977
FXUS63 KJKL 181201
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
801 AM EDT Tue Aug 18 2026

.KEY MESSAGES...

- Mainly dry and cooler weather returns today through Wednesday,
  though locally dense river valley fog is expected late tonight.

- A cold front brings scattered to widespread thunderstorms
  Wednesday night and Thursday, with a few strong wind gusts and
  localized flooding possible.

- Noticeably cooler and less humid air arrives this weekend and
  continues into early next week.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 400 AM EDT TUE AUG 18 2026

A cold front has finally settled south of the area early this
morning, bringing an end to the repeated daily torrential downpours.
It is still quite mild and muggy, though, as temperatures remain
mostly in the lower 70s with relative humidity values near 100%.
This moisture is manifesting as low stratus and fog in a weak but
still damp post-frontal northwesterly upslope flow. The moisture
is sufficiently deep for patchy drizzle or perhaps even some
sprinkles at times, especially along and east of the Pottsville
Escarpment. The latest surface analysis shows this northwesterly
flow is associated with anticyclonic flow around a ~1017 mb high
centered near St. Louis, MO. Farther upstream, a cold front
extends southwestward from a low near James Bay to over the
Northern Plains ahead of a digging 500 hPa trough.

That 500 hPa trough translates eastward and digs across the Great
Lakes, reaching its greatest depth on Wednesday morning, but only
glancing the Ohio Valley. As a result, the surface high pressure
will build eastward today, bringing drier air with it, cresting
over eastern Kentucky tonight, with PWATs bottoming out near 1.0
inch. The high pressure will then subside southward on Wednesday
as the upstream cold front approaches, yet slowing to a crawl as
it reaches the Lower Ohio River. In the southwesterly return flow
ahead of this boundary, PWATs over eastern Kentucky rise to
between 1.50 and 1.75 inches by the end of the day on Wednesday.
Showers and thunderstorms approach our Bluegrass counties late in
the day but are currently favored to not reach us until after the
end of the short-term period.

In sensible weather terms, a dreary mixture of fog, low stratus,
and/or drizzle this morning will gradually transition over to an
extensive cumulus field this afternoon. It will be cooler and
less humid than recent days, with high temperatures only in the
lower to middle 80s while dew points dip back into the 60s. For
tonight, mostly clear skies and light winds should allow for
extensive radiational fog formation in sheltered river valleys,
perhaps even growing deep enough to impact adjacent ridges. It
will be cooler, with lows in the lower to middle 60s. For
Wednesday, fog will mix out in the morning under mostly clear
skies, which will then give way to increasing mid-and high-level
cloud cover during the afternoon. Temperatures will rebound into
the mid to upper 80s by the afternoon.

.LONG TERM...(Wednesday night through Monday)
Issued at 435 AM EDT TUE AUG 18 2026

By Wednesday night, the cold frontal boundary will sag closer to
the area and shortwaves riding through the broader upper level
troughing will aid in forcing convection. This will lead to an
increasing threat of showers and thunderstorms Wednesday night,
with chances peaking in the 50 to 60 percent range near/north of
I-64 and lesser chances (20 to 30 percent range) toward the
Virginia border. The chance of showers and thunderstorms then
increases further Thursday (50 to 70 percent range), as the
frontal boundary sags deeper into Kentucky and a more pronounced
shortwave arrives. There is a decent surge of moisture noted with
the boundary, with PWAT values generally peaking in the 1.7 to 1.9
inch range, but the overall movement of this activity is expected
to be rather progressive. Even so, locations that experience
multiple rounds of convection could be at risk of minor flooding
issues, and WPC does have all of eastern Kentucky in a Marginal
Risk (1 out of 5) for Thursday into Thursday night. There is at
least some question on the potential for a few stronger storms,
with MUCAPE in the 1000-2000 J/kg range and effective shear in the
30-40 kt range. This is a reasonable enough parameter space to
aid in organizing convection, with the main risk being strong wind
gusts. This comes as DCAPE values increase toward 900 J/kg
Thursday afternoon.

By the end of the week, the cold front is expected to slowly sink
southward. There is some uncertainty as to how far, but enough to
keep rain chances lower for Friday and Saturday, generally in the
slight chance/chance range. Then by the late weekend into early
next week there remains at least some model uncertainty with
regard to the depth of the eastern CONUS trough as stronger
shortwave drops out of the Northwest Canadian Arctic. Some
guidance shows a closed upper low developing across the northern
Ohio Valley/Eastern Great Lakes while 500 hPA ridging pumps back
up over the Western CONUS. This could set the stage for a Canadian
cold front to cross eastern Kentucky late Saturday or early Sunday
with a subsequent early fall-like high pressure system to start
the last full week of August.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 801 AM EDT TUE AUG 18 2026

Widely varying conditions ranging from VFR to LIFR were present
across the terminals at 12Z TAF issuance. The worst conditions,
due to low stratus and fog, were present across most locations
east of I-75. The low stratus and fog will gradually lift through
the morning and scatter out into a cumulus field during the
afternoon as high pressure builds in from the northwest. More
widespread fog is probable tonight as that high pressure system
crests over eastern Kentucky. Light and variable winds at forecast
issuance time will become northwest at less than 10 kts by late
morning/early afternoon.

&&

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

&&

$$

SHORT TERM...GEERTSON
LONG TERM...DJ/GEERTSON
AVIATION...GEERTSON