752
FXUS63 KLMK 180150
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
950 PM EDT Sat Aug 17 2024

...Forecast Update...

.KEY MESSAGES...

*   Strong to severe storms will be possible this afternoon and
    evening if morning convection doesn`t limit diurnal warming. The
    main threats are damaging winds and hail.

*   Scattered showers and storms will be possible Sunday afternoon,
    but severe weather is not expected. Lingering isolated showers
    will be possible on Monday, mainly east of US 127.

*   Dry weather is expected Tuesday through Friday.

&&

.UPDATE...
Issued at 950 PM EDT Sat Aug 17 2024

Cold front trailing from a pretty strong late summer surface low
over eastern Canada is currently bisecting our CWA NE to SW.
Scattered showers and storms continue across southern and eastern KY
ahead of this feature, and have maintained some strength so far a
bit removed from sunset. There has been a bit of a surface/near
surface stable layer that has set up, however gusty winds are still
possible with the strongest thunderstorm cores in a strongly
unstable and high DCAPE airmass. Overall, expect t-storm activity to
continue sliding ESE and exiting our area over the next 2-3 hours,
with a relatively quiet overnight on tap after that.

Given the pockets of heavier rainfall from earlier this afternoon
and evening, do expect that fog may become a concern through the
overnight, at least in spots. Added some to the forecast, but
overall confidence is a bit hindered by dropping dew points behind
the front. With that in mind, it would make sense that points
farthest south and east that saw a good amount of rain would stand
the best shot at some fog.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 353 PM EDT Sat Aug 17 2024

This Afternoon through Tonight...

Over the past hour to 90 minutes, thunderstorms have blossomed along
a line from north of Elizabethtown all the way into southwest Ohio.
Temperatures which surged into the upper 80s and lower 90s and
dewpoint values in the low-to-mid 70s have provided ample
instability for storms to work with, as SPC Hourly Mesoanalysis
shows 2500-3000 J/kg MLCAPE in the vicinity of where storms have
developed. Marginally strong bulk wind shear around 30 kt has
supported multicell clusters so far, although one or two storms have
briefly gained supercell characteristics. The main limiting factor
for storms so far appears to be modest mid-level lapse rates of 5.5-
6 C/km, and storms have generally struggled to develop above 30 kft.
While this will limit overall severe hail potential, dry mid-level
air and steep low level lapse rates will continue to produce an
elevated damaging wind threat through this evening (Downdraft CAPE
values range from 1000-1200 J/kg).

As we head through the afternoon and evening hours, this initial
wave of storms should push into eastern KY. Where storms have not
developed so far today, lingering MLCAPE greater than 1500 J/kg will
still be available, and enhanced low-level convergence ahead of a
descending cold front could lead to additional rounds of showers and
storms. Showers and storms should begin to wind down around sunset,
with showers potentially lingering in southern KY until around or
just after midnight. For the rest of the nighttime hours tonight,
quiet conditions are expected, with patchy fog possible in areas
which receive rainfall this afternoon and evening.

Sunday...

By sunrise tomorrow, the surface cold front will have pushed through
the area, causing winds to swing around to the west-northwest and
bringing cooler air into the region. As is typical when an upper low
is nearby, low stratus clouds should be in place across the region
tomorrow morning, gradually scattering out and lifting during the
day. There should be a general SW-NE gradient in temperatures
tomorrow, with more cloud cover the farther north and east you go
keeping temperatures cooler across the KY Bluegrass region. There
should still be modest amounts of instability (around 1000 J/kg
MLCAPE) tomorrow, so additional waves of showers and thunderstorms
will be possible. However, shear will be much weaker tomorrow
compared to today, and the instability profile will be not be as
favorable for explosive convective development. As a result, severe
weather is not anticipated tomorrow, with more typical
summertime thunderstorms expected.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 353 PM EDT Sat Aug 17 2024

A large upper level trough translates slowly eastward across the
Appalachians heading into Monday. Upslope flow will likely enhance
scattered convective potential across eastern KY Monday afternoon.
Cannot rule out a shower or two east of I-75, but much of central KY
will remain dry. Drier air will advect in from the northwest, and
overall, it`ll be a nice start to the week. Expect morning lows in
the low to mid 60s, with afternoon highs around 80 F.

The rest of next week is still expected to feature an extended
stretch of fair weather. Strong upper level ridging centered over NM
gradually shifts east over TX, with heights steadily rising over the
Ohio Valley. Sfc high pressure builds southeast from Ontario to the
Mid-Atlantic coast, with sfc northerly to easterly flow throughout
the week.

The middle of the week looks very pleasant with lows in the 50s and
afternoon highs in the mid 70s to near 80 F. Cannot rule out some
40s early Wed and Thu mornings. Temperatures do creep back up toward
the end of the week due to increasing heights/thicknesses and the
development of southwesterly flow WAA. Highs in the low to mid 80s
look likely for Thursday, with mid/upper 80s Friday. The end of the
week still won`t be very humid, so expect a large diurnal
temperature range each day.

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 735 PM EDT Sat Aug 17 2024

Scattered thunderstorms continue across the region, and have
included VC mention for the next couple/few hours until peak heating
is lost. Any storm will be capable of very gusty winds and brief IFR
visibilities in heavy rain. Will amend as necessary if any terminals
are to be impacted by storms, otherwise will stay optimistic given
low coverage over the next few hours.

Once storms clear the area tonight, VFR conditions are expected
through much of the overnight, with localized fog possible where
heavy rainfall is observed today. Tomorrow morning, low stratus will
move in from the north, bringing MVFR ceilings primarily between 13-
17Z. Winds will veer to W/NW behind the cold front.

&&

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

&&

$$

UPDATE...BJS
SHORT TERM...CSG
LONG TERM...EBW
AVIATION...BJS