Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 261125 AAA

National Weather Service Jackson KY
725 AM EDT Mon Sep 26 2016

Issued at 715 AM EDT MON SEP 26 2016

Another quick update to fine tune temps, dewpoints, and sky cover
through the next few hours based on current obs and trends. These
have been sent to the NDFD and web servers.


.SHORT TERM...(Today through Tuesday)
Issued at 425 AM EDT MON SEP 26 2016

07z sfc analysis shows a well defined cold front moving into the
western portions of the Ohio Valley. However, in the far eastern
parts of Kentucky high pressure remains in control with mostly
clear skies and light winds. As in the past few nights, this has
allowed for a decent ridge to valley temperature difference.
Specifically, readings vary from the low 70s on the ridges to the
low and mid 60s in the more sheltered spots. Dewpoints, meanwhile,
are in the low to mid 60s while the winds remain light. There are
some mid level clouds around, but for the most part skies for
eastern Kentucky are clear while lowering ceilings are approaching
the state from the northwest. The front shows up well on radar,
too. We can see the showers and thunderstorms rolling northeast
along this boundary as they approach western Kentucky. Again in
the east this night, river valley fog has started to form and
some locally dense spots are anticipated through dawn but likely
clearing out quicker this morning than the past few considering
the inbound clouds and winds likely picking up sooner.

The models continue to settle on a similar solution aloft. They
all take the ridge, that has brought extended summer weather to
the area for the better part of a week, east and flatten it out.
The culprit for this pattern change is an impressive early fall
season closed low/trough plowing into the Great Lakes this
morning. This system brings strong height falls, a dynamic wind
field, and ample mid level energy to the Ohio Valley today,
initially brushing by Kentucky to the north. The best dynamics
associated with this will pass by and through the JKL CWA between
18 and 21Z. Following this, heights will continue to fall as the
parent upper low bottoms out, turns over on itself, and starts to
head south down through the Great Lakes. Given the models`
tandem movement to this more extreme solution will favor a
blended starting point with emphasis on the latest NAM and HRRR
for details. Confidence on the specifics is only average at best
given the sense that the models are still in a state of flux
working to resolve this closed low.

Sensible weather will feature any river valley fog burning off
quickly this morning with early sunshine giving way to increasing
and thickening clouds from the northwest. A band of showers and
thunderstorms are expected to enter northwest parts of the area
by late morning, grow in coverage, and sweep through the rest of
eastern Kentucky by late afternoon. Should enough instability
build up ahead of the convective band a few of the storms could
start to organize and become strong with wind gusts the main
threat. Look for the timing of the front to keep the worst of the
storms from developing until they get east of Kentucky, later
this afternoon, but they will still need to be watched closely.
The clouds and pcpn will keep temperatures in check today with
much of the area not likely to get out of the 70s. Much cooler air
arrives tonight in the wake of the front with some 40s anticipated
by morning, especially in the higher terrain and more open areas.
The valleys should hold up a bit better as the cooler air takes a
bit longer to scour them out. Also, anticipate that northwest
winds through the night and the cloud cover will keep fog to a
minimum - for a change. A full fledged fall day will then unfold
on Tuesday with partly sunny skies anticipated and a quite
noticeable change to the air with temperatures only reaching the
low to mid 70s for highs along with much lower humidities.

Started with the CONSShort/ShortBlend for grid population into
the evening and SuperBlend thereafter to 00z Wednesday. Made some
substantial changes to the terrain derived edit areas and
forecast points early this morning and tonight in the temperature
grids to better reflect ridge and valley differences in a neutral
pattern this morning and a cold air advection one tonight. As for
PoPs - ramped them up for later this morning into the likely
category through the afternoon and then dropped them quickly from
west to east after 00z. This is a bit higher than MOS guidance
matching up better with the MAV numbers rather than the MET.

.LONG TERM...(Tuesday night through Sunday)
Issued at 310 AM EDT MON SEP 26 2016

The models have come into better agreement regarding the upper low
currently over the Upper Mississippi Valley. This low will become
closed off and gradually drop southeast towards our area. At the
start of the extended period, the low is progged to be over the
Great Lakes states and then drop southward and be centered over
Kentucky late Thursday. The low will then meander back into the Ohio
Valley region on Friday before weakening and eventually lifting out
of the area over the weekend. Models still struggle with the lows`
exit over the weekend with the GFS taking the low up through New
England while the ECMWF only lifts it into the Great Lakes. Given
these differences, have opted to stay close to the CR Superblend
solution which lifts the showers and thickest cloud cover north of
the area on Sunday.

In terms of sensible weather, it looks like showers and additional
cloud cover will persist from Wednesday afternoon through Saturday
as the upper low remains over the area. With the additional cloud
cover, afternoon highs will be a bit cooler and overnight lows
shouldn`t be as cold as yesterday`s forecast. The coolest days
appear to be Thursday and Friday with highs only in the upper 60s.
Overnight lows will generally remain in the upper 40s and low 50s
through the period.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)

High pressure is losing control of the weather through east
Kentucky as a well defined cold front approaches from the
northwest. Ahead of this, though, VFR conditions will exist for
most areas through mid morning along with light and variable
winds. Patchy valley fog will be around again towards dawn,
possibly affecting LOZ and SME with some MVFR BR for an hour or
two. The cold front will cross into eastern Kentucky by early
afternoon. This will result in increasing chances of showers and
thunderstorms for the remainder of the afternoon and into the
early evening. Best potential is centered between 18 and 21Z and
the TAFs reflect this, with MVFR vis and cig conditions possible
at all TAF sites during this time frame and VCTS a concern for a
couple hours either side. VFR conditions will then return quickly
in the evening from west to east with the winds settling to light
and variable. During the best chances for showers and storms,
along and with the front, winds will shift from the southwest at 5
to 10 kts to the northwest at similar speeds. Some gusts to 15 and
20 kts can be expected for a few hours accompanying the pcpn, with
higher gusts possible - associated with any storms. VFR conditions
and light winds follow into Tuesday morning with fog less of an
issue due to lingering clouds, a drier air mass, and light
northwest winds.




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