115
FXUS63 KLMK 250711
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
311 AM EDT Sat May 25 2024

.KEY MESSAGES...

*   Severe storms possible Sunday into Sunday night. Main hazard is
    damaging winds with localized hurricane-force gusts possible.
    Tornadoes, large hail, and flooding cannot be ruled out either.

*   Unsettled pattern will continue into Monday with additional
    shower and thunderstorm chances.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 309 AM EDT Sat May 25 2024

A subtle upper level shortwave trough is shifting east across the
Lower Ohio Valley early this morning, while a primary closed low
lifts NNE near the MN/SW ON border. At the surface, an attendant
cold front extends through eastern WI, central IL, and southern MO.
Robust convection out ahead of the cold front has been diving
southeast along the instability gradient, and is now arriving in
portions of west-central KY. These storm clusters are likely to
continue into south-central KY while remaining sub-severe. MUCAPE
near 1000 J/kg should allow these storms to at least maintain their
intensity over the next couple of hours before gradual weakening. A
low-level nocturnal inversion is likely to continue strengthening
with time. However, given their current intensity and upstream
ASOS/KY Mesonet observations, wind gusts to 40 mph are possible.
Small hail, frequent lightning, and brief torrential rainfall are
also expected.

Additional scattered showers and storms will be possible in central
KY and southern IN through mid-morning as convective outflow and
modest mid-level ascent interact with sufficient moisture and
elevated instability. Brief heavy downpours, lightning, and gusty
winds will be the main hazards with any storms. Lows this morning
will be in the 60s.

Conditions will trend drier this afternoon in the wake of the
morning wave. However, the arrival of the weak sfc cold front should
spark off isolated showers and storms this afternoon and evening.
Partial clearing this afternoon will allow the atmosphere to
destabilize some, but deep-layer shear will be quite weak. So storm
activity should be sparse and disorganized, with most staying dry as
temps warm into the lower 80s. With the loss of daytime heating,
mainly dry conditions look likely tonight with lows in the 60s.
Attention then turns to a developing low pressure system over the
Plains. We`ll see increasing high clouds during the early morning
hours of Sunday.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 309 AM EDT Sat May 25 2024

Organized severe storms are possible on Sunday, with a few spots of
uncertainty to work through. Low-level jetting increases and a warm
front lifts through the region early in the day, which could touch
off scattered showers and storms. We`ll break into the warm sector
in the afternoon, with low-level and deep-layer shear increasing as
the day progresses. Timing of when we destabilize, and the presence
of forcing, could make a significant difference in convective mode
and timing of the severe threat.

Any storms that can break through a mid-level cap should be able to
organize into a squall line, with significant damaging wind
potential, especially late in the day. Not sold on forcing,
especially within the warm sector, so confidence is limited through
at least mid-afternoon Sunday. If the atmosphere reloads
quickly enough to destabilize the warm sector, that could open
the door to severe weather sooner than later if there is any
kind of forcing.

Some model soundings are hinting at sfc dewpoints in the mid 70s,
which seems a bit overdone. Confidence is higher that dewpoints will
be around 70, which still supports ~2000J/kg of CAPE, which is
sufficient for deep convection with the strengthening shear.

Most likely scenario for a squall line capable of significant
damaging winds would be initiating ahead of the cold front over
southern Illinois, and pushing across southern Indiana and
central Kentucky Sunday evening. Damaging wind and QLCS tornado
potential would be the greatest on any line segments that can
become oriented perpendicular to the shear vector.

The cold front finally pushes into the Ohio Valley Monday morning,
bringing an end to the severe weather threat, but shower and storm
chances will remain with us through the day as the upper trof axis
lags behind slightly. Faster westerlies and deep mixing will yield a
breezy day in between the scattered showers. Drier air finally
arrives Monday night, ushering in cooler than normal temperatures
and more comfortable dewpoints for most of the remainder of the
week.

&&

.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 115 AM EDT Sat May 25 2024

Ongoing TSRA near and SW of OWB is likely to continue diving
southeast toward BWG while gradually weakening. Confidence is much
lower in prevailing TSRA or even VCTS at SDF/LEX over the next 3-6
hours. However, cannot rule out an isolated thunderstorm near SDF
through mid-morning.

MVFR stratus is expected to overspread areas near and west of I-65
around or shortly after 12Z. Confidence is lower on exactly how far
east the MVFR ceilings make it before clouds begin lifting this
afternoon. A few isolated to widely scattered showers/storms are
possible later this afternoon and evening as a cold front dips in
from the northwest.

&&

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

&&

$$

SHORT TERM...EBW
LONG TERM...RAS
AVIATION...EBW