652
FXUS63 KLMK 111045
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
645 AM EDT Mon Aug 11 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

* Hot and humid conditions expected all week, with daily highs
  in the upper 80s to lower 90s. Heat indices near 100 possible.

* Isolated showers and storms are possible this afternoon, but not
  all will see rain. Any showers or storms will be very slow moving.

* Scattered shower and storm chances increase Tuesday through
  Thursday as a weak frontal boundary approaches the region. Severe
  weather chances are unlikely, but stronger storms will be capable
  of heavy downpours, frequent lightning, and gusty winds.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 257 AM EDT Mon Aug 11 2025

Southeastern US upper level ridging will be spreading over the Ohio
Valley today, with sfc high pressure still mainly centered over the
mid-Atlantic coast. With the upper level trough still over the High
Plains today, we will be in a deeper south-southwest flow aloft,
which will help increase our moisture fetch today. PWATs will
increase slightly, with sfc dewpoints peaking in the upper 60s to
lower 70s. Temps are expected to peak in the lower 90s this
afternoon, making for hot and humid conditions. Steep low level
lapse rates will help agitate some cu over the region, but without
much of any trigger today, any convection today will be fairly
isolated. Any outflow boundaries that kick out from other cells will
act as a good trigger to fire off additional cells in this type of
patten. Model soundings show rather dry mid-levels, which elevate
our DCAPEs for this afternoon. However, the wind profiles are very
weak, with little shear for storms to work with. As a result, we
should have some isolated development per the 00z HREF paintballs,
but showers and storms will be nearly stationary and should mainly
be unorganized. Some heavy downpours may occur, but again this will
be pretty isolated chances.

For tonight, clouds clear out once again, leaving us with a dry
overnight period. Little change to the upper level pattern is
expected, so it should be similar the last couple of nights. Light
winds and clear skycover will aid in some patchy fog development in
the valleys, and anywhere else that gets some rainfall today may see
some fog by tomorrow morning. Temps in the lower 70s are likely.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 257 AM EDT Mon Aug 11 2025

===== Tuesday - Thursday Night =====

The upper trough will be swinging across the Great Lakes during the
mid-week, which will also drive a weak frontal boundary across the
Midwest and toward the forecast area. Sfc high pressure will be
anchored across the southeastern US, which will continue to funnel
rich Gulf air northward into the TN and OH valleys. We`ll see PWATs
creep up to near 2" on Tuesday, leading to some isolated to
scattered showers and storms. Precip activity for the week will be
amplified by afternoon peak heating, with less coverage expected
overnight and in the mornings.

Wednesday will feature our highest PoPs of the week, with scattered
to numerous showers and storms expected. We`ll see the frontal
boundary sag across Indiana during this time, providing better low
level moisture convergence when our PWATs are expected to surge over
2" as we get into a deeper moisture plume. A narrow mid-level
vorticity wing will add additional forcing for increased precip
coverage. Model soundings still indicate meager wind profiles, so
shear parameters are expected to remain weak. Most convection will
be messy, though given the PWATs around the daily max of sounding
climatology, heavy downpours and slow storm motions will make for
some localized flooding concerns. As such, WPC continues to
highlight the area for excessive rainfall.

By Thursday, the stationary boundary will be nearly over the Ohio
River, which will continue to provide a trigger for additional
shower and storm chances through the day. With the boundary
essentially over the river, expect precip chances to be lower for
southern IN counties, and the main focus for PoPs to be on the
south side of the boundary and across KY. This is shown quite well
in the WPC ERO for Thursday. Model soundings show a very similar
profile to both Tuesday and Wednesday, which we should see steep low
level lapse rates (given the hot temps), plenty of CAPE but little
to no shear. Slow storm motions and high PWATs will allude to
additional heavy slow moving downpours.

During this stretch of the week, daily high temps in the upper 80s
to lower 90s are forecast. The humidity will ramp up by mid-week,
with dewpoints creeping up into the mid to upper 70s by Wednesday.


===== Friday through the Weekend =====

The sfc high will likely remain over the southeastern US for the
weekend, which will keep pulling rich Gulf moisture northward into
our region. We`ll keep daily afternoon shower and storm chances in,
though the stationary boundary may fizzle out by this time.
Regardless, a hot and humid airmass in place could produce at least
some isolated pop-ups each afternoon. Forecast highs in the lower
90s, and dewpoints peaking in the low 70s, are possible for the
weekend. This combo would lead to heat indices around 100 degrees.

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 644 AM EDT Mon Aug 11 2025

Even though we have some mid-level clouds overhead and some patchy
fog in the valleys, the terminals are VFR this morning. These VFR
conditions are set to continue today, with a diurnal cu field
developing this afternoon during peak daytime heating. Winds will
remain rather light and generally from the south for the period. A
few isolated showers are possible this afternoon, but coverage will
not be enough to be worth mentioning in TAFs. Expect clouds to clear
by this evening, with winds becoming light and variable for the
overnight.

&&

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

&&

$$

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