335
FXUS63 KLMK 251031
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
631 AM EDT Tue Jun 25 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   The Heat Index may rise above 100 degrees today, especially west
    of the I-65 corridor. Highs throughout the area will be above 90.

*   Isolated to scattered showers and storms will be possible late
    this afternoon into the evening. A few storms may be strong to
    severe with locally damaging wind the main threat.

*   Better shower and storm chances arrive Wednesday, bringing much
    needed rain to the region. A few storms may produce locally
    enhanced gusty winds and hail.

*   Shower and storm chances will return to the forecast by Saturday
    evening into Sunday morning.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 310 AM EDT Tue Jun 25 2024

Things are quiet across the CWA this morning with mostly clear skies
and light SE winds. A N/S oriented warm front is expected to pass
through the area later today, and will bring more steady SSW-SW
winds by late morning/midday, perhaps gusting up around 15-20 mph at
times through the afternoon. The warm advection combined with mostly
sunny skies is expected to allow for temps warming to the low and
mid 90s across the area. The passing warm front will also bring a
notable dew point gradient from W to E across the area, with
locations west of I-65 likely seeing some low 70s values combined
with some mid 90s readings. As a result, max heat indices are likely
to peak around 100 degrees this afternoon along and west of the
corridor. Am a bit concerned that areas around Jasper, IN may touch
a brief 105F heat index, however given upstream convection, upper
cloud cover is a bit in question. Plan to SPS areas along and west
of I-65, where a couple hours of heat index in the low 100s is
possible.

Outside of the heat and humidity, the big question with this
forecast is convective chances later this evening into the
overnight. Before we get to that, do want to address the current
convection ongoing across northern IL/IN. Models did not handle this
initiation well, and it is quite a bit farther south than any
solution i`ve seen to this point. As a result, confidence is pretty
low in convective initiation, timing, and placement as we go through
the day. This initial cluster is diving SE toward our area at a
pretty good clip currently, however the downstream environment
toward central and southern IN looks to be less favorable given weak
deep layer shear and a weakening instability gradient south and east
of the Wabash River Valley. So, overall don`t expect this cluster to
cause any problems for our area later this morning, however also
can`t completely let our guard down given models not handling this
at all.

With initial uncertainty in models pretty strong, that also makes
the evolution of the rest of the day quite uncertain. What we do
know is that we should become quite unstable this afternoon with
2000 to 2500 J/KG of ML CAPE expected across our NW CWA. This
unstable environment should be somewhat capped around 800-850 mb
based on forecast soundings, but steep mid level lapse rates above
that look to yield large positive area in the presence of a pretty
dry overall sounding. The end result yields a sounding that could
yield some pretty gusty downdrafts, given dry low levels as well.
Not sure we`ll have enough triggering down here alone to lift
parcels above/through the inversion, however do expect that anything
that gets going upstream and then survives/cold pool surges into our
area will have a strong to severe wind gust potential with it. SPC
has upgraded portions of our area to a Slight Risk, and given the
gusty look to the soundings certainly see the potential. The big
question really is just where/when storm initiate upstream. At this
point, like our best chances to be between 21 to 03z across the
northern half of our CWA. More storm chances/redevelopment is
possible overnight into the pre-dawn, but confidence is even lower
in how that evolves. Essentially, have increasing pops from N to S
from 21Z onward.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 310 AM EDT Tue Jun 25 2024

Wednesday - Wednesday Night...

Troughing will strengthen and swing through the Great Lakes, sending
a cold front south through the Ohio Valley on Wednesday. Ahead of
this front, ample deep-layer moisture will be present. Dew points
are forecasted to be in the upper 60s and low 70s, with PWATs near
2.0 inches. Along and ahead of the front, forcing will bring lift to
present moisture and increase the potential for showers and storms.
With greatest potential for storms being in the afternoon, daytime
heating will likely bring enough instability for at least marginal
convection. A 40kt LLJ along and ahead of the cold front will help
to increase shear and storm organization. Main threats with strong
storms is damaging winds, hail, and heavy rain. Should see a
widespread 0.25-0.5 inches of rain with locally higher amounts
possible. Showers and storms will move out of the region as the
front pushes through Wednesday evening.

Thursday - Friday Night...

Behind the the `cold` front, much drier and near normal conditions
will settle in. High pressure overhead will lead to clear skies and
light winds. Thursday should be a pleasant day with temperatures in
the mid-upper 80s and dew points in the low-mid 60s.

On Friday, high pressure will shift to the east and winds will veer
to a southwesterly direction. Moisture will quickly return to the
region raising dew points 6-10 degrees through the day. Ridging over
the southern US will bring low-mid 90s temperatures in the
afternoon. Friday will be warm and muggy with heat indices in the
upper 90s.

Saturday - Early Next Week...

Troughing will build and swing through the Great Lakes, sending
another cold front south through the Ohio Valley. The cold front and
troughing will bring forcing and lift to present moisture and
instability leading to another chance for showers and storms on
Saturday afternoon through Saturday night.

Behind the `cold` front, high pressure will build into the region
bringing near normal and drier conditions. Relief from heat seems to
be short lived as most guidance shows strong ridging moving over the
eastern US. Would likely see above normal and muggy conditions
return at the end of this long term period.

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 630 AM EDT Tue Jun 25 2024

VFR conditions are expected to mainly prevail through this TAF
cycle. The only caveat to this will be for some scattered t-storm
activity at the I-64 corridor sites later this afternoon and early
evening. Continued a Prob30 mention with this issuance to account
for that. Otherwise, look for a quiet early morning and much of the
day with only a few afternoon cu and upper clouds to speak of at
times. Light SE winds this morning will give way to more steady SSW
winds through afternoon. A few gusts up around 15 to 20 mph are
possible as we get into the afternoon hours, especially at
SDF/LEX/HNB/RGA.

&&

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

&&

$$

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