290
FXUS63 KLMK 270517
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
117 AM EDT Mon May 27 2024

.KEY MESSAGES...

*   Severe weather and flash flood threat coming to an end
    overnight.

*   Breezy Monday with isolated to scattered showers possible.

*   Dry and cool for most of the upcoming week.

&&

.UPDATE...
Issued at 1111 PM EDT Sun May 26 2024

Individual supercells have congealed into a QLCS and is entering the
region from the west and northwest. A strong LLJ is enhancing low
level SRH, for tornado potential in the region. 0-3km shear over the
region is around 35kts, which is effective for maintaining the QLCS
line. The worked over environment from this morning still remains a
limiting factor for these storms. However, there are strong
kinematics with this line to build confidence for its maintenance
through the region.

Due to these reasons, the Tornado Watch has been extended into the
Bluegrass region. Now all counties are under the Tornado Watch at
this time.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 252 PM EDT Sun May 26 2024

Round 1 will be ending over the next hour or two across the southern
CWA. Pretty tight boundary just south of the KY/TN state line that
is the difference between stable and unstable airmasses. Will be
continuing to keep an eye on that boundary to make sure that surface-
based potential doesn`t creep back up into our southern tier of
counties before it exits the Lake Cumberland region. Still, with the
near-surface stable layer, expect that 40 to 50 mph winds could
still make it to the surface.

Still expecting a lull in action between 4 and 7 PM EDT before
activity likely ramps up again. Seeing clearing on satellite imagery
starting to move into SW Indiana and western KY. May get a few hours
of heating in place before the next wave development. Although we
aren`t totally sure how well we`ll re-destabilize we are seeing obs
jump back up into the mid 70s/mid 60s type of obs over southern IL
after an hour or two of heating. That is concerning, and given that
the HRRR has not back off the secondary development, do think we can
still have high confidence in those storms developing.

Speaking of development, it does look like there will be plenty of
trigger. Expect the low level jet to ramp up between 40 and 50 knots
by 00 to 03z, beneath good exit region mid to upper level jetting.
This should set the stage for potential of initial cells being able
to rotate (supercells). Do expect that there may continue to be a
near-surface stable layer, as indicated by hi-res models
consistently, which could limit our tornado threat/keep them a
little elevated. Initial cells would probably have a large hail
threat give good mid level lapse rates and MUCAPE values.

It appears that storms will congeal quickly into a line and then
begin to bow out along the I-64 corridor from 8PM to 10 PM. From
there, it should work steadily across KY and exit our SE between 2
and 3 AM EDT. Once the expected cold pool gets going, then would
fully expect that the stable layer could be overcome and that those
pockets of severe winds could again be mixed down. Still our
expected main threat going through the late evening and into the
overnight.

Will be looking to clear the Watches from Wave 1 shortly.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
Issued at 252 PM EDT Sun May 26 2024

Monday through Tuesday Night...

Deep low pressure is forecast to reach Lower MI by 12Z Monday, with
a trailing cold front advancing through central IN and western KY. A
trailing upper level shortwave trough will swing across the Ohio
Valley Monday morning as the cold front moves through the region.
This could touch off a few weak showers and storms early in the day,
though most will see a dry start to the day in the wake of severe
storms late Sunday.

There is a slightly greater chance (30%) for showers and storms in
the Bluegrass/Lake Cumberland regions in the afternoon. Slightly
richer moisture and a bit more time for the airmass to destabilize
prior to fropa results in the slightly higher rain chances. However,
precip will be sparse overall. Expect a mostly cloudy start to the
day, with lower clouds thinning during the second half of the day.
It will be breezy with gusts of 20-30 mph. Highs will range from the
mid 70s to around 80 F.

Notable upper level troughing lingers over the Great Lakes and Upper
Midwest through Tuesday night, keeping deeper moisture bottled up to
our north. An amplifying upper level ridge builds from the Rockies
to the Plains as sfc high pressure strengthens over the northern and
central Plains. Largely dry weather is expected with lows in the 50s
and afternoon highs in the mid 70s to near 80 F.

Wednesday through Saturday...

Ridging builds east across the MS and OH Valleys through late week,
resulting in a stretch of pleasant weather. Highs will be in the 70s
Wednesday and Thursday with comfortable humidity levels. Morning
lows will generally be in the 50s, though some spots will see
readings in the 40s Thursday and Friday mornings. Temperatures will
warm back to around 80 degrees Friday afternoon.

A highly meridional flow pattern will be in place heading into next
weekend. Ridging slowly drifts to the east as a Plains low pressure
system moves toward the region. Rain returns to the forecast for
late Saturday or Sunday, though timing remains uncertain.

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 117 AM EDT Mon May 27 2024

Convective line moving through LEX at the moment, but may well taper
off to stratiform before the valid time of the TAF. Expect a post-
convective environment at all the terminals roughly 06-08Z, with
light rain out of a mainly mid-level ceiling and chaotic, often E-NE
winds. Will handle the odd rumble of thunder with VCTS.

Sfc cold front arrives near daybreak with a shift to westerly winds
and a few hrs of MVFR stratus.  Will keep SDF just above 2000 feet
but take LEX and BWG a bit lower. As mixing deepens through the day,
look for cigs to lift to VFR and winds to pick up to near 15 kt with
20-25 kt gusts.

Loss of heating will allow the boundary layer to decouple after
sunset.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Flood Watch until 8 AM EDT /7 AM CDT/ this morning for
     KYZ023>043-045>049-053>057-061>067-070>078-081-082.
IN...Flood Watch until 8 AM EDT /7 AM CDT/ this morning for
     INZ076>079-083-084-089>092.

&&

$$

UPDATE...SRM
SHORT TERM...BJS
LONG TERM...EBW
AVIATION...RAS