272
FXUS63 KLMK 081421
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1021 AM EDT Sat Jun 8 2024

.KEY MESSAGES...

*   Showers and a few thunderstorms this weekend, with extended
    breaks in the rain expected. Locally heavy downpours possible
    late Saturday night into early Sunday morning across western and
    southern Kentucky.

*   Temperatures will begin a warming trend Tuesday, with 90 degrees
    a possibility by late week, especially Friday.

&&

.UPDATE...
Issued at 1021 AM EDT Sat Jun 8 2024

Light radar echoes are spreading across western Kentucky and
southwestern Indiana this morning as expected, with the dry airmass
eroding what`s left of a decaying overnight MCS. Morning ACARS data
from SDF confirms a dry layer in the lowest 3 km, which will linger
into the afternoon. The forecast remains in good shape, with no
major changes planned this morning. Similar to this morning, expect
to see PoPs generally decrease the farther south and east you go,
given that the remnants of the MCS should be falling apart as they
move east across central KY and southern IN. Best chances for any
light measurable precip will be north of the Kentucky Pkwys.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 330 AM EDT Sat Jun 8 2024

Across the region early this morning, mostly clear skies are
observed on latest nighttime microphysics satellite imagery, with
the first few convective debris clouds from an ongoing MCS over
eastern KS and western MO reaching our area at this time. As we head
toward dawn, additional clouds will begin to move toward the region
as the convective system moves eastward. This system should weaken
considerably as it loses its source of instability; however, an area
of light to moderate rain showers will approach areas west of I-65
by the mid-to-late morning hours.

Since the pre-existing air mass over our area is abnormally dry,
would expect initial radar returns to struggle to make it to the
ground later this morning. While current analysis and short range
progs do show increasing PWAT values later today, inspection of the
moisture profile via hi-res soundings reveals that much of this
moisture increase will take place above 700 mb, with the lowest 10
kft being slow to saturate. Accordingly, have lowered PoPs from NBM
guidance, though this still leaves chance PoPs across much of the
area later today. PoPs generally decrease the farther south and east
you go, given that the remnants of the MCS should be falling apart
as they move east across central KY and southern IN.

With the additional mid- and upper-level moisture present, mostly
cloudy skies are expected for much of the day today. Clouds are
expected to keep temperatures in the mid-to-upper 70s outside of
southern KY, though there is a low confidence possibility that brief
breaks in the clouds later this afternoon could allow temperatures
to quickly surge up into the 80s (10-20% likelihood). With the sfc
high pressure axis shifting to the southeast U.S. later today, SW
winds on the order of 5-10 mph are expected during the daytime hours.

This evening into tonight, an upper-level shortwave moving through
the upper Midwest will help to push a sfc cold front into the region
from the north. To the west of the region, waves of convection are
expected to initiate over central MO as convergence and lift in the
vicinity of the aforementioned front combines with a quite unstable
air mass over the Ozarks. Once this convection fires up, it should
move to the ESE along with deep-layer flow, taking it into the lower
Ohio and Tennessee valleys. Early Sunday morning, rain showers and
embedded thunderstorms should begin to move into the region, with
latest guidance generally favoring a track into southern KY and TN.
These convective complexes should be weakening as they move east of
the greatest instability; however, these showers and storms could
still produce areas of heavy rainfall, though exact positioning is
somewhat uncertain. 00Z HREF rainfall LPMM has swaths of greater
than 1" QPF over portions of southern KY, though this does appear to
be driven largely by one (HRRR) solution. Farther to the north,
light to moderate rain showers will be possible late tonight, with
rain chances falling off precipitously as you get north of I-64.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 330 AM EDT Sat Jun 8 2024

Sunday...

Cold frontal passage from north to south will take place on Sunday,
accompanied by showers and a few thunderstorms. QPF is highest over
southern Kentucky where there will be the longest residence time of
shower activity ahead of the front, and where there could be some
locally heavy downpours in rich PWAT air.

Rest of the week...

On Monday an upper trough reaching from the Canadian Maritimes to
the Ohio Valley will pass overhead. There should be very little
moisture for this system to work with and a strong mid-level cap
will be in place, so right now the forecast calls for partly cloudy
skies and no more than perhaps a stray low-topped light rain shower
along/east of I-75.

Tuesday through Thursday continue to look dry as high pressure
translates from the Midwest to off the mid-Atlantic coast and the
main storm track is well to our north along the Canadian border.
Temperatures will moderate from highs Tuesday in the middle and
upper 70s to the middle and upper 80s Thursday as we get into return
flow behind the departing surface high along with increasing 1000-
500mb thicknesses.

A cold front may approach by Thursday night or Friday, but
uncertainty is great this far out in the forecast and most ensembles
and operational runs keep us dry with the main sources of available
moisture to our south over the Gulf and our north over the Great
Lakes, so will stick with a dry forecast here for now.

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 655 AM EDT Sat Jun 8 2024

VFR conditions are expected for much of the current forecast period,
although ceilings will gradually drop today into tonight as a cold
front approaches the region from the north. Two rounds of rain
showers are expected during the current forecast period. The first
one is associated with the remnants of an area of thunderstorms
currently over southern IL which will weaken as it moves east later
this morning. Have gone ahead and included SHRA at HNB where
confidence is higher in showers reaching the terminal, while going
with VCSH at SDF and BWG where confidence is lower. Impacts are
generally not expected with this area of rain, as upstream obs
indicate VFR CIGs/VIS as this wave passes over.

Winds today will be out of the SW at 6-10 kt. A rogue 15 kt gust
cannot be ruled out at SDF and LEX, but winds will be lighter today
than the past few days. Tonight, winds will go light and variable
before veering to northerly after the cold front passes.

A second area of showers (with a few thunderstorms possible at BWG)
are expected to move across the region toward the end of the current
forecast period. Ceilings will also begin to approach MVFR levels by
around sunrise Sunday, but due to lingering forecast uncertainty,
will keep CIGs VFR for now.

&&

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

&&

$$

UPDATE...CJP
SHORT TERM...CSG
LONG TERM...13
AVIATION...CSG