557
FXUS63 KLMK 260657
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
257 AM EDT Sun Jul 26 2026

.KEY MESSAGES...

* Spotty showers continue early this morning, but severe weather is
  not expected.

* Heat and humidity begin to increase today, with temperatures
  nearing 90F and heat index values close to 100F.

* Max afternoon heat indices could be in the triple digits for some
  by early next week, but this remain conditional on any
  thunderstorm chances. A Heat Advisory may be needed for Monday
  and/or Tuesday.

* Rounds of strong to severe storms are possible starting early
  Monday and last through Tuesday. Pockets of wind damage will be
  the main threat, and the most likely time for severe weather is
  currently later Monday evening into Monday night.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 257 AM EDT Sun Jul 26 2026

Overall, things are fairly quiet this morning however lots to
consider in the near term. We`re gonna hang onto some lingering
pockets of drizzle and/or very light rain through the pre-dawn hours
as 1000-800 mb moisture is slow to thin out. The bulk of the
coverage will be across southern and eastern KY, but can`t
completely rule it out anywhere at this point. Look for some patches
of fog through the morning also, but think it will mainly be a low
stratus show.

Looking for things to trend mostly dry through the daylight hours as
rather unremarkable NW flow aloft holds overhead. There was an
upstream MCS over the upper Midwest that looked as though it could
threaten our western CWA later this morning into early afternoon,
however it has fallen apart of the past couple of hours. We`ll have
to watch to make sure any remnant outflow boundaries and/or a
remnant weak MCV isn`t able to trigger a new complex later this
afternoon once we get strongly unstable, but right now most of the
CAM data keeps things pretty quiet. Speaking of instability, HREF
probabilities suggest pretty solid chances of 3000-4000 J/KG of SB
CAPE along and west of I-65 by this afternoon. East of I-65, 1500-
2500 J/KG of CAPE is expected.

So, given the moderate to strong instability there is some concern
that any thunderstorm that is able to get going could briefly become
strong to severe. There does appear to be enough deep layer shear
(30-40 knots of 0-6 km shear) thanks to a seasonably strong exit
region of a mid to upper level jet nosing into the Ohio Valley
region. These are the reasons SPC has place our area in a Marginal
Risk for severe weather. However, the good news is that there really
doesn`t appear to be much of a trigger around today and this
evening. We will have to watch for any upstream MCS activity to
possibly dive into our area in the pre-dawn hours of Monday, but
CAMs continue to be consistently inconsistent with their scenarios.
Any convective complex that is able to make it into our area would
carry a damaging wind threat with it. So bottom line, we`ll be quite
unstable today but lacking any notable triggers. Think we`ll stay
mostly dry and have to keep an eye on late tonight into Monday
morning.

Assuming we don`t get a bunch of convective activity today, the
other main focus will be building heat and humidity. The eastern
periphery of the upper ridge will become more established over the
area today, and 1000-850mb thickness will rise. Looking for highs to
reach into the 85 to 90 degree range today, along with increased dew
points into the 70s. This is going to yield max afternoon heat
indices in the upper 90s and low 100s along and west of I-65. Not
quite enough concern for a Heat Advisory in our western CWA, but
won`t be too far from it. There is some concern that lingering
stratus through the morning and plenty of upper sky cover from the
upstream convective complex could keep temperatures in the
underachieving range. Still, the humidity will see quite a notable
jump so it is going to feel more muggy regardless.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 257 AM EDT Sun Jul 26 2026

Monday - Tuesday Night...

Complicated early week forecast with multiple hazards possible, in
addition to a temperature forecast that will be dependent on
convective activity. We`ll be situated in a NW flow aloft pattern on
the eastern periphery of a strong western/central CONUS ridge
through early week. This will put us in a strongly unstable airmass
(SB CAPE over 3000 J/KG), and also in the presence of seasonably
strong mid and upper level wind fields thanks to a persistent exit
region of an upper level jet nosing into the Ohio River Valley. It
is possible that a convective complex could be ongoing across the
area on Monday morning, although confidence is lower than normal at
this range as model data (including CAMs) have been inconsistent
with this scenario. For now, let`s assume a dry start to the day.

The first concern for Monday will be temperatures warming into the
lower 90s in addition to dew points climbing well into the 70s for
most, especially along and west of I-65. This would yield max heat
indices in the 105-110F range along and west of I-65, and in the
upper 90s and low 100s across our eastern third or so of the CWA. A
Heat Advisory for half to two-thirds of our western CWA is likely in
this scenario, although it comes with a caveat. The potential for
the morning MCS and its convectively reinforced cold pool wrecking
the temperature forecast, and/or an afternoon MCS diving into our
area from upstream. As a result, won`t be too quick to lift a
headline until we are more confident in the convective evolution of
upstream MCS potential. The same type of scenario also applies for
Tuesday with similar values both in the T/Td department, maybe
slightly less. So, we`ll take a "wait and see" approach but will
also continue to message the conditional heat/humidity threat to
partners.

Back to the severe threats for Monday/Tuesday. Regardless of whether
we get a Monday AM MCS, we do expect to become strongly unstable
again by later Monday afternoon and evening. Forecast models
continue to suggest upstream MCS activity gets going, and then has a
good chance of diving into our area. The combination of 700-300 mb
mean wind fields combined with any notable instability gradients are
usually pretty good at steering these cold pool driven / forward
propagating MCS`s. As a result, do think we`ll see impacts from at
least 1, if not multiple thunderstorm complexes Monday and Tuesday.
Given the amount of instability, deep layer shear (especially mid to
upper level speed shear), and the likelihood of additional help from
a developed cold pool from upstream activity think the main concern
will be damaging winds. Perhaps a widespread damaging wind threat
could develop if things really get going. Most likely locations for
this would be across our NE CWA. Prolific lighting, and some
potential for localized heavy rainfall may also develop. These
systems usually tend to be progressive, however will have to watch
for some training potential where the western flank of any MCS gets
left behind by the surging cold pool. Will still be tons of
instability in these areas, but will be oriented more parallel to
the mean deep layer flow and could overachieve on rainfall. Right
now, the most consistent signal for an impactful MCS would be later
Monday evening into Monday night. Like the idea of SPC messaging the
severe risk, albeit it is still conditional upon storm track.

Wednesday - Friday...

The mid to late week time frame looks fairly quiet as we remain in
NW flow aloft, but this flow will be rather unremarkable with
respect to any triggering shortwave features. In addition, surface
high pressure builds in behind the departing cool front associated
with the late Monday/early Tuesday system passing through the Great
Lakes. The end result should be a mostly dry forecast with
temperatures settling back around normal for this time of year in
the upper 80s.

Saturday...

Quite a bit of uncertainty by early next weekend. It appears a
stronger shortwave may round the top of the upper ridge and try to
dig into the mid Mississippi River Valley. This could be a trigger
for scattered showers and storms by Saturday. Quite a bit of complex
upper pattern evolution before we get to that point, so will keep
this low confidence for now. Temps should generally be around normal
for this time of year, still in the upper 80s.

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 127 AM EDT Sun Jul 26 2026

RGA/BWG are the most likely sites to experience some drizzle and vis
reduction through the early morning hours. These will be in addition
to MVFR/IFR ceilings. The low ceilings are expected for all TAF
sites, and have put the expected timing for category jumps in there.
Surface winds will be light and variable for much of the morning
before eventually finding a more steady W-E component around midday
through the afternoon. Expect a return to VFR also by late morning
to midday. Shower and storm coverage confidence is low for later
tonight, and not quite ready to put in any Prob30 mentions just yet.

&&

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

&&

$$

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