JKL issues Area Forecast Discussion (AFD) at Sep 20, 8:09 PM EDT834
FXUS63 KJKL 210009 AAA
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
809 PM EDT Sat Sep 20 2025
.KEY MESSAGES...
- A few thunderstorms could become strong to severe Sunday afternoon
and evening, especially for the western half of eastern
Kentucky. The main threat will be isolated damaging wind gusts.
- Widespread, beneficial rainfall is expected next week, which
will help to improve ongoing drought conditions.
- An additional threat for strong thunderstorms may develop on Thursday,
but there is still high uncertainty in the forecast for late
next week.
&&
.UPDATE...
Issued at 659 PM EDT SAT SEP 20 2025
Any lingering isolated convection should dissipate over the next
hour leaving partly cloudy skies for the overnight. Fog formation
can be expected in the favored river valleys and may be more
extensive in areas that received rainfall this afternoon and
evening.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 235 PM EDT SAT SEP 20 2025
A longwave trough remains across the north-central US, with a
negatively-tilted shortwave bringing today's convective activity
before moving northeast and away from the area tonight. The
longwave trough takes on a positive tilt Sunday into Sunday night,
allowing for increase southwesterly upper flow across the region,
thus increasing warm advection across the Ohio Valley, including
eastern Kentucky. The associated disturbances moving through this
southwesterly flow will be triggers for the associated showers and
storms over the region Sunday and into early next week.
An upper tropospheric disturbance combined with sufficient moisture
and instability will allow for continued shower and isolated
thunderstorm development this afternoon, but the better upper-level
support will move out of the area to the northeast by mid- to late
evening, and surface instability will also wane with the loss of
daytime heating. Skies should clear as drier air moves over the area
and warm advection weakens considerably despite continued southerly
low-level flow. This will allow for fog formation in the typically-
prone river valleys, and may be locally dense especially where skies
are clear and where it rained this afternoon.
Warm advection increases again through the morning Sunday ahead of
an approaching disturbance, with moisture and instability
increasing. Wind shear will also increase by early afternoon ahead
of a subtle disturbance passing ahead of the primary disturbance
back to the west, and this may be just enough to support the threat
for a stronger storm or two. For this reason, the SPC has issued a
Marginal Risk for severe storms for northern and parts of central
and east Kentucky. The best wind shear arrives Sunday evening into
the overnight, but by that time the atmosphere is most likely worked
over from expected afternoon activity. However, at least isolated
showers and possibly a few storms can be expected into the
overnight Sunday night with warm advection continuing. During this
time, highs will continue to moderate downward closer to normal
while lows trend upwards with lesser ridge-valley splits than what
we have become accustomed to in the last few weeks of drier
weather.
.LONG TERM...(Monday through Saturday)
Issued at 328 PM EDT SAT SEP 20 2025
The long-term forecast period dawns Monday morning with a broad,
low-amplitude 500 hPa trough, its axis extending from Lake
Superior southward along the Mississippi River. Upstream, a 500
hPa Pacific trough is traversing the northern Rockies. At the
surface, a wavy front extends from weak low pressure north of Lake
Huron to another area of low pressure over South Dakota. Abundant
moisture will be feeding northward across much of the CONUS
between the Appalachians and Rockies in advance of these troughs.
Model agreement is good initially, but spread increases markedly
as the pattern becomes more complex later in the period.
The trough over the Mississippi Valley will retreat northeastward
on Monday and Tuesday while the Pacific trough digs deeply as it
descends the Rockies. A substantial portion of the LREF ensemble
members favor this new trough closing off near or over Missouri on
Wednesday, becoming the primary weather driver for the Ohio
Valley later in the week as it and an associated surface
reflection drift eastward. Pieces of upper-level energy ejecting
from the developing low will interact with a moist airmass over
the Ohio Valley (PWATs of 1.3 to 1.6 inches), supporting
diurnally-modulated convection through Wednesday. As the systems
associated surface low drifts just north of the Lower Ohio River
from Thursday into early Friday, a cold front is favored to wrap
around the southern side of the occluding low. The proximity and
probable position of the low on Thursday still appears to support
the most favorable shear/instability environment of the week for
a few strong to severe thunderstorms. The greatest forecast
uncertainty comes after Thursday. Yesterday, the system had
overall been favored to push eastward and perhaps tend northward
and become recaptured by the mid-latitude westerlies over Southern
Canada. However, recent model solutions also support other
outcomes, including a scenario where most of the energy shears
southward, causing the upper low to reorganize near or over
Western Kentucky before dropping south of the region by week's
end. This outcome would favor the unsettled pattern lingering over
eastern Kentucky through Saturday. Thus, forecaster uncertainty
is high for the late-week period. By far the greatest material
forecast change over the last 24 hours has been a marked increase
in forecast rainfall amounts. Probabilities for at least one inch
of rainfall through Saturday have climbed, now ranging from a 70%
chance in the far east to a 90% chance near Lake Cumberland.
Furthermore, there is now a 30% chance in the east and a 50%
chance in the west for at least two inches of rainfall through
Saturday. The LREF 10th- to-90th- percentile spread suggests
reasonable rainfall totals could range from 0.75-1.00 inch on the
low end to as much as 3.00-3.50 inches on the high end. This
guidance confidently suggests that a drought-reducing, or perhaps
even drought-erasing, rainfall is possible for much of the
Commonwealth.
In terms of sensible weather, expect variable cloud cover with
daily shower and thunderstorm chances: mainly scattered from
Monday through Wednesday, becoming numerous on Thursday, with
activity likely lingering into the weekend. The most extensive
activity can be expected during the afternoon and early evening.
Daily high temperatures will gradually cool from the low to
mid-80s on Monday to the mid-70s by Saturday. Nighttime lows range
in the mid 50s to mid 60s through Thursday night before likely
cooling into the 50s for the weekend. Fog formation is favored
each night in the typical river valley locales but is also likely
to be more extensive in areas that receive substantial rainfall in
the afternoon/evening hours followed by at least partial clearing.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 807 PM EDT SAT SEP 20 2025
Convection had mostly dissipated at issuance time and a trend of
mostly clear or clear skies is anticipated overnight. This should
promote valley fog development as early as 04Z and then this fog
dissipating by 14Z. This is currently not expected to affect TAF
sites. However, some of the valleys generally near and south of a
KSJS to KJKL to KLOZ line could experience reductions to MVFR and
IFR if not locally lower between 06Z and 12Z. With rain having
fallen near KJKL and KSJS it is possible that a few wisps of fog
could sneak into one or both of those sites briefly between 09Z
and 13Z, but confidence was too low to include at this point. More
showers and storms should develop between 16Z and the end of the
period. Isolated to scattered storms could affect some or all of
the TAF sites during that time with reductions to MVFR or lower.
Winds outside of showers and storms will be light and variable,
becoming light out of the south and southwest at 5 to 10 KT after
about 15Z.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...GEERTSON
SHORT TERM...CMC
LONG TERM...GEERTSON
AVIATION...JP
Source:
JKL issues Area Forecast Discussion (AFD) at Sep 20, 8:09 PM EDT---------------
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