932
FXUS63 KJKL 111207
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
807 AM EDT Mon Aug 11 2025

.KEY MESSAGES...

-Hot and humid conditions are expected today, with afternoon heat
 indices reaching the mid-90s. Scattered pop-up thunderstorms are
 possible, with the best chance (40-50%) for counties adjacent to
 the Virginia-Kentucky border.

-An unsettled weather pattern is forecast from Tuesday through
 Thursday, bringing multiple rounds of showers and thunderstorms.
 Some storms will be capable of producing torrential downpours,
 leading to a threat of localized flash flooding.

-For the upcoming weekend, the rain threat decreases and a more
 typical summer pattern of isolated popup showers and thunderstorms,
 along with hotter temperatures climbing back to near 90F, will
 return.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 418 AM EDT MON AUG 11 2025

Another tranquil early morning is underway across eastern
Kentucky as the region remains under the influence of an ~1023 mb
surface high pressure centered just east of the Delmarva
Peninsula. Skies are clear and winds are relatively light,
allowing for fog to develop and expand through many of the
sheltered deep river valleys. Temperatures are seasonable, ranging
in the middle to upper 60s. Looking aloft, 500 hPa ridging
extends from the Tennessee Valley northeastward across New
England. A broad trough is found west of the ridge with an axis
extending from Manitoba to Texas. This trough supports a cold
front spanning from near James Bay southwestward into the Texas
Panhandle.

The 500 hPa ridge aloft will break down today/tonight and the
associated surface high will drift offshore as the aforementioned
upper-level trough slowly propagates eastward. The trough will be
filling as it approaches, but will still contribute to gradual
height falls, primarily during the day on Tuesday. Upper-level
model analysis does favor an upper-level high consolidating
between Bermuda and the Bahamas later tonight and Tuesday but it
will have limited impacts on our area in the short-term. Instead,
southerly return flow between the departing high and approaching
surface cold front will funnel tropical moisture toward the Ohio
Valley beginning today. Initially, there is enough of a downslope
southeasterly component in the return flow to limit PWAT rises
today to around 1.5 inches along Virginia-Kentucky border and 1.25
inches north of I-64. With the rising moisture levels, we will
see greater destabilization this afternoon, especially in the
vicinity of the Virginia-Kentucky border. Differential surface
heating, a subtle perturbation approaching aloft, and this
increased moisture/instability are likely to be enough for at
least scattered convection to fire off over the first two tiers of
counties closest to Virginia. Further north and west, deep
convection is still possible up to about the Mountain Parkway but
is likely to be much more isolated. RAP13 soundings suggest that
CAPE profiles may be thick enough for stronger updrafts to
overcome very weak lapse rates (~5.0C/km) in the 700 to 500 mb
layer, surpass the -20C level and produce sporadic lightning,
though the best chances of this are again over those counties
close to Virginia. Convection will diminish with the loss of
daytime heating this evening, with clearing skies setting the
stage for fog formation in the favored locales. As the low-level
flow turns more southwesterly, the moisture advection will become
unobstructed, allowing PWATs to surge to 1.8+ inches on Tuesday.
The deeper moisture, slight steepening of mid-level lapse rates,
and multiple weak perturbations ejecting northeast from the
approaching trough will promote rain chances expanding to the
entire forecast area.

In sensible terms, look for any valley fog this morning to yield
to mostly sunny skies area-wide by mid to late morning. An
extensive cumulus field should bubble up late morning and
afternoon with the most robust towering cumulus maturing into the
typical popup showers and thunderstorms. Locations between the Hal
Rogers Parkway/KY-80 corridor and the Virginia-Kentucky border
have the highest rain chances, 40-50 percent, but those chances
taper off further northwest to under 15 percent north of the
Mountain Parkway. It will be hot with high temperatures in the
upper 80s to lower 90s and rising humidity levels will make it
feel more like the middle 90s. Any leftover convection should fade
this evening, leaving partly cloudy skies overnight. Fog is a
good bet in the favored valley locales. It will be mild with low
temperatures in the mid 60s to near 70. On Tuesday, mostly sunny
skies fade to scattered to numerous showers and thunderstorms.
Activity is likely to be most extensive south of the Mountain
Parkway. It will again be humid, but not as warm, with high
temperatures in the mid to upper 80s expected.

.LONG TERM...(Tuesday night through Sunday)
Issued at 525 AM EDT MON AUG 11 2025

The long-term opens Tuesday evening with 500 hPa ridging breaking
along much of the Atlantic Seaboard and consolidating near the
Bahamas as an upstream upper-level trough advances across the
Upper Great Lakes/Mid-Mississippi Valley. The surface cold front
associated with the trough is initially progged to stretch from
~995 mb low along the southern shore of the Hudson Bay south
southwest across Lake Superior and then more southwesterly across
Iowa and into northern Kansas. Deep tropical moisture (PWATs
generally 1.8 inches or higher) is streaming northward in the mid-
Mississippi and Lower Ohio Valleys in the return flow ahead of
this boundary.

The 500 hPa trough will continue translating eastward and fill on
Wednesday as the new upper-level high retrogrades westward into
the Gulf of America. This will effectively render the pattern over
the Ohio Valley quasi-zonal and leave the cold front stranded
north of the Ohio River. Remnant energy from the trough will still
transit eastern Kentucky on Wednesday and almost certainly foster
deep convection in the tropical air mass. Skinny CAPE profiles,
weak Corfidi upshear vectors, nearly unidirectional flow, and a
deep warm cloud layer are all supportive of backbuilding and/or
training convection with high rainfall rates. Thus, WPC is
carrying a Marginal ERO to highlight the threat of localized
excessive rainfall. That threat of localized heavy rainfall
persists on Thursday and Friday as well though it gradually wanes
as the 500 hPa high strengthens and retrogrades to over the Lower
Mississippi Valley, turning the flow aloft more northerly and
causing PWATs to subside. Hence, deep convection is forecast to
become more isolated and also confined to primarily the afternoon
and early evening hours heading into the weekend. After reaching a
minimum on Wednesday/Thursday, 850 mb temperatures on the
northern side of the high will begin moderating a little each day,
reaching ~20C by next Sunday. This is warm enough to support
temperatures flirting with or surpassing the 90-degree mark across
most of eastern Kentucky.

In sensible terms, look for rather unsettled weather from Tuesday
night through at least Thursday with rounds of showers and
thunderstorms. The stronger activity could produce torrential
downpours leading to isolated instances of high water or flash
flooding. Temperatures will be cooler on both days, currently
forecast to top out in middle to upper 80s, but could be lower if
cloud cover is more abundant. Nighttime lows won`t be far from 70
degrees. Shower and thunderstorm chances become more isolated
from Friday through Sunday and confined mainly to the afternoon
and evening. Temperatures are likely to warm a bit as well with
many areas near or above 90F by Sunday afternoon with plenty of
sunshine, while nighttime lows range in the upper 60s to lower
70s. Nighttime fog is a good bet in the favored sheltered river
valley locations and could be a bit more widespread on certain
nights, depending upon temporospatial distribution of rainfall.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 806 AM EDT MON AUG 11 2025

VFR conditions were observed at TAF terminals. Any fog in the more
sheltered valleys should dissipate by 13-14Z. Convection is
expected to develop again this afternoon, with the highest
chances generally over the higher terrain along and adjacent to
the Virginia-Kentucky border. Outside of any convection,
terminals will remain dry with VFR conditions and light and
variable winds under 5kts.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...GEERTSON
LONG TERM...GEERTSON
AVIATION...GEERTSON