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369
FXUS63 KJKL 180542
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
142 AM EDT Wed Sep 18 2024

.KEY MESSAGES...

-- Changed Discussion --
- Additional shower (and possible thunderstorm) chances will occur
  through Thursday.

- A warming trend will lead to temperatures around 10 degrees
  above normal over the upcoming weekend.
-- End Changed Discussion --

&&

.UPDATE...
Issued at 1214 AM EDT WED SEP 18 2024

Forecast is on track, and meaningful precip looks to be done for
the night. Have blended late evening obs into the forecast without
any substantive changes.

UPDATE Issued at 909 PM EDT TUE SEP 17 2024

Precip has been on an overall decline this evening. The most
significant showers remaining are in our southwest counties. Have
updated the POP for this evening based on these trends, with
mainly a sub-20% POP to follow for the overnight, as models and
radar would suggest.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 507 PM EDT TUE SEP 17 2024

Upper level low and associated surface wave will spin its way up
the northern half of the Piedmont during the short term, opening
up into a trough as it tracks towards New England. Short wave
energy rotating around the low will keep the threat of some type
of afternoon convection in place across portions eastern Kentucky
through the period. There is a band of showers, and further
upstream, thunderstorms lining up along the NC/VA state line that
is moving downstream into eastern Kentucky. SPC mesoanalysis shows
a lobe of MLCAPE nosing its way as far northwest as Wise, VA. But
otherwise, the better instability remains outside of our forecast
area. This line takes on an increased east to west orientation
with time. Consequently, this source of moisture into eastern
Kentucky will eventually get shunted off to the south of our area
by this evening.

Sensible weather features an unsettled short term, with the bonus
of the chance of receiving some much needed rain, even if
relatively meager in amounts. Being at an upslope location, Big
Black Mountain has come out on top with almost 1.5 inches of
rainfall today. Totals drop off quickly from there with around a
half inch directly down from Black Mountain, across the immediate
tier of counties from the VA state line. From there, the next tier
of counties going west- northwest had just under a quarter of an
inch of rainfall, with lesser amounts further to the west-
northwest, around a tenth or less of precipitation. Up to another
tenth of an inch on average will be possible through the short
term...where showers pass. Have not seen any thunder thus far and
expect that to remain the case in general through the remainder of
the late afternoon and evening. However, with MLCAPES of 750-1000
J/kg, there is slightly better instability to work with on
Wednesday.

.LONG TERM...(Thursday through Tuesday)
Issued at 438 PM EDT TUE SEP 17 2024

The 17/12z model suite 500H analysis beginning Thursday morning
shows a lingering trough from southern New England SSW into the
Carolinas. Meanwhile, a narrow but robust, positively-tilted
ridge extends from an ~591 dam high over Coahuila, Mexico NE over
the Mid-Mississippi Valley and Western Great Lakes and then N
across the Hudson Bay. West of the ridge, there is a mean trough
with embedded closed lows over southern Saskatchewan/Manitoba and
also along the Central California coast. At the surface, a subtle
trough lingers along the western slopes of the Central
Appalachians amidst a larger area of high pressure extending into
the Ohio Valley from out of eastern Canada. A potent ~990 mb low
is found under the first upstream low over southcentral Canada and
is attended by a wavy cold front that extends down the High
Plains all the way into Mexico.

The 500H troughing to our east slowly departs on Thursday/
Thursday night and any surface disturbance dissipates, ending the
threat for any lingering PoPs. Ridging subsequently becomes more
positively tilted across Ohio Valley by Friday as the first 500H
low and its surface reflection become vertically stacked and decay
over Central Canada while the associated cold front slows out
over the Upper Midwest and stalls. Ahead of that boundary, an
increasingly mild west to southwesterly flow sends 850mb
temperatures back into the 17-19C range across eastern Kentucky
for Saturday and Sunday, setting the stage for well above normal
temperatures. Meanwhile, the second 500H low passes over the Four
Corners on Saturday and ejects out onto the Central Plains Sunday.
This next upper low fosters renewed cyclogenesis in the
baroclinic zone of the remnant cold front near/over eastern
Colorado on Saturday night. This new surface low tracks northeast
to near Chicago, IL by late Monday/early Tuesday, dragging the
trailing cold front to over the Lower Ohio Valley. By this point
in the forecast period, there are substantial model-to-model
differences in the intensity and timing of the front. Given the
uncertainty, the NBM was left unchanged, aside from some very
minor adjustments to account for topography.

In sensible terms, a lingering small chance (15-30 PoP) for showers
and thunderstorms will still be possible east of a Paintsville-to-
Jackson-to-Barbourville line. Otherwise, mostly sunny skies are
expected to accompany maximum temperatures in the lower to middle
80s. Fair skies follow for Friday and the weekend with temperatures
reaching the mid 80s for most locations on Friday and then mid to
upper 80s on both weekend days. A few thermometer readings near
90F cannot be ruled out on either Saturday or Sunday. Nighttime lows
range from the mid 50s to mid 60s through the weekend. Normal
daily high temperatures for September 21st and 22nd are in the
mid 70s to near 80 and lows range in the 50s. Heading into the
new work week, forecaster confidence is low due to model spread.
NBM-based forecast favors increased cloud cover, slight rain
chances, and closer to normal temperatures returning the forecast
on Monday and Tuesday as the next cold front approaches.

&&

.AVIATION...
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(For the 06Z TAFS through 06Z Wednesday night)
ISSUED AT 142 AM EDT WED SEP 18 2024

A combination of conditions exist across the area with this TAF
issuance. Southern terminals (KJKL, KSJS, KLOZ and KSME) are
expected to fall into categorical IFR to MVFR overnight. Terminal
KSYM is expected to fluctuate between MVFR/VFR overnight.
Fog/low- level stratus will continue through the early morning
before improving to MVFR/VFR by the early afternoon. As this
system, that`s brought the lowered CIGS and showers, continues to
impact the area; a renewed chance of showers and thunderstorms
will develop Wednesday afternoon after 18Z through 22Z before
dissipating. Showers and storms may cause brief reductions in
VSBY. Toward the end of the period, CIGS are expected to fall
again into categorical MVFR overnight Wednesday. Light and
variable winds are forecast to persist through the period.
-- End Changed Discussion --

&&

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

$$

UPDATE...HAL
SHORT TERM...RAY
LONG TERM...GEERTSON
AVIATION...VORST