-- Discussion containing changed information from previous version are highlighted. --
520
FXUS63 KJKL 220102 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
902 PM EDT Tue May 21 2024

.KEY MESSAGES...

- Dry weather is expected area wide through Wednesday morning.
  High temperatures may approach or exceed record levels this
  afternoon.

- There is a potential for showers and thunderstorms at times from
  Wednesday afternoon through Monday.

- Very warm temperatures will persist through Wednesday. An
  increase in clouds and the possibility of rain will bring
  somewhat lower temperature after that.

&&

.UPDATE...
-- Changed Discussion --
Issued at 901 PM EDT TUE MAY 21 2024

Hourly grids were freshened up based on recent observations and
trends. The Afternoon convection diminished and a fresh ZFP was
sent accordingly. Some valley fog should again develop around or
shortly after midnight, with likely a bit less coverage compared
to last night as most locations remained rain free today.
-- End Changed Discussion --

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 308 PM EDT TUE MAY 21 2024

The afternoon surface analysis shows high pressure is posted up
along the Mid-Atlantic coast. Meanwhile, a low pressure and cold
front is pushing into the Midwest. In the mid-levels, a shortwave
trough axis is pushing eastward into the Midwest. We see subtle
mid-level height rises in the Lower Ohio Valley ahead of this
negatively tilting trough axis. This shortwave ridging will keep
our weather mostly quiet through the afternoon into tonight.
However, an isolated (chances of rain around 15-20 percent) shower
or thunderstorm remains possible through the afternoon before we
loose the diurnal heating and perhaps a weak shortwave noted
pushes east. After this, expect mostly clear skies to prevail
tonight, with some patchy to areas of fog mainly along the river
valleys late tonight into Wednesday morning.

Wednesday, the previously mentioned cold front will move eastward
toward the Ohio Valley late tonight into Wednesday. There is decent
agreement in the ensembles and deterministic guidance that
another low will develop along the weakening frontal boundary.
Particularly, as another shortwave is noted in the mid-levels
pushes east. However, the better height falls in the mid-levels
comes later in the day. Given the nearby cold front and some
shortwaves riding through the flow expect shower and thunderstorm
chances to increase through the day, with rain chances increasing
to 20-50 percent in the afternoon. SPC does have a risk of some
scattered severe weather for Wednesday, but overall the risk seems
low. However, if we can build some instability in the 1000-2000
J/kg of MUCAPE you would have decent kinematics to work with, as
effective shear climbs to around 30-40 knots. The best chance of
stronger storms would be generally along and north of the
Mountain Parkway. The main threat would be an isolated damaging
wind threat. We will not be as warm as the last few days owing to
cloud cover, with highs climbing into the lower to mid 80s in most
cases. Wednesday night, the diffuse cold front will stall out
nearby, with showers and thunderstorm chances continuing into the
night. Particularly given many of the CAMs, ensembles and
deterministic models show a shortwave trough riding through the
flow. This will lead rain chances around the 30-60 percent range.

.LONG TERM...(Thursday through Tuesday)
Issued at 422 PM EDT TUE MAY 21 2024

Overall the extended is characterized by a a series of short wave
disturbances riding through a general low amplitude, broad zonal
flow aloft. Operational models show a general agreement with the
timing and strength of most of these disturbances through the
period, particularly the stronger ones. At the surface and by the
start of the period, a frontal boundary has dropped into the Ohio
River Valley. While this feature tends to wash out with time,
there is enough of a residual presence that the threat of showers
and thunderstorms will persist through the period, with PoPs
peaking with each particular disturbance that tracks through the
region.

Sensible weather features a seasonably warm and unsettled
extended. Temperatures will average around or slightly above
normal, or generally upper 70s to lower 80s for daily highs.
Overnight lows will tend to run in the 60s until the very end of
the period, where some mid and upper 50s will possible. Hazards
are limited to thunderstorms and an occasional round of locally
heavy rain. The Storm Prediction Center has a portion of our
southwest forecast area in a Slight risk for severe weather on
Sunday. This potential would seem reasonable with MUCAPEs climbing
to around 2000 J/kg combined with 40-50 kts effective shear. This
time frame is still far out in time and things will change a bit
between now and then. Otherwise, there could be periods of locally
heavy rain as well. The weather Prediction Center has expanded
its Marginal threat area for Day 4, Saturday, to cover all of
eastern Kentucky. More to come on all of these threats as we get
closer to the times of interest.

&&

.AVIATION...
-- Changed Discussion --
(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 835 PM EDT TUE MAY 21 2024

Lingering cumulus and altocumulus continues to diminish with just
some high clouds working through portions of the OH Valley region.
VFR was reported at issuance time and VFR should prevail through
the period. Other than fog in the deeper valleys that is not
expected to affect the TAF sites, VFR should largely prevail.
However, isolated to scattered convection is expected from around
15Z on, and this could lead to some brief reductions to MVFR or
perhaps lower. Winds will be light and variable through 14Z in
valleys while south to southwest winds averaging less than 10KT
are anticipated on the ridges and in areas of more open terrain
during that time. Then winds will become southwest areawide to end
the period at generally 5 to 10KT, with some gusts possibly
nearing 20KT.
-- End Changed Discussion --

&&

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

$$

UPDATE...JP
SHORT TERM...DJ
LONG TERM...RAY
AVIATION...JP