140
FXUS63 KLMK 222306
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
706 PM EDT Sun Sep 22 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*  Multiple waves of scattered showers and storms are expected
   this afternoon through Tuesday night. There is a low chance for
   strong to severe storms Monday and Tuesday.

*  Unsettled weather is a possibility into late week with the
   remnants of a tropical system potentially moving into our region.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 333 PM EDT Sun Sep 22 2024

This afternoon and evening...

Sensible weather across the area is quite variable this afternoon.
Across much of southern IN and north central KY, clouds and light
rain showers have led to a more stable, cooler environment with
temperatures generally in the upper 70s and lower 80s. Along and
south of the western KY/Bluegrass Parkways, more sunshine and
heating this morning has allowed temperatures to warm into the upper
80s and lower 90s, with scattered showers and thunderstorms
developing in an increasingly unstable environment. As we head later
into the afternoon and evening, recent high resolution guidance
suggests that much of the northern half of the FA will be stable
enough to preclude convective re-development, with just isolated to
scattered light rain showers continuing into the evening hours. For
the southern half of the FA, we`ll have to watch an area near the
confluence of the Wabash and Ohio Rivers for development of showers
and storms, as there is a strong differential heating boundary left
over from clouds and showers/storms earlier today. Any stronger
storm could produce gusty winds and small hail, though widespread
strong/severe storms are not expected. Any convection should begin
to dissipate by around 02Z tonight, though isolated showers may
continue into the overnight.

Tonight...

A surface cold front will settle across the area tonight, with
pooling moisture and light winds expected across the region. This
combination of ingredients will allow for either low stratus, fog,
or a combination of both, as near-sfc winds are expected to be just
light enough to allow stratus to settle into fog. Coverage of rain
showers should decrease through the nighttime hours, with most
locations remaining dry into early Monday morning. Low temperatures
will be mild for late September, with lows ranging from the mid 60s
to the low 70s Monday morning.

Monday...

Tomorrow morning, the initial upper-level trough which brought the
sfc cold front into the region this afternoon will lift off to the
northeast of the region, as a secondary upper shortwave lingers back
over the central Plains. As a result, the sfc front should become
quasi-stationary and eventually begin to lift back to the north by
tomorrow afternoon as the next upper wave approaches from the west.
As a result, ample moisture will remain over the region, leading to
mostly cloudy or even overcast skies across most of southern IN and
central KY. The primary forecast question for tomorrow will be how
much, if any, destabilization we see, as continuing low cloud cover
will make it difficult to get much surface heating.

12Z HREF guidance has the highest amounts of CAPE tomorrow afternoon
along and south of the western KY/Bluegrass Parkways, with
probabilities of greater than 40 dBZ Reflectivity highlighted in
these areas as well. With deep-layer shear expected to be around 20-
25 kt, one or two strong storms will be possible, with gusty winds
and small hail being the primary severe hazards. North of wherever
storms develop, light to moderate rain will be possible, though a
lack of instability should preclude the development of
thunderstorms. Temperatures Monday afternoon will vary from north to
south, with upper 70s and lower 80s expected in north central KY and
southern IN, while mid- and upper 80s will be possible in southern
KY.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 333 PM EDT Sun Sep 22 2024

===== Monday Night - Wednesday =====

A shortwave trough embedded within a larger central CONUS trough
will rotate from the lower Missouri/mid Mississippi River Valleys up
into the Great Lakes Monday night through Tuesday. Meanwhile, an
associated surface low takes a similar path. As the surface low
moves by to our north and east, we`ll see the quasi-stationary
frontal boundary that had been draped over our region try to lift
north as a warm front. How much of a warm sector gets established
over our area remains to be seen, but much will depend on the
strength of the surface low, of which there is still some spread in
guidance. Regardless, there there looks to be plenty of forcing and
available deep moisture for scattered showers and a few storms
overnight, and then better coverage of showers and some storms
Tuesday morning just ahead of the main shortwave trough axis and
surface cold front. This mainly morning timing may play to our favor
as we don`t appear to get a whole lot of instability in here, and
given an uptick in the deep layer shear profile could be the limiting
factor to a larger severe weather concern. Can`t rule out some
stronger storms, especially if a stronger surface low scenario ends
up being reality, but too early to have a whole lot of confidence
just yet. Something to watch.

Later Tuesday into looks to be overall dryer in the wake of the
shortwave and post-frontal regime. That being said, may have to hang
onto some lingering shower chances across our far south and east as
the frontal boundary hangs up down there and a renewed source of
moisture transport develops on the east side of an Ozark region
closed low. Temps should generally run in the upper 70s and low 80s
into mid week.

===== Thursday - Sunday =====

Quite a bit of uncertainty with respect to the late week/weekend
forecast. Much will depend on the interaction between a likely
tropical system coming out of the Gulf and the aforementioned closed
low. A third complicating feature will be a blocking ridge between
the two systems to our southeast and a third closed low over eastern
Canada and New England. This complex interaction between all parties
makes for a tricky and very low confidence forecast at this time.
There has been a sporadic PRE type of event that shows up in various
deterministic runs from time to time, all the way to a pretty much
dry late week and weekend as the blocking ridge becomes our dominant
feature. Right now, could go either way, or more likely something in
between. For now, will keep chances for rain in every day with temps
in the upper 70s and low 80s. Stay up to date of the latest
forecasts as details become more clear.

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 706 PM EDT Sun Sep 22 2024

Surface frontal boundary is edging closer to the Ohio River at this
hour.  Ahead of the front this evening, scattered showers and
perhaps a few storms down across southern KY will be possible. This
activity should diminish considerably by 23/02-03Z.  After that,
look for cigs to build down overnight with a decent chance of
fog/low stratus developing.  Agree with previous forecaster that the
worst conditions may be between 23/06-23/11Z with drops into IFR due
to the fog/low stratus.  Low stratus is likely to continue into the
morning hours with slow clearing possible by afternoon.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...CSG
LONG TERM....BJS
AVIATION.....MJ