779
FXUS63 KLMK 190253
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
953 PM EST Tue Nov 18 2025

.KEY MESSAGES...

* Additional round of showers and thunderstorms expected later this
  afternoon and this evening.  Heavy rainfall and small hail are the
  primary threats.  An isolated spin up over our far western and
  southwestern areas can`t be ruled out.

* Active weather pattern will bring additional rainfall to the area
  Thursday through Saturday.

* The late weekend and into early next week will see drier
  conditions.

&&

.UPDATE...
Issued at 952 PM EST Tue Nov 18 2025

Closely monitoring a cluster of storms that is moving from
southwestern IN into central KY, which appears to be riding a
Effective Bulk Shear gradient per SPC Mesoanalysis. RAP sounding
profiles ahead of this cluster suggest we could be dealing with
around 100 J/kg of MLCAPE and around 40 kts of bulk shear. However,
a sharp low level inversion is keeping most instability elevated, so
believe overall severe potential continues to wane as the focus for
instability remains mostly over western KY. Still have PoPs over the
next several hours as we will see these showers and storms slide
southeast through the forecast area, so can`t rule out hearing some
rumbles of thunder.

Overall forecast remains in good shape, but did add mention of
patchy drizzle and increased fog coverage for the overnight period.
As the convective precip shield slides southeast, low stratus will
be filling in from the north. Forecast soundings show a strong
nocturnal inversion with ample moisture stuck underneath, leading to
a very low stratus deck that is already visible on GOES Satellite
imagery and regional sfc obs. This scenario seems to be a pretty
good candidate for drizzle and checks all the boxes. We expect the
low stratus to be around or under 1k ft for most of the night, along
with cloud thickness between 2500-3000 ft. Being in the proximity of
the stationary boundary, along with a low level inversion, and low
level saturation up to 850-800mb all add to the confidence to add
drizzle to the wx grids. Model soundings continue to show a
favorable profile through the morning, but for now will only run
drizzle mention through 14z, and will let the midnight shift take a
look and decide on adding drizzle later in the day.

Otherwise, guidance has been persistent on the most fog impacts
could be in the Bluegrass region, including LEX, for the overnight.
Updated wx grids to expand mention of `areas` of fog, with majority
of the region elsewhere with just `patchy` wording.

Forecast products have been updated and sent.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 332 PM EST Tue Nov 18 2025

Surface analysis this afternoon shows a warm frontal boundary
stretching along the I-64 corridor.  This warm front is producing an
impressive temperature gradient across Kentucky with lower 40s over
the northern Bluegrass region and into northeast Kentucky, while
areas along the KY/TN border are in the lower 70s...a 40+ degree
temperature gradient.  For much of the afternoon, we have been
watching several band of showers and storms move east across the
region.  Much of this activity has been elevated in nature given a
strong inversion seen on model soundings and ACARS soundings out of
KSDF.  Currently, an area of convection continues from Grayson
county northeastward through the Lexington metro area.  This
activity is sub-severe and is not expected to strengthen as it
continues eastward.

To our west, an area of surface low pressure was located just east
of St. Louis.  Aloft, a shortwave trough axis and small scale mid-
level jet streak will push eastward into the middle Ohio Valley this
afternoon and evening.  This wave and jet max will weaken with time
and this will also allow the surface low to gradually weaken as it
moves eastward along/just north of the I-64 corridor.  As the
afternoon wears on, additional convection is likely to redevelop
across portions of southern IL/SW IN/W KY in the pre-frontal trough
axis.  This activity should slide southeastward this evening while
weakening.  There remains the possibility that a narrow corridor of
instability still could develop, but it looks increasingly likely
that this corridor of instability will stay to our west and
southwest.  Most likely area of strong/severe storms is likely to be
in the SE MO/far western KY area where sufficient clearing and
destabilization has taken place.  Further east across southern IN
and central KY, ongoing cloud cover and continued convection is
likely to keep the warm front nearly stationary with surface based
instability remaining large limited.  Most storms across our region
are likely to remain elevated in nature and poise a threat of heavy
rainfall and perhaps some small hail in the strongest cores.  By
19/2-3Z much of the convection should be on the wane as large scale
forcing diminishes and the boundary layer grows increasingly stable.

Surface cold front is forecast to push through during the overnight
hours with winds shifting to the northwest.  However, low-level
inversion will remain and keep moisture trapped beneath, so plenty
of low stratus and fog/mist/drizzle will linger into the overnight,
resulting in reductions in visibility for Wednesday morning. Lows
tonight will remain mild with readings in the lower 40s across the
far north with lower-mid 50s elsewhere.

For Wednesday, mostly cloudy skies are expected as shortwave ridging
builds into the region from the west.  Highs look to warm into the
55-60 degree range over southern IN and the northern half of
Kentucky.  Highs in the lower-mid 60s are expected across southern
Kentucky.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 332 PM EST Tue Nov 18 2025

Thursday through Saturday Night...

An unsettled weather pattern is expected through this portion of the
forecast period as broad west-southwest confluent flow aloft sets up
across the Plains and into the Ohio Valley.  A large upper level low
will be found across the southwest portion of the CONUS with smaller
scale perturbations shearing off an moving east-northeast.  A good
flow of moisture will be advected northward into the region which
will bring widespread rain showers to the region.  Model soundings
do not show much in the way of surface based instability here.
Additionally, the wave aloft doesn`t have much amplitude, so the
risk of significant synoptic scale lift does not look supportive
enough to generate deep convection.  Nonetheless, steepening lapse
rates aloft may provided enough instability to produce some rumbles
of thunder across the region.  Rainfall amounts of 1-2 inches
continue to look reasonable here, though some locally higher amounts
will be possible.  Overall, the flood threat looks very minimal here.

Highs through the period will likely feature a gradient of sorts,
with lower 60s across southern Indiana and much of the northern half
of Kentucky.  Across southern Kentucky, highs in the upper 60s look
attainable. Overnight lows will generally be in the 50s, though they
should cool a bit Saturday night into the upper 30s/lower 40s.

Sunday through Tuesday...

Moving into the late weekend, a split flow pattern looks to emerge
aloft as there will be an upper level cut off low over the
southwestern US with mainly zonal/confluent flow downstream across
MO and into KY.  This should result in a rather dry forecast for
Sunday and Monday.  By Tuesday, the upper level low will likely move
into the Plains with warm advection type showers gradually
overspreading the region.  Generally seasonal temperatures are
expected here with highs in the upper 50s to around 60 with
overnight lows in the 40s.

Extended Forecast Discussion...

An interesting period of weather looks possible as we head toward
the Thanksgiving holidays.  A decent mid-latitude cyclone looks to
pass to our west/northwest in the late Tuesday night and Wednesday
time frame.  Models show plentiful moisture and shear for widespread
showers and perhaps some thunderstorms.  However, the usual
uncertainties on instability remain and will not be resolvable
until early next week.  The GFS/GEM are the quickest bringing this
system through, while the Euro is slightly slower, by 12-18 hours.
This system will then likely usher in a much colder airmass as we
head into Thanksgiving Day.

Since our last extended discussion, several iterations of signal
analysis has been completed.  While earlier signal analysis had a
weak signal centered around 11/28, the latest iterations have a much
stronger signal for the same period.  Taking into account the
possibility of the upper pattern becoming a bit more amplified, this
signal may pass through the region in the 11/28-11/30th time frame.
All three dynamical models (GEM/Euro/GFS) are hinting at the
emergence of a southern stream system in this time frame which could
bring wintry weather to the region late Thursday and into Friday.

&&

.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 632 PM EST Tue Nov 18 2025

Weather impacts are expected to continue throughout this TAF period
as a cold front stalls across the region. A mix of VFR and MVFR
flight cats are ongoing, with light rain continuing to shift
southeastward. We`ll have a few more hours with TSRA chance, but BWG
has the best chance. Otherwise, the main impacts for this period
will be the cigs, which are forecast to drop to LIFR levels
overnight. LEX and RGA may have addition vis impacts, but low
stratus appears to be the primary concern for all terminals,
including SDF. Conditions should slightly improve to IFR around
sunrise, and should continue to improve to MVFR throughout the day.
Winds will be somewhat variable overnight with the sfc low passing
through, though we do expect more of a N-NE flow by tomorrow.

&&

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

&&

$$

UPDATE...CJP
SHORT TERM...MJ
LONG TERM...MJ
AVIATION...CJP