233
FXUS63 KLMK 180518
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1218 AM EST Thu Dec 18 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

* Above normal temperatures expected Thursday.

* Gradient wind gusts of 35-40 mph are expected on Thursday ahead of
  a strong cold front. Widespread showers and a few thunderstorms
  will be possible. The risk of a stronger storm or two looks
  limited.

* Quick shot of colder air will arrive late Thursday behind the
  front and continue into Friday.  Temperatures will then trend
  warmer through the weekend and into next week.

&&

.UPDATE...
Issued at 939 PM EST Wed Dec 17 2025

Regional radars showing some shower activity down in the Lake
Cumberland region of south-central Kentucky.  This activity will
continue to trek on northeastward this evening.  Have updated to
forecast to put in some PoPs down that way.  Otherwise, remainder of
the forecast appears to be in good shape.  Went ahead and did a
quick refresh of the other weather elements to bring them in line
with current obs.  Updated products will be available shortly.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 419 PM EST Wed Dec 17 2025

Currently, mostly zonal flow is in place overhead with surface high
pressure sitting to our southeast. To the west, a small upper trough
in the zonal flow has developed with a surface low near the
Alberta/Montana border. The resulting pressure gradient over the
Lower Ohio Valley has driven warm air advection by generally
southern gusty winds. High temperatures have overachieved, pushing
into the low to mid 50s.

Tonight, the aforementioned upper trough will continue to strengthen
as it pushes towards the Midwest, developing into a closed low. The
system`s surface low will track towards the western Great Lakes,
dragging its cold front towards east towards the Missouri Ozarks.
The increasing pressure gradient will cause winds to increase
overnight from around 5-10 mph early in the night to 10-20 mph
Thursday morning. Cloud cover is also expected to increase during
the night as the front approaches. These things should limit falling
temperatures in most places to the low to mid 40s.

Tomorrow, ahead of the approaching front, very strong isentropic
lift will begin moving into the CWA from the west around 12z with
rain chances expected to begin shortly after. This will be driven by
a strong low level jet with winds reaching around 50-65 knots with
the higher values over southern Indiana and northern Kentucky, but
the heaviest rain arrives during the afternoon and evening hours
closer to the front and its extra forcing. Rain will come to an end
around 02z in Dubois County, IN to around 06z Thursday night in the
far eastern Bluegrass and Lake Cumberland area counties.

Model soundings show very impressive deep layer shear with 0-6km
shear in the 50-70+ knot range with 50-60 knot winds only 2-3,000
feet off the ground, but with low level inversions in place for most
of the day. Some of this wind could have trouble reaching the
ground. This is expected to limit gusty winds to 35-40 mph. A gust
over 40 mph isn`t out of the question, but currently leaning just
short of 40 mph for most places.

With the front not arriving until near sunset, WAA is expected to
lift high temperatures during the day into the mid to upper 50s, but
behind the front with CAA, temperatures dive into the 20s by Friday
morning. Any remaining water should be expected to freeze, but with
winds staying elevated behind the rain and before freezing
temperatures arrive, most surfaces should see a decent amount of
drying.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 419 PM EST Wed Dec 17 2025

Friday, the axis of the upper trough continues to move east away
from the CWA as surface high pressure, behind the front, slides from
east Texas towards the Tennessee Valley. This keeps CAA in place
through the day, limiting highs to the low 30s to low 40s, but as
the high passes east of the region Friday night, WAA returns to the
region. After a cool night Friday night with lows in the 20s,
temperatures rebound into the 50s under mostly sunny skies for
Saturday.

Saturday night, as a low pressure system passes east, north of the
Great Lakes, its trailing cold front pushes southeast through the
Lower Ohio Valley. This front will separate two surface high
pressure centers. It will likely only bring some passing cloud cover
the the region and more CAA. Sunday`s highs get limited to the 40s
to near 50.

Zonal flow will push the surface high over the Midwest east across
Indiana, bringing WAA back to the CAA. Highs return to the 50s and
maybe a few 60s across southern Kentucky by Tuesday and Wednesday.
Some additional chances of light precipitation are possible during
this time, but there remains a lot of uncertainty in the guidance.

&&

.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 1218 AM EST Thu Dec 18 2025

VFR conditions are expected during the overnight hours.  The
nocturnal low-level jet will strengthen and move into the region
from the west overnight resulting in LLWS conditions after 18/09Z.
Look for rain showers to develop across the region by mid-morning
with cigs lowering into the MVFR range.  Gusty gradient winds will
be seen with gusts of 25-30kts being possible and perhaps 35kts
within heavier showers.  Frontal boundary will enter the region in
the west by early evening and pass through the TAF sites between
18/23Z and 19/03Z.  Look for winds to quickly shift to the west in
the post frontal airmass.  Winds will remain gusty overnight with
gusts of 20-25kts possible through 19/12Z.

&&

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

&&

$$

UPDATE.......MJ
SHORT TERM...KDW
LONG TERM....KDW
AVIATION.....MJ