JKL issues Area Forecast Discussion (AFD) at Sep 23, 1:26 PM EDT562
FXUS63 KJKL 231726
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
126 PM EDT Tue Sep 23 2025
.KEY MESSAGES...
- Multiple rounds of showers and thunderstorms will bring a
soaking rain this week. While beneficial for the drought, this
rain could cause localized flash flooding, especially on
Wednesday.
- A few thunderstorms on Wednesday could become strong, with
damaging wind gusts as the main threat. The potential for these
storms will depend on how much the atmosphere can destabilize
during the day.
- A wet and unsettled pattern will continue through Friday before
cooler and drier, fall-like weather arrives for the weekend.
&&
.UPDATE...
Issued at 1129 AM EDT TUE SEP 23 2025
Just a quick refresh of the grids based on the latest surface
observations and radar trends. Late morning text and radio
products have been updated to reflect the changes and grids have
been saved and sent.
UPDATE Issued at 731 AM EDT TUE SEP 23 2025
Forecast is on track. Showers and any embedded thunder are
already diminishing and most of the forecast area should be dry,
outside of widely scattered showers, by ~10 AM.
&&
.SHORT TERM...(Today through Wednesday)
Issued at 453 AM EDT TUE SEP 23 2025
Regional radar at 8z shows numerous to widespread showers across
eastern Kentucky, with more intense thunderstorm activity lifting
northeast through Middle Tennessee. This activity is being forced
by a potent vorticity maximum (embedded within a large-scale
trough over the Eastern U.S.) moving into Central Kentucky.
Mesoanalysis shows up to a 1,000 J/kg of skinny MUCAPE near Lake
Cumberland waning to less than 250 J/kg east of US-23. As a
result, lightning activity is substantially greater toward the
southwest. PWATs are also high, ranging from 1.5 to 1.7 inches,
with moderate moisture transport occurring on a 20 to 25 kt, 850
mb southwesterly flow. Model soundings also reveal a deep warm
cloud layer, supporting efficient rainfall processes and
torrential downpours under the heavier cores. Cell motions are
progressive at around 30+ knots but the tropospheric profile is
supportive of training.
Heading through the remainder of the morning, the ongoing
convection will gradually lift northeastward and diminish in
coverage as the 500hPa trough axis and associated forcing shift
further east. Locally heavy rainfall leading to high water or even
an isolated instance of flash flooding cannot be ruled out. For
most locations, however, this rainfall is beneficial due to
antecedent abnormally dry to moderate drought conditions. Once the
wave pulls away, flow will turn quasi-zonal regionally. There
should be enough diurnal destabilization for some convective
redevelopment this afternoon, but a combination of weak height
rises, the lack of a notable forcing mechanism, and subsiding
PWATs should keep activity sparse. A positively-tilted trough of
Pacific origin, presently over the Central Plains, will begin to
pivot toward the east later tonight and Wednesday while fostering
cyclogenesis over Oklahoma. The first of multiple rounds of
vorticity energy will eject from this trough toward the Ohio
Valley tonight, ahead of a surface low that will move into the
Mid-Mississippi Valley on Wednesday. With that approaching surface
low, PWATs will surge higher again as the low's warm conveyor
belt jet feeds tropical moisture northward from the Gulf of
Mexico. The successive rounds of energy will lead to persistent
episodes of shower and thunderstorm activity tonight and Wednesday
across eastern Kentucky. Ongoing rains are priming soils, thus
making flooding more likely with this renewed rainfall. A general
1 to 2 inches of rain is expected for many locations from 00z
Wednesday through 00z Thursday. However, while there is not much
spatial model-to-model consistency, multiple CAMs are generating
swaths of concerningly high rainfall tonight and tomorrow with
23/00z HREF 24 hour ensemble max values locally approaching 5
inches. Accordingly, the Weather Prediction Center (WPC) has
maintained a Slight Risk for Excessive Rainfall on Wednesday. The
system's evolution will need to be monitored closely, and a Flood
Watch may be needed if confidence in the location and magnitude
of excessive rainfall increases. If cloud breaks develop between
rounds of rainfall, there will be enough shear to support
organized convection, including the potential for weak supercells.
All of eastern Kentucky is under a Marginal Risk for severe
weather on Wednesday.
In terms of sensible weather, rain with embedded thunderstorms
will gradually fade eastward by mid-morning. A mix of clouds and
sun can then be expected, with isolated to scattered showers and
thunderstorms developing during the afternoon before fading again
in the evening. It will be seasonable with temperatures topping
out in the upper 70s to lower 80s. Additional rounds of showers
and thunderstorms return tonight and continue for much of the day
on Wednesday. Some of this activity could become very persistent,
leading to high water and isolated to widely scattered instances
of flash flooding. An isolated strong to severe thunderstorm is
also possible, with gusty winds as the main concern. Temperatures
are expected to fall into the 60s tonight before rebounding to
similar highs in the upper 70s to lower 80s on Wednesday.
.LONG TERM...(Wednesday night through Monday)
Issued at 516 AM EDT TUE SEP 23 2025
The only change to the long-term forecast was to ensure sufficient
nocturnal ridge-valley temperatures splits from Friday night on
into early next week. Also, the most recent analysis discussion
for Wednesday is provided in the short-term discussion.
Previous discussion issued at 755 PM EDT Mon Sep 22 2025...
Active, wet weather is expected to continue for the first half the
long term forecast period across Eastern Kentucky. The forecast
guidance suite collectively resolves longwave troughing over the
Eastern CONUS through Friday before the pattern shifts and model
solutions begins to diverge. As various disturbances rotate around
this parent troughing feature, multiple rounds of showers and
thunderstorms appear likely to impact the region. That activity is
poised to give the Greater Ohio River Valley some highly
beneficial rainfall, although some of these storms could be on the
stronger side. Likewise, the cumulative nature of the rainfall
could lead to some hydrological concerns by the end of the work
week. Headed into the weekend, guidance generally points towards
synoptics that would advect a cooler and drier continental airmass
into the area. As the early-period pattern breaks down, a
cutoff/closed upper level low is expected to emerge over the Gulf
Coast. The latest deterministic model runs have moved closer to a
consensus regarding the positioning of said low on Saturday, but
continue to struggle to resolve the amount of moisture wrapping
around this feature early next week. Thus, confidence in the
forecast is much lower for Sunday and beyond.
When the period opens on Wednesday morning, the aforementioned
troughing is expected to be in a deepening phase. The forecast area
will be positioned to the east of this positively-tilted trough
axis, and this set-up favors cyclogenesis in the Ohio River Valley.
A surface low pressure system is expected to develop and then move
northeast as the day progresses. The system's warm front is expected
to lift north that morning, producing an initial round of rainfall.
Likely PoPs continue into Wednesday afternoon/evening, and some of
this rain is likely to be accompanied by thunder as temperatures
warm into at least the upper 70s. Questions linger regarding the
amount of available instability for storms in this time frame, as it
is uncertain whether or not temperatures will warm further into the
80s behind that warm front. Antecedent cloud coverage from the
morning activity could mitigate the thermodynamic environment for
stronger storms, although shear parameters look more favorable. The
LREF joint probabilities for favorable MUCAPE/bulk shear parameters
are currently in the 30-45% range on Wednesday afternoon/evening
across northern/western portions of the forecast area. Mean bulk
shear values of 30-35 knots would support a damaging wind gust
threat if enough instability is realized and frontal forcing could
allow for the development of multicellular clusters or a QLCS. With
a warm front nearby, we will also need to monitor the potential for
localized low-level shear enhancement. The Storm Prediction Center
has outlined most of the forecast area in a Marginal (Level 1/5)
Risk for severe thunderstorms on Wednesday, but noted that the risk
appears conditional due to these mesoscale uncertainties. As higher-
resolution models begin to provide more detailed insight into this
set up, confidence in details related to timing/coverage/hazard
types will increase. Interests are accordingly encouraged to stay
tuned to future forecast updates, especially because the evolution
of Wednesday's event will play a role in Thursday's forecast.
Shower and thunderstorm chances will persist into Thursday as the
aforementioned features propagate eastward. The LREF joint
probabilities for convective parameters are slightly higher (35-50%)
on Thursday afternoon in places along/south of the KY-80/Hal Rogers
Parkway corridor relative to the previously-discussed Wednesday
probs. Damaging wind gusts would be the primary threat with any
storms that take advantage of 30-35 knots of shear and frontal
forcing, but compounding uncertainties preclude the mention of
specific severe weather outlook details at this moment in time.
Thursday generally looks cooler than Wednesday, with afternoon highs
in the low to mid 70s and plenty of cloud cover in the sky. This
will likely limit instability across the area relative to Wednesday,
but the better frontal forcing will arrive on Thursday. Furthermore,
a remnant outflow boundary or a differential heating boundary could
serve as a focal point for convective initiation on Thursday. The
currently-available model guidance is too coarse to pick up on these
finer details, and this forecast is likely to change as higher-
resolution data comes in.
Regardless of severe weather potential, this activity is poised to
bring an additional 1.5 to 2.5 inches of rain to the forecast area.
Given the recently-worsening drought across the commonwealth, that
rain should be highly beneficial. However, if any given location
sees multiple rounds of heavy rainfall multiple days in a row or
multiple times in one day, this activity could culminate in some
localized hydrological impacts. The mean values for modeled
atmospheric precipitable water content in the LREF Grand Ensemble
are between 1.75 and 1.85 inches on Wednesday, and these values
remain elevated between 1.45 and 1.55 on Thursday. Wednesday's
values are above the 90th climatological percentile, and Thursday's
are above the 75th. These PWATS, along with the long/skinny CAPE
profiles visible in model soundings in this time frame, suggest that
rainfall rates will be efficient with this mid-week convection. WPC
has outlined the entirety of Kentucky in a Slight (Level 2/4)
Excessive Rainfall Outlook for Wednesday. This means that there is a
15% chance of rainfall exceeding flash flood guidance thresholds
within 25 miles of any given location in the forecast area on
Wednesday. These probabilities decrease to 5% (Marginal, Level 1/4)
on Thursday, but if soils become saturated by Tuesday or Wednesday's
rainfall, these odds could increase in future forecast updates.
While widespread main-stem river responses are not currently
forecast, localized instances of flash flooding are possible across
the forecast area on Wednesday and Thursday. Remember - turn around,
don't drown!
As the northern stream synoptic features responsible for all of the
above activity begin to eject on Friday, a piece of southern stream
energy will get cut off near the Gulf Coast. This yields the
development of a closed low in the SE CONUS, placing the
commonwealth in a weak regime of northerly flow headed into the
weekend. As drier and cooler air advects into the forecast area
behind Thursday's cold front and the flow aloft returns to
continental origins, skies should gradually clear. A few
orographically-enhanced showers cannot be ruled out on Friday, but
cooler highs in the low/mid 70s and much lower atmospheric moisture
parameters will mitigate the potency of any showers that develop.
Saturday and Sunday look generally drier as the northerly winds
persist, leading to the return of overnight ridge/valley temperature
splits and valley fog formation. However, some guidance suggests
that flow throughout the column may turn easterly by the very end of
the forecast period. If this shift were to materialize, a deep
moisture fetch off the Atlantic could develop, and a moist conveyor
belt around the aforementioned cutoff Gulf low could bring about the
return of shower chances early next week. Model spread begins to
increase around this time frame, so confidence that far out is
fairly low. Before then, expect pleasant fall-like conditions for
the first weekend of astronomical autumn.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 126 PM EDT TUE SEP 23 2025
A combination of categories exists across all TAF sites with this
issuance. TAFs are fluctuating between MVFR and VFR as low CIGS
exist across the area. Showers are starting to redevelop this
afternoon across the area; therefore, opted to go with a PROB30
through the remainder of the afternoon through 00Z/Wednesday. A
brief lull in activity is expected before another PROB30 goes into
effect through 05Z-09Z/Wednesday morning. Decreasing conditions
are expected after 10Z as a warm front lifts north through the
area. Showers and thunderstorms coupled with low CIGs and poor
VSBY will lead to near LIFR, IFR and MVFR conditions for the
remainder of the period. Winds are forecast to be light and
variable through the period; however, gusty and erratic winds will
accompany thunderstorms through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...VORST
SHORT TERM...GEERTSON
LONG TERM...MARCUS/GEERTSON
AVIATION...VORST
Source:
JKL issues Area Forecast Discussion (AFD) at Sep 23, 1:26 PM EDT---------------
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