NWS Area Weather Forecast Discussion
Louisville, KY
LMK
LMK
572
FXUS63 KLMK 180849
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
349 AM EST Sat Jan 18 2025
.KEY MESSAGES...
* Colder and blustery on Sunday with light to moderate snow
showers. A Winter Weather Advisory has been issued for Sunday for
the Bluegrass and Lake Cumberland regions.
* Frigid temperatures are expected late in the weekend into the
middle of next week. Lows will be in the single digits, with wind
chills below 0 at times. High temperatures Monday and Tuesday
will only reach the teens to low 20s.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 348 AM EST Sat Jan 18 2025
Synopsis...Southern-stream shortwave trough will move across the
region this morning while assisting a cold front transition from the
Midwest to the Lower Ohio Valley. Further south, weak low pressure
area lags behind the faster southern-stream wave; however, another
wave embedded in an amplifying longwave trough will allow the low
pressure to intensify as it lifts towards the Appalachians and Mid
Atlantic region.
Model Evaluation/Confidence...There is medium to high confidence in
the temperature, precipitation timing, and QPF elements during this
period. The most challenging element is the snowfall amounts during
the 0-6Z timeframe on Sunday as deterministic GFS and CMC have been
displaying significantly greater accumulations. As a result, lower
snowfall during the aforementioned 6-hr period following a blend of
ECMWF/UKMET/ICON/NAM and 18/0Z GFS.
Today...Synoptic lift from southern-stream wave and moisture
advection from associated low-level jet have generated widespread
shower activity this morning, as expected. Rain rates are mostly
light to moderate with a few pockets of heavy rainfall at times.
Lightning activity is not anticipated at the moment based on
virtually non-existent instability. Precipitation coverage and
intensity will decrease after sunrise as the souther-stream wave
departs to the east, with forecast soundings supporting more of a
drizzle environment through the early afternoon. Furthermore, cold
front will move in from north to south shortly after sunrise
tapering off precipitation chances for the day and promoting
constant cold air advection so that temperatures will steadily fall
throughout the day.
Tonight...Second (northern-stream) wave accompanying the amplifying
trough moves across the region, steering the surface low pressure
towards the northeast and closer to the forecast region. The
presence of below-freezing temperatures, sufficient moisture, and
increasing broad-scale forcing associated with the intensifying low
will support increasing snowfall chances this evening and especially
tonight. Snowfall rates at the beginning of the event will be light,
mostly confined to the Bluegrass and Lake Cumberland regions, and
although temperatures will be below freezing, pavement temperatures
could still be warm enough to avoid road impacts (except on bridges
and overpasses). All in all, minor snow accumulations (0.1-0.2") are
forecast by Sunday sunrise in the fat eastern third of the forecast
area.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 348 AM EST Sat Jan 18 2025
Cold and Blustery Sunday with Snow Showers...
Large scale upper level troughing will be centered over Ontario and
the North-Central United States on Sunday. Of note, a mid-level
shortwave trough rotating through the cyclonic flow will move ENE
over the region Sunday. This feature will provide weak to moderate
ascent over the region before it exits off to the ENE by Sunday
evening. In the lower levels, the 850 mb trough axis will be over
the Appalachians as a sfc low deepens northeastward over the
Carolinas. Potent low-level CAA will continue Sunday via breezy NW
flow.
Plentiful low-level moisture will linger throughout the daytime,
with this moisture layer reinforced by a trajectory off the Great
Lakes. Mid-level moisture depth will be briefly enhanced by the
passing shortwave trough. This results in favorable DGZ saturation
even through the afternoon hours, due to the lower levels cooling
into the -10 to -20 C range.
Expect a period of snow showers on Sunday, especially through
the first half of the day, along with cold conditions and breezy NW
winds. Snow showers should mostly taper off west of I-65 during the
afternoon. Steepening lapse rates and very cold air aloft may allow
scattered light snow showers to linger in the Bluegrass and Lake
Cumberland regions through the evening. Expect mainly dry conditions
by 00-03Z Monday.
Based on the latest 18.00Z suite of model data, including HREF
guidance, the best snow accumulation potential is still east of I-
65. East-central KY (Bluegrass and Lake Cumberland regions) could
see 1-2 inches of accumulation, with a locally higher total not out
of the question east of I-75. Given the much colder air arriving
Sunday along with blustery conditions, confidence has increased in
minor impacts in the eastern forecast area. A Winter Weather
Advisory will be issued for the Bluegrass and Lake Cumberland
regions, which will be valid 1 AM - 7 PM EST Sunday. This area has
the highest confidence of seeing minor travel impacts due to
occasional moderate snow showers, slick roads, and low visibility
due to snow showers and gusty winds. The Advisory area can be
adjusted in subsequent forecast updates if needed.
Bitterly Cold Sunday Night - Wednesday...
Arctic high pressure really starts to build in by Sunday night, so
will go dry by this time. The big story will be the cold as lows dip
into the single digits by Monday morning. Corresponding wind chill
values are expected to dip into the -8 to 2 above range, which may
necessitate a Cold Weather Advisory for much of the area. Will hold
off on that headline for now as that is still 48 hours out, but plan
on a bitterly cold Monday. Highs only reach the teens to low 20s,
with Monday night lows in the single digits to low teens.
A reinforcing arctic high/shot of frigid air moves over the region
through midweek. Highs on Tuesday will only reach the 16-25 degree
range, with the warmest readings across southern KY. Lows Wednesday
morning will again be in the single digits with the high overhead.
Meanwhile, a potent winter storm will impact the Deep South Tue-Wed,
but precipitation still looks to remain well south of KY.
Wednesday Night - Friday...
Forecast confidence drops a bit for the end of the work week, though
moderating temperatures are looking increasingly likely. Developing
low-level SW flow should bring warmer air to the region, with highs
back in the 30s and 40s Thu and Fri. Precip chances still look
fairly low through Friday, so will continue with a dry forecast.
&&
.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 1241 AM EST Sat Jan 18 2025
Confidence/Impacts:
- Medium to high confidence in MVFR/IFR ceilings this morning
- Medium confidence in periods of MVFR/IFR VIS with showers
- Medium confidence in light snowfall accumulations Sat night
Discussion...Deteriorating flight conditions this morning as a wave
of rainfall moves in ahead of a cold front located over the Midwest.
Radar imagery shows extensive coverage of light-to-moderate showers
under SW flow. There could also be a brief period of gusty winds at
the beginning of the TAF period before the heavier rainfall sets in.
Ceilings are expected to become predominantly MVFR before sunrise
and fall into IFR threshold by midmorning. On the other hand, VIS
will mainly stay MVFR, but strongest shower activity could yield
periods of IFR. No lightning is anticipated. Rain will let down by
13-14Z with probably drizzle/mist thereafter. Winds will gradually
shift to the NW as the cold front sweeps through the area in the
morning. Finally, there is a signal for light snow showers after
19/0Z with overall minor accumulations.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Winter Weather Advisory from 1 AM EST /midnight CST/ to 7 PM
EST /6 PM CST/ Sunday for KYZ036-037-039>043-046>049-
054>057-065>067-077-078-081-082.
IN...None.
&&
$$
SHORT TERM...ALL
LONG TERM...EBW
AVIATION...ALL|
Forecast Discussion from: NOAA-NWS |
Script developed by: El Dorado Weather Adapted by FrankfortWeather.us |
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