Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 171815 AAC

National Weather Service Jackson KY
115 PM EST Tue Jan 17 2017

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

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

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...(Wednesday night through Monday)
Issued at 305 AM EST TUE JAN 17 2017

Pretty good agreement between the model for the extended period. The
general consensus is that a series of upper level southern stream
weather systems will move across the Ohio and Tennessee valley
regions. The first systems is forecast to move out of the souther
Plains Wednesday night and Thursday. This system should bring rain
to our area Thursday and Friday. The models agree that rain showers
should being entering our area early Thursday morning. The rain will
overspread the area from south to north through out the day on
Thursday. The best chance for rain with this initial system should
be from late Thursday afternoon through early Friday afternoon, as
an area of low pressure by just to the north of the Ohio River and
into the central Great Lakes region. After this first round of rain
exits the area, we should experience a short break from
precipitation, as a weak ridge of high pressure aloft sets up over
the southeaster CONUS Friday night through early Saturday night. A
second slightly strong area of low pressure is then expected to
approach the area from the southern Plains Saturday night. This
system may be slower moving than the first, so we could see a longer
period of rain this weekend and into the beginning of next week. The
first showers with this second system should move into eastern
Kentucky late Saturday night. The rain will then gradually spread
across the area on Saturday, with the entire area likely seeing
accumulating rainfall by Saturday evening. The period from Saturday
night into early Sunday morning looks to be quite wet, as the area
of low pressure nearly stalls over top of us. This would allow the
rain to linger across the area through Monday night.

Temperatures through out the entire period will be well above normal
for the time of year. Highs during the extended will vary from the
50s to the 60s each day, with nightly lows generally in the 40s.
Some locations could fall into the mid to upper 30s Thursday
morning. Some locations along and south of the Hal Rogers Parkway on
Friday morning may only bottom out at or slightly above 50


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)

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.




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