-- Discussion containing changed information from previous version are highlighted. --
214
FXUS63 KLMK 222318
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
718 PM EDT Sat Jun 22 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Scattered showers and storms possible Sunday, and again by the
    middle of next week. Gusty winds the primary threat in any
    stronger storms that develop.

*   Heat Index may rise above 100 degrees on Tuesday, especially
    west of the I-65 corridor.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 304 PM EDT Sat Jun 22 2024

It`s another hot and humid afternoon with temperatures as of 2pm at
or just above 90 degrees with dew points near 70 making it feel like
the mid/upper 90s. The forecast is still on track for locations to
see heat index values over 100 later this afternoon. Along with the
heat we`ve seen the development of scattered cumulus and even a few
isolated showers. SBCAPE is 1000-2000 J/kg with steep low-level
lapse rates but mid-level lapse rates really fall off and any
activity that gets started dissipates as quickly as it got started.
Most will remain dry but can`t rule out a very brief isolated
shower/storm this afternoon into the early evening before sunset.

The overnight will remain dry, muggy and warm as the focus in the
short term turns to a weak shortwave trough and associated sfc low
working across the Great Lakes overnight into tomorrow. Hi-res
models continue to show the development of a convective line of
showers and storms across northern IL into western MI this evening
ahead of an approaching cold front. As this convective system
quickly works east and south, it will outpace the best forcing
dynamics and dissipate as it works towards southern IN and the Ohio
River by daybreak tomorrow. By the time this activity arrives
between 10-12z tomorrow, expected a few scattered showers and
embedded thunderstorm across southern IN/north central KY before
dissipating into central KY. Lows will remain warm tomorrow morning
only dropping into the low/mid 70s.

Residual outflow left over from the morning activity as well as the
arrival of the weak sfc boundary will help to develop more
convection late morning into the afternoon. With highs once again
approaching the upper 80s to near 90 and dew points in the low 70s
SBCAPE will be between 1500-2500 J/kg. SPC has most of our area in a
marginal risk for strong to severe storms with hail and gusty winds
being the main threat with deep layer shear values marginal or under
30kts but DCAPE over 1000 J/kg. A lot of this activity will depend
on how well we clear out from the morning activity and how our
low/mid level lapse rates recover in the afternoon.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 304 PM EDT Sat Jun 22 2024

High pressure overhead will bring us dry weather once the Sunday
evening showers/storms dissipate and move out. With clearing skies
and light winds, after possible scattered Sunday afternoon/evening
rain, we may see some valley fog by sunrise Monday, especially in
the Lake Cumberland region. During the day on Monday, while it will
be another very warm day with highs around 90, dew points behind the
Sunday front will be slightly more comfortable in the low-mid 60s.

That minor relief will be short-lived as moisture returns on Tuesday
behind the departing high. A weak 5H shortwave trough over the
Midwest and surface cold front will approach from the northwest by
afternoon/evening. There will be plenty of instability available and
while shear and mid-level lapse rates won`t be impressive, and the
forcing will remain rather far off to our northwest, isolated heat-
of-the-day summertime thunderstorms can`t be ruled out especially in
the evening in southern Indiana closer to the forcing to our north.

The bigger story on Tuesday will likely be the heat. With dew points
edging back up a few degrees, possibly over 70 west of I-65, and
temperatures rising into the lower and middle 90s, the afternoon
heat index should touch 100 along and west of I-65.

The Tuesday front will push through our area Wednesday and Wednesday
night, bringing us our best shot at rain over the next 7 days as
surface dew points rise into the lower 70s. Instability and shear
will once again not be particularly strong, but with frontal forcing
and some upper level divergence under the entrance region of a
slightly enhanced upper jet from Ohio to the St Lawrence Valley,
some stronger storms will be possible. Right now general QPF for
Wednesday-Wednesday night is around a third to half an inch, but
amounts will vary given the convective nature of the precipitation.

Dry weather will return Thursday and Friday as high pressure
advances form the Great Lakes to New England. Forecast data have
been trending warmer recently for these two days, with highs around
90 on Thursday and in the low-mid 90s Friday.

Saturday a cold front will approach from the northwest, but there
are timing differences in the model output. As of now the consensus
seems to be that the front will still be pretty far away on
Saturday, with a better chance of fropa, and rain, on Sunday.

&&

.AVIATION /00Z TAFS THROUGH 06Z MONDAY/...
-- Changed Discussion --
Issued at 717 PM EDT Sat Jun 22 2024

Expect VFR conditions throughout most, if not all, of this TAF
period. Currently, satellite shows advancing scattered cirrus from
the W while cumulus is beginning to slowly dissipate we move beyond
peak heating. Quiet conditions overnight before increasing mid cloud
cover advects over the region by sunrise Sunday morning, with
showers and possible storms weakening as they advance SE out of
IL/IN. Model soundings show abundant low level dry air, so it could
be more of a virga show. With another hot and humid day in store for
Sunday, diurnal destabilization along with forcing from a weak
surface cold front will result in isolated to scattered afternoon
showers and possible storms. Confidence in exact location of any
storms remains low. Winds will also pick up by late morning with
gusts 20-25kt possible throughout the day.
-- End Changed Discussion --

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Air Quality Alert until midnight EDT tonight for KYZ029>031.
IN...Air Quality Alert until midnight EDT tonight for INZ091-092.

&&

$$

SHORT TERM...BTN
LONG TERM...13
AVIATION...CG