-- Discussion containing changed information from previous version are highlighted. --
458
FXUS63 KJKL 220931
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
531 AM EDT Sun Sep 22 2024

.KEY MESSAGES...

- A potential for showers and thunderstorms will persist through
  much of the next week.

- After high temperatures well into the 80s to near 90 today,
  readings will trend downward during the week.

&&

.SHORT TERM...
-- Changed Discussion --
(Today through Monday)
Issued at 446 AM EDT SUN SEP 22 2024

Early this morning a diffuse frontal boundary is stretched NW/SE
through eastern KY. Somewhat drier air tried to make its way in on
the northeast side of the front. However, abundant surface
moisture lingered below drier air aloft and has resulted in
extensive fog in valleys. The fog will dissipate after sunrise.

Aloft, high pressure over TX is ridging northeast over the Great
Lakes, with troughs on both sides and a weak upper low over CO.
The trough impinging on the ridge from the west will work to
flatten the ridging today and tonight and allow systems to become
more progressive. The front currently over our area will lift
northeast as a warm front, leaving all of our area firmly in a
warm and humid air mass (dew points near 70) by Monday afternoon.
Warmer and more humid air returning, along with the ridge aloft
breaking down, may allow for a few showers/thunderstorms to
develop this afternoon.

There may a be a little bit better chance at showers/storms
tonight as another cold front approaches from the northwest. This
front is expected to stall over KY on Monday and aid in further
thunderstorm development then, especially after some heating
occurs. Meanwhile, the CO upper low will be moving to the ENE over
the Midwest and providing a modest increase in our flow aloft.
With modest shear expected to result, SPC has placed roughly the
southwest half of our forecast area in a marginal outlook.
However, there is considerable uncertainty regarding
timing/placement of convection and the degree of destabilization
that will be possible due to increased clouds and possible precip.

.LONG TERM...(Monday night through Saturday)
Issued at 529 AM EDT Sun Sep 22 2024

While confidence is high that the first half of the long term
forecast period will be defined by wet and cloudy sensible weather,
model guidance continues to disagree on how the upper air pattern
will evolve in the second half. Because of this atypical amount of
uncertainty, it is important to note the overarching trends within
the forecast model ensembles rather than latching onto one
particular deterministic solution. In the most recent model runs, a
few of these trends have been observed, and their localized effects
have been outlined below.

The period opens with leftover convection from the daytime hours on
Monday. Given that limited levels of instability will mitigate the
severe weather risk earlier in the day, any remaining storms on
Monday night will weaken with the loss of daytime heating. However,
showers and perhaps some more thunderstorms remain in the forecast
for Eastern Kentucky through Wednesday. The first observable trend
in the latest model guidance has been the slower propagation of the
longwave troughing responsible for this disturbed weather. Ahead of
this troughing, modestly strong midlevel flow out of the southwest
will pump plenty of moisture into the atmospheric column.
Correspondingly cloudy skies will once again relegate diurnal
warming processes, and highs will struggle to climb above 80 degrees
on Tuesday afternoon. Despite the meager thermodynamics, sufficient
wind shear and better forcing/lift will foster the development of
more general thunderstorms on Tuesday. By Wednesday, most of the
activity looks to be in the form of low-impact, highly-beneficial
rain showers. The aforementioned longwave trough will have shifted
further east, allowing a cold front will push into the region.
High/low temperatures will accordingly decrease into the the mid
70s/lower 60s on Wednesday, and the air will become increasingly
stable as a result.

For Thursday and beyond, the focus shifts towards the Gulf of
Mexico, where the National Hurricane Center has diagnosed an area
with a 70% chance of tropical cyclone formation in the next 7 days.
Here in Eastern Kentucky, the sensible weather forecast for late
next week will depend on how this developing tropical system phases
with the upper level synoptic features. As discussed above, models
agree that some form of positively-titled troughing will exist in
the Mississippi River Valley by mid week. However, they do not agree
on the strength and exact positioning of this feature. The second
observable trend in the forecast guidance suite is that the European
ensemble of models collectively resolves this upper low further to
the southwest and stronger. Some Euro members depict a closed,
cutoff upper low over the Ozarks; this would signal a slower, less
progressive upper air pattern. On the other hand, the American
ensemble continues to show a weaker upper low over the mid-south and
thus a more progressive pattern. A stronger, western feature aloft
would pull the tropical system`s remnants further to the northwest,
which, in turn, could lead to downsloping and dry slotting over our
forecast area. If this particular trend becomes the consensus, the
extended forecast may need to be adjusted towards drier conditions,
but the chance PoPS from the NBM have been kept in the grids for
now. The third observable model trend is that both ensembles have
trended the system towards a faster forward motion and a further
northeast position on Friday morning. Both the speed and location of
this tropical cyclone will contribute to how it phases with the
previously-discussed upper level synoptic features, which, in turn,
will determine the sensible weather specifics. Given this recent
change, the uncertainty shrouding this system remains high, and we
will need these trends to continue in several more model runs before
drawing more definitive conclusions about localized impacts in the
Commonwealth. As such, we continue to encourage interested parties
to stay tuned to future forecast issuances.
-- End Changed Discussion --

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 232 AM EDT SUN SEP 22 2024

Fog was prevalent in most of the larger stream valleys at the
start of the period. It will continue to expand in coverage
through sunrise, and is expected to bring IFR or worse conditions
to all TAF sites, at least at times. The fog will dissipate during
the few hours after sunrise, leaving mainly VFR conditions to last
into Sunday night. Isolated thunderstorms are forecast to develop
on Sunday afternoon and last into the evening before dissipating.
They will bring localized sub-VFR conditions.

&&

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

$$

SHORT TERM...HAL
LONG TERM...MARCUS
AVIATION...HAL