977
FXUS63 KJKL 261825
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
225 PM EDT Thu Sep 26 2024

.KEY MESSAGES...

- The remnants of tropical system Helene will bring a widespread,
  soaking rain event tonight into Friday.

- Flash flooding could result from the remnants of Helene, but the
  overall potential may be limited by its quick movement.

- Wind gusts of 40 to 60 mph are possible at times from late
  tonight through Friday as the remnants of Helene pass by the
  area.

&&

.UPDATE...
Issued at 1245 PM EDT THU SEP 26 2024

The Flood Watch was expanded to include more counties further to
the north to account for the potential of higher totals further
north in the 12Z HRRR and NAMNEST as well as the 12Z HREF LPMM
values. The other concern is the gust potential for later tonight
and on Friday and further adjustments to wind headlines will be
needed this afternoon.

UPDATE Issued at 740 AM EDT THU SEP 26 2024

No real changes to the forecast with just the inclusion of the
latest observations and trends for the T/Td/Sky/PoP grids. These
minor adjustments have been sent to the NDFD and web servers.

&&

.SHORT TERM...(Today through Friday)
Issued at 520 AM EDT THU SEP 26 2024

08Z sfc analysis shows a weak pressure pattern over eastern
Kentucky with a hint of an inverted trough ahead of a stalled
frontal boundary to the west of the area. This boundary has been
interacting with the high PW air in place over the area to keep
showers and a stray thunderstorm on the scope through the night.
Much of the convection is falling over grounds that have been
soaked the last few days - especially Bell, Harlan, and Letcher
counties. Plenty of clouds at various levels have kept
temperatures and dewpoints fairly uniform through the area
overnight - generally in the low to mid 60s. Amid light winds,
areas of fog - locally dense along with some low stratus clouds
have developed during the night, as well. Meanwhile, Hurricane
Helene appears to be starting to undergo its rapid intensification
process as it moves north through the eastern Gulf of Mexico.

The models, and their individual ensemble suites, are in pretty
good agreement aloft through the short term portion of the
forecast despite a complicated forecast for this part of the
Country. They all depict a 5h closed low seemingly stuck over
western parts of the state with spokes of mid level energy
rotating around - maintaining the convection for at least up in
the east. To its south, the core of Helene is steadily approaching
the Mainland U.S. It is this feature that will be the main focus
for the weather over the next few days across eastern Kentucky.
Helene looks to lift into the southern Appalachians and in a
Fujiwhara manner rotate around the mid level low to our west
later tonight into Friday. As a result, the core of Helene`s
remnants push into the JKL CWA on Friday forming - and locking in
place for a bit - a deeper 5h low over the region. There is enough
general agreement among the models through the short term portion
of the forecast, to favor the NBM as the starting point for the
grids but with significant adjustments needed to the QPF, Winds,
and PoPs from the CAMs through Friday evening.

Sensible weather features a complicated and dynamic forecast on
account of the remains of Helene tracking near and through eastern
Kentucky. The strength of this system at landfall later today will
have an effect on how well it can maintain its core of winds/rain
into the southern Appalachians. East Kentucky will benefit from
its easterly winds downsloping into the area and likely limiting
the rainfall totals for much of the JKL CWA through Friday.
However, much of the southeast is approaching saturation from the
past three days of convection and the expectation of more rains
today from the front to the west and the ongoing tropical fetch.
High PW air and an increasingly tropical air mass will enhance the
warm rain processes making for efficient rain producing showers.
Expect limited thunder but that will likely not stop pockets of
rain from reaching 2 to 3+ inches in a few hours for some places.
On account of the expected rains and the antecedent soil
conditions for the Cumberland Valley have gone ahead and hoisted a
Flood Watch through Friday evening there. Could see the need for
this to be extended west and north as the core of Helene`s path
dictates later today and tonight. Look for the best rain chance to
shift westward by Friday afternoon.

Winds will be the other big concern from this event as the wind
core of Helene will not have as much time to spread out and weaken
as we typically see in these situations. Accordingly, anticipate -
with significant support from the CAMs runs - strong winds and
gusts over our higher terrain later tonight through Friday. A
High Wind Watch remains in effect for our southeast higher terrain
counties - above 2000 feet - for a potential of wind gusts in
excess of 50 to 60 mph. Of heightened concern is the indicators in
the CAMs that show drying from the east early Friday with a
potential for the higher winds to mix down better in this
environment in which case a wind advisory would probably be
warranted for much of he area into Friday afternoon. Will keep
watching this potential for possible additional headlines dealing
with Helene.

Otherwise, temperatures will be near normal for highs today and
mild at night with warmer conditions in the east on Friday due to
that drying and downsloping on tap. Any fog will likely be
fleeting and associated with times of rain or any brief clearing
of the lower clouds.

The changes to the NBM starting point mainly consisted of
increasing winds and winds gusts per the CAMs tonight and on
Friday, as well as adding in more details from those higher
resolution models for PoPs and QPF through Friday evening.

.LONG TERM...(Saturday through Thursday)
Issued at 225 PM EDT THU SEP 26 2024

The forecast period begins with the area still largely under the
impacts of the remnants of Hurricane Helene. At upper-levels, the
remnants of Helene will begin to merge with a largely stationary cut-
off circulation that`s been situated over western Kentucky through
much of this week. As the two systems merge into one circulation,
shower and storm chances will persist through the day Saturday and
linger through the weekend. Models continue to remain in rather good
agreement going into next week with the circulation getting picked
up by the mean flow and ejecting out of the area by Monday morning
but lingering PoP chances will exist through the end of the period
as an upper-level trough, moving through southern Canada, drags a
cold front through the region Tuesday afternoon which will then
usher in cooler and drier weather for the middle of next week.

Overall, the forecast period will be highlighted by multiple rounds
showers and storms. Shower and thunderstorm chances drop a little
bit with the merging of the closed circulation and the remnants of
Helene but chances (40-70%) exist through the weekend. Temperatures
through the period will remain rather seasonal as highs are forecast
to in the upper-60s to upper-70s. Overnight lows, will be warmer
with the insulation of the system overhead but with the approach of
a cold front on Tuesday, cooler temperatures and fall-like weather
will be in place for the end of the period.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
ISSUED AT 800 AM EDT THU SEP 26 2024

Variable aviation conditions were reported at TAF issuance time
as areas of fog, low clouds, and a few showers are impacting much
of eastern Kentucky. Anticipate conditions to generally continue
to be variable in the IFR to MVFR range into the afternoon. A
rumble of thunder cannot be ruled out, but confidence in any
affecting a particular TAF site remains too low to mention. There
will likely be an uptick in the rainfall rates later today and
tonight. Winds will be light and variable away from any storms
through the first part of the evening but begin to pick up
thereafter from the east to northeast at 10 to 20 kts with higher
gusts into dawn Friday. LLWS will be a threat later tonight into
Friday morning, as well, with winds up to 50 kts a few thousand
feet off the sfc - blowing from the east northeast.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 5 AM to 8 PM EDT Friday for KYZ044-050>052-
058>060-068-069-079-083-104-106>109-111-112-114-119.

Flood Watch through Friday evening for KYZ058-068-069-079-080-
083>088-107>120.

High Wind Warning from 2 AM to 8 PM EDT Friday for KYZ080-
084>086-110-113-115>117-120.

High Wind Warning from 11 PM this evening to 8 PM EDT Friday for
KYZ087-088-118.

&&

$$

UPDATE...JP
SHORT TERM...GREIF
LONG TERM...VORST
AVIATION...GREIF