731
FXUS63 KLMK 081744
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1244 PM EST Wed Jan 8 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

* Scattered light snow showers and flurries are expected today, with
  little impacts outside of a few slick spots.

* Bitterly cold temperatures are likely tonight, though exactly how
  cold it gets is still uncertain.

* Winter Storm WATCH has been issued for roughly the southern half
  of Kentucky for Friday and Friday Night.

* Forecast confidence increasing on significant snowfall Friday and
  Friday night.  The highest potential for heavy snow (>4")
  accumulations remains across the southern part of Kentucky, mainly
  along and south of the Western Kentucky and Bluegrass Parkways.
  North of the Parkways, 1-3 inches of snow will be possible.

&&

.UPDATE...
Issued at 1243 PM EST Wed Jan 8 2025

Sufficient lifting ahead of a weak shortwave trough moving across
the Wabash Valley has generated scattered, light snow showers this
morning as the cloud top layer pushes into the DGZ. Although only
minor snow accumulations (under an inch) are expected, the dry
character of the snowfall combined with the residence time of the
showers will allow isolated amounts over an inch. As a result, the
previous Special Weather Statement was extended to 21Z this
afternoon while adding some caution statement for slick conditions
on already-treated roads. Rest of the forecast remains on track with
potential issuance of Cold Weather Advisory tonight for southern
Indiana and the Bluegrass pending clearing skies and optimal
radiational cooling.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 354 AM EST Wed Jan 8 2025

Scattered pockets of flurries and light snow showers continue to
move across the region according to KY Mesonet/traffic cameras as
well as ASOS/AWOS obs. The air mass in place is cold enough that the
low-level stratus deck extends into the DGZ, which is helping to
produce these areas of light snow in spite of very limited moisture
overall. Temperatures have been fairly steady in the low-to-mid 20s
so far this morning as low clouds have inhibited radiational
cooling.

Today is expected to be another mostly cloudy and cold day across
central KY and southern IN, with temperatures struggling to warm
into the low-to-mid 20s this afternoon. A mid-level shortwave
disturbance, visible on latest water vapor imagery, will swing
across the Ohio Valley later today. While this system lacks much in
the way of deep moisture, there is a shallow saturated layer in the
vicinity of the trough axis between 8-12 kft. As this area of mid-
level moisture passes by today, it could enhance areas of flurries
and snow showers via seeder-feeder methods; however, the depth
between the two saturated layers is almost too great for this to
happen. With that being said, continued saturation and reasonably
steep lapse rates into the DGZ should lead to at least scattered
flurries continuing through much of the day, with flurries expected
to diminish from NW to SE this evening.

Tonight, much of the 00Z high resolution guidance suite shows
clearing from west to east as the 850 mb temperature trough moves
east of the area. How quickly these clouds clear will have a
significant impact on temperatures, with conditions otherwise
favorable for maximal radiational cooling, particularly where there
is lingering deep snowpack. Forecast uncertainty is fairly high,
with 10-15 degree spreads in temperature guidance amongst the 00Z
HREF members. The highest confidence in clearing skies is across
southern IN, with temperatures expected to fall to near or slightly
below zero by sunrise Thursday. Areas with snowpack across north
central KY are more uncertain for temperatures, as clouds may linger
well into the night tonight. Given peak cooling conditions,
temperatures will approach thresholds for a cold weather advisory,
but because forecast confidence in these conditions is still
relatively low, will hold off on issuance at this time. Across areas
in south central KY which do not have a deep snowpack, lows tonight
are expected in the high single digits and low teens.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 354 AM EST Wed Jan 8 2025

==============================================================
* SIGNIFICANT SNOWFALL EXPECTED FRIDAY AND FRIDAY NIGHT
* WINTER STORM WATCH ISSUED FOR THE SOUTHERN HALF OF KENTUCKY
==============================================================

Thursday and Thursday Night...

After a cold start to the day, we should see mostly sunny skies
during much of the day on Thursday with highs in the lower to middle
20s over the snow/ice pack areas of southern Indiana and the
northern half of Kentucky.  Slightly warmer temperatures are
expected across southern Kentucky with highs warming into the upper
20s to the lower 30s.  Clouds will increase ahead of the next
weather system that will push into the region late Thursday night.
With winds shifting to the southeast overnight, low temps Thursday
night will not be as cold with single digits across the Bluegrass
region and increasing into the mid-upper teens in the I-65 corridor.
South of the Cumberland Parkways, lows will be in the lower 20s.
Some light snow/flurries will be possible toward the very end of the
period west of the I-165 corridor late Thursday night as the next
winter storm take aim at the region.

Friday through Tuesday...

Fairly strong upper trough axis is forecast to be pushing through
the southern Plains/TX at the start of the period with surface
cyclogenesis occurring near the NE TX Gulf coast.  The surface low is
forecast to move through the Gulf coast states bringing a swath of
heavy snow from TX northeast through the TN and southern portions of
the Ohio Valley, including Kentucky.  Snow is expected to break out
across far southwestern KY early Friday morning and then overspread
southern Indiana and central Kentucky during the daytime hours.
Moderate to occasionally heavy snow will be seen from Friday
afternoon into Friday evening with a quick diminishing trend late
Friday night into Saturday morning.

Tonight`s model guidance is fairly similar to the previous 07/12Z
suite, although there was a slightly southward shift in the QPF
swath in the global deterministic and ensemble runs.  On the other
hand, the higher resolution models such as the NAM12 and the
Canadian regional suggest stronger forcing and potentially banded
precipitation occurring over the region.  The overall forecast
confidence in snowfall for Friday through early Saturday is very
high and snowfall accumulations are expected.  However, the
challenge to this forecast is where will we see warning criteria (>4
inches) across the CWA?

While the GFS and Euro ensembles trended more south, most likely due
to the larger spread within the ensemble members, the deterministic
runs continue to support moderate to heavy snowfall across much of
southern KY during the period.  These models have support from the
longer time-range mesoscale models such as the NAM40/12 and the
Canadian regional runs.  We`ll have strong moisture advection along
with fairly decent synoptic scale lift as we`ll be in the left exit
region of a 160kt 300 mb jet streak passing just south of the
region.  Model time-height cross sections did show a good bit of
frontogenetical forcing mainly across the TN valley and
extending northward into southern KY, but just how far north
this stronger forcing for banded precipitation remains in
question. The global models continue to favor more of southern
KY in tonight`s data. However, the mesoscale models suggest that
banded precipitation may occur a bit further north.

In general terms, this event looks to produce a solid 1-3 inches of
snow across southern Indiana and portions of northern Kentucky.
Across portions of southern Kentucky, a solid 3-5 inches with
locally higher amounts will be possible.  Utilizing the entire multi-
model suite, the highest risk of exceeding 4 inches of snowfall
appears to favor southern Kentucky.  After coordination with WPC and
surrounding offices, we`ve gone ahead and hoisted a Winter Storm
Watch for areas mainly south of the Western KY and Bluegrass
Parkways.  Our highest confidence right now is across the southern
half of Kentucky given the relative good agreement with the
deterministic and ensembles.  Drawing the northern extent of the
current watch was rather difficult, but we decided to give ourselves
a little buffering on the northern edge to account for some of the
more reliable mesoscale models.  The current watch may need to be
augmented in future runs depending on the model trends.

After this system pushes through, we`ll see a slight break in the
weather for the remainder of the day on Saturday.  However, another
mid-level disturbance looks to push through on Sunday/Sunday night
bringing another chance of light snow and possible additional
accumulations to the region.  As far as temperatures go,
temperatures will continue run below normal through the remainder of
the forecast period.  Overall highs will range in the 20s to lower
30s with overnight lows in the upper single digits to lower-middle
teens.

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1243 PM EST Wed Jan 8 2025

Stratus layer has been moving at a good clip today and after
tracking the cloud edge approaching southern Indiana, have indicated
a more optimistic forecast with earlier VFR conditions returning to
the terminals. In addition, light snow showers will diminish in
intensity and coverage this afternoon as clouds push to the south
and east. As a result, LEX/RGA/BWG will see a few more hours of
light snow with MVFR/IFR visibility this afternoon while HNB and SDF
will clear shortly after TAF beginning time. For tonight, clear
skies and calm/variable winds as surface high pressure moves
overhead.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Cold Weather Advisory from 11 PM EST /10 PM CST/ this evening
     to 10 AM EST /9 AM CST/ Thursday for KYZ023-025-030>037-
     040>043-049.
     Winter Storm Watch from late Thursday night through Saturday
     morning for KYZ026>028-045>048-053>057-061>067-070>078-
     081-082.
IN...Cold Weather Advisory from 11 PM EST /10 PM CST/ this evening
     to 10 AM EST /9 AM CST/ Thursday for INZ076>079-083-084-
     089>092.

&&

$$

UPDATE...ALL
SHORT TERM...CSG
LONG TERM...MJ
AVIATION...ALL