479
FXUS63 KLMK 150520
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
120 AM EDT Mon Jul 15 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Triple-digit heat index values continue through Tuesday.

*   Shower or storm possible along and north of I-64 later this
    evening with gusty winds, heavy rain.

*   Shower and storm chances look to increase by the middle of this
    week as a frontal boundary sinks into the area.

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

&&

.UPDATE...
Issued at 914 PM EDT Sun Jul 14 2024

The forecast is in good shape this evening. We had just a few small
showers move through the northern Bluegrass earlier in the evening.
Skies are partly cloudy to mostly clear this evening. The overnight
period looks dry with very light winds. We`ll see an increase in
cloud cover over southern IN and northern KY Monday morning as a MCS
dives southeast through portions of IN. There remains at least a low
chance convection makes it to southern IN, but the complex should
steadily weaken through the early to mid-morning hours.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 324 PM EDT Sun Jul 14 2024

Under mostly sunny skies, temperatures have warmed into the low-90s
for majority of the region. With dewpoints in the upper-60s and low-
70s, heat indices so far have been around 100F. While we have been
dry here, have been watching the evolution of the convection move
across Indiana today. Radar shows an outflow boundary being kicked
out ahead of the line of convection, heading south-southeast into an
uncapped environment that has been heating up all day. Additional
storms may pop up along this outflow boundary just to our north, so
it`s possible a few storms could sneak into our southern Indiana
counties, depending on how far south the outflow boundary can go.
Will keep a 20% chance for the rest of this afternoon and early
evening from Scott County IN to Nicholas County KY and pointing
northeastward. With practically no shear to work with this far
south, do expect the convection to diminish as it struggles to
remain organized.

For tonight, could have some thin upper clouds from the convective
debris at first, but do expect a mostly clear night. Winds will
become light and variable, so could have some patchy fog develop in
the pre-dawn hours. Best potential for fog appears to be in the Lake
Cumberland region. Will also watch for potential development of a
second MCS over northern Illinois tonight, which would be basically
following the same path of today`s convection. Hi-res guidance does
struggle with the evolution of this secondary wave, which makes
sense given the uncertainty of cold pools and lots of CIN to deal
with. Regardless, it appears this second MCS will struggle across
Indiana, and likely will dissipate before making it to the Ohio
River. Perhaps a few light showers from the remnants could make it
to our southern Indiana counties before 12z, but soundings show us
well capped by the nocturnal inversion. Will keep a dry forecast
going for now due to the uncertainty, but will raise PoPs to a
silent 10-14% for mostly southern Indiana.

For tomorrow, mostly dry and hot expected again as temperatures rise
into the upper-90s. With dewpoints in the low-70s, we should have
heat indices in the 100-105F range again. Will go with another SPS
for heat tomorrow, mainly for sensitive groups and for those working
outdoors.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 324 PM EDT Sun Jul 14 2024

Monday Night - Tuesday

Mostly dry conditions hang on for Monday and Tuesday as a cool
frontal boundary and stronger westerlies will be displaced to our
north, and the eastern fringes of upper ridging holds one final
grasp over our area. After a mild Monday night with lows into the
low and mid 70s, Tuesday will bring one more hot day with highs
likely topping out in the mid 90s once again. With dew points
hanging out in the lower 70s for most, this combination will yield
heat indices mostly in the 100 to 105 degree range again. Areas
along and west of I-65 will have the best shot at more common values
in the 102 to 107 degree range, and a heat headline isn`t out of the
question for some. Some isolated late afternoon convection chances
do hurt overall confidence on those values, so nothing planned just
yet other than the going highlights in the Key Messages, HWO, and
graphics.

Tuesday Night - Thursday...

A more active, but overall cooler, pattern looks to set up for mid
to late week as eastern CONUS troughing becomes more established
thanks to a digging shortwave out of the upper Midwest on Wednesday.
This will help drag a surface cold front into our region, helping to
spark scattered thunderstorms from as early as Tuesday night across
our northern CWA, to as late as Thursday afternoon across southern
KY. Between that, Wednesday looks to be the best day with the
greatest coverage of showers and storms as peak heating/instability
align with fropa, and some forcing ahead of the upper trough axis.

Tough to tell exactly how unstable we will become on Wednesday,
especially if leftover debris from Tuesday night convection bleeds
into Wednesday`s destabilization period. Nevertheless, the pattern
would suggest at least moderate destabilization with overall pretty
weak shear profiles. Could maybe squeeze out 20-25 knots of deep
layer shear (more across our northern CWA) where mostly pulse type
storm modes would be expected. Perhaps a few brief multicell
clusters could occur if we get closer to the 25 knot range. Gusty
winds and locally heavy rainfall would be the main threats with mid
week storms. Can`t sleep on potential for any upstream, cold pool
driven wind producers to sneak into our north late Tuesday evening.
If so, we`ll should have plenty of MUCAPE still hanging around along
with a sounding that would likely favor some gusty winds (high DCAPE
values). The SPC Marginal Risk across our north for late Day 3 makes
sense.

As far as temperatures go, looking for a gradual cool down through
mid week as the frontal boundary slowly sinks through. 85 to 90
degrees on Wednesday gives way to the low 80s by Thursday. Thursday
pops look to range from dry along and north of the Ohio River to
scattered to numerous across southern KY the first half of the day.

Thursday Night - Sunday...

Thursday night and Friday look to be mostly dry as we sit in the
post-frontal airmass and high pressure centers just to our NW. The
frontal boundary will stall out just to our SE, but may have to keep
some lingering pops for the Lake Cumberland area into the weekend. A
somewhat concerning pattern could develop over the SE CONUS heading
into the weekend as strong ridging develops over the SE CONUS, while
a baggy trough axis hangs out from the southern Mississippi River
Valley up through the Ohio River Valley and into New England. This
creates a nearly stationary frontal boundary/baroclinic zone between
those two features stretching from the southern Gulf Coast States,
up the Appalachian spine, through the mid Atlantic states. This
would be a pattern were repeated rounds of moisture laden showers
and storms would occur up through that corridor, fed by a fetch of
deep Gulf moisture. Right now, the main precipitation axis looks to
be to our SE, but will have to keep an eye on where a heavy rainfall
axis could setup through our weekend, especially if aforementioned
upper ridge is stronger and the baroclinic zone sets up farther NW
than currently progged. For now, will have to keep chances
continuing at least in the Lake Cumberland region through the
weekend, with drier overall conditions the farther NW you go toward
the Ohio River. Temps through the weekend should generally be in the
80s.

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 117 AM EDT Mon Jul 15 2024

Forecast continues to have VFR flight categories. Highs clouds
associated with the convective complex currently over northern
IL/northern IN could spread southward into the region overnight.
Mainly for SDF and HNB. Then maybe some mid clouds later this
morning and tomorrow but no significant issues are expected. Biggest
reason will be the presence of sfc high over the region keeping our
weather quiet but hot through the day.

&&

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

&&

$$

UPDATE...EBW
SHORT TERM...CJP
LONG TERM...BJS
AVIATION...BTN