692 
FXUS63 KLMK 082330
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
730 PM EDT Mon Aug 8 2022

...Updated Aviation Discussion...

.Short Term...(This evening through Tuesday)
Issued at 305 PM EDT Mon Aug 8 2022

Flow aloft remains very weak over the Ohio Valley with faster mid 
and upper level flow confined to the Great Lakes and Canada. An 
upper level shortwave trough will continue to move east across 
southern Canada tonight into Tuesday. 1008 mb sfc low pressure is 
analyzed over Lake Huron this afternoon, with a cold front 
stretching southwest through Chicago, Kansas City, and Tulsa. 

It's a very warm, humid day in the warm sector of the low pressure 
system to the north. Plenty of early day sunshine has caused 
temperatures to warm into the upper 80s to lower 90s. With dewpoints 
in the mid 70s, heat indices are in the low 100s. 

Convective temps have been easily surpassed, and widely scattered 
showers and storms have developed. Deep-layer shear is very weak and 
storm motion is relatively slow due to weak flow throughout the 
column. Vertical updraft growth will be limited by the lack of wind 
shear, but a briefly stronger cell will be capable of locally heavy 
rainfall, gusty winds, and lightning. The near-term flooding threat 
is limited by storm coverage, and only very localized issues are 
possible into the evening hours. 

Most shower/storm activity is expected to gradually diminish this 
evening with the loss of heating. However, weakening convection to 
our north across central Indiana will attempt to push south into 
southern Indiana late this evening and overnight. As outflow pushes 
south, additional SCT showers and storms will be possible into the 
early morning hours. 

Convective coverage will be at a minimum Tuesday morning before 
showers and thunderstorms blossom area-wide Tuesday afternoon and 
evening. The effective cold front will sink to southern Indiana on 
Tuesday and will help force numerous showers and storms during the 
second half of the day. 

The latest 12z SPC HREF features neighborhood probabilities of 
greater than 70% for at least 1 inch of rain in 3 hours east of I-65 
between 21-00z Tue evening. 1- and 3-hr FFG is notably lower in the 
eastern CWA, including the Bluegrass and Lake Cumberland regions. We 
opted to start a new Flood Watch at 16z Tuesday for the area most 
likely to see scattered instances of flash flooding through 
Wednesday. The flash flood threat will linger over these same areas 
on Wednesday (see details in Long Term discussion below).

It will remain very humid Tuesday, but abundant cloud cover and more 
showers and storms later in the day will help keep temperatures 
slightly cooler than today. Highs should range through the 80s.

.Long Term...(Tuesday night through Monday)
Issued at 320 PM EDT Mon Aug 8 2022

...Potential Heavy Rainfall and Flooding Concerns Wednesday...

The beginning of the extended period will be active across central 
Kentucky and southern Indiana as the mid- and upper-level ridge over 
the eastern CONUS begins to break down and retrograde westward. At 
the surface, a weakening quasi-stationary front will be located 
along the Ohio River by Wednesday morning. While this boundary will 
have little in the way of temperature contrast, a sharp moisture 
gradient is expected along the front with a moist air mass (PW > 2 
inches) located along and south of the front and much drier air (PW 
< 1 inch) located north of the front. The location and evolution of 
the frontal boundary will play a key role on the forecast Wednesday 
through Thursday morning, as widespread showers and thunderstorms 
are expected along and south of the moisture cutoff. Where 
precipitation does develop, heavy rain and flash flooding will be 
possible as a combination of deep warm cloud depths, tall and skinny 
CAPE profiles, and slow storm motion (thanks to weak mean cloud-
layer winds) will promote heavy rainfall amounts.

It is important to note that while conditions are favorable for 
heavy rainfall, cells will be scattered and thus precipitation 
totals will vary considerably across small distances. Area-wide, 
ensembles generally support around 1 inch of QPF, but isolated 
regions where storms persist for extended periods of time may see 
well over this amount. Flooding will be the main threat with any 
thunderstorms as environmental shear will be negligible, although 
isolated strong wind gusts could occur in a few strong storms. 
Temperatures on Wednesday should be slightly below normal, with 
highs reaching the low-to-mid 80s and lows in the upper 60s and 
lower 70s.

As we head into Thursday, the large-scale pattern should become more 
progressive as a stronger mid- and upper-level trough dives 
southward from Hudson Bay into the eastern third of the CONUS. This 
trough, and an associated surface cold front will push the remnant 
stationary front and the moisture ahead of it well off to our south. 
There is still some variance among guidance as to timing of the 
moisture's exit, but generally think that Thursday will be dry for 
areas north of the Western KY/Bluegrass Parkways, with only a few 
lingering showers expected across the south. As the aforementioned 
stronger cold front will still be located north of the region, 
expect temperatures to recover well on Thursday, with highs 
generally reaching the mid-to-upper 80s.

Beyond Thursday, drier and cooler conditions are expected for the 
end of the week and the first half of the weekend as strong high 
pressure works into the Midwest and Ohio Valley during the day on 
Friday, with deep NW flow aloft. Temperatures will be 5-10 degrees 
below normal with highs Friday through Sunday topping out in the 
upper 70s and lower 80s and lows falling into the mid-to-upper 50s 
to near 60. Dewpoint temperatures in the 50s will also make things 
feel very comfortable, especially for August. For the second half of 
the weekend, medium-range guidance depicts a weak disturbance 
swinging down along the western fringe of the mid- and upper-level 
trough. While some deterministic support (particularly the GFS) 
exists for precipitation chances on Sunday with this wave, ensembles 
are less optimistic, so will keep things dry for now.

&&

.Aviation...(00Z TAF Issuance)
Issued at 730 PM EDT Mon Aug 8 2022

IMPACTS: Showers/storms,especially tomorrow

DISCUSSION:

A cold front stretches along a DTW-STL-SPS line early this evening. 
Scattered thunderstorms formed along the front earlier this 
afternoon over central Indiana but fell apart as they moved away 
from the boundary. However, additional convection has been 
redeveloping back along the front this evening. How far south the 
showers and storms make it tonight into Tuesday morning is the big 
question. The front will plod forward very slowly, likely only 
making it as far as the Ohio River during this TAF period. There's 
not much mid/upper support for storms, so the greatest chance for 
bumpy weather should be in a relatively narrow corridor along and 
ahead of the front. For tonight, will bring scattered -SHRA into 
HNB, closest to the front, but leave it out of the other TAFs for 
now. Can't rule out some convection at SDF late tonight, but 
confidence just isn't there yet to include a VCTS.

Daytime destabilization and the approaching front will lead to more 
widespread shower and thunderstorm development Tuesday afternoon. 
Some of the storms will be capable of very heavy downpours and 
gusty winds.

CONFIDENCE:

Low on timing/chances of TSRA, medium/high on ceilings, high on 
winds.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...Flood Watch from Tuesday afternoon through Wednesday evening for 
     KYZ033>043-045>049-053>057-063>067-073>078-081-082.

&&

$$

Short Term...EBW
Long Term...CSG
Aviation...13