372
FXUS63 KLMK 190713
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
313 AM EDT Tue Aug 19 2025

.KEY MESSAGES...

* Peak Heat index values around 105 are likely, mainly along and
  west of I-65 today. Heat Advisory in effect for those areas.

* Scattered thunderstorms are expected for some later this evening
  into the overnight. The strongest storms could produce locally
  gusty winds and heavy rainfall.

* Drier and temperatures closer to normal for mid to late week.

* Below normal temperatures expected for the second half of the
  weekend into next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 312 AM EDT Tue Aug 19 2025

Things are quiet this morning under clear skies and mild
temperatures in the 70s for most. It should remain that way for the
morning hours before heat and humidity take center stage for the
afternoon, and then showers and storms for the evening into the
overnight.

Currently, a complex of showers and storms is ongoing across north
central IL into northern IN ahead of a cold front trailing from a
weak surface low. This convection should decay through the early
morning hours, but may send some convective outflow down closer to
our northern CWA border around or just after daybreak. Hi-res models
continue to suggest we stay dry through the morning, but can`t
completely rule out a stray shower or storm. The more likely
scenario is that we stay mostly sunny with temperatures quickly
warming into the low and mid 90s. This, combined with dew points
pooling into the low and mid 70s ahead of the approaching cold front
should yield another day of hot and humid conditions, especially
along and west of I-65. Other than a low chance that early
convection plays spoiler, don`t see a whole lot of limiting factors
to us getting hot during the afternoon, even with a few-sct
afternoon cu field likely to develop. Even with NBM 25th percentile
dew points (pretty good mixing this afternoon) still getting max
heat index values around 105 for several hours I-65 west. Decided to
go with a Heat Advisory for those areas to cover that, and it
matches pretty will with PAH/OHX headlines as well. Farther north,
there is too much uncertainty with convection.

The other concern will be for evening convection, possibly into the
overnight as a cold front sinks into our area. Ahead of this front,
it appears we get moderate to strongly unstable with 2000-3000 J/KG
of ML CAPE pooling ahead of the front across southern Indiana and
north central KY. Surface convergence ahead of the front should be
enough of a trigger in the unstable airmass. No real deep layer
shear to work with so storms will be pulse in nature, however
soundings suggest the atmospheric profile will support isolated
microburst potential (especially with deeper mixing) given steep low
level lapse rates and favorable DCAPE values. SPC Marginal Risk for
damaging wind looks good. The final question is just how long into
the late evening/overnight storms last, and whether we get any
repeated training with slow movement and "chain reaction" type storm
evolution to create a localized heavy rain threat. Something to
watch.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 312 AM EDT Tue Aug 19 2025

Wednesday - Wednesday Night...

Cold front is expected to be across our southern CWA, or already
south of the area by Wednesday morning. Will likely keep some low
chance pops down in that area for Wed, but overall should be a
drying trend from north to south by this time, along with some
slight temperature/humidity relief. Still looking for highs near
normal this day with max values in the upper 80s (north) to the low
90s (south). Wednesday night lows will be similar to the previous
night with most lows around or on either side of 70.

Thursday - Friday Night...

The late week time frame looks to be mostly dry with with
temperatures near normal for this time of year. Highs should mostly
be in the upper 80s to around 90, with lows mostly in the upper 60s
to around 70. Will hold onto a few isolated shower/storm chances
down across southern KY where a bit of a weakness in the upper ridge
will be noted. Slow moving showers or a few efficient thunderstorms
could put down briefly heavy rainfall each afternoon/evening, mainly
south of the Parkways.

Saturday - Monday...

Eastern CONUS troughing will steadily take hold of our area through
the weekend. As this occurs, we`ll see a reinforcing cold front drag
through our area Sunday morning. Looks like a notable airmass change
behind this front as Sunday highs should be a touch below normal in
the low to mid 80s. Then, Sunday night lows dip into the upper 50s
and low 60s. Monday highs only top out in the low 80s for most.

Expect to be mostly dry through this stretch as even the cold
frontal passage looks to be mostly moisture starved. Perhaps a few
showers will be possible. Will also have to continue carrying some
slight chances across our SE CWA on Saturday to account for that
weakness in the upper ridge before the trough and cold front arrive.

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 140 AM EDT Tue Aug 19 2025

VFR expected through this most of this forecast cycle, however a few
showers and storms could develop by late afternoon, and especially
later this evening. Until then, expect mostly clear skies and light
and variable winds. Any notable wind should be out of the ESE to SE
early this morning, gradually veering to S-SW by late morning, and
then W by mid afternoon. A few high-based cumulus (6-7 thousand
feet) will likely develop through mid to late afternoon, along with
a few isolated to widely scattered showers and storms across the
northern TAF sites through the evening.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory from noon EDT /11 AM CDT/ today to 8 PM EDT /7
    PM CDT/ this evening for KYZ023>030-061-062-070>073.
IN...Heat Advisory from noon EDT /11 AM CDT/ today to 8 PM EDT /7
    PM CDT/ this evening for INZ076>078-083-084-089>092.

&&

$$

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