JKL issues Area Forecast Discussion (AFD) at Dec 11, 10:27 AM EST327
FXUS63 KJKL 111527
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1027 AM EST Wed Dec 11 2024
.KEY MESSAGES...
- Rain transitions to a period of snow early this morning before
ending from west to east.
- Some snow accumulations are expected this morning, most notably
at elevations above 2,000 feet with up to 3 inches possible,
but an inch or less expected in the valleys. The snow could be
heavy for a time in the southeast parts of the area around mid
morning.
- Snow showers, a few briefly heavy and gusty, could bring
additional minor, but highly variable, snow accumulations this
evening.
&&
.UPDATE...
Issued at 1027 AM EST WED DEC 11 2024
The back edge of the steady snowfall now extends from Morehead to
Campton to Barbourville line. This will continue to shift eastward
through the remainder of the morning, likely exiting Pike County
during the 1 PM EST hour. The KYTC webcam atop Pine Mountain at
the US-119 crossing has shown slushy travel conditions at times.
There are also some patches of snow starting to stick at the
US-23/US-119 intersection near Payne Gap. Still expect up to
around 3 inches of accumulation over the highest elevations
through early afternoon. Meanwhile, webcams in valley locations
such as Pikeville, Hyden, and Whitesburg show just wet roadways
with accumulations remaining on grassy and elevated surfaces.
UPDATE Issued at 640 AM EST WED DEC 11 2024
The transition to snow continues to work eastward with enhancement
evident in the radar imagery east of the JKL office. The Winter
Weather Advisory for those counties are now in effect and
thoughts remain that a period of a few hours of moderate to heavy
snow will occur in an environment of mostly warm road sfc
temperatures limiting the threat for accumulations of impact to
locations generally above 2000 feet, though some heavier bursts
of snow could bring slush to the roads for a time even in the
valleys. Have updated the forecast to better time this transition
and include the latest obs and trends for the T/Td grids. These
small adjustments have been sent to the NDFD and web servers
along with a freshening of the zones, HWO, and SAFs.
&&
.SHORT TERM...(Today through Thursday)
Issued at 320 AM EST WED DEC 11 2024
07Z sfc analysis shows a cold front stalled right along the
border with Kentucky and Virginia. Along this, a wave of low
pressure is lifting northeast past the state. This process is
keeping rain going over the eastern portion of the JKL CWA early
this morning with lighter pockets of mainly drizzle found to the
west. Northwest winds of 5 to 10 mph, with occasional higher
gusts, are bringing in colder air and cooling the column. This
will eventually change the lingering rain in the west over to snow
and progress the transition eastward through sunrise. Currently,
temperatures vary from the upper 30s in western parts of the JKL
CWA to the lower 50s in the far east with the sustained rain and
closer to the front. Dewpoints, likewise, vary from the upper 30s
west to the upper 40s in the far east amid areas of fog and very
low clouds.
The models, and their individual ensemble suites, remain in
excellent agreement aloft through the short term portion of the
forecast, even as a very dynamic and impactful pattern evolution
occurs. They all depict a large and full latitude 5h trough
bottoming out over the Deep South early this morning as it gears
up to plow through the southern Appalachians. As part of this, a
strong 3h jet streak passes over Kentucky through 12Z placing the
area in the right entrance region for a time - enhancing lift for
several hours as it moves on by. The southern extent of the trough
brings its energy core through far southeast Kentucky this
morning before the trough axis passes and the mid level flow
switches to northwest. This northwest flow will carry with it a
weak but strengthening impulse that passes over our area this
evening. Following the dynamics of these features exiting stage
right later tonight, low 5h heights will continue along with fast
but generally benign west-northwest mid level flow while the
large trough consolidates north of the Great Lakes. The still
quite small spread among the models again endorsed using the NBM
as the starting point for the forecast grids, though the dynamics
of today is better captured in the latest CAMs guidance,
especially with respect to the PoPs and snow potential through
early afternoon as well as the evening impulse.
Sensible weather features a very active day starting before dawn
in the west when the CAA changes lingering light rain to snow
before ending later in the morning from west to east. As this
freezing line works deeper into this part of the state the sfc low
to the east will also strengthen and flare out its comma head of
pcpn westward and deeper into our CWA. This, combined with the
quickly cooling column, will change the pcpn over to snow
starting at the higher elevations first and working to valleys
shortly after sunrise. The CAMs consensus is for a few hour period
of moderate to heavy snow through late morning from this - likely
resulting in slushy accumulations during the heavier snow even in
the valleys. Above 2000 feet, the snow will have a better chance
of accumulating and not compact as much resulting in closer to 2
inches of accumulation on those ridges with as much as 3 inches
atop Black Mountain. The snow will have limited impacts most
places, though, due to the record warmth we saw on Tuesday and
still warm road surfaces. However, the robust nature of that
snowfall and higher rates, even for the relatively short window
of time, looks to be enough to warrant an advisory. The snow will
end west to east across the area by noon with a swath lingering
in the far east into early afternoon. Dry weather and temperatures
above freezing, for all but the higher elevations, follow through
the rest of the afternoon giving the area a breather from the
snow.
For this evening, we will see a secondary cold front arrive from
west to east with colder temperatures but also arriving more
moisture starved. The steepening lapse rates could make some of
these snow showers robust with squall-like impacts through
evening and a rumble of thunder cannot be ruled out. The areas
affected will be highly variable, though, and this threat will
continue to be addressed via an SPS with the main concern
temporary low visibility in the snow showers, brief light
accumulations, and a refreeze potential towards midnight for any
leftover wet spots as temperatures drop into and through the 20s
overnight. Brisk and chilly conditions continue on Thursday, in
the wake of the trailing cold front, even as some sunshine returns
with temperatures struggling to make the upper 30s and lower 40s
for highs.
The changes to the NBM starting point again consisted primarily
of adjusting PoPs and snowfall this morning and also this evening
per the latest CAMs timing and placement through the early
overnight hours.
.LONG TERM...(Thursday night through Tuesday)
Issued at 305 AM EST WED DEC 11 2024
The large scale flow pattern to begin the extended will feature a
trough of low pressure moving through the four corners region, and
quickly into the central Plains. East of this system, we will see
weak ridging aloft moving across the Rocky Mountains and into the
central and northern Plains. A very intense and large scale trough
will be pushing across southeastern Canada and New England, with
surface ridging in place south of that feature. The eastern ridge
will bring dry and mild weather to eastern Kentucky Thursday night
through Friday, as persistent southerly flow sets up across the
region. The quiet pattern will change over the weekend, however, as
the western trough crosses the Rocky Mountains, and intensifies over
the northern Plains. Temperatures will continue to warm across the
region, as winds shift to the south ahead of the approaching storm
system. This should allow for daily highs to max out in the 50s
across our through the end of the period. Cloud cover will increase
rapidly ahead of the low pressure Friday night into Saturday. We
will see widespread rain showers moving into and across eastern
Kentucky over the weekend, as a strong trough aloft moves by to our
north, and a weak surface cold front moves through. The rain will be
most widespread Saturday night and Sunday, as the front becomes
temporarily hung up over the region. The rain will persist through
Tuesday, as another system quickly takes shape over the Plains, and
moves through the Great Lakes and Ohio and Tennessee Valley regions
to begin the new work week.
Temperatures look to be above normal through out the period, with
daily highs in the 50s for most locations, and nightly lows in the
upper 30s to mid 40s during the rainy periods. We will, however, see
very cold temperatures in the 20s and lower 30s Thursday night and
Friday night, as Canadian high pressure remains in place for a bit.
With no thunder, heavy rain, or wintry weather expected, there are
no weather hazards anticipated in the extended portion of the
forecast.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
ISSUED AT 705 AM EST WED DEC 11 2024
The transition to all snow is underway at the TAF sites. As this
occurs VIS restrictions to IFR will be possible (even lower for a
brief time at KSJS and perhaps KJKL) with the snow. CIGs will also
be quite low through the morning for most sites. Conditions
improve from west to east into the late morning and early
afternoon. Later, towards sunset, scattered snow showers develop
and move into the area from the west, mostly after 22Z. Though
extremely low confidence, a few lightning strikes are possible,
along with brief squall conditions with these toward the end of
the TAF period. Winds will be generally from the northwest at 5 to
10 kts through the day, but look for an uptick in the evening to
10 to 15 kts with gusts up to 25 kts from the west, for a time,
accompanying any of the more robust of the scattered snow
showers. Winds settle and clouds should break up and lift later
tonight into Thursday morning.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 2 PM EST this afternoon for KYZ087-
088-110-113-115-117>120.
&&
$$
UPDATE...GEERTSON
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...GREIF
Source:
JKL issues Area Forecast Discussion (AFD) at Dec 11, 10:27 AM EST---------------
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