Deputy, Indiana Weather Forecast Discussion

203
FXUS63 KLMK 241945
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
345 PM EDT Wed Sep 24 2025
.KEY MESSAGES...
*  A few strong storms and locally heavy rainfall possible through
   late this afternoon across south-central KY.
*  Overnight moderate rain expected to spread over the area, with
   additional rainfall amounts between 1 to 2.5 inches for most.
   Locally higher amounts, or training of showers, could lead to
   localized flooding issues.
*  Mostly dry with warming temperatures expected this weekend
&&
.SHORT TERM /THROUGH THURSDAY/...
Issued at 344 PM EDT Wed Sep 24 2025
After the morning wave of showers, most of the area has been in a
lull of precip activity so far this afternoon, except for the
cluster of light showers over the Bluegrass region now. KLVX radar
is actually picking up on a very thin line of reflectivity
stretching from Crawford County (IN) to Henry County (KY), sitting
along or just north of I-64, which is believed to be the sfc frontal
boundary. Our southern IN wind obs have been of NW flow, while KY
obs still show a SW flow. A good example is the difference between
Clark Regional Airport (JVY) and Louisville International (SDF),
which is only separated north to south by approximately 12 miles.
JVY has reported 330 (NNW) winds in previous obs, while SDF is
currently reporting a 220 (SW) wind direction. On a bigger scale,
the amplified positive tilt upper trough will continue to be the
driving mechanism for additional shower and storm chances in the
short term period. Mesoanalysis this afternoon shows the core of the
upper level jet situated over St. Louis, but we will see this upper
trough and jet slide to the east by tonight.
For the remainder of the afternoon, we could see some convection
fire up within the warm sector of the region, which ultimately will
be central KY. GOES satellite imagery does show some gaps in between
the different cloud layers, mainly across portions of south-central
KY this afternoon, which is allowing temps to be a few degrees
warmer. This is seen well on the KY Mesonet obs, with obs north of
the Parkways generally in the lower 70s due to more cloud cover.
CAMs indicate some scattered storms to be possible across the
southern half of the forecast area, which is where SPC Mesoanalysis
already depicts upwards to 1000 J/kg of SBCAPE. However, meager mid-
level lapse rates and modest shear values will likely keep a
limitation on how well storms can become organized. Still see the
potential for a few strong to marginally severe storms late
afternoon, but it will be a small window of opportunity and a race
against time.
The bigger concern comes tonight, as we become positioned under the
right entrance region of the upper level jet core structure. In
response, the LLJ will ramp up over portions of south-central and
eastern KY, which will bring stronger forcing and moisture to the
area. There is good agreement among guidance of seeing better
forcing and moisture transport along and south of the Ohio River
tonight, which will support increasing coverage of showers and
storms for the overnight period. PWATs approaching 2 inches,
combined with lingering instability will allow for some efficient
rainfall, which could cause some flooding issues if we see training
set up in a southwest to northeast component. HREF 6-hour PMM does
indicate just a few very isolated instances of up to 2 inches of
rainfall in 6 hours over parts of central KY, which has the highest
FFG ratios of around 2.5 inches in 1 hour, 2.5-3.5 inches in 3
hours, or 3.5-4.5 inches in 6 hours. However, if training storms set
up a bit more north or south of this corridor, then lower FFG ratios
will pose a greater risk for some flash flooding concerns overnight.
Debated on a Flood Watch with this package, but think most rainfall
overnight will add up to 1-2 inches across our KY counties, with
locally higher amounts that could cause a few flooding issues. Less
than an inch is forecast north of the Ohio River.
Precip coverage will diminish in coverage after sunrise tomorrow as
the LLJ core shifts off to the east. However, the upper trough axis
will be still be amplifying just to the west of the area throughout
the day, with the upper jet core remaining overhead and providing
additional forcing for more precip chances. However, coverage of
precip tomorrow looks to be much more isolated, so QPF is much
lower. At the sfc, the attendant cold front will gradually be
pushing east, and should be east of our area by the afternoon. We`ll
see a drier trend settle in from NW to SE, along with clearing cloud
cover by late afternoon. Temps will only peak in the mid to upper
70s due to all the cloud cover for most of the day.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 344 PM EDT Wed Sep 24 2025
Thursday Night - Friday Night...
A positively-tilted upper trough will extend from Hudson Bay down to
the lower Mississippi Valley Thursday evening, with the main
northern stream energy over Canada ejecting quickly eastward on
Friday. The southern edge of the upper wave will get left behind and
is expected to evolve into a closed low which will meander across
the Tennessee Valley for Friday into the beginning of the weekend.
The sfc cold front associated with this feature should be pushing
across eastern KY at the beginning of the forecast period, with
lower sfc dewpoints filtering in across the region behind the front.
Any lingering rain showers across east central and southeast KY
Thursday evening should quickly subside with the loss of daytime
heating, leading to mostly dry weather for Thursday night through
Friday night. Given that the pressure gradient behind the departing
cold front should be relatively weak, moisture trapped in sheltered
valleys could lead to patchy fog Friday morning, especially if any
lingering low- and mid-level clouds clear our southeast counties.
As the southern stream trough cuts off to our south on Friday, low-
level moisture is expected to linger mainly across southeastern KY.
With our eastern CWA counties remaining just downstream of the mid-
level trough axis during peak heating Friday, an isolated shower or
storm cannot be ruled out; however, most of the coverage should be
across the Appalachians. High temperatures on Friday should be near
normal in the upper 70s to around 80, with cooler low temperatures
expected Friday and Saturday morning, primarily in the 50s.
Saturday - Middle of Next Week...
Over the weekend, the closed low over the Tennessee Valley will
drift over the southern Appalachians as mid- and upper-level ridging
builds along and west of the Mississippi Valley. Between these two
features, light northerly flow should keep most of the deep moisture
associated with the closed low suppressed to the south and east.
However, there should be enough residual moisture between the sfc
and 800 mb for diurnally-driven cumulus, and a stray shower along
and east of US 127 can`t be ruled out over the weekend.
Nevertheless, for the vast majority, a dry weekend with warming
temperatures is expected. Highs should range from the upper 70s to
the low-to-mid 80s with lows in the 50s and low 60s.
By the first few days of next week, forecast confidence gets a bit
murky due to complex interactions between the previously-mentioned
closed low and approaching tropical systems off the coast of the
Carolinas. At this time, the upper low over the southern
Appalachians is not expected to eject out, and its interaction with
the tropical systems could lead to an enhanced east-northeasterly
flow from the mid-Atlantic into the Ohio Valley. As the previous
forecaster mentioned, while this would draw a fetch of greater
moisture into the region, this flow orientation would likely have a
downslope/rain shadow component to it, contradicting factors for and
against precipitation development. It continues to look mostly dry
as we head through the first half of next week, especially along and
west of I-65, with better chances for isolated to scattered showers
and storms across east central and southeast KY. However, we`ll have
to continue to monitor any interactions from tropical disturbances
which could augment or limit the coverage/likelihood of rain early
next week. Temperatures should be a few degrees above normal during
this period, with highs in the low-to-mid 80s and lows in the upper
50s and low 60s.
&&
.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 141 PM EDT Wed Sep 24 2025
MVFR cigs are across the area today, with a cold front boundary seen
on radar reflectivity just north of SDF. This boundary will meander
across the region today, resulting in winds at SDF to be VRB for
most of this afternoon and evening. Otherwise, isolated to scattered
pockets of showers will continue to remain possible. For tonight, a
richer moisture plume will move into the area, bringing much more
shower and storm coverage to the terminals. Cig and vis restrictions
are expected, with some period of IFR forecast. Also possible to see
terminals drop to LIFR for some time tomorrow morning. Restricted
flight cats will linger through much of the morning, along with
additional -SHRA or DZ. We`ll see conditions gradually improve
throughout the day tomorrow, with SDF returning to VFR in the
extended forecast period.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...CJP
LONG TERM...CSG
AVIATION...CJP

NWS LMK Office Area Forecast Discussion