738
FXUS63 KLMK 032342
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
742 PM EDT Wed Sep 3 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

* Two cold fronts will bring additional chances for rain tonight
  into Thursday and Friday night/Saturday. Rainfall amounts may make
  minor improvements to drought conditions, though drought removal
  is unlikely.

* Cooler and drier air returns by Sunday.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 351 PM EDT Wed Sep 3 2025

Scattered showers and thunderstorms have developed this afternoon
across east central and southern Kentucky as a modestly unstable
environment with around 2000-2500 J/kg SBCAPE is present. Areas to
the north and west have seen some scattered cumulus clouds develop;
however, a pocket of drier air aloft has mixed down to the surface,
lowering dewpoints and limiting instability along and north of the
Kentucky Parkways. This area of drier air is expected to spread east
across north central KY over the next few hours, with the main area
of showers and storms expected to shift into southern KY by late
afternoon.

This evening into early tonight, most of the showers and storms
should diminish with the loss of daytime heating, though a few
isolated showers may continue into the early overnight hours. An
upper-level trough will descend into the Midwest overnight, bringing
a surface cold front into the region after midnight. Ahead of this
front/upper trough, low-level response from height falls aloft
should support the development of a 30-35 knot SW LLJ, particularly
along and south of the Ohio River. This LLJ will bringing warm and
moist air into the low-to-mid levels, steeping lapse rates and
increasing instability aloft. This should lead to an increase in
showers and thunderstorms along and just ahead of the cold front as
it approaches the Ohio River in the pre-dawn hours tomorrow.

Most model soundings show a fairly meager amount of instability,
with between 500-1000 J/kg in the 12Z HREF mean MUCAPE field over
central and southern KY. Additionally, sounding profiles do show a
poor lapse rates within the boundary layer, so it should be fairly
difficult to get any strong winds down to the surface. As a result,
would expect the severe threat to be pretty low with convection
tonight. While HREF localized probability-matched mean QPF progs do
show high-end potential of 2" of rain in the heaviest swaths tonight
into tomorrow morning, the most likely rainfall amounts will be
between 0.25-0.75", with even less possible across far southern KY.

The cold front will be slow to push through the region tomorrow,
with showers and thunderstorms likely continuing across south
central and east central KY through the morning and into the early-
to-mid afternoon hours before exiting by early evening. South of
ongoing convection, areas may be able to destabilize enough to
realize some stronger wind gusts at the surface during the late
morning and afternoon hours. This is likely why the SPC has
highlighted a marginal risk for damaging winds south of the Kentucky
Parkways.

Through the late morning and afternoon hours, drier air will work in
behind the cold front, bringing a gradual end to clouds and
precipitation from NW to SE. Cold advection behind the front
combined with low cloud cover will keep temperatures down tomorrow
across north central KY and southern IN, with highs only expected to
reach the low-to-mid 70s. Farther south, where some heating may
occur in the morning, temperatures should be warmer, with highs
potentially reaching the upper 70s and low 80s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 351 PM EDT Wed Sep 3 2025

Thursday Night - Saturday...

A bit of a topsy-turvy pattern is in store for the end of the week
across the region. While the mean longwave trough will remain
established over the eastern half of North America, the leading
shortwave which will bring the front tonight into tomorrow will
quickly lift northeast Thursday night as another shortwave amplifies
over the mid- and upper-Miss. Valley. Before this second shortwave
brings another cold front into the region, there should be
considerable recovery of the warm sector on Friday as southwest
winds bring warmer temperatures and higher dewpoints back into the
area. Highs should be some 10-15 degrees warmer across the area on
Friday, and there should be a strong gradient between highs in the
low 80s across southern IN to highs reaching the low 90s across
southern KY.

Increasing moisture should allow for some instability to develop
Friday afternoon, with medium-range guidance showing between 1500-
2500 J/kg of SBCAPE, particularly across Kentucky. Stronger cyclonic
flow around the base of the trough should provide broad support for
ascent, and the sfc cold front may also be close enough to provide a
trigger for convection Friday afternoon and evening. Additionally,
stronger flow aloft (30-35 kt bulk shear) should support more
organized convection. As a result, there is a modest threat for
strong to severe storms Friday afternoon and evening, and this
thinking is supported by AI/ML convective hazards guidance. At this
time, it looks like gusty winds would be the main threat with
storms, though more details on timing and confidence will come as we
begin to get CAM guidance over the next 24-36 hours.

Showers and thunderstorms should continue Friday night, gradually
diminishing in intensity and coverage as we lose instability. The
slower trend in the cold front`s southward progression Saturday has
continued with today`s 12Z guidance, with showers appearing to be
more likely than not across much of the southern 2/3 of the CWA on
Saturday. With the front draped over the area on Saturday,
temperatures will drop once again, with highs only expected to reach
the low-to-mid 70s.

Late Weekend and Early Next Week...

By Saturday evening, the passage of the second shortwave should help
push the cold front through the area as drier air brings and end to
rain chances. Cool, dry northerly flow should set up over the region
for Sunday into Monday as high pressure moves across the lower Great
Lakes. Temperatures should be about 10-15 degrees below normal, with
highs in the 70s and lows in the mid-to-upper 40s and lower 50s.

As we head into the middle of next week, the upper level trough over
the eastern CONUS will retreat to the north as upper ridging over
the southwest US creeps eastward. While temperatures should begin to
warm next Tuesday into Wednesday, dry conditions are likely to
continue as higher moisture remains blocked to the southwest of the
region. All in all, fairly pleasant conditions are expected for the
first half of next week.

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 741 PM EDT Wed Sep 3 2025

We have VFR conditions across the region this evening, though a
change to flight cats are expected during this forecast period. A
cold front will be approaching the region tonight, and we will see a
line of showers and storms ahead of this front enter the area from
the northwest after 06z, and push through all terminals before
sunrise tomorrow. Mostly SHRA is expected, with a PROB30 for -TSRA
mentioned for each site. After the overnight round of precip,
lingering showers and a few storms are possible through the first
half of the daylight hours. Additionally, vis drops will be possible
with any moderate to heavy rain.

There is high confidence we will see cigs drop to MVFR as the front
approaches the area, with less confidence in a brief period of IFR.
By the early afternoon, improvements to flight cats are expected,
with VFR returning for the end of the period. Winds will veer from a
southerly component tonight to NW flow as the front passes through
during the daylight hours tomorrow.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...CSG
LONG TERM...CSG
AVIATION...CJP