794
FXUS63 KLMK 280718
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
318 AM EDT Fri Jun 28 2024

.KEY MESSAGES...

*   Hot and muggy with a few showers around today.

*   Storm chances increase Saturday into early Sunday. Locally heavy
    rain and gusty winds will be the main threats. Above normal
    temperatures return by early/mid next week.

*   Another period of unsettled weather returns to the region by
    late Wednesday and Thursday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 317 AM EDT Fri Jun 28 2024

Fairly quiet weather expected in the short term as our region sits
between upper ridging over the SE CONUS and a stronger belt of
westerlies across the northern CONUS. That being said, a couple of
sensible weather items worth discussing.

Surface high pressure centered over the NE CONUS will continue to
slide eastward today. Meanwhile, a surface low will slide through
the upper Midwest and into the Great Lakes region. We`ll see light
SE surface winds this morning take on a more steady S component
through the afternoon as a warm front develops and moves east of our
area. As previous discussion mentioned, we`ll see an uptick in theta-
e advection with our area in the warm sector, and PWATs will rapidly
accelerate up above 2" through the column. As a result of this,
expect to see convective development initiate, however forecast
soundings continue to show a pretty stout inversion around 650 mb or
so. Looks like there could be a good 8-10 thousand feet of vertical
depth between where parcels are convectively released and where they
encounter the inversion, which will be sufficient for some isolated
rainfall. However, the cap looks unlikely to break and this seems to
be confirmed by forecast models continuing to only show light qpf
blips (showers) rather than more intense pockets of QPF (t-storms).
So, will elect to just put shower mention in the forecast with the
idea that the inversion/cap will hold. Good thing the cap is there,
as the overall sounding is fairly unstable with plenty of positive
area up to the EL.

Best coverage of pops should be along and east of I-65 through the
afternoon and evening, and then across our northern CWA toward dawn
on Saturday. Overall, most folks should stay dry.

Outside of the precipitation chances, temperatures look to recover
back above normal. Given the warm advection component and enough
solar insolation through thin upper clouds and few-sct afternoon cu,
highs are expected to mostly reach into the 89-93 degree range. Max
heat indices could peak around 100 for some. Continued warm
advection, some upper sky cover, and high dewpoints all point to a
mild and muggy overnight. Lows will mostly stay in the mid to upper
70s.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 317 AM EDT Fri Jun 28 2024

===== Saturday - Sunday =====

An upper shortwave will be swinging across the Great Lakes region on
Saturday, which will drag an associated sfc low across southern
Ontario and into Quebec. A southward extending cold front will
stretch as far south into Texas, and will be pushing east-southeast
towards the Ohio Valley through the day. Ahead of the arrival of the
front, we will have plenty of time for temps to reach the lower 90s.
Additionally, a more humid airmass will be in place, with sfc
dewpoints likely approaching the mid-70s. This temperature and
dewpoint combination will result in afternoon heat indices exceeding
100 degF.

The cold front will gradually approach the Ohio River late in the
day, which will provide the opportunity for a marginal severe risk
in the afternoon. Plenty of sfc heating in a humid airmass will
support afternoon destabilization ahead of the front. The 100-member
LREF has a 70-80% probability of exceeding 1000 J/kg of SBCAPE
Saturday afternoon across the forecast area. A 50-60% prob of
exceeding 1500 J/kg exists west of the I-75 corridor. It`s possible
some areas could realize upwards up 2000 J/kg of SBCAPE, though the
probabilities fall below 40%. Along with the instability expected, a
very high PWAT airmass will be present. Model soundings suggest we
could have PWATs exceeding 2 inches. LREF mean-ensemble paints 2.05-
2.15" across the region, which would be near the daily max values
from SPC sounding climatology from BNA and ILN. Despite these two
favorable indicators, wind shear appears to be fairly weak, with
model soundings generally agreeing around 20kts of bulk shear.
Sounding profiles show tall CAPE profiles, with deep warm cloud
layers, which will support precip-loaded storms capable of wet
microbursts and heavy rain rates. With rather marginal flow, storm
motions will also be fairly slow, leading to an additional concern
for localized flooding issues. SPC continues with the Marginal risk
in Day 2.

PoPs will continue into Saturday night and early Sunday morning as
the front sweeps through the region. Drier air aloft will be
increasing overnight, though low level capping will help decrease
any storm strength as we get later into the night. Still see the
potential for some storms, but the loss of heating will be in our
favor. PoPs will gradually exit from NW to SE through Sunday morning
and afternoon, with the front taking it`s time to clear our southern
counties until later in the day. This delay will keep low chance
PoPs going across south-central Kentucky through the early afternoon
hours. Eventually we`ll be PoP-free by late Sunday afternoon. Temps
will also respond to the post-frontal regime, with lower 80s across
southern IN, and temps back to near normal for Kentucky counties. The
real difference will be felt in those dewpoints. Dewpoints are
expected to be in the low-60s north of the Ohio River, mid-60s
across central Kentucky, and low-70s along and south of the
Cumberland Pkwy due to the front lingering. This will result in a
pretty big difference in heat indices from north to south for the
forecast area.


===== Monday - Tuesday =====

Dry weather will be around to start July, thanks to upper ridging
and sfc high pressure shifting cross the Midwest. Monday`s high
temps will be below normal for July 1, with readings only expected
to be in the low-80s. Sfc high pressure will continue to shift off
to the east for Tuesday, which will place us into a more warm return
flow pattern. Highs on Tuesday will exceed 90 degF, though mild
dewpoints will keep heat indices below triple digits.


===== Wednesday and Beyond =====

An upper shortwave riding in the flow will flatten out the upper
ridge by Tuesday night. Another cold will be approaching the region
by Wednesday, leading to PoPs making their way back into the
forecast. It appears this front could stall out somewhere within the
region by Thursday, which would promote additional shower and storm
development as we get into the end of the week.

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 147 AM EDT Fri Jun 28 2024

VFR conditions expected through this forecast period. Light
northeasterly winds early this morning will veer to a more E and
then SE component through the morning hours, eventually finding a
steady S direction between 5 and 10 mph through afternoon. Sct upper
clouds are expected through much of the forecast cycle, and do
expect some afternoon cumulus development between 4-6 K feet.

&&

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

&&

$$

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