Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 200551

National Weather Service Jackson KY
151 AM EDT Thu Jul 20 2017

Issued at 138 AM EDT THU JUL 20 2017

clear conditions across eastern KY so far this overnight.
Continuing to monitor temperatures as the latest observations
showed some sites dropping a bit quicker than expected. This may
ultimately lead to some updates in overnight lows as well. Will
continue to monitor this next hour and make adjustments as needed.
This may also result in a few tweaks in the dew points, though
winds should have minimum impacts. All updates thus far have been
published and sent to NDFD/web.

UPDATE Issued at 735 PM EDT WED JUL 19 2017

23z sfc analysis shows high pressure (and heights aloft) in
control of the weather through eastern Kentucky. This has kept the
majority of clouds and any convection at bay through the afternoon
and into the evening - even over the higher eastern terrain in
contrast to yesterday. Nevertheless the heat and humidity laid
into the area today with readings just now starting to settle back
down into the lower and middle 80s while dewpoints are generally
in the mid and upper 60s - along with light winds. Persistence
conditions will continue this night with low temps expected
close to last night`s values along with a similar pattern to the
fog formation. This all is well handled in the forecast zones and
grids so just a touch up to the T/Td/Sky grids was performed
based on current observations and trends. These updates have been
sent to the NDFD and web servers.


.SHORT TERM...(This evening through Thursday night)
Issued at 355 PM EDT WED JUL 19 2017

As of mid afternoon, the region remains under the influence of mid
and upper level ridging while surface high pressure is in place
across the southeastern Conus. Outside of very isolated showers
that developed west of JKL and near Dewey Lake that formed and
dissipated over the past couple of hours, cu has generally
remained shallow. Recently, cu is a bit more robust near the
escarpment/Daniel Boone Forest where a surface trough/wind shift
is present and evident on radar. A dampening shortwave is moving
across western and central KY with some shower activity associated
with it.

Through this evening and tonight, the dampening shortwave moving
around the center of the ridge will drop into the TN Valley region
and stay south and southwest of the area while the axis of the
upper ridge remains in place across the region. Surface high
pressure is expected to remain in place across the Southeastern
Conus. This should lead to similar conditions than last night.
Current dewpoints/crossover temperatures are mainly in the mid
60s to around 70 degree range and with high pressure in place,
temperatures should drop to this range with river valley fog and
fog along the larger creeks likely to develop. Some of this could
become dense late tonight in a few spots right along the rivers.

Thursday and Thursday night, the center of the mid and upper level
ridge will remain west of the area over the Plains to MS Valley
region. Meanwhile, an upper level low is expected to generally
move east from the western portion of Hudson Bay and into northern
Quebec while a shortwave trough moves into and across the Great
Lakes and into St Lawrence Valley and the Northeast Conus. At the
surface and area of low pressure will move across the Great Lakes
and into the Northeast with a cold front dropping south of the
Great Lakes toward the Ohio River. However, convection associated
with this should remain north of the area through the period with
high pressure dominating. At this point, the mid and upper level
ridge should keep the atmosphere capped with only shallow to
moderate cu expected to remain develop on Thursday. An increase
in clouds should lead to less in the way of fog on Thursday night.

Temperatures will remain mild through the period with lows tonight
and highs on Thursday similar to, if a degree or two warmer than
last night and today. Dewpoints should creep up a couple of
degrees tomorrow afternoon compared to today with the higher
dewpoints persisting in the warm sector ahead of the front to the
north that will begin to stall. This should lead to milder
overnight lows from near 70 or the lower 70s on Thursday night.

.LONG TERM...(Friday through Wednesday)
Issued at 255 PM EDT WED JUL 19 2017

We will remain under the influence of mid/upper level ridge
through Saturday which means more of the same with heat and
humidity staying around. A stray afternoon shower or storm is
possible, but coverage will likely remain at or under 5 percent

Better rain chances look to return on Sunday as a weak cold front
inches southward across the area during the day. Still some
question as to the aerial extent of the showers and storms as
forcing will remain weak. Shortwave trough will then swing east
across the great lakes early next week, but the better forcing
with that trough will remain to our north. However, it could help
to refocus convection along the slowly moving front as it slow
pushes southward. Thus, it looks like rain chances will continue
through Monday.

Tuesday and Wednesday will see a return to slightly cooler
weather behind the exiting front. However, depending on where the
front dissolves, some moisture could linger to provide a
lingering shower into the midweek period, especially in the south
or southeast. Still lots of uncertainty on this potential.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)

Surface high pressure and an upper level ridge building into the
area will continue the rather stagnant weather pattern, with VFR
conditions and light winds prevailing through the period. Fog will
develop in the river valleys once again late tonight, dropping to
MVFR or IFR restrictions by near daybreak. As fog lifts near
daybreak, there is still a chance that SME could once again be
affected, as has been the case for previous mornings. However,
impacts have also shown a decreasing trend thanks to continued
drying, so actually not confident enough of the fog being
impactful enough to even include in the SME TAF. Once fog
dissipates across east KY Thursday morning, expect mostly clear
skies with mainly just diurnally driven CU developing in the
afternoon, generally around 4k ft.




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