815
FXUS63 KLMK 260115
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
915 PM EDT Fri Apr 25 2025

.KEY MESSAGES...

*  Scattered showers ending around midnight tonight, with cooler and
   drier conditions toward daybreak Saturday.

*  A cold front will bring storms to the region Tuesday evening and
   night. Some strong to severe storms will be possible.

*  Showers and thunderstorms will continue into Wednesday and
   Thursday as Tuesday`s cold front gets hung up over the area.
   Localized flooding will be possible under stronger storms,
   especially Thursday.

&&

.UPDATE...
Issued at 915 PM EDT Fri Apr 25 2025

Coverage of showers is decreasing and thunder is getting harder to
come by with the loss of instability. Upper shortwave axis is
pushing eastward into the Ohio Valley at this time, and the sfc cold
front is just this side of Interstate 70, so there is some remaining
window of opportunity in the next few hrs.  Will carry scattered
showers with at least a slight chance for thunder, but that should
end around midnight.

Still some potential for fog just after fropa, but that will quickly
become limited to the valleys once the cold advection surge sets up.
This is handled well in the previous forecast.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 322 PM EDT Fri Apr 25 2025

Scattered showers and storms are currently moving northeast over the
region. Most areas are seeing a break in precip and even some sun
breaking through the clouds. Temperatures are in the low to mid 70s
over the region and will top out in the mid 70s. This little bit of
clearing will help to boost the surface based instability.
Forecasted to see 1200-1500+ J/kg of SBCAPE. Upper trough swinging
through and a cold front sinking south will increase lift over the
region and introduce 20-25kts of Effective Shear. Plentiful moisture
is present with few points in the mid 60s and PWATs between 1.5-1.7
inches. Marginal outlook is outlined over the eastern half of the
region through this evening. This is mostly a wind and hail threat,
but wouldn`t completely rule out a weak, spin-up. Some stronger
cells are currently developing over the western portion of the
region and will continue through sunset and then dissipate.

After the cold front pushes through the region overnight, high
pressure will build in behind. Low clouds will stick around through
the morning hours before lifting. Low temperatures are expected to
be in the 50s. Patchy fog will be possible in river valley areas.

Quiet weather will continue on Saturday with high pressure over the
region. Northwesterly winds 8-12mph in the afternoon with gusts up
to 20mph. High temperatures will be slightly below normal in the
upper 60s and low 70s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 242 PM EDT Fri Apr 25 2025

Saturday Night - Monday Night

Canadian high pressure will advance from the upper Great Lakes to
the mid-Atlantic coast during this time, providing the Ohio Valley
with quiet weather and cool temperatures Saturday night and Sunday
night. As most locations fall into the 40s early Sunday morning, a
few of the traditionally cold spots in the Blue Grass could briefly
touch the upper 30s. Models still want to produce some QPF on Monday
in return surface flow, but with upper ridging in place, shallow
moisture, and no QPF from WPC, will keep PoPs very low.

Tuesday - Tuesday Night

Low pressure crossing southeast Canada will drag a cold front into
the Ohio Valley Tuesday night. Storms are expected to erupt ahead of
the front from Oklahoma to Ohio by late afternoon or early evening
in a corridor of 40-50% joint probability of SBCAPE > 1000 J/kg and
0-500mb bulk shear > 40 kt. Right now the deep layer shear looks
fairly unidirectional on hodographs, supporting a wind threat with
bowing segments as initial supercells congeal into a line and head
ESE. Timing will be important, with a general decrease in intensity
expected after nightfall with decreasing instability and forecast
soundings indicating that the storms may become slightly elevated.

Wednesday - Friday and Beyond

The aforementioned cold front is still expected to lay out east-west
as it sinks into Kentucky, becoming quasi-stationary in the region
and, thus, not making much forward progress. This will prolong the
shower and storms chances through Wednesday and Thursday. Severe
parameters lessen quite a bit for Wednesday, but then increase some
for Thursday as a wave rides along the front from the Ozarks to the
Ohio Valley.

Precipitation amounts Tuesday evening through Friday night are
difficult to pin down given the convective nature of the rains such
that spots that get hit repeatedly by thunderstorms could accumulate
significant amounts of rainfall, while other locations receive quite
a bit less. EC EFI indicates QPF amounts typical for this time of
year. However, PWAT anomalies will be above normal with deep warm
cloud depths supporting efficient rain-producers that could very
well lead to localized flash flooding, especially by Thursday. We`ll
also have to keep an eye on the line of storms Tuesday night that
may change its orientation enough to support a threat of training
cells.

Looking ahead to Friday and peeking at Saturday, present indications
are that rain will end from west to east Friday as the mid-week
storm system pulls off to the east, with dry and pleasant weather on
Saturday courtesy of surface high pressure and deep N/NW flow.

&&

.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 729 PM EDT Fri Apr 25 2025

Clusters of showers moving through the terminals will result in
occasional MVFR cig/vis through mid/late evening, except HNB where
the precip is pretty much over.  Can`t rule out some embedded
thunder but by 0Z the probabilities will be too low to include in
the TAF.

Fropa will be shortly after midnight with MVFR cigs below 2000 feet
for a few hrs behind the boundary. Narrow window of opportunity for
MVFR vis before the wind surge picks up.  Best chance of IFR cigs
will be in LEX and RGA as we get closer to daybreak Saturday.

Cold advection regime on Sat with MVFR cigs and winds from the north
around 10 kt, though we`ll see a gradual lifting of the cloud deck
through the day.

&&

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

&&

$$

UPDATE...RAS
SHORT TERM...SRW
LONG TERM...13
AVIATION...RAS