170
FXUS63 KLMK 121924
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
324 PM EDT Sat Sep 12 2026

.KEY MESSAGES...

* Isolated to scattered showers and storms continue this afternoon,
  with precipitation chances diminishing tonight.

* Patchy, locally dense fog is possible Sunday morning, especially
  in sheltered valleys and in areas which receive rain today.

* Overall drier and hotter conditions arrive early next week while
  an upper level ridge builds.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 324 PM EDT Sat Sep 12 2026

This Afternoon and Evening...

Isolated showers and thunderstorms are observed across the area at
this hour, with temperatures generally in the low-to-mid 80s.
Satellite imagery shows a scattered cu field across the area, with
more organized and robust areas of cu/cb extending from Shelby
County north/northeastward toward the Cincinnati metro. For the
remainder of the afternoon, scattered showers and storms should
continue to develop as plentiful low-level moisture and forcing from
a mid-level trough axis and vort lobe pivots through the area. Since
deep-layer shear is fairly weak, mainly pulse storms are expected
with heavy rain and lightning being the main storm threats. As we
get later into the evening, coverage should decrease and move toward
eastern KY, with more clearing and drier conditions expected along
and west of I-65.

Tonight...

This evening, the mid-level trough axis and associated vort max will
move across the Appalachians, with better forcing for ascent and
moisture content exiting the region along with it. While most of the
deeper moisture will be east of the region tonight, there should be
some shallow moisture left over near the surface, especially in
areas which receive a shower or storm this afternoon. With the bulk
of the low- and mid-level cloud cover expected to move out of the
area by around midnight and light winds expected in the boundary
layer, conditions will be favorable for fog development, some of
which could be locally dense in river valleys and other sheltered
locations. 12Z HREF guidance shows at least a 20% chance of less
than 1/2 mile visibility Sunday morning across the area, with higher
probabilities in the Hoosier National Forest and near Lake
Cumberland. Low temperatures are expected to range from the mid 60s
to the low 70s across the area.

Sunday and Sunday Night...

Tomorrow, a mid- and upper-level shortwave is expected to eject from
the Dakotas across the Great Lakes, amplifying only slightly as it
moves to the east. As the upper wave moves to the north of the
region, it will nudge a sfc cold front toward the Ohio Valley during
the afternoon and evening hours. With our area expected to be ahead
of the cold front for much of the day, temperatures should surge
into the upper 80s and low 90s for highs. Additionally, with
moisture pooling ahead of the cold front, things should be quite
humid tomorrow. This moisture should also allow for a decent amount
of instability to develop, with around 1500-2000 J/kg of MLCAPE
expected. Stronger forcing along the front and with the upper trough
should remain to the north of the area, but this still could be
enough to get isolated to scattered showers and storms to develop
along and north of I-64.

As we head into Sunday evening and Sunday night, the cold front
should gradually sink toward the Ohio River. A few showers and
storms may continue along this boundary, though coverage should
diminish by early Monday morning. Cooler and drier air is expected
to drop in behind the front, which should result in a spread between
low temperatures near 60 across southern IN and near 70 in southern
KY Monday morning.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 324 PM EDT Sat Sep 12 2026

On Monday, surface high pressure will move across the Midwest as
upper-level ridging will begin to build from the lower Mississippi
Valley into the Ohio Valley. What is left of a sfc cold front should
linger over southern KY and into TN, with northeast winds moving in
across the region. This cooler flow should hold temperatures down on
Monday, with highs expected to range from around 80 across southern
IN and the KY Bluegrass region, to the mid- and possibly upper 80s
along the TN border.

During the middle of the upcoming week, upper ridging will build
over the region, with low-level flow veering to the south-southwest.
This will bring much warmer air into the region, with well above
normal temperatures expected Tuesday through at least Thursday. High
temperatures are expected to range from the low-to-mid 90s each day,
with lows in the upper 60s and low 70s. With subsidence underneath
the upper ridge, rain chances should be suppressed Tuesday and
Wednesday, with hot temperatures being the main weather impact. Peak
heat index values are currently expected to make it into the upper
90s and low 100s, resulting in moderate to locally major HeatRisk
categories.

Forecast confidence begins to decrease Thursday into Friday as the
upper ridge tries to break down across the southeast US. Medium-
range ensemble families diverge on how quickly the ridge erodes,
with the GEFS breaking down the ridge and bringing higher moisture
and precipitation chances into the region faster than the ECMWF. If
the ridge is more resilient, then Thursday and Friday may end up
being the hottest days of the week, with elevated heat impacts
continuing. In contrast, a weaker upper ridge would bring a gradual
return of shower/storm chances and slightly milder temperatures. As
we head into next weekend, it becomes more likely that the upper
pattern will shift enough to allow a sfc cold front to at least
approach the Ohio Valley, bringing increased rain chances and milder
temperatures.

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 129 PM EDT Sat Sep 12 2026

Spotty showers and storms expected throughout the afternoon for all
TAF sites except HNB. VFR conditions prevail except for within the
passing showers; a potential exists for a FEW cloud deck below VFR
heights. Will clear out clouds this evening, but expect lower
visibilities with fog possible in the morning, especially at HNB and
BWG. Winds will be light out of the south-southwest and dropping to
very light to none overnight.

&&

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

&&

$$

SHORT TERM...CSG
LONG TERM...CSG
AVIATION...JPH