Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/02/24

Area Forecast Discussion

National Weather Service Louisville KY

 1032 PM EDT Mon Apr 1 2024

...Forecast Update...

.KEY MESSAGES...

* Severe storms possible late tonight toward daybreak Tuesday, with
  damaging winds, large hail, and spin-up tornadoes possible.

* Severe storms are likely Tuesday. Damaging winds, large hail, and
  tornadoes are all possible. Localized flash flooding is also
  possible in areas impacted by repeated heavy rainfall.

* Perhaps a rain/snow mix Wednesday night early Thursday then much
  colder with freeze potential Friday Night.

* Eclipse weather starting to come into the 7-day forecast.

&&

.UPDATE...
Issued at 1031 PM EDT Mon Apr 1 2024

Convective complex has set up across central IL/IN at this hour, and
the latest trends in the data suggest that the farther north
solution is winning out to this point. As a result, thinking that
timing for the arrival of the convective complex can be pushed back
to the 4 or 5 AM time frame across southern Indiana, then pushing
ESE through the I-64 corridor through sunrise and the morning hours.
We do expect to see an uptick in warm advection showers and storms
picking up over the next 3 hours across our NW CWA as the low level
jet ramps up to 45-50 knots by 09-12z, but overall this isn`t
expected to be the main show. When the convective complex does
arrive in the pre-dawn to sunrise hours, expect it to be weakening
with mainly a wind threat. Can`t rule out a brief spin up tornado,
but would be more focused on the wind. Given the northward trend in
recent data, decided to hold off on the flood watch expansion
westward across more I-64 north counties, but still a bit concerned
heading into Tuesday with some training storms in this area.

After the morning wave, concern is still pretty high for what
happens in the dry slot ahead of the cold front for Tuesday
afternoon and evening. Soundings take on a pretty convincingly
tornadic look, including the threat for some strong and longer track
tornadoes with support from SARS sounding analog data. Low level
hodographs with very strong 0-1km shear would be supportive of good
streamwise vorticity ingestion in the presence of very strong
forcing and moderate instability nearing 1500 J/KG of ML CAPE.
02/00z run of the HRRR shows plenty of concerning UH tracks across a
large region, so the current threat/outlooks seem warranted, if not
some potential for upgrades. One factor hurting confidence for a
full blown outbreak is how much time we will have to clear out in
the dry slot, and build some instability. Right now, it does appear
we break out into the afternoon, and if that continues to be the
trend then confidence in some tornadic storms with all hazards will
continue to grow.

Previous Update...
Things are quiet across the CWA at this hour, with the warm front
analyzed from central IL, through southeast IN, and down into far NE
KY at this hour. The cap held through the afternoon and into the
early evening, although a 0005z AMDAR sounding shows the cap has
mostly eroded. Given the lack of any notable forcing at the moment
expect us to stay quiet for several more hours before activity picks
up. We`ll see the low level jet increase to around 45-50 knots
between 03 and 12 z tonight beneath strong exit region upper jet
structure. This will provide favorable deep layer shear across our
area as upstream MCS begins to impinge on our area.

The current picture upstream is becoming increasingly active with
supercells and strong to severe storm clusters across MO and IL, and
this activity is expected to ride generally W to E along the warm
frontal boundary through the overnight. Latest cams suggest that a
pretty concerning train of supercells and mixed QLCS modes could
train along the boundary somewhere between the I-64, and I-70
corridors, with the favor currently more on the Indiana side of
things. Given this training worry about a Flash Flood threat in
addition to the wind, hail, and tornado threat. Some of the latest
data has this activity pretty far north, and keeps our northern CWA
out of the game until 4 or 5 AM, while other data is a bit further
south and gets us going after 2 AM, which is when the LLJ should be
starting to ramp up pretty good. Am inclined to strongly consider
adding some more of our southern Indiana counties into the Flash
Flood Watch with the caveat that the farther north solution would
likely make this a bust. On the other hand, training of this
magnitude does lend to some potentially serious flooding concerns
somewhere between those two corridors.

Overall the severe threat through the overnight, and especially in
the pre-dawn hours to dawn still looks on the table, although feel
most confident in the 4 AM to midday time frame for the first wave,
mainly along and north of I-64. No changes to the main threat of
damaging winds and perhaps some flooding, with threats of some brief
tornadoes and hail also on the table.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 341 PM EDT Mon Apr 1 2024

Complex weather scenario starting to unfold over the next 24-36 hrs
with multiple opportunities for severe weather. Going in
chronological order, and increasing SVR potential...

Through This Evening...
Quasi-stationary front hung up over southern Indiana has started to
lift back north as a warm front. Isolated storms have popped over
the Wabash Valley and are mainly on track to slide just north of our
Indiana counties. However, as they generate outflow, redevelopment
is possible in our area of responsibility in southern Indiana, and
we have enough shear and steep enough mid-level lapse rates to
support large hail. We`re also sufficiently rooted at the sfc to see
damaging winds. This threat will diminish within an hour or two
after sunset.

Overnight...
Convection is underway over southern Kansas and northern Oklahoma,
and is expected to congeal into a squall line and accelerate
eastward this evening. This activity will cross the Mississippi
around midnight or shortly after, running just north of due east
into southern Indiana and northern parts of central Kentucky during
the pre-dawn hours. These storms will be mainly a damaging wind
threat, but large hail is also possible. The orientation of the
shear vector nearly parallel to the line doesn`t support prolific
spin-up tornado production, but anywhere the line becomes wavy, the
tornado potential will ramp up. Main focus on timing will be 2 AM to
7 AM EDT, with the line decaying around sunrise as it pushes into
the Bluegrass region of Kentucky.

There`s also some potential for training cells, especially along and
north of the I-64 corridor. However, with the lack of rain so far
today, am not inclined to expand the existing Flood Watch.

Tuesday (mainly afternoon)...
Severe risk on Tuesday could be highly dependent on how much the
overnight/early morning squall line works over the environment, and
how much precip lingers into the morning. Overall we do expect the
atmosphere to reload, but only so much agreement on the ability for
storms to fire ahead of the incoming cold front. Strong low-level
and deep-layer shear supports fast-moving supercells if it can
overcome the modest CIN, but some of the models are only developing
storms right on the cold front. All severe modes are on the table,
including damaging winds, large hail, and fast-moving, potentially
strong tornadoes. The SVR threat declines quickly with the passage
of the cold front, but that won`t happen until sunset or just after
in some of our south-central and east-central Kentucky counties.

&&

.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 341 PM EDT Mon Apr 1 2024

Tuesday evening expect the cold frontal system responsible for
Tuesday daytime stormy weather to be pushing through southern IN and
central KY. The sprawling upper level system will slowly push across
the Midwest during the day Wednesday. With the tight pressure
gradient on the back side of the front, and moisture associated with
that upper low, expect Wednesday to be cold, windy, and dreary with
some light rain showers moving across the region. Any deeper cores
that develop during the afternoon could have some small hail. Not an
ideal day for the 50th anniversary of the Super Outbreak. In fact,
Wed. night we may briefly get cold enough to have a rain/snow mix in
a few spots. Activity shouldn`t be heavy enough for any impactful
snow on the ground though.

Clouds and precip chances will slowly shift east through the day
Thursday. Ridging will slowly build in Thursday night and
potentially hold onto to Sunday. That ridging will bring in less
cloud cover, and combined with winds dying down could bring a freeze
Friday night and Saturday night. Thursday night temperatures look to
fall into the 30s, but winds should stay up enough to preclude frost
formation, save for in very sheltered locations.

Sunday night/Monday the deterministic models (12Z GFS/00Z CMC/00Z
Euro) all bring an upper low into the Northern Plains. Our area will
be in the southwest flow between the narrow ridge pushing east of
our and this upper low.  This pattern tends to bring high clouds
over our area. Those deterministic models pull in some rain chances
as well, and the 00Z ensemble runs tend to agree with that
chance...with several members showing at least light QPF through
Monday. Sky cover grids still have a fairly wide spread in coverage
for Monday afternoon, but the means line up with climo for sky cover
on Eclipse Day...so no big signal seen just yet.

&&

.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 752 PM EDT Mon Apr 1 2024

Very active and challenging forecast over the next 24 hours as
several rounds of storms, including some strong to severe, could
impact the I-64 corridor TAF sites. Currently we are VFR and expect
increasing mid clouds through the evening hours, along with steady S
or SSW winds. Perhaps a few gusts between 15 and 20 mph will linger.

Ceilings are expected to lower and around and after Midnight, with
solid MVFR setting in (likely below 2 k feet at times) just before
and around sunrise. Some gusty winds between 20 and 25 mph will be
possible at times. However, the biggest concern overnight will be
for a strong complex of storms working along and north of I-64. Have
tried to time this wave for the HNB/SDF TAF sites, as well as some
potential to impact LEX. Stayed a bit more optimistic at RGA/BWG for
that first wave.

Another wave of showers and storms is then expected just after
sunrise into early afternoon, where more strong to severe storms are
possible. A final wave could then develop along the cold front late
afternoon into early evening. Wind gusts through afternoon and
evening could be 20 to 25 mph sustained out of the SW with gusts of
30 to 35 mph outside of any t-storm activity.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Flood Watch through Tuesday evening for KYZ032-033-035>037-
     040>043-049.
IN...Flood Watch through Tuesday evening for INZ079.

&&

$$

UPDATE...BJS
SHORT TERM...RAS
LONG TERM...RJS
AVIATION...BJS