Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 170755
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
355 AM EDT Mon Jul 17 2017

.SHORT TERM...(Today through Tuesday)
Issued at 355 AM EDT MON JUL 17 2017

A shortwave will be present across the central Appalachians and
eastern KY during the next couple of days, as upper level ridging
continues to expand eastward into western KY today and central KY
Tuesday. At the surface, a weak stationary boundary will be
present along the Ohio River and portions of northern KY, where it
will remain through the short term portion of the forecast as it
slowly continues to fizzle out. A ribbon/skinny area of high
pressure will be be stretched across the state, just south of this
stationary front.

As such, showers and thunderstorms will be possible, mostly
confined directly along the frontal boundary and to our SE in
conjunction with the upper level shortwave. It is likely that we
may see no convection during the day, with the frontal boundary
setting just far enough to our north and west, though can`t rule
out a few stray showers/thunderstorms in our far northern counties
during peak heating. Coverage will be super isolated at best, but
did mention some slight chances in the far northern fringes of
the CWA between 18 and 21Z. Elsewhere, only a few fair weather CU
are expected throughout the afternoon. All convection and clouds
will quickly dissipate overnight, leaving another clear and calm
night across eastern KY conducive for potential fog development.
Continued with patchy to areas of fog for the river and deeper
valleys overnight tonight.

For Tuesday, much of the same set up is expected. The only
difference will be the slight strengthening of the shortwave
located over the Central Appalachians. As afternoon convection
develops, this slight uptick may be enough to expand coverage
across the high terrain along the VA and KY border. Kept mention
of slight chance pops here right along the border through the
afternoon as a result. While the frontal boundary to our north
will also still be present, it will be nearly fizzled out and
moisture starved. Not expecting any convection to affect the CWA
from this feature.

Temperatures will be similar both days as the pattern remains very
similar, reaching the upper 80s during the afternoon. A little bit
better moisture return during the day Tuesday, so humidity values
will be on the increase a bit compared to today. Overnight lows
tonight will be mild, generally in the 60s with a good ridge
valley split expected to set up once more.



.LONG TERM...(Tuesday through Sunday)
Issued at 425 PM EDT SUN JUL 16 2017

The period is expected to begin with an upper level ridge centered
over the eastern OK/western AR vicinity and another upper level
ridge centered over the Four Corners region. Meanwhile, an upper
level trough is expected to extend from Quebec south along the
East Coast. At the surface, high pressure is expected to be
centered over the Appalachians.

The upper level ridge is expected to build east into the Lower OH
Valley on Tuesday and reorganize in the Plains as a shortwave
passed north of the area through the Great Lakes. The axis of the
upper level trough should move east on Tuesday with mid level
height rises ensuing. With the ridge center to the west,
additional weak disturbances may pass through the region as they
move around the ridge on Wednesday. Heights should rise further on
Thursday though the region should remain in west to northwest flow
around the ridge with any MCS activity likely passing north and
east of the area. The GFS runs have convection further to the
south compared to the ECMWF as the ECMWF has higher heights
across the region.

From Thursday night into next weekend, a shortwave trough should
move from the northern Plains/Canadian Plains across the Great
Lakes and into the Northeast US. Model disagreement in timing and
placement of features then increases at the end of the period.
The general consensus is for the ridge to become centered over
the Southeast and extend across much of the Southern Conus while
becoming flatter as the shortwave moves into the Northeast and
eastern Canada. This should allow a cold front to drop south of
the Great Lakes by the start of the weekend, but it should stall
out from east to west north of the OH River on Saturday. This
boundary could return north by the end of the period with a
potential shortwave moving across the Northern Plains and Great
Lakes leading to surface low pressure developing over the Great
Lakes and the boundary lifting north as a warm front.

Overall, the period should be mainly dry with the region dominated
by high pressure although the center may be far enough west for
stray convection near the VA border on Tue and perhaps Wed. This
period should also consist of temperatures rising to above normal
by Wednesday with Thursday likely being the warmest day with
heights generally highest. As Friday and the weekend approach,
the potential for MCS activity to affect at least the north
increases. If convection does not affect the area on Friday, then
it could be equally as warm as Thursday if not a degree warmer.
For now have ridges in the upper 80s to around 90 for the Wed to
Friday period with the valleys topping out in the lower 90s. As
the ridge flattens a bit by the start of the weekend chances
should be areawide on Saturday. Uncertainty in timing and
placement of features increase by next Sunday, however, at least a
diurnal uptick in chances for convection should exist in the warm
sector.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 142 AM EDT MON JUL 17 2017

Flight conditions will be VFR for most of the period. The only
exception will be valley fog that will likely develop again
tonight. The fog is not expected to be as pervasive as it was in
our valleys yesterday morning, but it still may affect SME to
some extent due to its proximity to a larger lake. Have left it
out of the other TAF sites with a tempo for MVFR added at SME. No
other forecast concerns through 6z Tuesday with just some fair
weather cu during the day today and very light winds through the
period.

&&

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

$$

SHORT TERM...JMW
LONG TERM...JP
AVIATION...GREIF/JMW



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