538 
FXUS63 KLMK 151926
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
326 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 /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 138 PM EDT Mon Jul 15 2024

Peak heating this afternoon has led to the development of scattered 
cu clouds around 5k ft. Terminals are expected to remain VFR this 
afternoon and tonight. A convective system will be diving southward 
overnight from northern Illinois, and the cloud debris ahead of it 
will begin to filter into the region around sunrise. The system 
should weaken before approaching SDF/HNB tomorrow morning, but a few 
isolated showers may be possible. Not confident enough to include 
into the TAF at this time, but may be needed in future updates. VFR 
conditions and winds from the southwest expected tomorrow.

&&

.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/KRT
LONG TERM...CRG
AVIATION...CJP/KRT