JKL issues Area Forecast Discussion (AFD) at Dec 3, 5:17 AM EST045
FXUS63 KJKL 031017
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
517 AM EST Tue Dec 3 2024
.KEY MESSAGES...
- Despite some ups and downs, temperatures will remain below
normal into the weekend. Near normal readings should return by
early next week.
- The greatest chances for precipitation will be with a strong
cold front Wednesday night into Thursday morning, and again as
low pressure passes to our northwest early next week.
&&
.SHORT TERM...(Today through Wednesday)
Issued at 353 AM EST TUE DEC 3 2024
The shortwave trough aloft which led to light snow developing
Monday evening is departing to the east early this morning.
However, lower level moisture lingers in cold air advection and
upslope flow. The shallow, moist, lower levels with steep lapse
rates are resulting in extensive clouds, and since the moisture
extends to temperatures colder than -10C, a few snow flakes are
still flying. However, with the layer being very shallow and a
lack of upper support, it's only flurries. This scenario will
extend into the day Tuesday. As time goes by and warming occurs,
the layer will dry, flurries will end, and clouds will eventually
break up. This process will also be aided by the easing of cold
air advection.
In fact, low level warm air advection should get underway toward
evening, and then strengthen during the night. This will happen as
surface high pressure passes over and moves to our east, with the
next weather system then approaching from the northwest. The next
system will be a cold front propelled by a very large, deepening
surface low crossing southern Ontario, and supported by a very
strong upper low dropping southeast toward the Great Lakes. The
strength of the system will result in a tight pressure gradient on
Wednesday, which will give increasing southwest winds and
significant warm air advection. After overnight lows in the teens
in many places (especially sheltered valleys), daytime highs
should surge into the 40s despite increasing clouds.
.LONG TERM...(Wednesday night through Monday)
Issued at 516 AM EST Tue Dec 3 2024
On Wednesday evening, at the very beginning of the long term
forecast period, temperatures will be in the 40s across most of
Eastern Kentucky. The exception to this will be the highest
mountaintops (e.g. Black Mountain) in the Southeast, which will be
hovering around the freezing mark. As the night progresses, however,
temperatures everywhere are expected to plummet. A well-defined cold
front will sweep through the forecast area in the early hours of
Thursday morning. Its greatest impacts are expected to be on the
temperature side of the sensible weather forecast. By 8am on
Thursday, temperatures across most of the forecast area will be in
the upper teens/lower 20s, with breezy winds out of the northwest.
The flow aloft will also shift towards a northwesterly orientation
as the upper level support for our frontal system ejects eastward.
Combined, this yields in efficient cold air advection processes, and
a continental polar airmass looks to settle into the region by
Thursday afternoon. Despite clearing skies, temperatures on Thursday
will struggle to rise above 30 degrees, with bitterly cold wind
chills in the teens. Some locations in the Bluegrass region may see
minimum apparent temperatures well into the single digits on
Thursday morning. This downward temperature trend continues
overnight into Friday morning, which is poised to be one of the
coldest mornings of the season so far. Thankfully, winds are
expected to die down by then. This will foster efficient radiational
cooling and ridge-valley temperature splits, with ridgetops in the
upper teens and valleys in the lower teens.
With regard to precipitation on Wednesday night/Thursday morning,
the relatively warm air in place at the start of the period gives
credence to the idea that precipitation will start out as light rain
in most spots. Once again, the exception to this is in the colder
southeastern terrain, but as cold air advection kicks in, a quick
changeover to snow is expected area-wide by early Thursday morning.
The best upper level support and atmospheric moisture will remain
displaced from our forecast area, which means that precipitation
totals will be limited to less than half an inch in most places.
Some orographically-enhanced snow accumulations are possible in our
southeastern counties, where the snow starts earlier and could
linger around for longer on Thursday morning. Mesoscale trends will
be monitored closely as the time approaches, and interested parties
are encouraged to stay tuned to future forecast updates as this
event enters the temporal range of higher-resolution forecast
guidance.
Headed into the weekend, high pressure is expected to build into the
region. This will yield in sunnier skies and moderating
temperatures, especially after the high shifts to our south on
Saturday. On Friday, highs will remain in the 30s, but a return to
southwesterly surface flow will allow afternoon highs in the 40s on
Saturday. Aloft, flow becomes quasi-zonal and some weak/flattened
ridging builds into the Ohio River Valley. The resultant 500mb
height rises support temperatures recovering into to the 50s by
Sunday afternoon across the south, with our northern locations in
the upper 40s.
A signal for rather wet weather to return at some point early next
week has emerged in the available long term forecast guidance, but
the individual models are resolving the parent features responsible
for such activity quite differently. In general, models depict a low
pressure system tracking out of the Plains and into the Greater Ohio
River Valley region, but on different days and with different
amplitudes and orientations. The GFS continues to be the
quicker/eastern solution, while the ECMWF continues to be
slower/further northwest. The NBM appears to bridge the gap between
these two camps and depicts increasing precipitation chances through
the day on Sunday and Sunday night. These PoPs peak on Monday as
moisture advects into the region via southwesterly flow, and this
trend appears reasonable at this time. By Sunday night, the entire
forecast area is forecast to return to above-freezing low
temperatures, and probabilistic forecast guidance suggests that
widespread highs in the 50s are likely by Monday afternoon. As such,
any early-week precipitation is likely to fall as rain, which will
work to relieve any lingering drought/fire weather season concerns.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1229 AM EST TUE DEC 3 2024
A mix of mainly MVFR and VFR conditions was present at TAF
issuance. A few flurries lingered in southeast KY. Flurries will
wind down overnight and on Tuesday morning, and improvement to
VFR will occur for all locations.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HAL
LONG TERM...MARCUS
AVIATION...HAL
Source:
JKL issues Area Forecast Discussion (AFD) at Dec 3, 5:17 AM EST---------------
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