277
FXUS63 KLMK 070019
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
819 PM EDT Mon Oct 6 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

*  Showers, with a few embedded thunderstorms, continue tonight into
   Tuesday.

*  Widespread rainfall amounts of 1 to 3" are expected between this
   evening and Wednesday morning. Localized swaths of 4 to 6" may
   lead to minor flooding.

*  Cooler and more seasonal temperatures arrive by late week, with
   a mostly dry forecast anticipated.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 358 PM EDT Mon Oct 6 2025

This afternoon, a positively-tilted upper trough is ejecting out of
the northern U.S. Rockies and across the northern Great Plains. As
this trough moves eastward, upper ridging over the southeast U.S. is
gradually being eroded, with height falls taking place across the
Ohio Valley and Midwest at this time. These height falls throughout
the low-to-mid troposphere have allowed for continued southerly flow
over the past 12 hours, drawing rich moisture up from the Gulf and
into our area. This plume of moisture has contributed to the
development of widespread light to moderate rain showers across much
of central and western KY and southern IN, with many locations
having already received between 0.10-0.50". Areas along and east of
I-75 have seen lingering mid-level dry air limit precipitation so
far today, and temperatures have been able to warm into the upper
70s and low 80s while areas in the rain back to the west have
remained in the upper 60s and low-to-mid 70s.

As we head through the rest of the afternoon and into the evening
hours, continued southerly flow through the lower troposphere will
draw additional moisture into the region. By late tonight, PW values
are expected to range between 1.8-2.1", approaching the 99th
percentile of climatology. An area of sfc low pressure currently
over the lower MS valley will lift northward, eventually meeting up
with the approaching cold front from the northwest by tomorrow
afternoon. Recent runs of hi-res guidance develop several bands of
enhanced precipitation extending to the northeast of the sfc low
overnight tonight, likely supported by enhanced llvl convergence as
a subtle pressure trough/effective warm front sets up ahead of the
sfc low. Isentropic upglide as well as modest instability will also
lead to elevated rainfall rates. By Tuesday morning, the approach of
the larger cold front will help to turn the sfc low`s trajectory
eastward in addition to enhancing convergence along a southwest-to-
northeast oriented axis.

While forecast confidence is high in widespread 1-3" of rainfall
tonight into tomorrow, wherever these enhanced bands of rain set up,
there will be locally higher amounts, potentially leading to
isolated instances of flooding. The 12Z HREF 6 hr. localized PMM QPF
shows this scenario well, with isolated swaths of 4-6" of rain. In
general, there are two favored zones for the heaviest rainfall
amounts, one across central Indiana and another between the BG/WK
and Cumberland Parkways across Kentucky. Flash Flood guidance
generally ranges between 3-4" across these areas, so a few flood
advisories or flash flood warnings may be needed tomorrow. However,
given that these swaths should be relatively confined in area and
confidence in location is still modest, combined with pre-existing
drought conditions across most of the region, we decided to hold off
on issuing a Flood Watch at this time, though a targeted watch may
need to be issued if guidance continues to ramp up.

Outside of the heavy rainfall threat, given increasing flow aloft
tonight into tomorrow and the aforementioned sfc wave, there is a
very remote possibility for a strong to severe storm across south
central KY Tuesday afternoon and evening. The primary limiting
factor appears to be the lack of instability, with HREF mean progs
showing a brief window of 500-1000 J/kg SBCAPE along the TN border
Tuesday afternoon. With most hi-res guidance showing fairly
continuous low clouds and rain Tuesday, it may be difficult to
destabilize enough to realize any of the instability; however, if
there was a window of clearing, with 30-35 kt of deep-layer shear
and enhanced llvl curvature ahead of the sfc front, this would
introduce a low confidence severe threat.

Otherwise, temperatures over the next 24-36 hours will be strongly
moderated by ample moisture. Lows tonight should only fall into the
60s, with highs on Tuesday held down in the 70s. As the cold front
pushes across the region Tuesday evening, winds will veer around to
the north/northwest, bringing cooler and drier air into the area by
Wednesday morning. Precipitation is expected to wind down between
sunset and midnight across most of the area, though a few light rain
showers may linger across Lake Cumberland into early Wednesday
morning. Temperatures should range from the low 50s across southern
IN to the low 60s across southern KY Wednesday morning.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 358 PM EDT Mon Oct 6 2025

Cold front will be through by the start of the long term with sfc
high pressure building in over the Great Lakes. Aloft, ridging will
also return but unlike previous upper ridge, temperatures will not
be as warm. Cooler air will be over the Ohio Valley for the rest of
the week with 850mb temps will range 8 to 11C over the region. This
will put daily highs Wed mostly around 70, with highs on Thur cooler
struggling to reach 70, with upper 60s north of the parkways.

The current forecast looks to remain dry through the end of the week
and into the weekend. Weak trough coming out of Canada over the
Upper Midwest on Friday looks to break off from the main flow and
become an upper low. This will send a weak shortwave trough and sfc
boundary across the Great Lakes and into the Ohio Valley for late
Friday into early Saturday. Forecast remains dry as the bulk of this
features passes by to our north.

We remain dry for the weekend into early next week as ridging
expands along the eastern CONUS as the aforementioned closed low
interacts with a coastal sfc low off the Mid-Atlantic over the
weekend. Again while the trend is for us to be dry, not going to
rule out the idea that we see more clouds and the possibility of
some light showers over the weekend and into early next week. If we
do tend to go cloudier with low end rain chances this weekend and
early next week, temperatures would also trend cooler. Current
forecast has highs in the mid/low 70s Friday through Monday with
cool overnight lows in the 40s.

&&

.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 811 PM EDT Mon Oct 6 2025

The main focus for the forecast will be the deteriorating flight
categories over the forecast area tonight into tomorrow. Already
experiencing the first wave of showers moving through our area from
BWG-HNB-SDF. Other than HNB that has been bouncing between MVFR/IFR
most sites as of writing this discussion at 23z was VFR but as we
continue through the evening and overnight we will see CIG lower to
MVFR and IFR as well as lower VIS with increasing showers and rain.
While confidence is high in the deteriorating conditions, the main
challenge is the timing of when we will see the rain spread over the
area and when the heaviest rain will occur along with when we will
see the transition from one flight category over to a lower level.

There may be a lull overnight in the rain but we expect the main
wave to progress in from the south and west towards dawn. Heavy
rain, lower VIS and CIG are likely with a small chance of embedded
thunder as we go through the day. By the end of the period, we could
see slow improvement from west to east as the main wave pushes
through but could have MVFR CIG and some lingering drizzle and
showers.

&&

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

&&

$$

SHORT TERM...CSG
LONG TERM...BTN
AVIATION...BTN