JKL issues Area Forecast Discussion (AFD) at Jul 23, 8:10 AM EDT554
FXUS63 KJKL 231210 AAA
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
810 AM EDT Thu Jul 23 2026
.KEY MESSAGES...
- Mainly dry weather is expected into Friday, with temperatures
averaging around 5 degrees below normal.
- Unsettled weather is forecast to return this weekend, with
temperatures warming to near normal by early next week.
&&
.UPDATE...
Issued at 800 AM EDT THU JUL 23 2026
With any valley fog having lifted or dissipated, opted to remove
any fog from the database early this morning. Otherwise, grids
&&
.SHORT TERM...(Today through Friday)
Issued at 515 AM EDT THU JUL 23 2026
The period begins with an upper level low in the Hudson Bay
vicinity and the axis of an upper level trough/500 mb trough
extending into Quebec to the Northeastern Conus to mid Atlantic to
Southern Appalachians/Southeast. An upper level ridge was centered
over the Southern Plains with ridging east into the Lower MS
Valley/parts of the Southeast and also west into the Southwest
Conus. An upper low continues to meander off the Pacific
Northwest coast. Meanwhile an upper low shortwave was near the
northern BC and Alberta borders while well south of eastern KY
Bertha continues to move across northern parts of the Gulf.
Northwest flow between the trough from Canada to the eastern Conus
and ridging centered in the Southern Plains aloft was present
from the Northern Plains across the Great Lakes into parts of the
OH Valley and Appalachians. At the surface, an ridge of high
pressure extended from parts of the MS Valley across parts of the
Great Lakes to the Mid Atlantic states. Meanwhile a stalled or
nearly stalled frontal zone remains from east of the Northeast
coast to southeastern VA to near the TN and VA border to Southern
Plains.
Today and tonight, an upper level trough is progged to remain
from eastern Canada to eastern Conus and upper level ridging is
forecast to build into sections of the Great Basin and Rockies
and also along sections of the northern Gulf coast. Northwest flow
should remain from the Northern Plains to Great Lakes, OH Valley,
and Appalachians. The initial weak shortwave extending from MT to
WY and CO should move between this ridge and trough across the
Northern and Central Plains and near the mid MS Valley late
tonight. Meanwhile, the upper low and associated shortwave trough
in western Canada should move to Manitoba. At the surface, the
ridge of high pressure centered to the north of the Lower OH
Valley will become centered in the Northeast with ridging
extending into the Lower OH Valley and also south into VA. The
surface boundary nearly stalled to the south of eastern should sag
a bit south and become aligned from the NC coast to the northern
sections of the GUlf states to the Plains/KS vicinity. An inverted
trough may develop/move to the Southern Plains in between the two
sfc ridge axes. On Friday, the shortwave trough will continue to
approach eastern KY from the west and northwest while the sfc
boundary remains across the Southeast and the sfc ridge departs to
the northeast. Moisture will begin to increase and be deepest
nearer to the VA border.
Today with the ridging in place to the north, a dry airmass will
be ushered into the region with PW per the 00Z HREF progged in
the 3rd to 30th percentile (0.6 to 1.1 inch) range by this
evening. Tonight, the airmass remains dry with high pressure still
dominating with PW remaining in the 5th to 30th percentile (0.75
to 1.2 inch) range also per the 00Z HREF. Through Friday, the
northern two sections of the area remain dry with PW only
recovering by early Friday evening to the 30th to 55th percentile
(1.1 to 1.5 inch) range along and north of a Monticello to
Pikeville line. Values will become more modest right along the TN
and VA borders in the 60th to 75th percentile (1.55 to 1.7 inch)
range. As this occurs, sfc dewpoints should climb back to around
60 near and north of I-64 and ranging through the 60s further
south and southeast. This increase in moisture should result in
some cumulus formation in the southern portions of the area, with
some of the cumulus possibly becoming deep enough for a few
sprinkles or showers.
Forecast soundings from the 00Z HREF suggest rather warm air/capping
between 850 mb and 500 mb even for areas near the VA border. The 00Z
and 06Z HRRR runs as well as recent NAM and FV3 runs have very
little if convective development into the KY portion of the
Cumberland Mountains. The SPC Day 2 outlook does not have even
general thunder across eastern KY for Friday as well. With this in
mind, the NBM PPI01 appear too aggressive for the VA border
counties with POPS and thunder chances and capped pops at 30,
which is probably still on the aggressive side, and took thunder
chances to 10 percent due to the capping which should keep cumulus
development depth limited with isolated to perhaps scattered
showers at most.
.LONG TERM...(Friday night through Wednesday)
Issued at 446 AM EDT Thu Jul 23 2026
The long term forecast period continues to be defined by an
amplified mid/upper-level synoptic weather pattern. The antecedent
ridging over the west-central CONUS is progged to strengthen this
weekend, with 500mb heights over the Great Plains states rising
towards the 99th percentile of LREF model climatology on Saturday
and Sunday. At the same time, troughing will dig deeper into the
Eastern Seaboard, with heights off the Carolina coast plummeting
down below the 10th percentile early next week. Eastern Kentucky
will be positioned in between these two anomalously strong features
for the rest of the period, and guidance collectively resolves a
prolonged regime of northwesterly flow aloft as a result. A series
of shortwave disturbances is progged to navigate through this flow
and approach the forecast area over the course of the next week. As
they arrive, they will interact with increasing temperatures and
greater low-level moisture to produce periodic shower/storm chances.
Confidence in specific timing/intensity details decreases with time
though.
Forecast confidence is at its highest this weekend, during the
pattern's transition period. As the influence of the midlevel
ridging to our west grows on Friday, the surface high pressure
system responsible for today and tomorrow's pleasant will shift east
for Saturday. This allows low-level flow to adopt a more west-
southwesterly orientation and gradually return moisture to the
atmospheric column from SW to NE. Generic rain shower chances
accordingly re-enter the forecast in the southern half of the
forecast area after midnight on Saturday morning, when the first
shortwave impulse is expected to arrive aloft. This initial round of
activity is not expected to pose a risk for hazardous weather, but
the related cloud cover should keep Saturday morning's MinTs
insulated within the mid/upper 60s. It may also prevent the area's
conventional overnight ridge-valley temperature splits from coming
to fruition. Filtered diurnal warming and continued low-level WAA
yields high temperatures in the low/mid 80s on Saturday afternoon,
when relatively deeper moisture will begin spreading across the CWA.
LREF mean PWATs rise to between 1.5 inches in the Big Sandy region
and 1.8 inches closer to Lake Cumberland on Saturday evening, and
the arrival of the next impulse aloft should spark more meaningful
showers and storms by then. Saturday's PM activity is more likely to
come in the form of thunderstorms than anything that develops on
Friday night/Saturday morning, but that convection is still not
expected to be severe. While it may still produce frequent lightning
and heavy rainfall, it is generally expected to wind down overnight
with the loss of diurnal heating. If there is enough clearing in its
wake, the area's conventional ridge/valley temperature splits could
materialize by Sunday morning. Likewise, and especially if grounds
are wet across the area, nighttime radiation fog is plausible.
The pattern continues to amplify headed into next week, and the
growing influence of the ridging to our west should allow
temperatures to warm into the upper 80s on Sunday and then towards
the lower 90s on Monday and Tuesday. This corresponds with a return
to seasonably appropriate dewpoints in the upper 60s/lower 70s, and
together, this establishes a favorable thermodynamic environment for
relatively stronger thunderstorms next week. Additional disturbances
working their way around the ridge via the persistent NW flow will
provide the dynamic forcing necessary for storm initiation, but
there is considerable forecast uncertainty surrounding the arrival
time of each wave. Pattern recognition suggests that some of this
convective activity could take the form of more organized ridge-
riding MCSes, but the intensity of that activity would be highly
sensitive to both the evolution of upstream activity and its
relation to the diurnal instability cycle. The currently-available
deterministic model data lacks the resolution to resolve these finer-
scale convective details, but there are some useful signals showing
up in ensemble, analog, and AI/ML guidance.
Various machine learning outlook models continue to paint severe
hazard probability contours across our CWA early next week. There is
noticeably less of a signal with the experimental output for
Sunday's setup, but recent guidance suggests that there may be a
consensus time frame emerging between Monday night and Tuesday
night. There was a slight uptick in the latest ECMWF EFI/SOT joint
CAPE-shear output across our forecast area during the 8PM Monday to
8 PM Tuesday period. 70 to 80% of the ECMWF ensemble members are
resolving CAPE and shear values above what is considered normal for
this area in July, and 10% of the ensemble members are near the
model climatology's maxima. Trends in the above data will need to be
monitored closely in the coming days, as LREF mean ensemble
soundings depict favorable convective parameter spacing (1500+ J/kg
SBCAPE and 30-40 knots of effective bulk shear) during the afternoon
and evening hours on both Monday and Tuesday. However, these
soundings also show radiation inversions developing after sunset
each night, and if storms trend towards a late-night arrival, they
could certainly be in a weakening state.
The Storm Prediction Center has introduced a Day 5 (Monday) Slight
Severe Weather Outlook for upstream areas like Illinois, Indiana,
and Ohio. In the related forecast discussion, SPC mentions the
potential for an organized MCS to develop and then drop south-
southeast into the Appalachians into Tuesday. It would be working
against the diurnal instability cycle as it does so, but it should
be noted that the highest PoPs in the long term period now fall in
the aforementioned Monday night to Tuesday night time frame. If the
blended model data used to populate the long term grids continues to
increase PoPs around then and a consensus emerges, the evolution of
that upstream activity will need to be watched closely. It is
plausible for an additional wave of storms to develop later in the
day on Tuesday, but the quality of that wave's convective
environment would depend on the evolution of the previous night's
activity. It is far too soon to determine the effects of any
mesoscale/residual boundaries upon the setup, and the favored time
frame may shift in subsequent model runs. Given the potential for
multiple rounds of stronger thunderstorms, WPC has already gone
ahead and introduced a Marginal Excessive Rainfall Outlook to
portions of the forecast area early next week. So, we will also have
to monitor the potential for heavy rain to yield localized
hydrological impacts as the effects of the persistent pattern
accumulate. Altogether, this makes for a very active, but very
complex forecast for the end of July, and interests are encouraged
to monitor for further updates.
&&
.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
ISSUED AT 800 AM EDT THU JUL 23 2026
Clouds at the low, mid, and high level levels lingered from near
KJKL to KSJS and points south at issuance time. Overall, VFR was
present at the TAF sites, though some MVFR lingered at non TAF
site locations near the VA border including places such as K1A6
and KI35. High pressure will continue to build into the area as
it moves across the Great Lakes during the period with all
locations remaining or trending to VFR (in the case of areas along
the VA border) during the first 3 hours of the period. Once VFR
develops in all locations it should generally remain through the
end of the period. The only exception will be the chance for some
fog formation, mainly along the larger creeks, rivers, and lakes
that could lift into a couple of the TAF sites late in the period.
Confidence in any of the TAF sites was not high enough to include
at this point though recent LAMP data was showing some reductions
at KLOZ and KSME to MVFR or as low was IFR. Generally light and
variable to north to northeast winds in more exposed locations at
10KT or less are anticipated through 23Z, before light and
variable winds prevail to end the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...JP
SHORT TERM...JP
LONG TERM...MARCUS
AVIATION...JP
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 23, 8:10 AM EDT---------------
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