LMK issues Area Forecast Discussion (AFD) at Jan 11, 9:08 PM EST500
FXUS63 KLMK 120208
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
908 PM EST Sat Jan 11 2025
.KEY MESSAGES...
* Relatively pleasant Sunday with lows in the teens to 20s and
afternoon highs in the mid 30s to near 40 degrees.
* A weak clipper system could bring some light snow accumulations
to the area on Tuesday. Snow amounts under an inch expected at
this time.
* Very cold temperatures Tuesday and Wednesday with morning lows in
the single digits. Wednesday morning could feature temperatures
near zero in some locations.
&&
.UPDATE...
Issued at 908 PM EST Sat Jan 11 2025
It is quite across the region with stratus clouds slowly moving to
the east resulting in clearing trend in the western third of
forecast area. There is a non-zero chance of freezing fog developing
during the first half of the night in rural areas across west-
central Kentucky and southwest Indiana as these areas will cool down
quicker. However, confidence is low given streaming clouds moving
from the Mid-Mississippi Valley and strengthening winds during the
pre-dawn hours that could inhibit any ongoing freezing fog efforts.
Best chance for persisting freezing fog into the first morning hours
could occur in river valleys and well-sheltered locations.
&&
.SHORT TERM /THROUGH SUNDAY/...
Issued at 306 PM EST Sat Jan 11 2025
An upper level trough is over the Northeast US this afternoon, with
a sfc low now over the western Atlantic Ocean. Shortwave ridging,
both at the surface and aloft, will build over the Ohio Valley this
evening before shifting off to the east on Sunday. Skies are mostly
cloudy this afternoon, with low-level cold air in place and low-
level moisture trapped beneath an inversion. A few breaks in the
thin cloud deck are letting peeks of sun through, especially along
and north of I-64.
Clouds will continue to thin and scatter late this evening and
overnight. As the low-level ridge axis shifts east, developing W/SW
flow will advect warmer air into the region. However, low-level flow
will be light and at least partial clearing will allow temps to
tumble into the mid teens to lower 20s early Sunday morning. Some
patchy fog looks possible late tonight into early Sunday.
On Sunday, low pressure spins over the Upper Midwest, dragging a
cold front through portions of the Midwest and Mid-MS Valley. Low-
level SW flow will increase between the high to the east and the
cold front to the west. As for highs on Sunday, the fresh snowpack
will counteract the effects of low-level WAA to some degree. Expect
temperatures to warm into the mid/upper 30s in the afternoon, with
perhaps some areas near 40 degrees in southern KY. Skies will be
partly to mostly sunny, with more cloud cover across southern IN.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 306 PM EST Sat Jan 11 2025
===== Sunday Night - Monday =====
Sfc high pressure is expected to depart to the south and east during
Sunday evening, which will make way for a weak mid-level shortwave
that is set to pivot across the central Plains. Cloud cover will be
increasing from west to east through the evening hours, and we
should become completely overcast by the overnight time frame. A
meager cold front associated with the shortwave will pass through
the area Sunday night and into Monday, which could produce a few
snow flurries. This front will be quite moisture-starved, with
soundings showing a shallow saturated layer that will keep us from
fully saturating the DGZ. PoPs have been trending drier, and will
continue with this trend based on latest model guidance. Will keep a
silent 10% PoP for the overnight, but no accumulation is expected.
Temperatures for Sunday night and into Monday will be in the 20s,
with areas west of I-65 on the cooler side as the cold front brings
in some CAA in the wake.
Dry weather is forecast for Monday as another sfc high pressure
builds across the southern Plains and Ozarks. While this will keep a
CAA regime in place, we should be able to clear out some of the
clouds, especially by the afternoon. Temps will be below normal due
to the CAA, so highs will struggle to get above freezing for most.
Best chances of that will be along the I-75 corridor and pointing
eastward.
===== Tuesday - Wednesday =====
A much colder airmass will be filtering into the Ohio Valley by
Tuesday morning, with us starting off the day with temperatures near
single digits. Best chance for any area to see single digit temps
Tuesday morning will be north of the WKY/BG parkways, with lower
teens more likely to the south across south-central Kentucky.
A weak clipper system appears to bring a quick hitting round of
light snow to the area on Tuesday afternoon. While this system is
also expected to be lacking deep layer moisture, sounding profiles
do show slightly better saturation into the DGZ than the Sunday
night system. Tuesday afternoon sfc temps, as well as the
temperature profile in the column, would support all snow as the p-
type. Uncertainty remains on exactly where the best forcing will
line up, as well as how much moisture will actually be available. As
of now, better chances for light snow accumulations under an inch
are generally north of south-central Kentucky and the Cumberland
Parkway. Will keep PoPs limited to 10% for now due to confidence,
but it appears PoPs could be on the upward trend in future forecast
packages.
By Tuesday night, another sfc high pressure will be moving across
the Midwest and building into the Ohio Valley. However, this time it
will be a stronger high pressure system and of Canadian origin. This
sfc high, combined with at least partly clear skycover, and
lingering snowpack, appears to be a good candidate for possibly
bringing our coldest air of the season by Wednesday morning.
Forecast probs continue to show a glaring signal for single digit
temperatures, with a possibility for some negative readings as well.
The 100-member Grand Ensemble paints a 45-55% probability for
temperatures below zero along and north of I-64, and a 20-40% prob
between the Cumberland Parkway and I-64. The NBM is not as excited
for sub-zero temps, and only has a 20-30% prob north of I-64. As for
the probabilities for single digits, the NBM has at least a 50% prob
north of the Cumberland Parkway, with chances increasing to nearly
90% north of I-64. The Grand Ensemble has a similar probability for
single digit temperatures. Wednesday morning is the highlight of the
long term, as these potential cold temperatures could impact
vulnerable communities. These forecast low temperatures are
approximately 15-25 degrees below normal.
Our temperatures will remain in the 20s during the daylight hours on
Wednesday, which will be nearly 20 degrees below normal for this
time of year. With the high pressure directly overhead, strong
subsidence will help keep us dry and mostly clear for the day.
===== Thursday - Saturday =====
One more morning of frigid temperatures are forecast for Thursday as
NW flow and CAA remain in place. However, after the cold start with
single digits and low-teens, our temperatures will recover to the
upper 30s and near 40, which will be much closer to climatological
normals than in the previous few days.
Dry weather is expected for Thursday and Friday as broad sfc high
pressure sits across a large portion of the southern US. Friday
could actually see temps back in the mid 40s and at or above climate
normals. However, precip chances will return to the forecast by
Saturday as a cold front approaches from the west. For those looking
for a break from the snow, this weekend precip wave appears to be
all rain as our temps will be above freezing. Confidence on timing,
amounts, and locations, will increase through the upcoming week.
&&
.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 622 PM EST Sat Jan 11 2025
Impacts/Confidence:
- Low confidence in MVFR ceilings overnight
- Medium to high confidence in MVFR ceilings early Sunday evening
Discussion...High pressure ridge will extend from the Southeast US
towards the Appalachians tonight, allowing west-southwest winds to
shift to a southerly direction while remaining weak. Slow-moving
stratus deck will continue tracking to the east while generally
remaining VFR. However, there is low confidence in the
aforementioned scenario as models are hinting at periods of MVFR
ceilings, especially at LEX and RGA. On Sunday, pressure gradient
between high pressure ridge to the east and cold front sagging
across the Midwest will strengthen south winds and boost confidence
in MVFR ceilings towards the end of the TAF period and thereafter.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...ALL
SHORT TERM...EBW
LONG TERM...CJP
AVIATION...ALL
Source:
LMK issues Area Forecast Discussion (AFD) at Jan 11, 9:08 PM EST---------------
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