404
FXUS63 KJKL 251821 AAC
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
221 PM EDT Wed Sep 25 2024

.KEY MESSAGES...

- Showers and thunderstorms could result in heavy rain and
  isolated flooding through tonight.

- The remnants of tropical system Helene are forecast to bring a
  widespread, soaking rain event later in the week.

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

- High temperatures will average near normal the rest of the
  week.

&&

.UPDATE...
Issued at 1236 PM EDT WED SEP 25 2024

Hourly grids were freshened up based on recent observations and
radar trends. This led to only minor adjustments to temperatures
and dewpoints, while pops across the southeastern portions of the
CWA near the VA border were increased per radar trends as well as
trends of recent CAMS.

&&

.SHORT TERM...(Today through Thursday)
Issued at 608 AM EDT WED SEP 25 2024

A large upper low will drop slowly south from the mid Mississippi
Valley during the period, becoming more closed with time. Our flow
aloft will initially be from the southwest, still pulling deep
moisture over our area, and continuing showers/thunderstorms at
times for most places today and tonight. Clouds and precip will
limit destabilization today and keep the severe weather threat
much lower than on Tuesday.

As we move into the day Thursday, tropical system Helene moving
north through the eastern gulf will interact more strongly with
the mid latitude upper low to our west. Our flow aloft will turn
toward the southeast while low level flow sets in from the east.
Even though precipitable water is expected to increase to near 2"
by evening, the downslope wind components will probably work to
limit precip amounts until Helene gets closer in the long term
period.

.LONG TERM...(Thursday night through Tuesday)
Issued at 419 AM EDT WED SEP 25 2024

A very interesting synoptic set up for the extended! Two systems
will come together to impact our weather for the duration of the
period.

First, a strong closed upper level low will be in place across the
Mid-Mississippi Valley, allowing for a deep pull of moisture into
the state. Meanwhile, Hurricane Helene will have made landfall
late Thursday, and will continue to push inland and northward. By
the start of the period Thursday night, the two systems will begin
to mesh, starting to rotate counter-clockwise around each other
while sitting over Kentucky and surrounding states. This will
continue until late Friday, at which point they will finally merge
together, again remaining nearly stationary across western KY.
The low center will finally start to shift eastward Saturday night
into Sunday. Models start to diverge in solutions at this point,
with the GFS being more progressive in pulling the system to the
east, being well out of the state by the end of the forecast
period, and the ECMWF keeping it more centered across the Central
Appalachians for a bit longer.

As for sensible weather, with two systems merging right across the
state, it`s no surprise that the amount of lift and moisture, we can
expect lousy weather. Friday will be the best day for pops and heavy
precip as the remnants of Helene rotate through eastern Kentucky.
By the weekend, when the two systems merge, the center of
activity will be more across western Kentucky, so this may be the
first break that we get in eastern KY through the week. That being
said, pops may still be scattered and could lead to precip in
some locations. More widespread pops will move back into the CWA
by Sunday as the consolidated low moves back eastward across
eastern KY. By Monday, kept with the NBM which is a mix of the
different model runs. This will keep pops across the CWA for the
remainder of the forecast period and scattered sky cover, but
depending on which model the forecast starts to trend towards,
this could either increase or decrease.

Given cloud cover through most of the period, this will limit
daytime heating, but also the overnight cooling. It also limits the
amount of ridge/valley temperature differences, along with the fog
potential. Did go ahead and keep some fog mention in for Friday
night, after the heavier rain shifts west of the CWA. Models are
suggesting some potential clearing in the cloud cover from the west,
which could aid in some fog development. Otherwise, did not make too
many changes to the temps or winds from the NBM.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 221 PM EDT WED SEP 25 2024

A mixture of mainly MVFR and VFR was reported at issuance time,
though IFR was reported in and near some of the heavier showers.
Showers and storms are expected from time to time through the
period. The prevailing MVFR or lower should prevail the longest
nearer the VA border during the first 6 hours of the period. A
couple of hours of MVFR or lower ceilings are probable at the TAF
sites to begin the period with the exception of KSME. A general
deterioration to MVFR is expected from southeast to northwest
between 00Z and 12Z with some IFR while MVFR should generally
prevail for most areas from 12Z to 18Z. Winds will be light and
variable.

&&

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

$$

UPDATE...JP
SHORT TERM...HAL
LONG TERM...JMW
AVIATION...JP