Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 170620 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
120 AM EST Tue Jan 17 2017

.UPDATE...
Issued at 120 AM EST TUE JAN 17 2017

Did a quick update to the forecast mainly to fine tune the PoP and
Wx grids through the rest of the night per the latest RADAR trends
and HRRR guidance. Kept thunder chances in through the night as
the higher reflectivity should push in at least for our western
counties in the pre-dawn hours. Also, fine tuned the T and Td
grids per the latest obs and trends. These have been sent to the
NDFD and web servers.

UPDATE Issued at 1047 PM EST MON JAN 16 2017

The initial surge of moisture from a low level ramping up across
the region has subsided. This will leave us in a relative lull
until after midnight, when another stronger jet core will begin to
move into the area. This will result in widespread showers, and
the possibility of a few storms closer to dawn. Meanwhile, some of
the thicker cloud cover has thinned, allowing for the eastern
valleys to dip below the 50 degree mark, as south to southeast
winds have remained light thus far. This should modify after
midnight, but until then, have allowed these valleys to only
slowly rise, if not remain steady over the next few hours. Updates
have been sent.

UPDATE Issued at 655 PM EST MON JAN 16 2017

Rain showers will brush locations north of the Mountain Parkway,
as a low level jet noses in across the area. Have increased POPs
closer to the I-64 corridor through this evening, as additional
shower activity is poised to move in behind this initial band.
Have also tweaked lows down in the far eastern valleys, as early
decoupling has allowed for some lower 50s. Thicker cloud cover is
moving in, so these should be about capped at this point.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 338 PM EST MON JAN 16 2017

As of mid afternoon, an upper level ridge extended across parts of
the Gulf of Mexico and Caribbean with ridging north into portions
of the Southeastern States and Appalachians. Meanwhile a trough
axis extended from the Hudson and James Bay regions south west
into the Northern Plans and then through the Rockies and into the
Baja of California area. Within this trough was a closed low over
Eastern KS with a shortwave trough trailing southeast toward the
MS Delta Region. Further to the west, a ridge extended into
portions of the Pacific Northwest and Northern Rockies. At this
time, the axis of the upper level ridge was beginning to move to
the east of Eastern KY and southwest flow aloft is bringing in a
return of mid and upper level moisture. Meanwhile, at the surface,
low pressure was centered over Northeast KS with a cold front
trailing south into the East TX with the warm front extending east
into the OH Valley and then arcing to the south near the Crest of
the Appalachians and into the Southeastern States. Most Eastern KY
is now in the warm sector with temperatures in many areas in the
60s. Some sun has also been observed in thin spots in the mid and
high clouds.

This evening and tonight, the axis of the upper level ridge will
continue to move to the east of the area while the closed low
tracks toward the Western Great Lakes and weakens to an open wave.
The upper level flow across the area should be diffluent with a
period of rather deep lift later on tonight as isentropic lift
increases and the shortwave passes by to the northwest. With
moisture also expected to increase widespread showers or light
rain is expected. Enough cooling may also occur in the mid levels
late for some isolated thunder with limited elevated instability,
particularly in the west. Transporting the moisture in the area
will be an increasing low level jet that should reach near 50KT
late tonight. Winds on the ridges should also increase late and
become a bit gusty and some lower elevation locations may become
more mixed as the gradient increases. As the lower levels
saturate, some stratus build down fog may again develop.

The shortwave should track across the Great Lakes and into the St
Lawrence Valley tomorrow while another wave moves into the Western
Great Lakes and approaches the Lower OH Valley. Meanwhile the
surface low should track into the Eastern Great Lakes by late on
Tuesday with the trailing cold front moving into Eastern KY on
Tuesday afternoon ahead of the next approaching wave. More
widespread showers are expected earlier in the day along with some
stratus build down fog with the deepest moisture that should
begin to depart as the initial wave passes by to the north and
east. However, as the next wave approaches, and combines with
daytime heating and the approach of a cold front, additional
scattered to numerous showers and perhaps a few thunderstorms
should develop. Inability as it is late tonight is more or less
elevated and limited to confidence in any thunder is low.

Chances for showers should wane behind the front on Tuesday night,
but low level moisture should linger. In addition, the low level
flow will have an upslope component and the moisture may be deep
enough for some patchy drizzle late on Tuesday night.

.LONG TERM...(Wednesday through Monday)
Issued at 234 PM EST MON JAN 16 2017

Decent model agreement continues through the rest of the week and
into next weekend...leading to good forecast confidence.  Starting
off Wednesday, lots of moisture will be in place to lead to some
lingering drizzle, especially with moisture extending just above the
low level inversion.  Model soundings support cloud cover holding
through the day and this would likely keep highs in the 40s behind
the departing cold front.  High/mid clouds will already be on the
increase ahead of our next system Wednesday night. In fact, whatever
clearing we see will be short lived Wednesday night.  A shortwave
trough will then move across the region from Thursday afternoon into
early Friday morning. Good moisture and tremendous forcing/lift will
lead to widespread rain, especially for the Thursday night period.
As the system exits north on Friday, rain chances will diminish.
Shortwave ridging will slide across the area Friday night and
Saturday, providing a dry period.  This will also set the stage for
some sunshine on Saturday which will help boost temperatures well
into the 60s.  This will probably be our best chance at reaching the
highs on guidance for the whole week.  Clouds and rain chances will
limit temperatures the rest of the week, but we will stay well above
normal regardless.  A deeper storm system may develop by Sunday,
bringing rain chances back into the area once again.  Despite the
active weather, all of the systems seem progressive this week,
keeping any flooding concerns at bay.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 105 AM EST TUE JAN 17 2017

VFR conditions will start out the TAF cycle for most places, but
as the cold front moves in from the west overnight widespread
showers will press west to east into the forecast area. With this,
ceilings and visibilities will gradually lower to MVFR, with some
low level wind shear threatening in the east generally between 09
and 15z Tuesday. A few thunderstorms will also be possible across
the entire area during this timeframe, with rain showers off and
on through the rest of the day - Tuesday. South winds of 5 to 10
kts through dawn, will become southwest at 10 to 15 kts, with
gusts of around 20 kts expected during the day Tuesday.

&&

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

$$

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



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