JKL issues Area Forecast Discussion (AFD) at Aug 26, 4:48 PM EDT178
FXUS63 KJKL 262048
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
448 PM EDT Wed Aug 26 2026
.KEY MESSAGES...
- Expect increasing temperatures and humidity before a cold front
approaches the area tomorrow afternoon and sparks scattered
showers and storms.
- A few of tomorrow's thunderstorms could contain strong to
locally damaging wind gusts, hail, and heavy rainfall, mainly
during the afternoon and early evening hours.
- Expect drier conditions to prevail this weekend as temperatures
climb towards highs in the upper 80s/lower 90s early next week.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 410 PM EDT WED AUG 26 2026
Late this afternoon and upper level low as centered over Hudson
Bay with an upper trough south across the Great Lakes to OH
Valley to Southern Appalachians to portions of the southeast while
upper ridging was centered in the western Atlantic to the east of
Bermuda with another ridge centered over the southwest Conus with
that ridge axis extending across the Four Corners region to
western MT/Northern Rockies/Canadian Rockies vicinity. A shortwave
trough moving through the long wave trough was moving across the
western Great Lakes to mid MS Valley region. Locally, mixed
dewpoints this afternoon have trended up a bit into the lower 60s
or roughly 5 to 10 degrees higher compared to 24 hours ago.
Temperatures have also trended upward a couple of degrees with
the passing high clouds cutting back in the 24 hour temperature
change the most over western portions of the area. At the surface,
a ridge of high pressure centered in the Northeast and extending
to the Southern Appalachians was starting to depart with the
return flow leading to the trend of increased moisture and
moderating high temperatures. South of the area a quasi stationary
frontal zone extended from the Carolinas across the Gulf coast
states to the Southern Plains while a sfc low in advance of
shortwave in the Great Lakes located just to the north of Lake
Superior and the trailing cold front extending into the mid MS
Valley to Central Plains. PW at present has increased quite
substantial over the past 24 hours from 0.9 inches or less to the
1.3 to 1.45 inch range.
The shortwave trough currently upstream is progged to move to the
eastern Great Lakes to upper OH Valley by late tonight with the
axis of the upper trough remaining west of eastern KY. Another
shortwave moving around the ridging in the western Conus and into
the trough will approach late tonight. This next subtle shortwave
ahead of the main 500 mb trough axis should approach during the
day on Thursday and then trek across eastern KY Thursday evening.
The main 500 mb trough axis should near eastern KY to end the
period. The associated sfc low should track across Ontario and
into Quebec with the trailing cold front sweeping across the
western and central Great Lakes tonight and then across eastern
KY Thursday evening into Thursday night and should be south and
southeast of the area by around or shortly after midnight. PW
should increase a bit more ahead of the front on Thursday to
roughly the 1.4 to 1.55 inch range or not much higher than the
70th to 75th percentile if that.
Despite mid level lapse rates generally not much more than 6C/km,
MUCAPE at least in recent RAP forecasts is 2500 to 3000 J/kg while
shear on the marginal side mostly at 20 to 25KT. Hodographs on
forecast soundings are fairly long and some hail, perhaps up to
the lower end of the severe range (Quarter to half dollar size),
is possible. MLCAPE peaking at roughly 2000 to 2500 J/kg per
recent RAP runs and effective shear round 25KT or so could result
in line segments or clusters of cells with strong to locally
damaging wind gusts. The recent HRRR runs that have less
convection than some from 6 to 12 hours ago could be over mixing
and leading to lower sfc/BL dewpoints and instability and less
activity than may occur. This scenario happened recently back on
Saturday though parameters appear weaker in comparison. Any cells
moving repeatedly over the same are could result in locally heavy
rain in the southeast half or two thirds of the area. 12 HREF max
3 hour rainfall in the JKL CWA and vicinity is on the order of
around 3 inches. The potential for heavy downpours, strong to
damaging wind gusts, and some hail is included in the HWO and will
be featured in social media posts. Some convection could affect
the region late tonight into Thursday morning, though chances
should peak in the afternoon to evening.
By shortly after midnight Thursday night, chances for showers and
thunderstorms should diminish across the entire area as the
boundary gradually moves into VA and TN. A sfc ridge of high
pressure building in behind it begin to usher in drier air from
the west and northwest and coolest overnight lows should generally
be in the these locations. Some fog may also develop pending the
degree of clearing and how much rain falls on Thursday/Thursday
evening and fog was included in the grids across the western half
to two thirds of the area where clearing should be more
substantial.
.LONG TERM...(Friday through Wednesday)
Issued at 439 PM EDT Wed Aug 26 2026
Eastern Kentucky enters the long term forecast period on the back
side of the upper level trough axis responsible for Thursday's
convective activity. A weak secondary boundary situated within the
resultant northwesterly flow regime will push through the CWA on
Friday, but with a drier airmass actively advecting into the column
aloft, this is not expected to yield any substantial sensible
weather impacts. Expect partly cloudy skies, a shift to north-
northeasterly surface winds, and slightly cooler conditions (highs
in the low to mid 80s) across the forecast area to wrap up the work
week. Ridge-valley temperature splits and river valley fog formation
is plausible for Friday night into Saturday morning, as post-frontal
high pressure is progged to build into the forecast area this
weekend.
Under the influence of that surface high pressure system, expect
mostly clear conditions to prevail on Saturday and Sunday. Sensible
weather conditions this weekend will be diurnally modulated, with
cumulus clouds developing in the afternoon hours and continued
valley fog formation at night. Temperatures will gradually warm
throughout the weekend though, as winds will veer back towards a
more southerly orientation by Sunday. Saturday's highs in the mid to
upper 80s accordingly trend up a few degrees on Sunday before
approaching the 90s early next week.
Confidence remains high that a warmer and drier pattern will remain
in place across the region early next week. Forecast guidance
collectively resolves mid/upper level ridging across the Ohio River
Valley on Monday and Tuesday. Modeled 850mb temps near/above 20
degrees Celsius in place favors high temperatures in the lower 90s
at the surface, but the blended model guidance used to populate the
long term forecast grids is likely a little bit too warm/moist.
Diurnally mixed dewpoints will likely under-perform NBM guidance and
remain in the low to mid 60s. This should prevent heat indices from
climbing into the triple digits. While it will feel seasonably hot
outside on these two days, heat headlines should not be needed.
That upper level ridge looks to broaden out by midweek, with a
series of disturbances expected to propagate around its flattened
northern periphery. The PoPs related to these disturbances have
actually trended downward relative to previous forecast packages,
with only slight chances for isolated convection included in
Tuesday's forecast grids. Slightly better rain chances arrive ahead
of a stronger disturbance and cold front on Wednesday, although that
system's specific forecast details are masked by the increase in
model spread at that temporal range. Despite that uncertainty, the
midweek increase in PoPs should work to provide some relief from the
early week heat. In short, temperatures should trend back towards
climatological norms as we transition from August into September.
&&
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 215 PM EDT WED AUG 26 2026
An upper level trough and cold front will gradually approach the
area during the period as high pressure departs to the northeast.
A few diurnally driven cumulus are expected in the 3.5 to 5kft
agl range during the first 4 to 6 hours of the period along with
some passing high and mid level clouds from time to time. Isolated
to perhaps scattered convection cannot be ruled out after 06Z with
some passing mid and high clouds, but most of the activity should
hold off until 15Z to 18Z, if not later. Outside of any storms
late in the period, winds will be light, generally 5KT or less
from the south to southwest.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...JP
LONG TERM...MARCUS
AVIATION...JP
Source:
JKL issues Area Forecast Discussion (AFD) at Aug 26, 4:48 PM EDT---------------
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