Surprisingly there is decent agreement at this point that another
round of surface high pressure may settle in across the Ohio Valley
for Friday, despite differing upper level solutions. Meanwhile, the
NBM is trying to bring some low-end isolated pops into the southeast
during the afternoon Friday, which doesn`t seem to be reflected in
the models. Wouldn`t be surprised if these were removed by the next
run, but also wouldn`t be surprised if the models completely
changed their solutions over the next few days either.

As for temperatures... This last week has been pretty stagnant,
temperatures in the 90s and humidity making it feel even hotter.
When we transition out of the ridging pattern, this also opens us up
to more temperature fluctuations. As frontal systems near, this will
increase SW flow across the state, providing warmer temperatures and
higher humidity. However, conversely, once the frontal system passes
through, this will bring some cooling NW flow to the region, albeit
even if it`s a few degrees and lower humidity. Tuesday is currently
the hottest forecasted day in the extended, as high pressure settles
overhead for much of the day giving maximum radiational heating,
despite having followed a cold frontal passage. Temperatures may
easily reach the mid 90s in many locations. Thankfully with more W
to NW flow aloft, the humidity hopefully won`t be as bad, but it
will still make it feel several degrees warmer than it already is.
The coolest day of the forecast period is currently Thursday, behind
the departing cold front and with sharper height drops (per the
ECMWF) allowing cooler air to advect in from the NW. Either way,
it`s late June...as long as the sun is shining, it`s likely going to
be a warm one.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 722 AM EDT FRI JUN 21 2024

VFR conditions are expected once any low stratus/fog burns off in
the next hour. A stray shower or storm can not be totally ruled
out yet, but almost assuredly will not impact any of the TAF sites
this afternoon. MVFR viz reductions were included at KLOZ and KSME
toward the end of the TAF period where models are in good
agreement on at least some fog impacts there, at least briefly.

&&

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

$$

UPDATE...CMC
SHORT TERM...CMC
LONG TERM...JMW
AVIATION...CMC