539
FXUS63 KLMK 172328
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
628 PM EST Wed Dec 17 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.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
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 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 /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 627 PM EST Wed Dec 17 2025

We are dry and VFR this evening, but we`ll see our next round of
rain chances during this forecast period as a strong cold front
approaches the region. Ahead of any rain, LLJ will strengthen out
ahead of the front, causing LLWS to ramp up during the overnight
hours. Rain and lowering cigs will move into the area as the LLWS
phases out tomorrow, leading to flight cats to drop to MVFR
progressively from west to east throughout the early afternoon.
Gusty sfc winds will accompany the rain showers, with gusts up to
30ks possible from the south. HNB has the best chance of dropping
into IFR with the frontal boundary passing through by the end of the
period. Impacts to flight ops are expected to continue through the
end of the forecast period, except for SDF, where they will return
to VFR in the extended time frame.

&&

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

&&

$$

SHORT TERM...KDW
LONG TERM...KDW
AVIATION...CJP