191
FXUS63 KLMK 211752
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
152 PM EDT Sat Sep 21 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*  Above normal temperatures continue, with upper 80s and low 90s
   for today.

*  Slight chance (20-30 percent) for spotty showers and storms this
   morning and early afternoon for central Kentucky as a weak
   frontal boundary stalls over the region.

*  More widespread precipitation chances arrive early next week
   ahead of a cold front.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 341 AM EDT Sat Sep 21 2024

The weak cold front remains north of the Ohio River this morning,
and is still expected to become stationary today as it struggles to
push south of the river. Ahead (south) of the front, a warm and
humid airmass is in place across Kentucky, with some areas still in
the mid 70s early this morning. PWATs are greatest along the front,
with 1.5-1.7 inches generally west of I-65 and nosing up into
central Indiana this morning. This frontal boundary, combined with
an increase in low level moisture convergence, with be responsible
for some isolated to scattered showers and storms this morning that
could possibly linger into the early afternoon to our south.
Considering the drought conditions we are experiencing, we
definitely could use a good widespread soaking. However, precip
coverage today will be very spotty, and not everyone will get rain.

The focus for PoPs this morning will generally be along and south of
the Ohio River, with around a 20-30% chance that will shift south
through the Commonwealth during the entire morning hours. A few
sporadic cells are already beginning to pop up on radar, and we
expect this trend to continue as the front provides forcing in the
warm and saturated environment. Morning ACARS out of SDF do show
quite a bit of instability, with MLCAPE values exceeding 1000 J/kg,
though a healthy nocturnal inversion will keep as stable at the sfc
for several more hours. Model soundings for later this morning
continue the trend of tall and skinny CAPE profiles, with weak shear
but high PWATs. After sunrise, we`ll continue to see spotty showers,
possibly with some heavy rain rates, and occasional thunder. PoPs
will be limited to 20-30% today, and will have the axis of precip
chances slide south of the Western Kentucky/Bluegrass Pkwys by the
early afternoon. Chances will fall off by late afternoon as our low
level moisture fades, leading to a dry forecast for all by this
evening.

Since the front will likely be hung up along the Ohio River
vicinity, most of our area will remain in the warm sector. Across
Kentucky, expect sfc winds to generally be from the southwest. While
cloud coverage remains a big question for today, the WAA regime
should still allow for sfc temps to warm above climate normals
again. Still expecting upper 80s and lower 90s, though sfc dewpoints
in the lower 70s will lead to heat indices being slightly warmer
today, with upper 90s possible.

Mostly dry weather will remain for tonight, but another cold front
will be approaching the region from the west. This boundary will
bring another round of rain chances, with PoPs returning to our
southern Indiana counties before sunrise tomorrow. However, the best
chances will eventually come in the Long Term period. Should be
another mild night, with temps ranging in the 60s. Cooler temps in
the east will be possible thanks to less cloud cover.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 341 AM EDT Sat Sep 21 2024

Sunday - Tuesday...

A more active, unsettled stretch of weather will bring some welcome
relief from the heat early next week. While Sunday may start off
dry, we should have quite a bit of upstream convection ongoing
across portions of MO, IL, and IN. A deepening low pressure system
wraps northeast toward Hudson Bay, with a long trailing cold front
slowing and eventually stalling as it sinks toward the Ohio Valley.

The deepest moisture and strongest lift will remain off to our
northwest Sunday, along with the sfc cold front itself. However, low-
level moisture will be plentiful and our proximity to more favorable
dynamics just off to the northwest should allow scattered showers
and isolated storms to spill over into portions of southern IN and
central KY. Convective organization and maintenance will be limited
by weak flow aloft, and the severe weather threat is low. Highs
Sunday are somewhat dependent on convection and associated cloud
cover. In general, highs should range from the low/mid 80s in
southern IN to the upper 80s/near 90 in south-central KY and the
Bluegrass.

Early next week, an upper level shortwave trough kicks east-
northeast out of the central Plains and moves over the Midwest. This
wave is likely to interact with the stalled baroclinic zone,
potentially bringing the Ohio Valley multiple waves of
showers/storms. Much of this rain is likely to fall Sunday night
through Tue/Tue night, with southern IN and northern portions of
central KY currently expected to see the most. This rain could make
meaningful progress toward alleviating drought conditions in some
areas.

Some stronger storms will be possible Monday into Tuesday. The
approaching mid-level wave will provide moderately strong westerly
to southwesterly flow aloft, allowing for better convective
organization. Rich low-level moisture will remain in place along and
south of the sfc boundary. Increased cloud cover may act to suppress
sfc heating and destabilization at times, resulting in some
uncertainty regarding the severe weather risk at this time range.

Wednesday - Friday...

Forecast confidence drops off considerably beyond Tuesday. Ensemble
cluster analysis reveals multiple competing solutions with relatively
equal membership for the mid to late week time frame. Unfortunately,
very few conclusions can be drawn regarding the sensible weather
details for this time frame. Amplified upper level flow over the
United States will likely impact the strength and track of a
tropical system churning slowly north through the Gulf of Mexico.
Exactly what that interaction looks like will become more clear as
additional model data comes in.

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 152 PM EDT Sat Sep 21 2024

Showers and a few storms have pushed south and east of the TAF sites
this afternoon. Outside of a chance for a few isolated pop ups this
evening, things should be pretty quiet. Look for some mid and high
clouds with a light WSW wind through sunset. Thereafter, look for
light to calm winds, with perhaps some fog concerns at BWG/LEX/RGA
if upper sky cover isn`t too prominent. Hinted at the best fog
chance for BWG tonight. Tomorrow another disturbance crosses through
our area with some afternoon showers and storms possible, mostly
notably at HNB or SDF. Have Prob30s to handle that for now.

&&

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

&&

$$

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