-- Discussion containing changed information from previous version are highlighted. --
638
FXUS63 KJKL 070115 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
915 PM EDT Mon May 6 2024

.KEY MESSAGES...

- Our main shower and thunderstorm potential lasts through
  Thursday, with a smaller possibility at times through the
  weekend.

- Severe thunderstorms are possible Tuesday through Wednesday
  night. Large hail and damaging winds are the primary threats,
  but there is also a small risk of tornadoes. Locally heavy
  rainfall could also lead to isolated flooding.

- Above normal temperatures are forecast through Thursday. A cold
  front should pass late in the week and turn temperatures below
  normal through the weekend.

&&

.UPDATE...
-- Changed Discussion --
Issued at 915 PM EDT MON MAY 6 2024

00Z sfc analysis shows deep low pressure approaching the area from
the west with most of the Ohio Valley in the system`s large warm
sector. As such, the storms of this afternoon and early evening
are starting to wind down with a few weaker cells still to move
across the area. Have updated the PoPs and thunder chances
through the rest of the night per radar and CAMs trends.
Currently, temperatures and dewpoints are fairly uniform in this
humid environment - generally in the low to mid 60s - along with
light southerly winds, away from any storms. Have also included
the latest obs and trends for the T/Td/Sky grids with this update.
These adjustments have been sent to the NDFD and web servers
along with a freshening of the zones and SAFs.
-- End Changed Discussion --

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 446 PM EDT MON MAY 6 2024

Going to be a busy couple of days. Currently, Kentucky finds itself
under the influence of a stationary front. This is adding extra
instability and lift in an already warm and moist atmosphere, which
is resulting in isolated to scattered convection across much of the
region. While the forcing on these storms is not that great, can`t
rule out some stronger storms that are SPS worth with gusty winds
and small hail.

Expect convection to begin dissipating in most places as we head
into the overnight hours and lose our best mixing. The stationary
front in place will also begin lifting north of the state as a warm
front. That being said, several of the CAMs show an area/line of
pops oriented from SE KY into east TN and western NC, so tried to
account for these in the forecast. These will shift northeast
throughout the night and dissipate by morning. Not expecting
anything too significant from these, but with overnight temps only
dropping into low 60s, it`s entirely possible that we could still
see some thunder with any of this convection.

Heading into Tuesday, things start to ramp up a bit. Kentucky will
find itself in a "unsafe" zone - the warm sector under the warm
front, with deep SW flow, and ahead of a cold front. The cold front
will be slowly inching its way towards the western state border
throughout the day. As we head into the daytime hours and things
start to warm up, the stage will be set for instability and lift.
CAMs show a line of showers and thunderstorms developing ahead of
the cold front and progressing eastward throughout the day. It will
likely lose form by the time it reaches east KY and Ohio, but pop-up
convection will also be occurring as well throughout the afternoon.
Based on the latest GFS soundings, lapse rates and CAPE will be
quite robust for this area. Instability parameters will increase as
you move north towards the warm front, but any storm that develops
in this area has the potential to produce large/damaging hail. It
should also probably be noted that as far as other severe potential,
the latest GFS soundings really don`t show very good llvl
directional wind shear during the afternoon for eastern KY (it
improves as you head farther north out of the state). So it could be
a scenario where a lot of storms pop up, grow large, and then
collapse and can`t sustain themselves. If any storm is able to tap
into a more directionally sheered environment in the low levels,
then they could build some rotation and sustainability. SPC has all
of eastern KY in a Slight Risk for severe convection tomorrow (along
with a 5% tor risk) , with a hatched hail riding along our I-64
corridor and northwards.

As we head into the overnight hours, pop-up convection will likely
begin to dissipate. However, nearly all the CAMs show another line
of clustered cells developing out to our west ahead of the cold
front during the afternoon, eventually passing through east KY from
NW to SE throughout the overnight. Again, with temperatures
remaining quite mild, in the mid 60s, it will still be warm enough
to support convection. Soundings show a llvl inversion eventually
taking hold during the late night hours, but still plenty of
elevated instability/convection potential. So while some rumbles of
thunder and some gusts of wind will continue to be possible, the
decreasing CAPE and llvl inversion may cut off the best hail
potential for the overnight. It will be a needed break if so, b/c as
we head into Wednesday and the extended portion of the forecast,
expect another very active day.

.LONG TERM...(Wednesday through Monday)
Issued at 356 PM EDT MON MAY 6 2024

A warm front will lift northward on Wednesday ahead a surface cold
front and low pressure across the Plains. This will put a good
portion of the Ohio Valley into the warm sector, with decent
agreement on this among the ensemble and deterministic data. The
caveat to Wednesday is how convection evolves Tuesday into Tuesday
night. This thunderstorm activity Wednesday will come in two
waves. The first will be any activity that is able to develop in
the warm sector. These would have to potential to be more
supercell like with all hazards possible. However, it would seem
the better parameter space for this would be central and western
Kentucky, as MLCAPE rises to 2000-3000 J/kg amid 40-50 knots of
effective shear. This would be ample for organizing convection and
all hazards would be possible. The further east you go leads to
less certainty given the potential for morning convection and left
over cloud cover here in eastern Kentucky. However, some medium
range CAM guidance such as experimental C-SHiELD do show some warm
sector supercell potential even here in the east. This will have
to be watched close in forecast updates. Now the second threat
will be a line of convection (QLCS type) that develops ahead of
the front and propagates east Wednesday evening into Wednesday
night. This would pose more of a wind threat, but a quick spin up
tornado can`t be ruled out. This as effective STP values climb to
around 2-3 and effective shear increasing to 40-50 knots through
the evening.

A cold front will push across the area Thursday and will keep
60-90 percent chance of PoPs going mainly in the morning. We will
see storm chances decrease through the day. By Friday, the
ensembles and deterministic show a positively tilted trough axis
pushes into and through the Ohio Valley. This will keep chances of
showers going Friday in the 20-40 percent range. This will also
usher in a cooler airmass, with afternoon highs topping out in the
low to mid 60s. This is around 10 degrees below normal for this
time of year. The somewhat active pattern does tend to roll on
into the weekend, as several shortwaves dive into the Ohio Valley.
The rain chances will generally be in the 20-40 percent range
during this period.

&&

.AVIATION...
-- Changed Discussion --
(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 820 PM EDT MON MAY 6 2024

An extended period of active weather continues this evening.
Showers and thunderstorms have been impacting the TAF sites
throughout the afternoon and into the evening with a scattering
out taking place currently. Following a relative lull in the
convection into the overnight look for activity to be ramping back
up during the daytime hours on Tuesday. A round of strong to
potentially severe storms will begin to push into eastern Kentucky
by the end of the day. Overall, TAF sites should remain VFR
outside of any showers or stray storms that move through into the
night, which could temporarily drop CIGs and visibilities.
However, CIGs will then begin to lower overnight, with several
sites expected to drop to MVFR into early Tuesday morning along
with patchy fog reducing visibilities to MVFR and IFR, for a
time. These lower CIGS may continue into the day Tuesday. As it
stands now, SYM`s CIGs  could drop below IFR criteria overnight,
recovering to MVFR during the day tomorrow. Winds will generally
be out of the southwest throughout the period and under 10 kts,
though any showers or storms could lead to some higher gusts as
they move through. The next round of storms will then move in
later Tuesday when strong wind gusts, along with the potential
for large hail, cannot be ruled out.
-- End Changed Discussion --

&&

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

$$

UPDATE...GREIF
SHORT TERM...JMW
LONG TERM...DJ
AVIATION...JMW/GREIF