LMK issues Area Forecast Discussion (AFD) at Jan 21, 11:16 AM EST141
FXUS63 KLMK 211616
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
1116 AM EST Tue Jan 21 2025
.KEY MESSAGES...
* Frigid temperatures through Wednesday morning with wind chills
occasionally dipping into the single digits below zero.
* Scattered flurries or light snow showers possible through mid
afternoon, especially in the Bluegrass region. A dusting possible
for some.
* Spotty flurries Thursday into Friday with moderating temperatures
towards the weekend. A mix of rain and snow is possible on
Sunday, but forecast confidence remains low.
&&
.UPDATE...
Issued at 1116 AM EST Tue Jan 21 2025
A band of flurries continues to move across the region this morning
along and behind an incoming cold front, which at 11am EST stretched
from Frankfort to Glasgow. Satellite is showing streets of flat
cumulus, from which the flurries are falling, popping up behind the
departing mid-level clouds from earlier this morning. As these low
clouds move east, a few could grow into light snow showers, with
isolated instances of a tenth or two of an inch of light, dry snow
not out of the question east of US 127 this afternoon...though that
would be much more the exception than the rule.
Expanded coverage of flurries for the remainder of the day, but no
other significant changes to the current forecast. Cold Weather
Advisory remains in place for tonight.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 342 AM EST Tue Jan 21 2025
Cold this morning with minimum wind chills mostly in the 5 above to
5 below range. Make sure everyone is bundled up for the bus stop
this morning. Given this morning's cold temperatures, and values
that will continue through Wednesday morning, no changes planned to
the ongoing Cold Weather Advisory headline.
Current water vapor and nighttime microphysics satellite imagery
show a SW to NE oriented plume of moisture streaming over our region
ahead of a positively tilted shortwave trough axis. We'll continue
to see increasing sky cover percentage and moisture depth through
the morning hours, lingering into the mid afternoon as the upper
trough axis swings through. Meanwhile, a surface cold front also
passes through. Ceilings will lower through the morning hours, with
a 4 to 6 thousand foot deck from around sunrise through mid
afternoon. Given the very cold temps (-20C to -25C) in the
saturation layer plus the lower cloud bases, do think we'll some
flurries or even brief light snow showers from around sunrise
through mid afternoon across the area. Snow ratios will likely be
15:1 or higher given the cold air, but overall don't expect more
than a dusting possible in most locations. Suppose the Bluegrass
region could see a dusting to a half an inch where moisture is a bit
deeper, but overall this dry/fluffy snow should not be impactful.
Skies are expected to clear from W to E through the afternoon, with
steady to occasionally gusty (20-25 mph) winds slackening toward
sunset. Surface high pressure traverses our area tonight, with calm
to light and variable winds beneath clear skies. This will yield
excellent radiational cooling conditions which will allow for lows
in the -5 to 5 above range. Winds mostly won't contribute to the
overall wind chill, but most spots should still see values in the 0
to -10 range. A few of the coldest spots could see lowest wind
chills in the -15 area. Cold Weather Advisory looks good to continue
through mid to late morning Wednesday as a result.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 342 AM EST Tue Jan 21 2025
Synopsis...The medium-range period begins with a couple of shortwave
troughs moving along the base of a lifting longwave trough allowing
a fairly stable temperature trend and isolated flurries/light snow
chances the second half of the week. For the weekend, mid-level
ridge will build across the Southeast US while another shortwave
trough digging across SW Canada splits and contributes to strengthen
southern-stream, cut-off low over the Southwest. Northern-stream
branch, on the other hand, will feature a reinforced shortwave
trough moving across the Upper Midwest and into the Ohio Valley.
Overall, expect moderating temperatures this weekend with increasing
precipitation chances on Sunday.
Model Evaluation/Confidence...Even though low chances are still
indicated by ECMWF p-type meteograms regarding flurries/light snow
Thursday evening into Friday, vertical profiles from GFS/ECMWF as
well as well below-freezing temperatures justify adding PoPs to the
forecast. Confidence remains low on the synoptic evolution Sunday
and onwards as dynamical guidance continues showing run-to-run and
model-to-model variability. Another point worth noting is that
probability of snow mixed-in with rain shield is increasing for the
Sunday-Monday period, most likely a result of several factors such
as timing of precipitation onset, lows Saturday night, and strength
of low-level warm air advection. In addition, there are also
discrepancies among models regarding precipitation duration which
could be traced back to the interaction between the northern-stream
shortwave and the Southwest cut-off low.
Wednesday - Friday...After a bitterly cold morning with potential
for single-digit negative lows, temperatures will quickly bounce to
mid 20s across southern Indiana to the freezing point in south-
central Kentucky thanks to southerly winds and periods of unblocked
radiation (although some mid to high level clouds could filter in
from the west ahead of an approaching wave). Warmer temperatures
(compared to previous days) are expected Thursday and Friday as the
shortwave and attendant frontal wave swing by with isolated coverage
of flurries along north-central Kentucky and southern Indiana.
Earlier model trends of heavier light snow showers have now
disappear from the solution set, so will refrain at this moment from
mentioning accumulating snow later this week with a dusting of snow
at best.
Saturday - Tuesday..Dry conditions return on Saturday behind the
weak cold front. Low-level winds will quickly turn to the south
allowing theta-e advection into the Lower Ohio Valley while
isentropic lifting slowly saturates the column. Precipitation is
anticipated to begin Saturday night into Sunday morning first as a
mix of rain and snow eventually becoming all rain in the afternoon
to possibly become a mix again the evening. Again, this is a low
confidence scenario at this moment based on a blend of several
models. Therefore, expect drastic changes in p-types, amounts, and
timing as the event window approaches.
&&
.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 618 AM EST Tue Jan 21 2025
Mostly VFR conditions expected through this TAF cycle, although do
have some lowering ceilings and a brief period of flurries in for
later this morning into the afternoon. Best chance for a brief
period of MVFR ceilings would be at LEX/RGA.
Best chance for ceilings in the 4-6K foot range will be from around
sunrise through afternoon, where we may also see a few flurries at
the northern TAF sites. LEX/RGA could see a brief vis reduction down
to around 6 SM as well. Surface winds will swing around to a steady
W component with perhaps a few gusts up around 20-25 mph. Skies
clear out this evening with winds slackening. VFR will continue with
another cold night on tap.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Cold Weather Advisory until 10 AM EST /9 AM CST/ Wednesday for
KYZ023>043-045>049-053>057-061>067-070>078-081-082.
IN...Cold Weather Advisory until 10 AM EST /9 AM CST/ Wednesday for
INZ076>079-083-084-089>092.
&&
$$
UPDATE...13
SHORT TERM...BJS
LONG TERM...ALL
AVIATION...BJS
Source:
LMK issues Area Forecast Discussion (AFD) at Jan 21, 11:16 AM EST---------------
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