693
FXUS63 KLMK 011130
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
630 AM EST Mon Dec 1 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

* Weather systems will come together over the region Monday night
  into Tuesday morning, bringing mixed wintry precipitation in the
  forms of snow, sleet, freezing rain and rain as they come together
  over the Ohio Valley.

* Snow accumulations of 1 to 3 inches is likely across portions of
  the area, especially along and north of the WK/BG Parkways. Brief
  periods of freezing rain/sleet are possible, and a glaze of ice is
  possible before changing to snow.

* Impacts to travel conditions are likely Tuesday morning.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 359 AM EST Mon Dec 1 2025

Main focus in the short-term is the impacts from the real first
winter system of the season. Sfc high pressure will keep the first
half of today quiet but also unseasonably cold. Temperatures already
this morning were in the low/mid 20s with even a few isolated spots
per the KYMeso in the upper teens. Sfc high will quickly push
eastward during the day and be across over the NE US by this
evening. A mid-level shortwave trough ejecting eastward out of the
Rockies and through the central Plains later today will help to draw
and advect warm Gulf moisture northward into the Ohio and Tennessee
Valley forcing and lifting it over the colder layer near the
surface. A developing weak sfc low will lift out of the western Gulf
and across the SE United States late Monday night into early Tuesday
morning. The interaction between these two system will result in
widespread wintry precipitation over southern IN and central KY.

Light snow associated with the upper trough will work out of the
Plains and spread into northern and central IL by Monday evening as
precipitation associated with the WAA/moisture advection comes in
from the south and across TN entering south central KY around the
same time. By late Monday night and early Tuesday morning these two
systems will come together over area with increased lift and forcing
associated by the isentropic lift from the weak sfc low to the south
and southeast and strong vorticity and from the approaching mid-
level trough and being co-located with upper level divergence
associated with the right entrance region of a 300mb jet streak.

Initial precipitation across southern KY should start off as rain,
as it lifts northward into central and northern KY and southern IN,
we will start to see a mix of snow, sleet and even a period of
freezing rain as the warm air/moisture advection area works
northward ahead of the upper trough axis. Current thinking remains
that most of the wintry mix of sleet, snow and even some freezing
rain falls along and north of the WK/BG parkways and to a certain
extent, into parts of the Blue Grass along and north of I-64 and
along and east of I-75. With mainly all snow falling along and north
of the Ohio River into southern Indiana.  At this time, we don`t
expect more than a light glaze of ice, especially on elevated and
untreated surfaces as ground and sfc temperatures will be near or
just above freezing. As the upper trough arrives, cold air aloft
will advect in along with a strong mid-level vort max developing
moderate to strong banding of snow over the area. Current forecast
calls for snowfall amounts to range from 1 to 3 inches from the
Parkways northward with potentially more associated with
strong/heavier snow bands. Because of the potential snow amounts,
along with a light glazing of ice, this being the first system to
bring accumulating snow/ice of the season and that it will likely
impact the Tuesday morning commute, went ahead and issued a Winter
Weather Advisory for Monday night into Tuesday morning.

There are potential bust in this forecast with growing discrepancies
between the hi-res short range models and the medium-long range
deterministic models. Both the GFS and ECMWF have remain fairly
consistent over the last couple of runs, with the more southern
track of the sfc low and the phasing of the two system taking place
over central KY with the main snow band setting up north of the
parkways, consistent with our forecast over the past several days.
On the other hand, the hi-res models of the NAM/HRRR delay the
phasing of these two system ultimately pushing the main snow band
further to the east and south. Potentially shift the main band of
snow outside of the current Winter Weather Advisory. This would
greatly reduce the snow amounts to the north and focus it more
along and south of the WK/BG parkways than had been previously
advertised over the past several days. There is also the challenge
of the WAA advection and how far into do we get before the mid-level
trough arrives across central KY and southern IN. This would also
limit snow amounts as it would make the thermal profile too warm for
all snow creating more rain and wintry mix instead reducing snow
amounts. Either way, this system will bring minor winter weather
associated impacts to the area, especially for the Tuesday morning
commute.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 359 AM EST Mon Dec 1 2025

Weather turns quiet going into the middle of the week. Zonal flow
aloft and sfc high pressure keeps the forecast mainly dry but also
colder than normal with highs ranging from the mid/upper 30s to low
40s.  A cold front is expected to move through between areas of sfc
highs Wednesday night into Thursday morning but it will lack
moisture outside of a few clouds.


Thursday night into Friday will feature a nearly identical setup to
what we will see later tonight into tomorrow , as another shortwave
upper trough ejects across the central CONUS, pulling a developing
surface low northward out of the Gulf and into the TN/lower OH
valleys. The cold air source ahead of this system does not appear to
be as supportive of wintry weather as the one tonight, with the
center of the sfc high shifting off the mid-Atlantic Coast. However,
given the amount of lead time and potential shifts in the model
guidance, we`ll need to continue to monitor this system later this
week for wintry weather potential. Forecast confidence decreases
after Friday, though a general signal for additional disturbances
swinging through the region later in the weekend is found in the
medium-range guidance. A modest warming trend over the weekend
should make it more likely that these systems end up being
mostly/all rain. However, temperatures should remain below normal
through next weekend.

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 629 AM EST Mon Dec 1 2025

Stubborn stratus has started to build in from LEX to SDF and could
see it push south towards RGA and HNB. Went more pessimistic for
flight categories this morning. We will get a period late
morning/early afternoon where we see high to mid clouds move in with
VFR flight categories but that will be short lived as the next
system will arrive later tonight. As rain and snow work in from the
south and west CIGs will start to lower with mainly snow for
HNB/SDF/LEX, mainly rain with a brief period of snow for BWG and
rain to snow for RGA. Timing is very complicated as there remains
some questions on where the heaviest snow band sets up overnight
into early tomorrow morning

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Winter Weather Advisory from 10 PM EST /9 PM CST/ this evening
     to 9 AM EST /8 AM CST/ Tuesday for KYZ023>043-045>049-053-
     061.
IN...Winter Weather Advisory from 10 PM EST /9 PM CST/ this evening
     to 9 AM EST /8 AM CST/ Tuesday for INZ076>079-083-084-
     089>092.

&&

$$

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