714
FXUS63 KLMK 181906
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
306 PM EDT Fri Sep 18 2026

.KEY MESSAGES...

* Unseasonably hot weather will continue for much of the area
  through at least Sunday. Barring any early day thunderstorms, heat
  indices will top out in the mid 90s to around 105 (highest
  southwest) each afternoon.

* There is a 20-40% chance for showers and storms late this
  afternoon and evening, with slightly higher chances tomorrow.
  Locally damaging wind gusts and heavy rainfall may accompany the
  strongest storms, especially tomorrow.

* A weather system will bring higher rain chances (50-70%) Monday
  into Tuesday, followed by a cooldown to more seasonable
  temperatures (highs in the 70s, lows in the 50s) by the second
  half of week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 306 PM EDT Fri Sep 18 2026

Remnant outflow from this morning`s convection over the NE CWA has
now settled NW to SE along a line from Campbellsburg, IN down
through the Louisville Metro, and southeastward through
Nicholasville, KY. This feature is going to be the focus for renewed
convection this afternoon and early evening as some moderate
instability is now pooling along it. Just recently had convective
initiation across southern Washington county Indiana, and expect
that initiation could occur anywhere along this feature over the
next 1 to 2 hours. Elsewhere, we could pop a few very isolated
showers or storms once convective temps in the mid 90s are reached,
however it is also worth noting that areas SW are closer to the
upper ridge center where mid level subsidence will be more notable.
So, mainly have isolated to widely scattered (20-40%) Pops for areas
in and around the aforementioned boundary through around sunset or a
little after. The overall environment lacks deep layer shear despite
the moderate instability, so expect only pulse storm modes with
brief heavy rainfall, CG lightning, and perhaps some gusts up around
40 mph with the strongest cells. Anything above that would be very
isolated in nature.

Outside of the shower and storm threat this afternoon and early
evening, the other issue continues to be the Heat Advisory across
the SW half of the CWA. Here, the remnant outflow and convective
cloud cover will not have an impact so temperatures have been
allowed to once again rise into the mid 90s coupled with lower 70s
dew points. No changes planned to the current Heat Advisory
headline, except that we have extended a similar portion of it into
Saturday. A few counties on the far NE and E fringes of today`s
advisory have been trimmed for tomorrow. Expect peak afternoon heat
indices once again up to 105F.

In addition to the heat and humidity for tomorrow, SPC has included
a Marginal Risk (level 1/5) for a very localized damaging wind
threat. The aforementioned boundary will stay stalled over our area
until tomorrow when it begins to push back to the ENE as a weak warm
front. Given some moderate instability between 1500-2000 J/KG of ML
CAPE expected, this should be enough of a trigger for scattered
afternoon and evening convection once again. Overall deep layer
shear will still be quite weak with pulse storm modes anticipated
again. Given the slightly stronger instability tomorrow, suppose a
few stronger pulse storms are possible warranting the 5% Damaging
Wind prob from SPC.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 306 PM EDT Fri Sep 18 2026

Sunday - Monday...

The upper ridge breaks down a bit across the southern CONUS to end
the weekend. As a result, a belt of slightly stronger westerlies
sinks a bit southward from the Corn Belt through the mid Atlantic. A
surface front will also accompany this southward shift as it settles
into the Ohio River Valley region by Monday morning.

We`ll still be hot and muggy on Sunday ahead of the boundary as it
approaches, however it looks like it will be displaced to the north
enough to not be a factor on Sunday. In addition, we`ll likely still
have enough influence from the weakening upper ridge to keep the
area dry. Given Max Ts and the low and mid 90s and dew points in the
65 to 70 degree range, we`ll still see max heat indices in the 95 to
100 F range on Sunday.

By Monday, the front does sink into the area with cooler
temperatures in the low and mid 80s across our northern CWA, but
still in the upper 80s and low 90s across southern KY. We`ll also
have scattered afternoon and evening showers and storms triggered by
both the frontal boundary and perhaps some subtle embedded shortwave
activity passing through the flow.

Tuesday - Wednesday...

The real cool down sets in through mid week as a notable shortwave
rotates through the lower Great Lakes and Ohio River Valley region.
The aforementioned surface front will push south of the area with
much cooler temperatures in the 75-80 degree range across southern
IN and northern KY, and in the 80-85 degree range across southern
KY. We`ll also have pretty good coverage of showers and storms (up
to 70% east of I-65) on Tuesday ahead of the shortwave trough axis.
By Wednesday, the shortwave trough axis will be slowly pushing east
of the area, but will likely be still carrying pops across our
eastern CWA, with better chances for drier weather across the
western CWA. Temps will even be cooler by Wednesday with low and mid
70s north, and highs near 80 across southern KY.

Thursday - Friday...

Good chance that we get back into dry NW flow aloft for late week.
This should be a drier pattern, with temperatures mostly in the mid
and upper 70s. It should be noted that the mid to late week "cool
down" really just ends up being temperatures back close to normal
for this time of year, maybe slightly below on a couple of the days.

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 152 PM EDT Fri Sep 18 2026

VFR conditions are expected to prevail through this forecast cycle,
outside of the 30% chance of a shower or storm at SDF/LEX/RGA this
afternoon and evening. Surface winds will be pretty tricky as a weak
frontal boundary slides into the area later this evening into
tonight, however they should eventually find their way to a light NE
component. That same boundary will then slowly lift back NE on
Saturday with winds steadily veering to SE and then SSW through the
day. Ahead of that, we could also see some brief vis reductions to
the MVFR level in fog. Not real confident in that scenario though
given some upper sky cover.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory until 8 PM EDT /7 PM CDT/ Saturday for
     KYZ023>028-053-061>063-070>076.
     Heat Advisory until 7 PM CDT this evening for KYZ064-081.
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Saturday for INZ083-
     089.
     Heat Advisory until 8 PM EDT this evening for INZ084.

&&

$$

SHORT TERM...BJS
LONG TERM...BJS
AVIATION...BJS