321
FXUS63 KLMK 180755
AFDLMK

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

.KEY MESSAGES...

* Above normal temperatures expected once again today.

* Gradient wind gusts of 30-40 mph are expected today ahead of a
  strong cold front.  Widespread rain showers are expected.
  Brief/isolated wind gusts of 40-45 mph will be possible in
  stronger showers along the front.

* Behind the front, dramatic temperature fall will be seen overnight
  with a few snow flurries and snow showers possible.  Cold weather
  will last through Friday.  Temperatures will then warm back up
  over the weekend and into next week.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 255 AM EST Thu Dec 18 2025

Early morning satellite imagery shows partially clear skies across
eastern Kentucky with low stratus in areas west of I-65.  Early
morning temperatures were generally in the upper 40s/lower 50s along
and west of the I-65 corridor.  Out across the east, in the more
clear skies, temperatures were in the lower 40s with the more
protected valleys in the lower 30s.  No significant weather is
expected through sunrise.  The pressure gradient will continue to
increase over the next several hours, so expect southerly winds to
become more breezy by sunrise.

For today, a rather active day of weather is expected across the
region as a strong cold front drives eastward from the Midwest and
into the Ohio Valley.  Potent shortwave trough axis aloft was moving
through the northern Plains this morning with an accompanying
surface low in the low 980s moving through Minnesota.  This upper
level shortwave trough will continue to dig and take on a neutral to
slightly negative tilt as it pushes into the Ohio Valley later
tonight.  Ahead of this upper trough and front, the pressure
gradient will increase markedly through the day.  Strong southerly
winds will boost temperatures into the upper 50s and lower 60s.

Ahead of the approaching shortwave trough, large scale height falls,
on the order of 200m, will overspread the Ohio Valley and result in
strong synoptic scale lift.  This will likely result in widespread
rain showers developing.  A low-level jet axis of 60-65kts will be
overhead as well.  Downward momentum transfer will likely not become
maximized in this regime due to poor lapse rates, abundant cloud
cover, and the presence of a low-level thermal inversion.
Probabilistic ensemble guidance only shows a 20-30% chance of
exceeding 40 mph gusts along/north of the I-64 corridor.  In
general, gradient winds of 20-25 mph with gusts of 35-40 mph will be
seen across the region ahead of the front.  The front will approach
the region from the west late this afternoon.  High resolution
guidance continues to show a thin squall line developing right along
the frontal interface.  HREF guidance continues to show very limited
amounts of instability this afternoon ahead of the front and based
on the aforementioned soundings, it appears that this squall line
will remain elevated as it passes through the region.  It still may
be possible to mix down some higher gusts right along the surface
front this evening, where we could see some isolated gusts of 40-45
mph briefly.  Given that the model guidance continues to trend
weaker with instability and the overall intensity of showers, QPF
values have also trended downward.  24h ago, it looked like we`d see
0.75-1 inch of QPF with this system, now most guidance is in general
agreement with 0.6-0.75 inches.

Still think we`ll see a double frontal structure with this system.
Front number one will pass through during the early-mid evening with
winds shifting quickly to the west in the post frontal airmass.  As
this front moves east, we`ll see precipitation shut off from west to
east.  Later in the night, likely after 19/08Z or so, the secondary
front with the arctic air will push through the area.  Lapse rates
will steepen in the wake of that front and we may be able to squeeze
out some snow flurries and/or some snow showers as temps fall into
the the upper 20s.  There is still a small possibility that a flash
freeze could occur by dawn Friday morning.  However, this threat may
be largely mitigated due to winds remaining gusty overnight which
will dry out road surfaces.  Secondly, pavement temperatures will be
quite warm given the recent warmth and temperatures overnight will
remain above freezing until very late.  So by the time temps drop
into the upper 20s, road temps will likely lag behind by several
hours.  Will keep a close eye on the snow shower chances late
tonight as those could yield a quick coating in spots, though the
highest risk of that looks to be in areas along/north of I-64.

For Friday, a rather cold/blustery day is expected with highs only
warming into the lower 30s over southern IN and northern Kentucky.
South of the Parkways, mid-upper 30s are expected though a few 40s
are possible down along the KY/TN border.  We should see clearing
work into the region late in the day and into Friday night with lows
dropping into the mid-upper 20s, though protected valley locations
could drop into the lower 20s.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Issued at 255 AM EST Thu Dec 18 2025

For the extended period, increasingly zonal flow aloft will be seen
on Saturday as high pressure moves over us early Saturday and then
off to our east Saturday afternoon.  Temperatures will rebound quite
quickly with highs in the lower 50s across southern IN and northern
KY with mid-upper 50s across southern KY.  Saturday night we`ll see
another low pressure system move eastward across the Great Lakes and
drag another front across the region.  Could see some light rain
showers with that which could mix with some snow showers by Sunday
morning as lows drop into the upper 20s/lower 30s.

Sunday and Sunday night look to remain rather dry with highs on
Sunday coming down a bit.  Readings look to top out in the lower 40s
across the north with mid-upper 40s across the south.  Temps will
tick slightly warmer on Monday with highs in the low-mid 40s in the
north and upper 40s/lower 50s in the south.

The pattern for Tuesday/Wednesday will feature an upper level ridge
gradually growing over the TX and the southern Plains while the Ohio
Valley remains in the eastern periphery within a northwest flow
regime.  Storm track will remain well to our north with periodic
disturbances moving through the Great Lakes and into the interior
northeast US.  These systems may drive some weak frontal boundaries
into the region producing light rain showers and a gradient of
temperature (cooler NE to warmer in the SW).  Highs Tuesday will
range from the upper 40s over the Bluegrass to the mid-upper 50s in
the Bowling Green/SW areas.  Slightly warmer temps are expected by
Wednesday with highs ranging from the low-mid 50s in the NE to the
lower 60s in the south/southwest sections.

&&

.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.

&&

$$

SHORT TERM...MJ
LONG TERM....MJ
AVIATION.....MJ