JKL issues Area Forecast Discussion (AFD) at Aug 9, 10:43 PM EDT284
FXUS63 KJKL 100243
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1043 PM EDT Sat Aug 9 2025
.KEY MESSAGES...
-Mainly dry conditions and seasonably hot temperatures expected
for through Sunday.
-A significant pattern change arrives for the new work week,
bringing a more humid pattern with daily chances for scattered
afternoon and evening thunderstorms starting Monday.
-Localized torrential downpours and strong, gusty winds are
possible with the thunderstorms that develop on Tuesday and
Wednesday.
&&
.UPDATE...
Issued at 1043 PM EDT SAT AUG 9 2025
Minor adjustments were made to hourly temperatures to better align
with recent observations particularly for valley locations.
Otherwise, with narrowing dewpoint depressions already for the
deeper valleys, fog should begin to develop over the next few
hours and increase in areal extent toward dawn.
UPDATE Issued at 631 PM EDT SAT AUG 9 2025
Some minor adjustments were made to pops through sunset based on
radar returns and trends in the cumulus fields. This activity has
been shallow enough for there to be no lightning observed due to
proximity of the upper ridging and should wane by around sunset.
In general, temperatures in the east were running a little below
the previous forecast and additional adjustments were made
through later this evening to align with observations from 24
hours ago. Otherwise, the fog forecast for the overnight appears
on target based on trends from previous nights.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 245 PM EDT SAT AUG 9 2025
Across the CONUS, the weather remains active according to the latest
surface analysis. Locally, a surface high-pressure system, centered
over the northern Mid-Atlantic and southern New England, is
maintaining tranquil weather in eastern Kentucky. However,
disturbances are present to the northwest and southeast. A slow-
moving surface low-pressure system is tracking east from the
northern Plains toward the Great Lakes, while a southern feature is
moving off the Atlantic seaboard. In the eastern part of the
Commonwealth, the weather will remain mostly dry, with temperatures
rising into the upper 80s to lower 90s.
Throughout the rest of the day, those upper-level features will
slowly drift eastward. Before moving offshore, the southeastern
feature could trigger a few very isolated showers and storms.
However, due to largely nonexistent moisture and rising upper-level
heights, the PoP is minimal but not zero. The Plains feature will
slowly drift eastward, but a strong upper-level ridge will
significantly limit its movement, resulting in very little shift in
the overall synoptic pattern. Consequently, high temperatures are
still forecast to climb into the upper 80s to lower 90s. Overnight
tonight, lows will fall into the mid-60s. River valley fog, a
climatological constant, will form overnight; however, its coverage
will be limited to the more sheltered and deeper valleys due to
dwindling moisture.
Sunday will bring very few changes to the forecast, as the synoptic
pattern remains steady. Even less moisture is expected tomorrow;
therefore, PoP chances will be nonexistent. Daytime highs will once
again climb into the upper 80s to lower 90s. Sunday night into
Monday will be similar to Saturday night into Sunday, with lows in
the mid-60s and the presence of river valley fog.
In summary, high pressure will keep eastern Kentucky dry and
tranquil this weekend, despite other active weather systems nearby.
Due to a strong upper-level ridge, the overall weather pattern will
remain steady. Expect high temperatures in the upper 80s to lower
90s, with lows in the mid-60s. Overnight, limited fog is expected in
deeper valleys.
.LONG TERM...(Monday through Saturday)
Issued at 458 PM EDT Sat Aug 9 2025
The beginning of the long term forecast period is marked by the
breakdown of the atmospheric ridging pattern that kept conditions
dry across Eastern KY. From Monday into Tuesday, the upper level
ridge previously positioned over the Appalachians will shift eastward
as troughing begins to dig deeper into the Upper Midwest. In this
same time frame, ridging begins to build back over the Southeastern
and South-Central CONUS. Collectively, these features will place
Eastern Kentucky in a persistent regime of quasi-zonal flow aloft
through the next work week. As shortwave features navigate through
this flow, and active weather pattern will set up over the forecast
area through the end of the period.
On Monday, atmospheric flow is expected to gradually veer towards
the south and then the southwest, leading to increasingly effective
moisture return. Ensemble data continues to suggest that the highest
PWAT values will remain across Southern Kentucky on this first day
of moisture return, and shower/thunderstorm chances are generally
contained to the KY80/Hal Rogers Parkway Corridor as a result. Any
convective activity that develops on Monday is likely to be tied to
the diurnal heating cycle, as there will be little synoptic forcing
present in the region early next week. Afternoon highs are forecast
to warm to near 90 degrees across the entire forecast area on
Monday, and as the humidity increases, maximum heat indices will
warm into the upper 90s. A few valley and urban locations could
flirt with 100 degree MaxApTs on Monday, but the convection chances
will limit the spatiotemporal coverage of any heat-related impacts.
After convection subsides with the sunset, expect overnight ridge-
valley temperature splits (ridge MinTs near 70 and valley MinTs in
the upper 60s). The synoptics at play support nocturnal valley fog
formation, especially in the river valleys and in locations with wet
grounds.
Precipitation chances spread across the entirety of Eastern Kentucky
on Tuesday and then increase further headed into Wednesday. This
increase in convective coverage is largely due to the persistence and
amplification of southwesterly-to-westerly flow throughout the
atmospheric column. The orientation of this flow favors persistent
Gulf moisture advection into the region, and LREF mean PWATs surge
to near 1.75 across the forecast area by Tuesday afternoon and then
to above 1.8 on Wednesday afternoon. Tuesday's convective activity
is likely to remain diurnally-driven, although guidance continues to
show a more well-defined disturbance in the vicinity of the forecast
area on Wednesday. Severe thunderstorm parameter spacing remains
unimpressive for the duration of the forecast period, although
increasing amounts of SBCAPE and the aforementioned PWAT values
suggest that isolated wet downbursts cannot be entirely ruled out on
Tuesday and Wednesday. It is more likely that these storms will be
efficient rainmakers, especially once the more vigorous shortwave
disturbance arrives on Wednesday. Some of the available 12z modeled
forecast soundings for Wednesday at KJKL show PWAT values
approaching 2 inches, with long/skinny CAPE profiles, low LCLs, and
a thick warm cloud layer present. If multiple rounds of convection
are able to pass over any given location in an environment like
that, localized flash flooding would be possible. WPC has introduced
a Marginal (Level 1/4) Excessive Rainfall Outlook for the entire
forecast area on Wednesday in response to this signal, although the
evolution of mesoscale factors such as antecedent/upstream
convective activity remain uncertain at this temporal range. At the
current moment, there is not a signal for widespread flooding impact
in any of the probabilistic river forecast guidance, which gives
credence to the idea that Wednesday's flood risk will be confined to
any locales that see multiple rounds of heavy rain or a particularly
persistent downpour. Interests are encouraged to monitor future
forecast updates as higher-resolution data becomes available and the
mesoscale details of Wednesday's forecast become more clear.
The increasing rain chances and cloud coverage on Tuesday and
Wednesday should suppress any heat impacts related to the increasing
humidity. Forecast highs have trended a little bit cooler for this
mid-week time frame, and the latest forecast grids reflect highs in
the mid to upper 80s. If an AM round of convection comes to fruition
on Wednesday and skies remain cloudier, the NBM-sourced forecast
highs could under-perform. Confidence was not high enough to deviate
from this baseline data with this forecast package issuance, but
these cooler temperatures could further mitigate the severe weather
potential.
In the wake of Wednesday's shortwave trough, high temperatures are
expected to linger in the mid to upper 80s on Thursday. The
commonwealth is likely to remain in quasi-zonal flow through the end
of the next work week, although a shortwave ridge should lead to
some atmospheric drying/warming late in the day on Thursday and into
Friday. Highs on Friday correspondingly tick back up towards 90
degrees, but the pattern remains favorable for diurnally-forced
convection. PoPs remain in the forecast through the end of the
period, and heat-related impacts are not expected. Likewise, expect
overnight lows near/above 70 on ridgetops and in the upper 60s in
the valleys. Valley fog grids have been added to the baseline NBM
grids each night through the long term forecast period, although it
is noted that any leftover cloud decks from Tuesday and Wednesday's
precipitation chances could mitigate fog formation on those nights.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 805 PM EDT SAT AUG 9 2025
Surface and upper level ridging will dominate through the period.
This will lead to mostly VFR through the period. Showers that had
developed during peak heating are waning with cumulus also
diminishing in coverage at this time. Terminals are generally expected
to remain VFR through the period; however, valley fog could lift
into a site or two per LAMP and NBM guidance though persistence
would keep the sites fog free. At this point, have continued to
leave any reductions in the 08Z to 12Z timeframe out of the TAF
sites. Non TAF site valley locations may experience MVFR to IFR
or in some cases locally lower reductions at times between 05Z
and 13Z. Otherwise, some diurnally driven cumulus in the VFR range
should develop across portions of the area after 15Z but with the
are more under the center of the upper ridge on Sunday, showers
are not expected. Winds will remain light and variable.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...JP
SHORT TERM...VORST
LONG TERM...MARCUS
AVIATION...JP
Source:
JKL issues Area Forecast Discussion (AFD) at Aug 9, 10:43 PM EDT---------------
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