-- Discussion containing changed information from previous version are highlighted. --
252
FXUS63 KJKL 240000
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
800 PM EDT Mon Sep 23 2024

.KEY MESSAGES...

- A potential for showers and thunderstorms will persist through
  much of the next 7 days, largely bringing eastern Kentucky
  beneficial rains after a lengthy period of dry weather for many
  locations.

- The remnants of Potential Tropical Cyclone 9, currently forecast
  to strike the Florida Panhandle as a hurricane late Wednesday,
  may impact parts of eastern Kentucky with an increased chance
  for a widespread yet likely brief rain event late this week.
  However, any flooding potential is likely to be mitigated by the
  quick movement of this system.

- High temperatures will climb into the mid 80s today, then trend
  downward through the week.

&&

.UPDATE...
Issued at 620 PM EDT MON SEP 23 2024

Showers and scattered thunderstorms continue to drift east early
this evening, primarily impacting locations south of the Mountain
Parkway. Expect activity taper to only isolated showers/storms by
10 PM EDT as instability wanes. A few of the storms could still
become strong over the next hour or two, with gusty winds and
hail being the primary concerns. Overnight forecast remains on
track.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 248 PM EDT MON SEP 23 2024

The Ohio River and Tennessee River Valleys lie within strengthening
southwest flow aloft between downstream ridging over the Southeast
US and an upstream trough over the Central US. This southwest flow
aloft will amplify through the short-term as the upper trough
deepens and closes off into an unusually strong upper low over the
Ozarks region, with downstream ridging strengthening just off the
Southeast US coast. Multiple disturbances will move through the flow
aloft and support rounds of showers and thunderstorms through
Tuesday night.

For this afternoon, the primary thunderstorm threat will reside
roughly along and south of KY Highway 80 in south-central and parts
of southeastern Kentucky, where effective shear has increased to 25
to 30 kts and instability of 1000-2000 J/kg MLCAPE is expected,
which marginally supports an organized storm threat. The primary
severe threats would be strong gusty winds and large hail, if a
severe storm or two were to develop.

Instability wanes tonight with the loss of daytime heating, which
should greatly limit the severe threat, with showers and storms
continuing to move east and northeast across the area, with the
greatest threat for storms in the south and southwestern parts of
the CWA.

A cold front approaching from the west during the daytime hours
Tuesday will help focus another round of showers and thunderstorms
across central and eastern Kentucky. This round of activity will be
accompanied by 40 to 50 kts of wind shear, with any areas of partial
clearing generating sufficient instability to support scattered
storms, a few of which may be severe, with damaging winds being the
primary threat. Any areas that see repeated rounds of heavy rain may
also see a localized flooding threat.

The aforementioned cold front will track will stall over the Ohio
and Tennessee Valleys, which will keep shower and thunderstorm
chances in the forecast through the overnight Tuesday night. With
the increasingly unsettled weather through the short term,
temperatures, especially highs, will continue an overall downward
trend.

.LONG TERM...(Wednesday through Monday)
Issued at 312 PM EDT MON SEP 23 2024

The latest runs of the GFS and ECMWF models feature a similar
amplified flow pattern aloft. A large and expansive ridge of high
pressure is progged to in place over the western half of the CONUS
to begin the period. A well developed area of low pressure is
still forecast to be move through the central Mississippi Valley
and into the Ohio and Tennessee Valleys on Wednesday. Meanwhile,
the models are still honing in on a tropical cyclone that would be
moving our of the western Caribbean and into the southern Gulf of
Mexico Wednesday and Wednesday night. A frontal boundary
associated with midwest trough is also forecast to extend
southward through the Tennessee Valley and into the Gulf of Mexico
to start things off. Further north and east, another large area of
low pressure aloft is still forecast to move through the Great
Lakes and into New England, bringing good chances for rain to
those regions to start the period.

Based on the latest data, it still appears that inland trough and
front will bring widespread showers and scattered storms to
eastern Kentucky Wednesday through Friday. However, the evolution,
progression, and track of potential tropical cyclone Helene is far
from certain at this time. This system could combine forces with
the midwest trough, and act to keep rain chances in our area
through the upcoming weekend and into the first of next week,
should things pan out that way. One mitigating factor to expansive
rainfall late in the period from Helene could be strong downslope
flow and drying, as the tc remnants move our way from the south.
Based on the latest forecast tracks, Helene would be moving across
both the Smokey Mountains and then central Appalachians as it
approaches, which is and ideal scenario for persistent downslope
flow and subsequent warming/drying. If this occurs, any
precipitation that the remnants of Helene produces, would be
strongly affected by the downslope flow, which could lead to much
lower rain chances than some of the current model data is showing.
This situation will need to be monitored closely over the coming
days as we get a better handle on potential tc Helene and her
track.

As it stands, it does look like that the entire extended period
will be quite active, with rain chances everyday. The main
question will be how much downslope flow we get toward the end of
the period and what the subsequent rainfall amounts. The best
chance for locally heavy rainfall and higher precipitation
probabilities will occur Wednesday through Friday, as the inland
low moves our way and sort of meanders about the region.

As for temperatures, we should see mainly below normal daytime
highs in the low to mid 70s around the area. There may be a few
locations through the period that might max out in the upper 70s
or perhaps lower 80s, but those would be few and far between,
especially considering the high amounts of cloud cover and
persistent precipitation we are expecting. Nightly lows should be
in the upper 50s and lower 60s on average.

&&

.AVIATION...
-- Changed Discussion --
(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 800 PM EDT MON SEP 23 2024

Convection with isolated thunder ongoing at TAF issuance is
expected to diminish to just an isolated shower by 2-3z. Just a
stray shower is possible through the overnight. VFR conditions
should generally prevail outside of convection at northern TAF
sites (e.g JKL, SJS, SYM). LOZ and SME both experienced a
rainfall and are favored to have fog developing and diminishing
visibilities to at least MVFR, if not worse, later in the night,
given sufficient clearing. VFR conditions should return to all
sites on Tuesday morning but additional rounds of showers and
thunderstorms are likely which could temporarily lead to IFR or
lower conditions. It is too early to pinpoint the exact timing of
the rounds of convection, so VCTS mention was included for the day
on Tuesday. Winds will be light tonight becoming south to
southwest 5 to 10 kts on Tuesday. Locally erratic and stronger
winds will be possible with storms on Tuesday.
-- End Changed Discussion --

&&

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

$$

UPDATE...GEERTSON
SHORT TERM...CMC
LONG TERM...AR
AVIATION...GEERTSON