Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 171722
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
122 PM EDT Mon Jul 17 2017

.UPDATE...
Issued at 948 AM EDT MON JUL 17 2017

Fog has lifted and burned off in the Cumberland Valley, but
patchy clouds continue to linger from Somerset to Middlesboro.
Updated hourly NDFD based on latest observational trends, but
there were no major changes. Will continue to carry a slight
chance of thunderstorms in a sliver of northern Fleming County
this afternoon, which is agreement with the latest Day 1 SPC
Convective Outlook.

UPDATE Issued at 653 AM EDT MON JUL 17 2017

No major updates needed this morning, other than some tweaks to
the temps, dew points, and winds to make sure they were on track
with the current conditions. A complex of showers/thunderstorms
to our north quickly dissipated overnight before making it to our
CWA. Now just a few VFR clouds remain, but are also few/sct in
nature as they reach our CWA. Fog is ongoing across portions of
eastern KY, mainly in the river valleys and in the southern
portion of the CWA. Whitley through Letcher counties seem to be
the most affected at the moment. Conditions should begin to
improve rather quickly over the next hour or so as the sun
continues to rise. All updates have been published and sent to
NDFD/web.

&&

.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 in our CWA, 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 359 AM EDT SUN JUL 16 2017

An upper low will remain anchored across the Nunavut territory and
Northwestern Passages of Canada into Hudson Bay through the
upcoming weekend, as an upper high dominates a majority of the
southern and central United States. This will bring a hot and
sultry airmass into eastern Kentucky for mid week through the
weekend as mid level heights of 590+ dam remain in place.

Any showers or thunderstorms will wind down quickly Tuesday
evening along the Virginia line with the loss of daytime heating.
Despite the eastern periphery of the approaching upper high
sprawling into eastern Kentucky Wednesday, west/northwest low
level winds may be enough to generate some upslope-induced storms
along the Virginia border once again during peak heating as
temperatures warm to near 90 degrees. A strengthening cap will put
a damper on any storms for Thursday as the core of the high makes
its closest approach while centered on the mid-Mississippi Valley.
This will spell temperatures soaring into the low-mid 90s, which
when combined with dewpoint temperatures in the mid 60s to near
70, will create some heat index readings of 100+ degrees. The one
saving grace to an even warmer and muggier airmass will be the
position of the axis of the high in all likelihood remaining west
of eastern Kentucky, therefore keeping northwesterly flow in place
aloft as opposed to a long duration of southwesterly flow out of
the Gulf of Mexico.

An upper impulse looks to swing far enough south into the Great
Lakes/upper Ohio Valley by Friday to send a weak frontal boundary
toward the Ohio River. While this feature should remain well north
of the Bluegrass, the high aloft may become suppressed far enough
south to allow for some convective initiation along southward
propagating outflow boundaries to make it into northern to central
Kentucky. Saturday looks to be a similar setup with high
temperatures still generally holding in the low 90s with overnight
lows only dropping into the low 70s. Will have to watch the
evolution of cyclonic flow by late weekend/early next week,
including how far south this can penetrate. A farther southward
digging system would bring more bonafide rain chances to eastern
Kentucky along with a reprieve from the stretch of heat.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 120 PM EDT MON JUL 17 2017

VFR conditions will prevail across most of the forecast area
through Tuesday. An isolated thunderstorm is possible over extreme
northern parts of the forecast area this afternoon near a weak
stationary front. However, the likelihood is very low, and even
if a storm was to develop it is expected to be well north of SYM,
our most northern TAF site. Fog will form in river valleys
tonight, but most TAF sites should not be affected by fog. The
exception will be SME where fog is expected to result in IFR
visibility late tonight and early Tuesday. Weak high pressure
across the area will keep winds light and variable through the
forecast period.



&&

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

$$

UPDATE...SBH
SHORT TERM...JMW
LONG TERM...GUSEMAN
AVIATION...SBH



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