JKL issues Area Forecast Discussion (AFD) at Jul 21, 1:23 PM EDT244
FXUS63 KJKL 211723
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
123 PM EDT Mon Jul 21 2025
.KEY MESSAGES...
- The current weather regime will last through today, with
showers/thunderstorms expected at times, and isolated
occurrences of flash flooding possible.
- The potential for rain will wane by mid week and heat is
forecast build. Heat indices should top 100 degrees in many
places by late week.
&&
.UPDATE...
Issued at 1214 PM EDT MON JUL 21 2025
PoPs have been increased over southern and southwestern parts of
the forecast area, with a heavy blend toward the WRF-ARW which is
best representing the convection that has developed over the
central and southeastern Kentucky over the last couple of hours.
The main threat today continues to be the potential for flash
flooding due to excessive rainfall. Poor mid-level lapse rates
preclude much if any of an organized severe weather threat,
despite extremely marginal shear values of 20 to 25 kts, but the
severe threat is also not zero, either.
UPDATE Issued at 1004 AM EDT MON JUL 21 2025
Grids were freshened up with the mid-morning update, utilizing
the latest observations as the starting point for the forecast.
Made a minor upwards revisions of PoPs for this afternoon compared
to the previous update. Otherwise, there were no other significant
changes.
UPDATE Issued at 649 AM EDT MON JUL 21 2025
Updated grids and the forecast through 12z Tuesday, with minor
changes overall to reflect latest model trends. The Flood Watch
will continue as-is for now, but may need to consider trimming
some of the northern/northeastern counties, though will likely
wait to analyze the 12z model runs before making any final
decision.
UPDATE Issued at 1135 PM EDT SUN JUL 20 2025
Have adjusted the forecast for the latest radar trends and CAMs
guidance into Monday which suggest a couple more rounds of heavy
rain and thunderstorms are possible through the night. Did also
include of the latest obs and tendencies for the T/Td/Sky grids.
These adjustments have been sent to the NDFD and web servers along
with a freshening of the SAFs and zones.
UPDATE Issued at 845 PM EDT SUN JUL 20 2025
00Z sfc analysis shows a washed out frontal boundary through the
area and this is feeding a steady supply of lift and convergence
for additional clusters of storms lasting well into the night.
The latest round should fade out over the next couple of hours,
but a renewed threat looks to arrive closer towards midnight for
much of the area with a 3rd possible towards dawn. The Flood
Watch remains in effect through the night and most of Monday for
this threat - already borne out in parts of our northern and
eastern counties. Currently, temperatures are mostly in the low to
mid 70s, where the rains have been, to the low and mid 80s
southwest. Meanwhile, amid southerly winds of 5 to 10 mph,
dewpoints are generally in the low to mid 70s. Have updated the
forecast mainly to add in the latest obs and trends for the
T/Td/Sky grids and guide the PoPs and Wx per the most recent radar
images and near term CAMs consensus through the rest of the
night. These adjustments have been sent to the NDFD and web
servers along with a freshening of the zones and SAFs.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 443 PM EDT SUN JUL 20 2025
Surface based convection continues to multiply and intensify as we
reach the peak heat of the day. The most substantial activity is
in southeast IN, southern OH and northern KY, along and a little
south of the outflow from a prior MCS which progressed through IN
and into OH. With weak forcing and subsequent convection depending
partly on the evolution of earlier activity, models continue to
really struggle in their handling of convection again today. The
best consensus solution suggests that the current activity will
peak late this afternoon and early this evening, with nocturnal
convection more elevated in nature then initiating to our
northwest and heading east southeast into the JKL forecast area
during the night.
Precipitable water remains high-- near or above 2". There is a bit
more flow aloft than in recent days, but shear is still modest and
largely unidirectional. While storm motion is a bit faster, the
regime still gives a potential for backbuilding/training, and
with the very moist atmosphere this will present a risk of heavy
rainfall and possibly flash flooding. Hence, the Flood Watch
remains in place. The increased flow may allow for a bit more
storm organization, and locally damaging gusts won't be ruled out
with the stronger storms.
The nocturnal activity should weaken overnight and early Monday.
This leaves the question of redevelopment on Monday after more
heating/destabilization occurs. An additional factor comes into
play on Monday. Slight amplification of a northeast CONUS upper
trough will allow a back door cold front to move into eastern KY.
Depending on how quickly this happens, it could limit precip in
our northeastern counties. Where additional thunderstorms do
occur, slow moving cells and the possibility of
training/backbuilding will again need to be watched.
Drier air will arrive behind fropa on Monday night, especially
aloft, and this will finally bring an end to the mulit-day repeat
of heavy rain threats
.LONG TERM...(Tuesday through Sunday)
Issued at 245 PM EDT SUN JUL 20 2025
Tuesday, surface heights will begin to rise as high pressure builds
into much of the Southern, and Central US, including the
Appalachians. Shower and storm chances look isolated to scattered in
nature, concentrated but not limited to the southern part of the CWA
(Cumberland Plateau and areas along and south of the Hal
Roger/Kentucky 80 corridor). Dew points look to be lower than
previous days, in the upper 60s to low 70s, as winds become light
and out of the northeast, where previous days they were out of the
southwest, leading to higher dew points and greater storm potential.
Beyond Tuesday, the 500-mb Cluster Mean Analysis shows good
agreement of higher height anomalies over the Great Lakes, and Ohio
Valley over the remainder of the week. This is consistent with a
overall warming trend Wednesday through Sunday. By Thursday, an
upper level trough moves through Southern Canada pushing the above
normal height anomalies deeper south into the Ohio and Tennessee
Valleys, all while the modeled 594-dm high strengthens to a 596-dm
high and moves over the EKY/WV area. It is in this period where
temperatures will be at their highest. NBM has temperatures in the
low 90s Wednesday through Sunday, with temperatures cooling into the
low 70s. Heat indices are currently forecasted to reach the upper
90s to low 100s in many areas over by the end of the week, with some
areas around or near 105, though there has been a noted trend
downward.
Back in June of this year there was a 4 day stretch from the 22nd to
the 26th where similar temperatures occurred. During those days,
observed 850-mb temperatures were 21-22 Celsius (69-72 Fahrenheit),
which roughly translated down to surface of 32-33 Celsius or 90-92
Fahrenheit. Current model runs such as the Euro suggest 850-mb
temps may be slightly cooler (19-20C). This may roughly translate
down to a surface temperature of 89-91 in valleys. This is if mixed
dry adiabatically down to the surface, fully optimizing the warming.
Models remain fairly split on temperatures for the extended period
with the GFS, National Blend, WPC, and NBM (which uses a good chunk
of the GFS in long-term), on the warmer side of solutions, in the low
to mid 90s (91-94F). ConsAll, Consshort, Euro, NAM, and SREF remain
slightly cooler with temperatures of 87-90. This is more in line
with recent trends, however opted to keep NBM in the forecast for
now. Dew points remain elevated in the 70s beyond Thursday, leading
to hot and humid conditions. At current, DESI is showing a 15-20%
chance of 850-mb temperatures meeting or exceeding 22C, using the
LREF Grand Ensemble. Showers and storms may also develop towards the
end of the week, especially Friday through Sunday. This might occur
as a fairly strong upper level low moves across Canada, with a
trailing cold front extending through the Great Lakes, Ohio, and
Mississippi Valleys. Showers and storms would be situated along or
near this cold front as it passes through the area to end the week
and heading into next weekend. The surface high pressure that was
previously over the area mixes out downstream, however a subtropical
high begins to rebuild further west, over West Texas. For sensible
weather in Kentucky that would imply temperatures Friday through
Sunday may be forecasted in the upper 80s to low 90s, but could
struggle or have a chance to underachieve that mark with any storms
that develop over the area in the afternoon. It also means that warm
weather may continue beyond the long term period.
&&
.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 122 PM EDT MON JUL 21 2025
Scattered to numerous showers and thunderstorms will continue
through the afternoon and into the early evening along and south
of a shallow front situated west-east just south of KJKL as of
17z. To the north of this front, activity will be more isolated
and not quite as strong. Nevertheless, any significant precip
will bring IFR or worse conditions to a terminal. Winds, away from
any storm, will be generally northwest at 5 to 10 mph through
this afternoon, but will become northeast around 5 mph this
evening into the overnight as building surface high pressure
pushes a shallow backdoor front through much of the area. Despite
drier air advecting into the region from the northeast this
evening into the overnight, would expect fairly widespread valley
fog development this evening into the overnight, which may impact
some terminals.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 8 PM EDT this evening for KYZ044-050>052-
058>060-068-069-079-080-084>088-104-106>120.
&&
$$
UPDATE...CMC
SHORT TERM...HAL
LONG TERM...GINNICK
AVIATION...CMC
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 21, 1:23 PM EDT---------------
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