-- Discussion containing changed information from previous version are highlighted. --
784
FXUS63 KLMK 042143
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
543 PM EDT Thu Jul 4 2024

...Forecast Update...

.KEY MESSAGES...

*   Scattered thunderstorms are forecast today, and thunderstorms
    will be capable of torrential downpours, gusty winds, and
    intense lightning.

*   Isolated flash flooding is possible today, especially across
    portions of southern Indiana and the Louisville Metro where
    heavy rain occurred yesterday. A Flood Watch is in effect for
    the most vulnerable locations.

*   Unsettled weather will continue through Friday with daily
    chances of showers/storms. Isolated damaging wind gusts,
    torrential rainfall, and lightning will be the primary hazards.

&&

.UPDATE...
-- Changed Discussion --
Issued at 542 PM EDT Thu Jul 4 2024

Several things to consider as we head into the early evening hours.
First off, convection remains across our southern CWA where the
airmass has yet to be untapped. While instability is strong, mid
level lapse rates are junk, and this is largely the limiting factor
for stronger/deeper development. Deep layer shear has been
marginally sufficient all afternoon with around 30 knots, however
expect to lose some 500mb flow over the next 3 hours, so likely that
0-6 km shear values will weaken a bit more. Still can`t rule out
some gusty winds/isolated severe through the evening, and will
continue to monitor. Keeping the last tiers of the Severe
Thunderstorm Watch going until planned expiration at 7 PM.

There is potential for some redevelopment later this evening around
sunset back along the synoptic frontal boundary still set to slide
through. However, confidence is low given much of the area has been
worked over and lingering convective debris is limiting
destabilization.

The final issue will be what to do with the going Flood Watch.
Waiting to see if we are going to get any new development this
evening, and we could possibly extend in that scenario. If not, will
likely let it go around sunset and then re-examine whether we need
another toward dawn.
-- End Changed Discussion --

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 315 PM EDT Thu Jul 4 2024

Just cancelled a portion of Severe Thunderstorm Watch 505, as the
line has pushed east of those area. A significant chunk of the watch
remains across portions of central and east central KY through 7 PM
EDT.

Currently a broken line of storms is moving through central
Kentucky. This line is bringing gusty winds, torrential rainfall,
and lightning. There is a non-zero tornado risk associated with this
line as slightly increased low level shear may allow for curling
within the line. A nose of 2500-3000 ML CAPE extends from the mid-
Mississippi Valley into central Kentucky. Best 0-3km shear is over
southern Indiana and northern Kentucky around 30-35kts. Therefore,
the northern half of the line is cold pool driven and the southern
half of the line is more pulse-like and has a higher potential for
microbursts. As this line continues over the Bluegrass, it will
outrun the best forcing and instability and begin to weaken.

Isolated convection outside of the line is still possible through
the evening hours.

In the overnight hours, winds will relax and skies will thin. Patchy
dense fog is possible in areas that received rain today. Low
temperatures in the morning will be in the low-mid 70s.

In the mid-morning, yet another round of showers and storms will be
possible as a weak shortwave moves through the lower Ohio Valley.
Scattered showers and storms will move through central and northern
Kentucky mid morning into the early afternoon. As these showers
reach the Bluegrass in the early afternoon, ample heating and a less
worked over environment will allow for some stronger storms. Main
threats will be gusty winds, lightning, and torrential rainfall.

The cold front associated with the low pressure system over the
great Lakes will move through the region in the afternoon and bring
much drier and cooler weather behind the front.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 315 PM EDT Thu Jul 4 2024

Cooler drier air will in advect in behind the departing cold front
Friday night into the weekend. Noticeably more comfortable dew points
in the low/mid 60s and temperatures near normal will be associated
with a sfc high that works in over the Ohio Valley on Saturday then
pushes east-northeast by Sunday afternoon. Highs will be mainly in
the mid 80s on Saturday with lows down in the low 60s Saturday
Night/Sunday morning. As upper heights increase during the day
Sunday, it will be warmer Sunday with afternoon highs in the upper
80s.

Pattern for early next week will feature strong ridging across the
western US with upper ridging out over the Atlantic. Longwave trough
across the central US will slowly work eastward through the first
half of the week. Current deterministic models show tropical cyclone
Beryl making landfall along the TX/Mexico border sometime Sunday
night early Monday morning. Some of this moisture may get pulled
north-northeast ahead of the approaching trough. Shortwave trough is
anticipated to cross the Great Lakes and Ohio Valley Tuesday into
Wednesday. This will keep chance of showers and storms in the
forecast (20-30 percent) for most of next week with higher PoPs (40-
60 percent) during the day on Tuesday. Highs for next week will
remain close to seasonable norms in the upper 80s for highs and
mid/upper 60s for lows. The exception looks to be Monday where highs
near 90 are possible.

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 315 PM EDT Thu Jul 4 2024

A line of storms is moving through central Kentucky currently and
will be through SDF in the next hour. The line will bring 20-25kt
gusts as it moves through. As the line continues east, it will begin
to dissipate over the Bluegrass. In the evening, winds will relax
through the overnight. Another round of showers and storms is
forecasted to move in from the east in the mid-morning.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Flood Watch until 8 PM EDT /7 PM CDT/ this evening for
     KYZ023>025-030.
IN...Flood Watch until 8 PM EDT /7 PM CDT/ this evening for INZ076-
     083-084-089>091.

&&

$$

UPDATE...BJS
SHORT TERM...SRM
LONG TERM...BTN
AVIATION...SRM