247
FXUS63 KLMK 152323
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
723 PM EDT Mon Jul 15 2024

.KEY MESSAGES...

*   Warm morning low temperature provide little relief.

*   Triple-digit heat index values Tuesday.

*   Shower and storms return mid week as a cold front pushes through
    the region.

*   Cooler temps in the 80s for Thursday into Saturday.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 325 PM EDT Mon Jul 15 2024

Scattered cu field across the region this afternoon is a result of
efficient daytime heating. Temps have warmed into the low to mid
90s, with heat index values ranging between 98-104 degrees. Dry
weather continues this afternoon, and should see the cu field
diminish as daytime heating is lost around sunset.

For tonight, dry weather will continue, but will be keeping eyes on
another MCS racing through Chicagoland and then diving
southeastward. A mid-level shortwave passing over the Great Lakes
will be pivoting around the parent upper low over Canada, which will
be the driving force for a cold front pushing the convection into
the Ohio Valley. Ahead of the front, low-level jetting will ramp up
moisture transport well to our north, and WAA even this far south.
Temps overnight will not provide much relief from the daytime heat,
especially in the urban areas. Lows will range in the 70s, but SDF
could remain closer to 80 overnight. The convection will be
weakening as it approaches our forecast area, largely in part due to
the nocturnal inversion still in place and keeping our low levels
stable. Some elevated instability will remain as indicated by model
soundings, so some thunder mention in the forecast will remain. Hi-
res models continue to struggle with the evolution of this MCS, so
confidence on how far south the precip will go remains in question.
Will draw in a 20% PoP to cover the possibility mainly north of the
Ohio River for the morning hours.

Any morning precip will likely lead to more humid dewpoints for the
afternoon. However, any lingering cloud cover from the morning could
slow down temps slightly. Still believe tomorrow will be a hot day,
with temps in the 90s, and dewpoints in the 70s. It appears that
temps might be a few degrees lower than today, but the dewpoints
will be higher. With it being the third day in a row for triple
digit heat indices, and the warm morning lows, the heat advisory
will continue for tomorrow. There`s a chance some afternoon
convective development may spark ahead of the front, which could
linger into the end of the period. Weak/Marginal deep layer shear
will limit any sort of severe threat, but gusty winds in downburst
along with heavy rainfall are likely in the strongest storms.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 325 PM EDT Mon Jul 15 2024

Showers and thunderstorms will be in progress at the start of the
long term as a cold front sweeps through the region. 560dm 5H low
will move E through the Great Lakes while at the surface an
elongated cold front stretching from Quebec into the Central Plains
slowly drops through the OH Valley. Moisture pooling just ahead of
and along the frontal boundary will provide enough fuel for
efficient rainers, with PWATs increasing to above 2 inches which is
reaching daily max values according to SPC sounding climatology.
Storm vectors closely parallel the boundary as well, leading to
training storm potential and flooding concerns. Highest QPF is
forecast to occur from 17/00Z thru 17/18Z with lingering rainfall
continuing into Thursday morning. ECMWF Extreme Forecast Index (EFI)
does highlight an area of higher than normal rainfall amounts among
ensemble members roughly along the OH River, which is coincident
with our highest QPF amounts. Areas north of the parkways can expect
to see an inch to around 2.25", while those south of the parkways
can expect less than an inch. With that said, WPC has included
portions of north central KY and southern Indiana within a Day 2
(16/12Z - 17/12Z) Slight Risk for Excessive Rainfall and a Day 3
(17/12Z - 18/12Z) Marginal Risk.

Environmental parameters regarding severe weather are meager for
Wednesday, likely due to the bulk of the activity passing during a
diurnal minima. CAPE values will range from 500-1500 J/kg by
Wednesday afternoon with most of the impressive shear remaining far
to our north closer to the stronger jet stream dynamics. DCAPE
values do increase during the day Wednesday, which lends to the
potential for stronger gusts associated with convection. As such,
SPC has included our region within a Day 2 (16/12Z - 17/12Z)
Marginal Risk, which is mainly wind driven.

Expect reprieve from the heat in the post-frontal airmass as daily
max temperatures drop into the 80s from Thursday through the
weekend, slightly increasing each day. Worthy of greater rejoicing
is the concurrent drop in dew points. The aforementioned cold front
is expected to stall over the northern Gulf States before meandering
northward into the TN Valley, bringing a return of shower and tstorm
chances back to the southern half of our CWA Saturday and Sunday.

Worth of mention is a shortwave that drops out of central Canada
Friday, which models show undergoing lee cyclogenesis before
becoming detached from upper jet support. This cut-off low will lead
to below normal temperatures across much of the central U.S. as
highlighted in CPC`s 6-10 Day Temperature Outlook.

&&

.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 723 PM EDT Mon Jul 15 2024

Expect prevailing VFR and generally southwest winds through the
valid TAF period. Look for sct diurnal Cu to dissipate this evening
once the sun sets, and light winds out of the SSW. Main impacts
overnight will hinge on the evolution of storms over Illinois and
Indiana. Could see a weakening MCS affect HNB toward daybreak, but
it remains unsettled whether storms will hold together that far
south or it will just be outflow. Will go with VCTS/CB and a period
of variable winds. Very low confidence in any convection reaching
SDF but can`t rule it out.  WIll not include in the TAF at this
time.

Tightening pressure gradient ahead of the incoming front will result
in gusty winds during the day on Tuesday. Direction will veer
slightly, so WSW with gusts near 20 kt. Better rain chances will
arrive Tue night, late enough to only impact the SDF planning
period. Will carry VCTS at this time, and refine timing of more
direct impacts in later issuances.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory until 9 PM EDT /8 PM CDT/ Tuesday for KYZ023>035-
     038-061-062-070>072.
IN...Heat Advisory until 9 PM EDT /8 PM CDT/ Tuesday for INZ076>079-
     083-084-089>092.

&&

$$

SHORT TERM...CJP
LONG TERM...CRG
AVIATION...RAS