JKL issues Area Forecast Discussion (AFD) at Nov 20, 12:45 AM EST990
FXUS63 KJKL 200545
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1245 AM EST Wed Nov 20 2024
.KEY MESSAGES...
- Colder temperatures arrive Wednesday night, with snow expected
to be seen in the air in most places at times from Thursday
into Friday.
- Locations most likely to receive light snow accumulations will
be at elevations above 1500 feet, mainly Thursday night.
&&
.UPDATE...
Issued at 1109 PM EST TUE NOV 19 2024
Hourly grids were updated based on recent observations and trends.
This led to holding onto slight chance pops longer north of the
Mountain Parkway over the next few hours and for the entire night
in the southeast.
UPDATE Issued at 725 PM EST TUE NOV 19 2024
An area of showers or light rain continues to move northeast
across the region and into WV, with some drizzle or light rain
lingering behind it. The steadier activity should diminish this
evening per the consensus of guidance and no adjustments were
needed to pops over the next few hours for this. Adjustments were
made to hourly temperatures and dewpoints based on recent
observations.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 332 PM EST TUE NOV 19 2024
Active weather pattern setting up across the country over the next
several days, as series of low pressure systems move through. The
overall large scale pattern will start off with a ridge of high
pressure situated just offshore of the southeastern part of the
country, with a large trough moving through the northern Atlantic
off the coast of southeast Canada. Meanwhile, another large trough
of low pressure will be in place over southern Canada, and will be
moving through the Great Lakes and into southern New England from
Wednesday onward. This system will bring repeated rounds of rain to
our area the next couple of days, as weak impulses rotate around it
aloft. High pressure will fill the void behind the aforementioned
low, and will bring a blast of much colder air into the region.
Further west, a powerful and explosively intensifying storm system
will be approaching the west coast, and will be moving onshore in
the Pacific Northwest Friday and Friday. That system will pack lots
of wind, rain, and mountains snows and is roars ashore.
The latest runs of the HRRR and NAMNEST models both have numerous
rain showers moving through eastern Kentucky through early this
evening, as a weak cold front, and an area of low pressure situated
on the south end of the front, move slowly through the Ohio and
Tennessee Valleys over the next several hours. Ongoing rain showers
should slowly taper off late this afternoon into early this evening,
before pausing briefly late tonight. By around dawn on Wednesday, a
secondary, and much stronger, cold front is forecast to move through
the region on Wednesday. This boundary will bring another round of
rain to the area on Wednesday. The highest rain chances tomorrow
should occur between roughly 16 and 22Z, as the cold front moves
quickly through the region. Temperatures will warm up quickly during
the first half of the day on Wednesday, ahead of the approaching
front, but will most likely begin to fall again late in the
afternoon/early evening time frame, as winds behind the front shift
to the west or west northwest, and begin bringing much cooler air
into the Ohio and Tennessee Valleys. Any rain ahead of the front
will steadily taper off late in the day on Wednesday, and should be
out of the area by around 0Z Thursday.
After seeing lows in the 50s on Wednesday morning, a large
temperature swing is on tap for Wednesday night, as a much colder
air mass filters behind a departing cold front. In fact, Wednesday
nights lows could fall into the mid 30s for most locations, or even
a bit colder than that depending on how quickly skies clear off late
Wednesday and Wednesday night. No weather hazards of note expected
in the short term.
.LONG TERM...(Thursday through Tuesday)
Issued at 523 PM EST TUE NOV 19 2024
Large, intense, stacked low pressure will be centered over the
upper Great Lakes at the start of the period and will be our
dominant feature until the weekend. Surface low pressure
developing along the northeast coast will become dominant Thursday
night as the Great Lakes surface low weakens and drifts south to
the central Appalachians. As this happens, the upper low will
migrate to the New England/Mid Atlantic region. The whole process
will result in multiple lobes rotating around the mean position of
the upper low, supporting precip. Strong low level flow around the
system will initially bring us cold air advection on Thursday,
with the air mass being cold enough for whatever precip occurs to
be primarily snow. Warm air advection wrapping completely around
the very wound up system will arrive on Thursday night, and the
resulting deep moisture brings us our highest probability of
widespread precip, with atmosphere still looking cold enough for
primarily snow. A switch back to low level cold air advection may
occur for a time late Thursday night and early Friday, before a
switch back to warm air advection later on Friday. The warm air
advection and associated deeper moisture could bring another
uptick in precip late Friday (especially in our east), but with
enough warming for a change to rain for most places. With that
said, this is of course based on today's model runs, and some
change/variation in these details is still possible. Even when
snow falls, temperatures will be too warm or only marginally cold
enough for any accumulation. As is typical in these marginal
situations, our higher elevations will stand the greatest shot at
accumulation. The highest total amounts currently forecast are
around 3 inches on Black Mountain and on some peaks in eastern
Pike County.
The aforementioned storm system finally makes a quick departure
to the northeast late Friday night and Saturday, and dry weather
will make a return for the local area under zonal flow aloft. Low
level warm air advection will return, especially as low pressure
takes shape well to our west. This should bring a developing warm
front north and northeast through our area on Monday and Monday
night with our next chance at showers. As the low pressure system
tracks northeast over the Great Lakes on Tuesday, its trailing
cold front approaches and continues our potential for showers.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
ISSUED AT 1245 AM EST WED NOV 20 2024
IFR/LIFR conditions are prevailing across all TAF sites and will
continue to be that way as low CIGS and low VSBY are plaguing all
TAF sites. There will be gradual improvement overnight toward 15Z
as a cold frontal boundary dives through the area. This will
bring increased PoP chances through the afternoon; as well as,
gusty westerly winds. Westerly winds sustained around 10 knots and
gusts to 20 knots are expected through frontal passage before
shifting to the northwest post-frontal. Once the front crosses
through this afternoon/evening, CIGS will gradually begin to
increase from IFR to MVFR and then VFR after 00Z and winds will
slacken to light and variable.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JP
SHORT TERM...AR
LONG TERM...HAL
AVIATION...VORST
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 20, 12:45 AM EST---------------
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