JKL issues Area Forecast Discussion (AFD) at Dec 29, 7:30 AM EST
168
FXUS63 KJKL 291230
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
730 AM EST Sun Dec 29 2024
.KEY MESSAGES...
- Well above normal temperatures will last through Tuesday,
followed by a return to winter cold to start the new year.
- Two main rounds of wet weather are forecast during the next
week: one tonight into tonight and another from Monday night
into Tuesday night.
- Winds will increase and become gusty out of the south to
southwest today, with peak gusts of 35 to 50 mph expected at
most locations.
&&
.SHORT TERM...(Today through Monday)
Issued at 418 AM EST SUN DEC 29 2024
Radar shows showers streaming northward out of the Deep South into
the Commonwealth this morning. This activity has been muted for
most of the night east of I-75 where southeasterly downslope flow
off of the Southern Appalachians has maintained rain shadowing
effects. Temperatures are very mild for this time of year -- in
the upper 50s and lower 60s at many locations. Localized
temperatures as warm as 67 degrees are noted at Whitesburg where
the downslope flow as induced mixing. Meanwhile, temperatures have
dipped into the mid/upper 40s through the most sheltered valleys
of the Kentucky and Big Sandy river basins displaced northwest of
the better downslope mixing. The latest analysis shows an ~1000
mb surface low centered over far western Kentucky. A cold front
extends southward from the low center to along the Central Gulf
Coast.
Bands of rain will continue to lift north through mid-morning as the
low pressure system gradually shifts north and east. Most of this
rain should be light to moderate, though some brief heavy
rainfall cannot be ruled out. At this point, the risk for any
hydro concerns appears minimal to nil. Moisture transport into our
area has been limited by convection over the Deep South as well
as the downslope component of the flow. Thus forecast rainfall
amounts have been lowered to between 0.30 and 0.75 inches --
easily handled by area creeks and streams. The more significant
hazard with this system appears the strong wind potential later
this morning and afternoon following the passage of the system's
cold front. The 29/00z ECWMF Extreme Forecast Index is showing
values between 0.8 and 0.9 across all but far southeastern
Kentucky indicating a heightened potential for climatologically
unusual strong wind event. Behind the cold front, the combination
of diurnal heating and low-level cold air advection should yield
a period of steep low-level lapse rates and efficient mixing of
the low pressure system's dry conveyor belt jet down to surface.
BUFKIT mixed-layer momentum transfer ranges from as high as ~45
kts over the Bluegrass at KLEX to around 30 kts at K1A6. This
parameter is a good proxy for surface wind gusts and is supportive
of peak wind gusts ranging from around 35 mph in the more
sheltered Coalfield valleys up to between 50 and 55 mph over the
Bluegrass. With recent rainfall, winds of this magnitude should be
more sufficient to knock down weakly rooted trees in saturated
soils as well as blow down a few limbs. A few power outages are
certainly possible as well. This has warranted the issuance of a
Wind Advisory from 9AM through 7 PM EST for the entire forecast
area. As that low level jet pulls away to the northeast, moisture
from the low pressure system's comma head will wrap back in from
the west later this evening and tonight with a resurgence of light
rain showers for overnight into early Monday. As the surface low
departs through the eastern Great Lakes on Monday, high pressure
ridging will bring brief drying for Monday afternoon before
another system approaches just beyond the end of the short-term.
In sensible terms, look for rain showers along with an isolated
rumble of thunder to gradually increase and spread eastward across
the remainder of eastern Kentucky early this morning. By around ~9
to 10 AM the system's cold front reaches Lake Cumberland and quickly
pushes northeast and reaches the Tug Fork Valley by ~1 to 2 PM
EST, bringing most of the rainfall to an end. Winds will quickly
strengthen out of the south at 10 to 25 mph with gusts of 35 to 50
mph (isolated stronger gusts north) with the frontal passage and
then gradually veer more westerly and slowly diminish through the
late afternoon/early evening. Temperatures peak in the mid 60s for
most (isolated upper 60s possible) ahead of the front, then drop
back into the 50s post-frontal. The winds continue to subside this
evening as light showers increase in coverage again and persist
for much of the overnight. Temperatures will cool off into the
mid 40s for most spots by sunrise Monday. During the day on Monday,
any leftover showers yield to at least partial clearing. It will
be quiet and cooler with high temperatures ranging in the 50s.
.LONG TERM...(Monday night through Saturday)
Issued at 514 AM EST Sun Dec 29 2024
After a dry Monday evening, residents of Eastern Kentucky will wake
up to rather wet conditions on New Year's Eve. Models continue to
collectively resolve the arrival of another upper level disturbance
to our forecast area by dawn on Tuesday. At the surface, this will
be represented by a low pressure system, and the area will be firmly
positioned within its warm sector at the onset of the event.
Confidence is fairly high that this low will remain to the north of
the Ohio River. As it ejects east-northeast, it will drag a cold
front across the commonwealth. Flow shifts to a westerly and then
northwesterly orientation post-FROPA, which will then foster cold
air advection by Wednesday afternoon/evening. Wraparound moisture
and upslope flow will allow PoPs to persist on the backside of the
system on Wednesday, but Thursday morning's forecast has trended
drier in the latest guidance. Given all of the above, a changeover
in precipitation type is expected during this first system.
Morning lows in the mid 40s and afternoon highs in the mid 50s
will initially yield rain on Tuesday. Snow will first mix in with
rain in the conventionally colder high terrain (e.g. Black
Mountain) early on New Year's Day, but the colder air may catch up
to the moisture in areas east of KY-15 later that evening to
produce some scattered snow showers. The trend towards a quicker
ejection has reduced snow chances across the western half of the
forecast area, and even in eastern locales, the antecedent warmth
will relegate accumulation to only trivial amounts.
The departure of this first system will mark a return to seasonably
colder temperatures for the start of 2025. Surface high pressure and
zonal flow aloft will keep the sensible weather quiet on Thursday,
with morning lows in the upper 20s and afternoon highs near 40
degrees under clearing skies. However, a clipper-type system will
approach the area on Thursday night and then move through on Friday
amidst this colder airmass. With sub-freezing overnight temperatures
at the onset of precipitation and favorable 850mb temperatures in
place throughout the entire event, this second disturbance favors
snow as its precipitation type. Its fast moving nature will once
again limit the areal extent and magnitude of accumulations, but it
is more likely to see measurable snow with this second event than
the first.
Aside from these two shots at precipitation, the big story in the
long term forecast will be the return to a colder weather pattern.
Temperatures trend downward through the duration of the long term
forecast, and high temperatures next Saturday may struggle to rise
above freezing. Expect overnight lows near 20 degrees next weekend,
a stark departure from the warm (50-65 degrees) nighttime
temperature observations across the forecast area at the time of
this discussion's publication. Some of the long-range guidance
points towards these colder conditions continuing into the first
full week of January, but it is important to note that model spread
increases drastically beyond Saturday. Confidence is not
particularly high in the sensible weather specifics for the first
full week of January, and interests are accordingly encouraged not
to read too much into individual deterministic model runs for that
time frame.
&&
.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 730 AM EST SUN DEC 29 2024
VFR conditions were present at the start of the period as numerous
to widespread showers were lifting across the area ahead of a
cold front. These showers will gradually become more scattered
from west to east through midday and then taper with the passage
of the cold front from southwest to northeast between 15 and 19z.
Low-level wind shear this morning will yield to strong south to
southwesterly winds mixing down to the surface along and behind
the cold front. Gusts peaking between 35 and 40 kts (locally
stronger near and north of I-64) are expected this afternoon. As
the low-level jet responsible for the strong winds pulls away to
the northeast, lower ceilings and the threat for scattered to
locally numerous showers returns for the evening and early
overnight.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 7 PM EST this evening for KYZ044-050>052-
058>060-068-069-079-080-083>088-104-106>120.
&&
$$
SHORT TERM...GEERTSON
LONG TERM...MARCUS
AVIATION...GEERTSON
Source: JKL issues Area Forecast Discussion (AFD) at Dec 29, 7:30 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412291230-KJKL-FXUS63-AFDJKL)
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