Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 171958
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
258 PM EST Tue Jan 17 2017

.UPDATE...
Issued at 100 PM EST TUE JAN 17 2017

Hourly grids have been updated for recent radar, satellite, and
observation trends. A cold front is still approaching the area
from the west and a shortwave trough is approaching the Lower OH
Valley. Thus, although showers are currently more numerous across
the south, some redevelopment will be possible from mid to late
afternoon with some limited heating and instability ahead of the
front. Higher pops have been carried across the south today while
recent radar trends and short term models supported lowering pops
in the norht. Moisture should be deeper and instability a bit
greater in the south this afternoon so have hold onto isolated
thunder chances there for a few more hours although no lightning
has been observed for several hours in the region. Confidence in
any thunder is low. Enough heating should also take place for the
record at JKL to be broken. It has already been tied through 1 PM
EST.

UPDATE Issued at 1040 AM EST TUE JAN 17 2017

Radar trends and many of the short term model runs were in good
agreement bringing an area of showers across the Lake Cumberland
Region and across the Cumberland Valley and Ky Cumberland
Mountains area. Pops in this area were raised to categorical for
a couple of hours with those transiting out by early afternoon.
However, with the cold front an a shortwave trough still upstream,
chance to low end likely pops were held onto for a few hours into
the afternoon as some redevelopment seems probable. Temperatures
behind this band are in the low to mid 60s and even warm air
advection ahead of the front without much in the way of sunshine
the CWA should experience similar temperatures during the early to
mid afternoon and this will be enough to break the record high
for the 17th at JKL. The current record is 62 from 1990.

UPDATE Issued at 640 AM EST TUE JAN 17 2017

Did a quick update to the grids early this morning primarily to
fine tune the PoPs and Wx through the next few hours based on the
latest RADAR trends and HRRR guidance. Also tweaked the T and Td
grids per the current obs and trends. These have been sent to the
NDFD and web servers.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 345 AM EST TUE JAN 17 2017

08z sfc analysis shows a well defined area of low pressure
lifting northeast into the Great Lakes. This is dragging a cold
front slowly east through the Mid Mississippi Valley and toward
Kentucky. Additionally a northward moving warm front is currently
lying across eastern Kentucky with a large area of convection
rolling east along it. This cluster of showers, with a potential
for embedded thunderstorms will continue to press deeper into
eastern Kentucky from the west with a healthy dose of soaking
rains expected for most places by dawn. The clouds and arriving
showers, along with south stirring winds, have mostly mixed out
the colder valleys, but there remain a few in the east that did
manage to get into the upper 40s while most of the rest of the
area reside in the mid to upper 50s with lower 60s found in
several places south of Jackson. Dewpoints, meanwhile are running
in the low to mid 50s most places. This is making for another
quite mild mid January night - sitting at or near record max
minimum temperatures - across the area.

The models are in only fair agreement aloft through the short
term as the southeast ridge holds fast no matter what troughs move
by to the northwest. This will mean deep level southwest flow will
continue supporting our current spate of mild and wet conditions
through the near term. Specifically, an opening, southern stream,
wave will shift off to the north of Kentucky today. This is
followed by a fairly strong northern stream trough digging through
the Ohio Valley tonight - only briefly dampening the heights over
the region. The model spread is rather large for this feature
particularly given that it is only 24 to 36 hours out. The ECMWF
is a tad sharper and slower with this when compared to the GFS -
but not as slow as the NAM. This wave will be driven in part by a
300 mb jet streak passing to our north with sustained upper level
divergence over Kentucky today and tonight on its right entrance
region. Ridging rapidly builds back over Kentucky later Wednesday
in all models in the wake of the northern stream wave. Given the
lowered confidence with that second wave tonight have favored a
blended solution along with a lean toward the higher resolution
HRRR for the near term.

Sensible weather will feature a wet start to the day as a leading
band of showers moves through eastern Kentucky followed by a brief
lull around midday. By late afternoon another round of showers and
potential thunderstorms will seep northeast into the area just
ahead of a weakening cold front that pushes through during the
first part of the night. Cooler and drier conditions follow into
Wednesday morning, but readings will still be well above normal,
as well as freezing, through the short term with a small rebound
by the afternoon as high pressure quickly moves into the Ohio
Valley.

Started with the CONSShort and ShortBlend for most elements
through the short term portion of the forecast - making only minor
adjustments to temps and winds today. Also, adjusted PoPs more
toward the HRRR in the near term.

.LONG TERM...(Thursday through Tuesday)
Issued at 258 PM EST TUE JAN 17 2017

Good model agreement continues into the upcoming weekend. An
active pattern will continue into early next week with several
rounds of showers expected. The added rainfall, combined with
rivers already running high could lead to some high water issues
as we head into early next week. However, confidence on actual
amounts remains low, so will continue to leave out any flooding
concerns into next week. The first round of rain will move in on
Thursday and Thursday night as a shortwave trough pushes
northeast across the region. Good forcing and lift will yield
widespread showers. As the trough exits north on Friday,
conditions will temporarily dry out, especially by Friday
afternoon. Looks like dry weather should last through Saturday,
although models are showing some support for a few widely isolated
showers on Saturday. Moisture is fairly limited and lack of any
significant forcing will keep the chance of rain out of
the forecast for now. If a shower were to pop up, best shot would
be somewhere across central Kentucky. As we head late into
the weekend, chances are increasing of a large cut off low
developing across the deep south, then slowly pinwheeling up the
spine of the Appalachians. This slow moving system could bring an
extended period of rainfall to the area late Saturday night
through Monday night. Depending on the exact track of this system
will determine exactly how much rain we receive. If southeast
downsloping flow prevails through much of the time, it would eat
away at potential rainfall. For now, going to go high on the rain
chances through this period with more of the uncertainty falling
on actual amounts. It certainly looks like it will be a mild and
damp period which has been the theme lately. It looks like a
brief shot of more normal temperatures for January will drop in
by Tuesday, but again this may just be a quick shot before we
start to warm again. Right now, no threat of any wintry weather
for eastern Kentucky through Tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 115 PM EST TUE JAN 17 2017

MVFR is currently observed across the area with some IFR locally
in showers near the VA border. MVFR and possibly brief periods of
VFR in breaks in the clouds should prevail through the 21Z to 3Z
period in norther section with showers possible. Shower and
perhaps a stray thunderstorm near JKL, SME, and LOZ are also
possible during this period. Some IFR will also be possible during
that time near the TN and VA borders. Otherwise, low level
moisture should return from the north and west behind the front
and MVFR or IFR expected to return and generally persist through
the end of the period. Some stratus build down fog and mist will
also be possible 3Z to 15Z especially on ridges. Southwest winds
will be gusty initially sustained generally 10 to 15 kts, with
gusts up to 25 KT or so. These should diminish and become more
west during the 21Z to 0Z period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...JP
SHORT TERM...GREIF
LONG TERM...KAS
AVIATION...JP



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