407
FXUS63 KLMK 191531
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1031 AM EST Sun Jan 19 2025

.KEY MESSAGES...

*  Bands of snow showers this afternoon in the Bluegrass, with heavy
   snowfall rates and wind gusts of 20-25 mph possible in the
   heavier showers/squalls. The greatest threat for the heaviest
   showers and squalls is between 3pm and 5pm along and a county or
   two either side of the I-75 corridor, including the Lexington
   metro.

*  The Winter Weather Advisory remains in effect for areas roughly
   along and east of I-65, where 1-3 inches of snow is expected.

*  Frigid temperatures are expected into the middle of this week.
   Lows will be in the single digits, with wind chills below 0 at
   times beginning tonight. Highs on Monday and Tuesday will barely
   reach the teens to low 20s.

&&

.UPDATE...
Issued at 1030 AM EST Sun Jan 19 2025

A band of slightly heavier snow at this time is moving across
Simpson and Warren Counties, into Allen County, so will keep the
Winter Weather Advisory going for the Bowling Green region. So far
we`ve received three reports from Warren County of snowfall around
an inch this morning, with amounts around 0.5-0.8" in nearby
counties. Traffic is still operating at near normal speeds in most
areas and the snowfall will continue to diminish in intensity over
the next couple of hours.

Another area of slightly enhanced snowfall over southern Indiana is
slipping southward into north central Kentucky. Visibility in this
area of snow has generally been in the 1-2 mile range.

Of greater concern at this time is the possibility of some briefly
heavy snow showers or squalls this afternoon in the Bluegrass.  Once
the general widespread light snow this morning moves out, SBCAPE
rises to around 30-40J/kg this afternoon with steepening low level
lapse rates. There`s decent model agreement on a north-south band of
moderate low level frontogenesis this afternoon and snow squall
parameter around 1-2. Though 925-850mb flow shows that most of the
influence from the Great Lakes will remain just to our north, there
is still plenty of moisture in place with the DGZ nearly saturated.
Model reflectivity progs show north-south bands of convective snow
showers.

The greatest threat for heavy snow showers/squalls appears to be
between 3pm and 5pm along and a county or two either side of the I-
75 corridor this afternoon, including the Lexington metro. Road
temperatures this morning are just a degree or two above freezing,
but with the light snow this morning and air temperatures falling
through the mid 20s this afternoon, rapid snowfall rates will easily
lead to accumulation. Wind gusts of 20-25 mph will possible in the
heavier cells, contributing to low visibility and tricky driving
conditions.


Issued at 850 AM EST Sun Jan 19 2025

The main question of the morning so far has been whether or not to
expand the advisory westward into the Bowling Green area. Traffic
cams this morning have shown a dusting of snow on roads, but with
black & wet tracks common, especially on the main roads. Traffic
speeds have been near normal other than a few spotty minor slow-
downs, especially on I-165 southwest of Bowling Green. Monitoring
social media, there have been reports of around half an inch of
accumulation and just a light coating on roads. Kentucky Mesonet
cameras also suggesting around half an inch of accumulation so far
in the region just outside the original advisory. KYTC was just spot
treating and patrolling for most of the morning. So, it seemed that
an SPS was likely handling the situation sufficiently.

However, our snowfall observer in Bowling Green called in at 7:30
CST with around an inch of accumulation just east of town. Some
counties that KYTC earlier had been merely spot treating or
patrolling have changed to general treating of roads, especially in
Warren and Simpson counties. Snow rates will be decreasing as the
morning progresses, but additional minor accumulation is expected.
While traffic is lighter due to it being a Sunday morning, there are
still motorists out on the roads. With a few more hours of snowfall,
albeit light, went ahead and issued a brief headline for Edmonson,
Warren, Allen, and Simpson counties. With the snow lightening up
over the next few hours and with KYTC treating the roads, the
advisory only goes through noon CST.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 326 AM EST Sun Jan 19 2025

Colder, Blustery Today with Snow Showers...

A round of light accumulating snow is on our doorstep this morning.
A broad area of light returns is noted on radar just upstream across
portions of AR/MO/IL. An upper level trough will deepen southward
over the central CONUS today, while a fast-moving mid-level
vorticity maximum currently over the southern Plains swings ENE
across KY/TN. Mid-level ascent will increase during the mid-morning
hours as the Lower OH Valley becomes positioned in the left exit
region of a strengthening mid-level jet streaming over the Lower MS
Valley. Increasing synoptic scale ascent will help eliminate a mid-
level dry layer in the 09-12Z time frame. This drier air aloft has
kept central KY and southern IN largely dry up to this point.

Coverage of light snow will blossom in the 09-12Z time frame. The
heart of the event will then be 12-18Z today, when moderate ascent
will overlap deepening moisture above 600 mb. The latest model data
remains pretty consistent with QPF and the areas with the best snow
accumulation potential. Areas along and east of the I-65 corridor
could see 1-2 inches of accumulation, with 2-3 inches of snow
possible in the Bluegrass Region. Amounts right along and perhaps
just west of the I-65 corridor are a little more uncertain, as we
could see a sharper cutoff in that area (Breckinridge, Grayson south
through Warren County). It`s really only a 4-5 hour window of
steadier light snow in that area (roughly 5-10 AM CST), and forecast
confidence is just not high enough to pull the Winter Weather
Advisory any farther west at this time.

By the afternoon, drier conditions are expected near and west of I-
65 with just a few lingering flurries. Meanwhile, scattered light
snow showers will continue east of I-65 (and especially the
Bluegrass Region) through early evening. More widely scattered snow
showers late in the day will take on a more cellular character as
low-level lapse rates steepen and steady CAA continues. Though more
localized in nature, streaks of higher accumulation/impact will be
possible. Expect low visibility (less than 1 mile) in any snow
showers this afternoon, which will be accompanied by gusty NW winds
of 15-25 mph.

Temperatures will fall through the 20s this afternoon and into the
teens this evening. The breezy conditions will drop wind chills into
the single digits by early evening. Low pressure will lift off to
the northeast this evening and tonight, with strong arctic high
pressure nosing in from the west early Monday morning. Expect mainly
dry conditions after 00Z this evening due to the loss of lift and
moisture. Frigid air continues to pour into the region from the
northwest tonight. Air temperatures will drop into the single digits
early Monday morning, with wind chills dropping below zero. Minimum
wind chills late tonight and early Monday are forecast to reach the
-10 to 0 range. A few spots in the northern half of the area could
see wind chills briefly colder than -10. But these latest values are
very much in line with the current Cold Weather Advisory, so no
changes are planned.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 326 AM EST Sun Jan 19 2025

Synopsis...Largely amplified upper-level pattern will be well
underway at the beginning of the medium-range period with longwave
trough and associated broad cyclonic flow stretching across the
Lower 48 while anomalous blocking ridge expands from the Northeast
Pacific to the Gulf of Alaska. A couple of  shortwave troughs
embedded in the larger circulation will pass through the Ohio Valley
Tuesday and Thursday, reinforcing the cold spell. The latter part of
the forecast will potentially feature a pattern change as the
longwave trough lifts to the north, positive upper height anomalies
develop across the Southeast US, and shortwave cuts off over the
Desert Southwest.

Model Evaluation/Confidence...Generally speaking, there is medium
to high confidence in the synoptic pattern evolution through Friday
when run-to-run and model-to-model variability substantially lowers
confidence in elements such as precipitation chances and
temperatures over the weekend. There is good agreement on frigid
temperatures at the beginning of the week given the presence of
Arctic airmass and potential cooling effects from fresh snowpack.
There is also a very low chance (less than 10%) of light
snow/flurries Tuesday and Thursday depicted by the ECMWF p-type
meteograms and linked to the embedded shortwaves. Finally,
precipitation chances will increase by the end of next weekend;
however, confidence is low in p-types, timing, and coverage as large-
scale details still need to be resolved.

Monday - Wednesday...The week will start off dry and very cold.
After single-digit temperatures at sunrise on Monday, mostly clear
skies and winds gradually shifting to the west-southwest will yield
highs in the upper teens to the low 20s. Still, feels-like
temperatures will be 5 to 10 degrees lower than actual readings.
Monday night lows won`t be as cold as the previous night given
increasing cloud cover and light southwest flow. Official forecast
continues reflecting dry conditions, but it is worth mentioning a
low possibility of spotty flurries Tuesday morning as mid-level
forcing and enough moisture advection saturate the upper portion of
the DGZ. By Tuesday afternoon, cloud cover will lift and winds turn
back to the northwest as a reinforcing boundary crosses the region.
Furthermore, high pressure moves overhead Tuesday night contributing
to near-optimal radiational cooling conditions. As a result,
anticipate another shot of single-digit temperatures across the
board.

Thursday - Sunday...For the rest of the workweek, persistent
southerly winds and periods of cloud cover will promote rising
temperatures with above-freezing values during the afternoon hours
starting on Thursday. Another shortwave trough and attendant surface
front might yield light snow or some flurries on Thursday, but as
mentioned above those chances are pretty slim at the moment.
Saturday should still be dry with warming highs well into the 40s.
Precipitation chances will increase on Sunday as a mid-level wave
transitions over the Great Lakes and better moisture advection
spreads from the western Gulf of Mexico. Although rain should be the
main p-type during the event, a brief period of frozen precipitation
cannot be ruled out Sunday morning.

&&

.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 624 AM EST Sun Jan 19 2025

Light to moderate snow showers will spread across central KY and
southern IN this morning, with snow showers lingering in the
Bluegrass Region through the afternoon hours. At least brief IFR
vsbys are likely in moderate snow, with a combination of IFR and low-
end MVFR ceilings this morning. Snow tapers from west to east this
afternoon, with mainly dry conditions after 00Z Monday. Expect
gradually improving ceilings from west to east this afternoon and
evening. Breezy winds out of the NW are expected, with gusts over 20
kt likely this afternoon. Winds will back from the WNW by early
evening and diminish late tonight.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Cold Weather Advisory from 7 PM EST /6 PM CST/ this evening to
     1 PM EST /noon CST/ Monday for KYZ023>043-045>049-053>057-
     061>067-070>078-081-082.
     Winter Weather Advisory until 7 PM EST /6 PM CST/ this evening
     for KYZ028>043-045>049-053>057-063>067-074>078-081-082.
     Winter Weather Advisory until noon CST today for KYZ062-
     071>073.
IN...Cold Weather Advisory from 7 PM EST /6 PM CST/ this evening to
     1 PM EST /noon CST/ Monday for INZ076>079-083-084-089>092.

&&

$$

UPDATE...13
SHORT TERM...EBW
LONG TERM...ALL
AVIATION...EBW