000
FXUS63 KLMK 241105
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
705 AM EDT Wed Apr 24 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Lows in the middle and upper 30s tonight from southern Indiana
    into the northern Bluegrass region, and the typical cold spots.
    Patchy frost possible in these areas.

*   Isolated to scattered showers expected for Friday. A few rumbles
    of thunder also possible. Can`t rule out some isolated showers
    for southern Indiana on Saturday either.

*   Weekend will feature temperatures in the 80s and breezy S winds.
    Wind gusts 30-35 mph possible both Saturday and Sunday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 312 AM EDT Wed Apr 24 2024

High pressure over the Great Lakes will build southward into the
Ohio Valley today, sending drier air into the region on NNW breezes.
Despite the northerly component to the wind, the heart of the cold
air mass associated with the high will stay off to our north,
allowing the late April sun to still pull temperatures into the
upper 60s and lower 70s for many, which is only a few degrees below
normal for this time of year. A possible spoiler to the MaxT
forecast, however, is the chance of more widespread morning
cloudiness than is currently forecast. Clouds developed just to our
north from southern Illinois to central Ohio overnight. Confidence
in the evolution of these clouds is low, and if they become more
widespread or long-lived than currently expected, temperatures would
be suppressed.

Tonight the Great Lakes high will strengthen and continue to build
into the Ohio and Tennessee Valleys. Northeast breezes will bring
chilly air and lower dew points into the area. Though skies will be
mostly clear, we won`t quite have ideal radiational cooling
conditions with the center of the cold dome of high pressure
remaining off to our northeast near Toronto, and a breeze of 6-9mph
here. The deterministic forecast calls for lows tonight ranging from
the mid 30s in southeast Indiana and the Kentucky Blue Grass to the
lower 40s near the Tennessee line. HREF mean indicates a greater
than 50% chance of slipping below 36 degrees by 7am in rural areas
northeast of a Jasper-Bardstown-Stanford line, and a 40% chance of
briefly dipping to or below the freezing mark northeast of a Salem-
Paris line, especially in the usual sheltered cold spots. Near-
surface dew point depressions will be on the order of 3 to 5
degrees. So, for now will just include patchy frost in the forecast,
which is in general agreement with neighboring offices, and will
continue to evaluate frost chances and the need for any headlines.
Though widespread fog is not expected for much the same reasons as
for holding off on more widespread frost, river valley fog will be a
possibility by dawn, especially along the Kentucky, Licking, and Ohio.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 312 AM EDT Wed Apr 24 2024

Thursday - Friday...

Sfc high pressure will be centered over Lake Erie for Thursday, with
deep NW flow aloft and cool easterly flow at the sfc to support
temps near climate normals or slightly cooler. Temps will be cooler
to our north, with areas north of I-64 expected to only reach the
mid 60s. In contrast, slightly warmer conditions will be confined to
our south, with south-central Kentucky counties possibly reaching
the low 70s. It`s possible we could see a temperature difference
greater than 10 degrees from north to south in our CWA on Thursday.
While all is quiet in the Ohio Valley, to our west we will see an
upper level low pressure system deepen as it pivots from southern
California to the Colorado Rockies throughout Thursday.

By Thursday night, the upper low and associated sfc low will be
tracking into the High Plains. At the sfc, an extensive warm front
will stretch from Nebraska to the Southeastern US and pushing
northward towards the TN/OH Valleys. Isentropic lift will support
rain chances as early as late Thursday night, but the better chances
will come Friday during the daytime hours as that`ll be when our
better overall forcing arrives. Precip coverage will be mostly
scattered for the morning hours, but should become more isolated by
the afternoon hours. Certainly not a washout by any means with QPF
under a quarter of an inch for the day. Model soundings still show
unimpressive instability, so only expecting some isolated embedded
thunder throughout the day. The overall best moisture transport and
instability will be well west of our area, located with the core of
the low level jet across Missouri and Illinois.

By Friday night, the aforementioned LLJ will be spreading eastward,
and combined with a tightening sfc pressure gradient, should see an
uptick in sfc winds for the overnight with not much of a nocturnal
inversion expected to keep winds aloft. Moisture axis will be
greatest from eastern Arkansas/western Tennessee and stretching into
central Indiana, so our precip chances will be mainly focused along
and north of the Ohio River.


Weekend...

Warm and breezy is the main story for the weekend. As the upper low
that brought rain chances for Friday weakens and tracks north of the
Great Lakes, a secondary upper low will be tracking into the Plains
from the southwestern US. This will keep the core of LLJ winds stuck
across the mid-Mississippi/Ohio Valley due to the upper low across
the Plains and a broad upper high across the East Coast.
Additionally, the sfc pressure gradient will be getting squeezed
between the sfc high over the East Coast and the sfc low to our
west, so this will further support WAA and gusty sfc winds. With
deep SSW flow, strong WAA will support temps surging into the 80s
for both Saturday and Sunday. Forecast is looking drier for the
weekend now, with the only chance for isolated showers being across
southern IN within that persistent moisture transport axis. PoPs
basically follow the Ohio River, so just about all of central
Kentucky is expected to remain dry for Saturday and Sunday.

The main challenge will be nailing down the wind gusts. The
probability of wind gusts around 30-35 mph is high, but confidence
of 40+ mph gusts is medium. Certainly could see some isolated 40+
mph gusts, but the current data does not support widespread gusts of
that magnitude.


Early Next Week...

PoPs will be making a return to the CWA by Sunday night and Monday
morning as a cold front approaches from the west. Better chances for
anything severe will be well off to our west, and essentially we`ll
have a low CAPE high shear environment by the time the cold front
and associated precip arrives Monday morning. Some elevated thunder
will be possible, but soundings do not suggest any sfc-rooted
convection.

&&

.AVIATION /12Z TAFS THROUGH 18Z THURSDAY/...
Issued at 705 AM EDT Wed Apr 24 2024

In-and-out low clouds and fog have been teasing the TAF sites early
this morning. This is expected to continue for the first few hours
of the TAF before returning to prevailing VFR conditions for the
rest of the day.

High pressure building into the region from the Great Lakes today
and tonight will provide quiet weather with NNW breezes and partly
cloudy skies for the afternoon hours, and mostly clear skies with
light NNE breezes tonight. There may be some river valley fog by
sunrise Thursday but TAF sites should stay VFR.

&&

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

&&

$$

SHORT TERM...13
LONG TERM...CJP
AVIATION...13