Area Forecast Discussion
Issued by NWS Jackson, KY

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471
FXUS63 KJKL 242320
AFDJKL

Area Forecast Discussion
National Weather Service Jackson KY
720 PM EDT WED AUG 24 2016

.UPDATE...
Issued at 652 PM EDT WED AUG 24 2016

Surface high pressure has now moved off the Mid Atlantic coast and
KY resides in the return flow side of this surface high. This is
introducing the warmer and more humid airmass into the
Commonwealth with dewpoints reaching back into the 70s. Upper
level wise strong upper level ridge is parked across the SE US and
will be the main influence on our sensible weather through the
rest of the week.

We are watching areas of storms developing across portions of the
Ohio Valley (north and west of the CWA) this evening. These are
influenced by stronger upper level dynamics/short wave and weak
surface trough in that region, but some of the CAMs do want to
bring some of this convection south and east tonight mainly across
central KY. Right now not buying into this and think influence
from upper level ridging aka little upper level support combined with
loss of daytime heating will lead to minimal chances. However will
keep a isolated threat focused along and north of the I-64
corridor. This is backed up well by the SSEO probabilities for
this evening.

In term of grids overall grid set is in good shape with the above
thoughts. Only minor tweaks needed at this point given latest
trends.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 324 PM EDT WED AUG 24 2016

A strong upper level ridge is in place across the southeast conus,
encompassing much of the Ohio River Valley. Meanwhile a closed low
is moving eastward across the central Canada/US border, with several
shortwaves located along the resulting troughing pattern across the
central conus. At the surface, KY finds itself in a return flow
pattern, with a high pressure feature located to the east of the
region, and a surface low pressure system located in conjunction
with the upper level low along the US/Canada border. A cold front is
trailing from this low, southeast across the upper midwest and into
the central plains. With the broad upper level ridge in place across
the southeast conus, this will prevent best forward propagation of
the upper level low through the short term, which will eventually
lead to its weakening into the day Thursday, then phasing out by
Friday. In lieu of the weakening upper level low, the surface
features will also wane, and the cold front will begin sheering out
as it slowly pushes toward the region through the day tomorrow. It
should eventually pass across the state during the day Friday.

As for sensible weather...Low and mid level southwest flow can
currently be found between the cold front to our west and the high
pressure system to our east. This is working to increase moisture in
the form of clouds and humidity across JKL this afternoon, as well
as boosting temps into the mid and upper 80s. Hi res/CAM models are
still pointing at isolated to scattered showers and thunderstorms
developing mainly across the central portion of the state this
afternoon under peak heating. A line of convection may form in this
location, however with little upper level dynamics to work with,
this will likely cause few problems. Furthermore, there is still
quite a bit of disagreement in the hi-res CAM models about whether
or not this precip will even make it to eastern KY this
afternoon/evening, before it falls apart with loss of daytime
heating this evening. As such, kept conditions dry across eastern KY
through the afternoon, with only isolated chances in the north
during the first part of the overnight, transitioning to the east
late tonight into tomorrow assuming the line can stay together to
some degree.

The NMM and ARW both show an uptick in isolated convection
throughout the day tomorrow under peak heating, likely due to
diurnal influences in a humid regime. However confidence is low on
this, with the larger scale models keeping any convection confined
to the far southeast in the upslope regions of the state. Kept
isolated pops across the far eastern portion of the CWA into the
afternoon, before drying out completely. Soundings support this as
well, with very little moisture to work with in the low levels, and
continued strong drying aloft. Temperatures should be similar to
today, if not a degree or two higher, rounding out near 90 degrees.

Despite the cold front reaching the Ohio River by Thursday
evening/Thursday night, it will be so weak by this point that little
influence is expected without the aid of diurnal heating. Some llvl
moisture may lead to isolated to sct cloud coverage, but otherwise
conditions should be clear with dry air entraining into the area
aloft. Low temperatures will be around 70 degrees both tonight and
tomorrow night.

.LONG TERM...(Friday through Wednesday)
Issued at 308 PM EDT WED AUG 24 2016

A stout upper level ridge will dominate our weather into early
next week. This will keep temperatures much warmer than normal
and muggy dewpoints in the upper 60s to mid 70s. Isolated
showers/storms will be possible each day over the weekend into
early next week in the warm and humid airmass. It appears the
ridge will weaken slightly by the end of the period, possibly
allowing a cold front to sag into the region. The front appears
very weak in the models so will keep PoPs low and diurnally
influenced even during these periods. Models keep any influences
from a potential tropical system developing in the Caribbean to
our south and east through Wednesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 720 PM EDT WED AUG 24 2016

Another period of VFR expected at this point. While showers and
thunderstorms are affecting areas NW of eastern KY, we are
expected little if any influence at this point. While a stray
storm may be able to make it in the far north, the chances were
low enough to keep out of TAF sites. The HRRR model does show
convection in the far east by Thursday morning think this may be
more in the way of a CU field, and would think best chances of
isolated storms would be in the higher terrain nearer the VA
border Thursday afternoon. Increasing moisture will continue to be
the story therefore valley fog chances will be on the increase,
however right now think this will stay out of the TAF sites. Given
the lack of jet energy winds will remain weak through the taf
period.

&&

.JKL Watches/Warnings/Advisories...
None.
&&

$$

UPDATE...DJ
SHORT TERM...JMW
LONG TERM...ABE
AVIATION...DJ



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