796
FXUS63 KLMK 161445
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1045 AM EDT Tue Jul 16 2024

.KEY MESSAGES...

*   Triple-digit heat index values possible today. Heat advisory
    remains in effect.

*   Storm chances increase tonight into tomorrow as a frontal
    boundary sinks into the region. Flash flooding possible in areas
    that see repeated storms. Isolated strong storms with gusty
    winds possible as well.

*   Cooler temps in the 80s for Thursday into the end of the week.

&&

.UPDATE...
Issued at 1044 AM EDT Tue Jul 16 2024

Remnants of the early morning MCS have struggled to make it south of
the Ohio River this morning, but the outflow boundary has surged all
the way to the Kentucky/Tennessee state line. A few showers fired
off along the outflow across central Kentucky, but meager lapse
rates and low level stability kept those showers from really ever
becoming organized.

We`ll continue to see the showers across southern Indiana dissipate,
and may end up with a lull in activity for the early afternoon.
Beyond that, confidence does remain somewhat limited. SPC extended
the Slight risk further east, and now encompasses the western half
of our CWA. While the best severe chances still remains to our west,
strong heating combined with a moisture-rich airmass will aid in
minimizing any morning CIN and realize some destabilization over
2000 J/kg. Depending on where remnant outflow boundaries are
located, some isolated storms could fire up along those boundaries
later this afternoon and evening. Model soundings show weak shear,
but steep low level lapse rates and high DCAPE to support a damaging
wind threat.

As for the Heat Advisory, there remains uncertainty whether the
northern parts of the forecast area will reach criteria later this
afternoon after the morning precip and lingering cloud cover.
However, after chatting with PAH, will keep the headline going and
see how temperatures recover this afternoon before making any
changes. Some tweaking may be needed, but that will be later.

The general forecast is in good shape without any major changes.
Will send updated forecast products.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 331 AM EDT Tue Jul 16 2024

A decaying line of showers and storms are steadily pushing
southeastward this morning from Illinois and Indiana. While this
activity is moving into a more stable environment, an outflow
boundary ahead of the main activity has helped to spark off some
precipitation across our southern Indiana counties this morning.
Additional showers/storms may filter in from the north/west later in
the AM, though it is expected to generally be weak.

Confidence in the forecast details remain low today given the
difficulty in forecasting evolving mesoscale features and details
that are often poorly captured by models. One particular aspect of
the forecast that remains uncertain is how warm we`ll get this
afternoon. The clouds and spotty precipitation will slow the rise of
temperatures this morning after dawn, though some clearing is
anticipated by the late morning or early afternoon hours. How long
the clouds linger will certainly have an impact on the overall highs
today, and it`s possible that we may not hit heat advisory criteria
across the region. With the advisory already in place, though, and
the potential to still see some +100 heat indices should we clear
out, plan to let the advisory ride out for time being.

A slow moving frontal boundary will begin approaching the region
tonight. Showers and storms are expected to develop along and ahead
of it, all of which will be capable of heavy rainfall given the
moist environment. SPC HREF guidance has honed in on southern IN and
portions of northern KY for heavy rainfall potential via the
Localized Probability Matched Mean (LPMM) product over the last
couple of runs, which seems feasible given that storm motions could
be nearly parallel to the frontal boundary as it comes sliding in
from the north, supporting a storm training threat. After
coordinating with neighboring offices, a flood watch has been issued
for the aforementioned areas starting this evening and continuing
into tomorrow afternoon. Outside of the flood threat, a low-end
severe threat of gusty winds in the strongest storms remains
possible from water-loaded downbursts.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 331 AM EDT Tue Jul 16 2024

On Wednesday, a upper trough centered near the Great Lakes will push
a surface low through the Midwest towards the Lower Ohio Valley
behind a weakly defined cold front. Moisture from the Gulf of Mexico
will keep precipitable water values ahead of the front in the 1.5 to
just over 2" range. Current model projections still lack agreement
on the exact placement and timing of precipitation, but early in the
day, there is a good chance that remaining precipitation from the
night before could remain in the area. Given the time of day, severe
weather wouldn`t be expected as instability would be limited.
Believe the day would begin as showers with some garden variety
thunderstorms being possible. Given the juicy air mass, any
convection would likely produce heavy rain. Behind any remaining
morning activity, the day could be mostly dry for most people with
showers and storms not increasing again until the front begins to
drop south through southern Indiana later Wednesday afternoon/
evening. By this time, the environment could recover from the
earlier convection. MLCAPE values could recover to 1,000-1,500 J/kg
with fairly steep low level lapse rates and DCAPE values nearing
1,000 J/kg, so some gusty winds will be possible with any convection
that forms ahead of the sinking front. If the front pushes through a
little earlier in the day, there will be less time for the
environment to recover which would lower instability and
thunderstorm strength. Showers and thunderstorms will work their way
south through central Kentucky and are expected to exit by early
Thursday.

The rain and cloud cover will help to limit high temperatures as the
front begins to work through the region on Wednesday. Highs in the
low 80s are expected in parts of southeastern Indiana with
temperatures closer to 90 along the Tennessee border in Kentucky.
Everyone else is expected to see the mid 80s. Behind the front on
Thursday, temperatures dip to the low 80s across the CWA before
clearer skies and sunshine bring the mid 80s back for the rest of
the week.

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 657 AM EDT Tue Jul 16 2024

A decaying line of showers and storms is pushing into the region
this morning. This activity is moving into a more stable environment
so expect the gradual weakening trend to continue. Anticipating this
activity to have minimal impacts to cigs/vis, though can`t rule out
an isolated heavier shower/storm resulting in brief sub-VFR cig/vis
reductions this morning.

We should see some drying/clearing in the wake of the morning
activity. Additional showers and storms are likely to develop this
evening into the overnight hours as a frontal boundary sinks into
the region.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for
     KYZ023>043-045>049-053>057-061>067-070>078-081-082.
     Flood Watch from 8 PM EDT /7 PM CDT/ this evening through
     Wednesday afternoon for KYZ023>025-030>037.
IN...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for
     INZ076>079-083-084-089>092.
     Flood Watch from 8 PM EDT /7 PM CDT/ this evening through
     Wednesday afternoon for INZ076>079-083-084-089>092.

&&

$$

UPDATE...CJP
SHORT TERM...DM
LONG TERM...KDW
AVIATION...DM