031
FXUS63 KLMK 041419
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1019 AM EDT Thu Jul 4 2024

.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...
Issued at 1019 AM EDT Thu Jul 4 2024

Washed out frontal boundary is situated over southern Indiana this
morning. This boundary is expected to push north some today, keeping
most of the widespread precip north of the region. Already this
morning, a line of heavy rain moved through southern Indiana
bringing an additional 1-1.5 inches of rainfall. Some CoCoRaHS sites
in Dubois County have reported 4-5 inches of rain in the last 24
hours. Our far northwestern counties will continue to see low Flash
Flood guidance through today, therefore there is a Flood Watch in
these areas.

The HRRR and RAP have initiated and handled this mornings convection
well. These models keep showers and storms isolated through the
afternoon and increasing in coverage in the late afternoon through
the evening. Other guidance has development over northern Kentucky
and southern Indiana mid-day through the evening. Forecast
confidence remains low as there are multiple factors at play...
atmospheric recovery over southern Indiana after multiple rounds of
rain, cloud coverage, and frontal boundary placement. High
confidence remains in very moist conditions through the overnight.
If we do get development, we will see an additional 1-2 inches of
rain with locally higher amounts possible. If the region does stay
drier through the early afternoon, strong to severe weather
potential will increase in the afternoon through the evening. Given
ample instability, moisture, little shear, and present MCV, gusty to
damaging winds and torrential rainfall will be possible.
Additionally, with MCV increasing low level shear, there is a
very low, but non-zero tornado threat.

Over central and southern Kentucky, mostly clear skies and afternoon
diurnal Cu development will allow for ample heating. Could see
scattered storms and isolated strong to severe storms in the later
afternoon after reaching convective temps. Shear is  very weak,
therefore, pulse storms would be lead to a gusty wind, heavy
downpour, and a lightning threat.

Independence Day festivities... use caution while recreating and
stay weather aware today.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 408 AM EDT Thu Jul 4 2024

Precip coverage has decreased considerably early this morning with
just some very isolated activity. Earlier convection has weakened
with more stable air near the surface. A stalled, washed out frontal
boundary extends from southern MO ENE through the OH Valley. An
extremely moist airmass remains in place, characterized by 2.0-2.3
inch PW vales and sfc dewpoints in the mid 70s. The key to the
forecast today is upstream convection in KS/MO and how it evolves. A
MCS is forecast to push ENE across MO and into the Lower OH Valley
later this morning. The overall convective complex should weaken
with time, and organized severe weather does not appear likely.

At this time, we expect increasing thunderstorm chances by mid to
late morning along and north of the I-64 corridor. Convection should
continue to push east across the northern half of the area from mid-
morning into early afternoon. By midday or early afternoon,
additional scattered storm development becomes more likely along the
southern flank of morning convection/convective outflow. This will
allow thunderstorm chances to increase in central and southern KY
this afternoon and evening. However, forecast confidence in detailed
evolution drops beyond early afternoon.

This morning, a swath of heavy rain appears possible across southern
IN - including areas that saw flash flooding yesterday with the
first round of convection. An additional 1-2 inches of rain is
possible with locally higher amounts likely with any training
storms. Given the now lower FFG in these more vulnerable areas, a
Flood Watch has been issued in southern IN extending east into the
Louisville Metro through this evening. Localized flooding issues
will still be possible today outside of the Flood Watch area.
However, HREF PMM QPF supports a greater than 50% chance for at
least 1 inch or more of rain in 3 hours this morning/early afternoon
in areas that received the heaviest rainfall yesterday.

Scattered storms will likely linger in central KY into the evening
hours before activity diminishes once again in both coverage and
intensity. A lull is then expected through the first half of the
overnight period. Rain chances ramp back up heading into early
Friday as a deeper wave of low pressure moves across the Midwest.

Partly to mostly cloudy skies will help keep temps in check to some
degree today. Afternoon highs are expected to range from the mid 80s
to lower 90s. Southern KY will see a drier first half of the day and
is more likely to see widespread low 90s by the afternoon. Heat
index values will likely creep back above 100 degrees this afternoon
in south-central KY. Scattered storms will then bring some relief
from the heat and humidity to some. Heat index values may approach
105 in a few spots, but confidence is not high given the very humid
environment and potential for clouds/rain during peak heating. Will
therefore issue an SPS for south-central KY to highlight the
elevated heat and humidity.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 408 AM EDT Thu Jul 4 2024

Friday through Sunday Night...

Surface frontal boundary will be in the vicinity of the CWA Friday
morning.  We may have one or more perturbations aloft move through
sparking one or two more rounds of showers/storms during the day on
Friday.  However, a stronger upper level wave moving across the
Great Lakes will send a cold front through the region Friday night
ending precipitation chances.  Convective evolution for Friday
remains a bit uncertain given that we may have ongoing convection
early in the day which may hinder afternoon insolation.  While we`ll
have a moist airmass in place, MLCAPE values could rise into the
1000-1500 J/kg range with about 25-30kts of shear.  Overall coverage
from the latest CAMs looks to be more sparse across our region with
a relative maxima possible over OH/PA where bulk shear values would
be larger.  Any storm could produce gusty winds, intense rainfall
along with plenty of lightning.  Highs on the day may be kept down a
bit by ongoing cloud cover, but readings in the mid-upper 80s look
likely.  After the cold front passes through, some cooler/drier air
will work into the region with lows Friday night dipping down into
the low-mid 60s.

For Saturday/Sunday, dry conditions with near normal temperatures
are expected across the area.  Dewpoints will be noticeably lower
with readings in the lower-middle 60s.  Highs Saturday will be in
the mid 80s (83-88) with overnight lows in the upper 50s to the
lower 60s. Sunday should feature slightly warmer conditions with
highs mainly in the upper 80s.  Lows Sunday night will dip back into
the mid-upper 60s.

Monday through Wednesday...

As we head into next week, upper level pattern will change quite a
bit as strong ridging builds across the far western US with a
longwave trough develops across the eastern US.  Tropical cyclone
Beryl looks to make land fall across Mexico/S Texas early in the
week and some of the remnant moisture may get pulled back to the
north and northeast into the Ohio Valley by mid-late week.  Decent
upper level wave looks to push through late Tuesday bringing a good
shot of showers/storms. Overall, generally kept PoPs in the extended
in the 30-40% with the exception of Tuesday where we`ll run 50% PoPs.

Highs on Monday will likely be the warmest of the period with
readings in the upper 80s to the lower 90s.  Tuesday and Wednesday
look to feature highs mainly in the upper 80s with overnight lows
in the upper 60s/lower 70s.

&&

.AVIATION /12Z TAFS THROUGH 18Z FRIDAY/...
Issued at 652 AM EDT Thu Jul 4 2024

Scattered showers and storms are likely this morning, especially
along the I-64 corridor. This activity could bring brief TSRA
impacts to HNB and SDF early in the forecast period. Rain and
thunderstorm chances will gradually increase further south and east
late morning into the afternoon hours. Outside of convection,
prevailing VFR is expected. Confidence in detailed timing for TSRA
remains rather low due to some uncertainty regarding exact coverage
and evolution.

&&

.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...SRM
SHORT TERM...EBW
LONG TERM...MJ
AVIATION...EBW