227
FXUS63 KJKL 182018
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
418 PM EDT Sat May 18 2024

.KEY MESSAGES...

- Dry weather expected area wide from Sunday through Tuesday
  night.

- Rain chances ramp back up Wednesday into Saturday.

- Warm weather will be the story Sunday through Wednesday, with
  afternoon highs topping out in the mid to upper 80s.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 417 PM EDT SAT MAY 18 2024

A very slow eastward moving, positively tilted upper trough lies
overhead late today. Drying aloft is making its way in from the
north as the trough advances. This is helping to limit
convection. Extensive clouds in the south also limited
heating/destabilization and have helped to hold back convection
there, despite greater deep moisture as compared to the north.

As the trough continues heading east and heating is lost, any
remaining precip will die out tonight. Much drier air aloft and
clearing skies will allow for good radiating conditions.
Meanwhile, only slightly drier surface air will try to advect in
on weak north to northeast flow. The combination will favor fog
development. Will expect it to be abundant in valleys, growing in
breadth and depth with time during the night.

As heating occurs on Sunday morning, the fog will dissipate and
likely transition to a rising cu deck. Although forecast soundings
show development of weak mixed layer CAPE which is deep, it is a
skinny profile in an extremely dry atmosphere aloft. Without upper
level support, it`s unlikely that convective columns will be able to
persist and develop precip, and a dry forecast is being used on
Sunday.

The same regime aloft carries through Sunday night. With cu drying
up and giving clear skies, along with weak low level flow, valley
fog will again develop. However, after good mixing and a bit more
drying during the day Sunday, the fog should be a little more
restricted.

.LONG TERM...(Monday through Saturday)
Issued at 338 PM EDT SAT MAY 18 2024

The period begins with shortwave ridging extending into the
Northeast states. This ridging will keep the weather quiet and warm
through mid week ahead of an advancing cold front, with good
agreement noted in the ensembles and deterministic guidance. The
afternoon high temperatures Monday and Tuesday are forecast to climb
into the mid to upper 80s. By Wednesday, we see the leeside low that
develops Monday night will be pushing northeast into the Great Lakes
and Canada by Tuesday night. While there are slight differences in
the guidance during this period the overall pattern looks fairly
close.

It gets a little trickier across the Ohio Valley going into mid-
week. This is because the various ensembles and deterministic are
struggling on how far south and east this cold front can go given
it looses the greater upper level support and the low pressure
pushes northward further into Canada. Right now, it looks like the
diffuse cold front would arrive Sometimes Wednesday night into
Thursday. This would usher in better chances of showers and
thunderstorms, with around a 20-40 percent chance Wednesday and
50-60 percent chance Thursday. Now there have been some indication
in machine learning products of severe weather potential with
this system. If this was to occur it would be late Wednesday into
Wednesday night before better storms arrive based on the latest
trends. However, confidence is low given the better shear and
instability stay northwest of the area.

Past this the guidance becomes more divergent, but it looks like
another mid-level shortwave rides in Friday. This would lead to a
renewed chance of showers and thunderstorms going into the weekend,
as an area of low pressure forms along the left over boundary
mentioned above. The best chances of showers and thunderstorms
right now would be Friday at 50-60 percent.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
ISSUED AT 238 PM EDT SAT MAY 18 2024

A mix of VFR and MVFR conditions (due mainly to ceilings) were
present at the start of the period. While most showers present
during the morning had dissipated, renewed development with
daytime heating/destabilization was starting.

A general improvement to VFR is expected by late afternoon as
ceilings continue to rise. However, additional development of
showers and possibly thunderstorms will lead to localized
sub-VFR conditions in the heavier precipitation. The showers and
thunderstorms will die out this evening and most clouds will dry
up. Good radiating conditions will lead to development of valley
fog late tonight. It will grow in breadth and depth through dawn,
but exactly how widespread it becomes is uncertain. At this
point, the best estimate is that TAF sites will be IFR at least at
times. The fog will dissipate early Sunday morning, leaving VFR
conditions through the end of the period.

&&

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

$$

SHORT TERM...HAL
LONG TERM...DJ
AVIATION...HAL