015
FXUS63 KJKL 261200 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
800 AM 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 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...(Friday night through Wednesday)
Issued at 436 AM EDT THU SEP 26 2024

The remnants of Hurricane Helene is going to be the main story of
the forecast heading into the extended. By 0Z Saturday the upper
level low associated with Helene will have merged with the upper
level low already in place across western KY. This merged mega
system will remain nearly stationary during the first half of the
day Saturday, before slowly moving eastward to the eastern half of
the state Saturday night. The ECMWF is a bit slower with this
progression, however, keeping the center of the low across western
KY during this time. This sets the stage for model differences
moving forward, with the ECMWF always being about 12 to 24 hours
behind and displaced farther west than the GFS. This could lead to
considerable differences in weather patterns across the
Commonwealth, as one has the center of the low across the state
(ECMWF) while the other (GFS) has moved well east of the state
leaving us in NW flow. Furthermore, the GFS brings a shortwave
through the Ohio Valley on Tuesday night into Wednesday morning,
while the ECMWF starts to build ridging across the area. All this to
say, held to the NBM after Saturday for sensible weather as a best
guess between the two solutions.

The swath of heavy rain that impacted us Friday will start to wrap
north and eastward by Friday night, centering over western and
central KY, with most models showing some drying taking place in the
eastern CWA. This will persist through the first part of the day
Saturday, until the system starts to make the above-mentioned shift
eastward. Again, this is with the exception of the ECMWF which keeps
the precip across the western and central portion of the state
through the day Saturday and into Saturday night, keeping eastern KY
dry. The NBM seems to be more in line with the GFS and NAM,
spreading precip back into the eastern CWA by the second half of the
day Saturday. Either way, QPF will have tapered off substantially by
this point, with the best chances of totals around half an inch or
so generally across the Bluegrass. The NBM has rain chances
lessoning overnight with the loss of daytime heating/mixing, but
ramps it back up across the eastern half of the state during the day
Sunday. Interestingly, the same thing occurs on Monday, which seems
more in line with the solution of the slower ECWMF, and a bit higher
than the exiting GFS suggests. Will be interesting to see if these
pops trend lower or remain likely depending on which solution the
models continue to trend towards.

After this point, the NBM continues to trend drier, with Wednesday
likely being our first dry day in well over a week. Granted this
isn`t exactly reflected in the models currently, especially with the
GFS shortwave moving through, so expect that it could change as
models hopefully come into better agreement over the coming days.

One thing is for certain, the NW flow into the region through much
of the period. This will likely peak by mid-week as part of the
upper level jet dips down into the Commonwealth. As such, this
northerly flow and presence of clouds plus precip will help to keep
temperature at bay, with daytime highs generally in the low to mid
70s. By the end of the period, the clearing skies and lack of
rainfall will help temperature to drop further overnight. Therefore,
if the forecast holds, can`t rule out some temps in the upper 40s
and low 50s for Tuesday night, and then down into the mid 40s by
Wednesday night with another day of drying and clearing. The rest of
the time clouds should keep us fairly insulated, with temperatures
only bottoming out in the upper 50s and low 60s for lows.

&&

.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...
Flood Watch through Friday evening for KYZ080-084>088-110-113-
115>118-120.

High Wind Watch from this evening through Friday evening for
KYZ087-088-118.

&&

$$

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