Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 220641 AAC

Area Forecast Discussion...UPDATED
National Weather Service Jackson KY
241 AM EDT SUN MAY 22 2016

Issued at 221 AM EDT SUN MAY 22 2016

Clearing from the northwest and west has been a bit more prolific
than was earlier anticipated. This has led to dense fog forming
near Lake Cumberland at KSME and other locations to the west over
Central Ky are also reporting dense fog. Dense fog has also been
reported further north at KSYM near the Interstate 64 corridor.
Somewhat drier sfc dewpoints are filtering in on relatively weak
northwest flow. Across the far southeast counties the upslope
component may prolong the low clouds and patches of drizzle.

Confidence in dense fog becoming more widespread is highest at
this point across portions of the Cumberland Valley north into
Rockcastle and Jackson counties where clearing has occurred and
dewpoints remain in the low to mid 50s. In that area, a Dense Fog
Advisory has been issued through 9 AM EDT. Across the northern
counties, formation of dense fog may be limited or impeded by
drier air filtering in from the northwest. Confidence in clearing
across the southeastern portions of the area by dawn is appearing
more probable on recent IR imagery as the back edge of the clouds
appears to be from near CRW to SJS to JKL to LOZ to BYL. As
clearing occurs in these areas, trends will be monitored for fog
development and a potential expansion of the Dense Fog Advisory.

UPDATE Issued at 1100 PM EDT SAT MAY 21 2016

Showers continue to dissipate. Seeing some fairly rapid clearing
upstream as well. Thoughts are we could see some fog development
depending on how quickly skies clear versus how soon drier air
manages to work its way into the area. Guidance has backed off on
the fog. Will keep an eye on this and adjust the forecast as
necessary. Otherwise updated the forecast package to remove
thunder and to freshen up the zones. Made some minor adjustments
to overnight lows based on latest hourly trends in sfc obs.

UPDATE Issued at 817 PM EDT SAT MAY 21 2016

Update this evening was mainly to adjust pops towards latest radar
trends. A fairly solid band of light rain is currently swinging
through the area, with some isold embedded thunderstorms within
the band for good measure. It appears our radar is overshooting
some of the activity based on sfc obs. The threat for thunder
should be waning through the remainder of the evening. While some
clearing is expected through the overnight it will only be
gradual. Did tweak temps towards hourly obs, which mainly resulted
in lower temps corresponding to rain cooled air. Will leave the
threat of thunder in until next update.


.SHORT TERM...(This evening through Sunday night)
Issued at 400 PM EDT SAT MAY 21 2016

19z SFC shows low pressure east of Kentucky but still swinging
showers and stray thunderstorms through the CWA. The latest
visible satellite loop shows mostly cloudy skies with only a few
breaks across the area. The clouds and isolated to scattered
showers also affected temperatures today with readings generally
kept in the mid to upper 60s this afternoon. Meanwhile, dewpoints
are holding in the mid to upper 50s most places. Winds through
East Kentucky are generally from the west at 5 to 10 mph with some
gusts to 15 mph or so in western areas.

The models are in good agreement aloft through the short term
portion of the forecast. They all depict the eastern trough
deepening and settling southeast of the area by Monday morning. A
key part of this development will be a mid level wave dropping
just west of the CWA tonight sending energy south through East
Kentucky. This will help to sharpen up the low and drag it
a tad southwest on Sunday. This upper low will further deepen and
close off Sunday night into early Monday as it shifts east. This
represents a return to an idea from a couple of days ago but with
more credence now given the good model clustering and zero hour
being only 36 to 48 hours out. Accordingly, have followed a
general model blend with a strong lean toward the HRRR and NAM12
for weather details through Monday morning.

Sensible weather will feature an unsettled evening with showers
and a couple of thunderstorms around. This will be followed by low
clouds and some patchy fog through the night. While Sunday will be
drier for most, as the upper low shifts southwest, there is a
decent shot at more convection in the east and even a few
thunderstorms. Sunday night will see the clouds start to break up
in the east and again some fog, especially for the valleys and
places that clear earlier in the night. Do expect temperatures to
be fairly uniform tonight and Sunday night owing to the clouds and
some slight CAA to neutral advection during the nights.

Started with the ShortBlend for most elements of the forecast
with only limited terrain adjustments to temperatures through the
period. During the latter part of the forecast the SuperBlend was
used to initialize the forecast with some tweaks made mainly to
increase the PoPs in the east Sunday afternoon.

.LONG TERM...(Monday through Saturday)
Issued at 350 PM EDT SAT MAY 21 2016

Patchy valley fog will kick off the week with surface ridging
extending from the Great Lakes into the Ohio Valley. Shortwave, but
amplified, upper riding will build across the Great Lakes through
the Mississippi Valley in wake of this weekend`s disturbance digging
across the Mid-Atlantic coast. Rising heights and deep layer
subsidence will bring clearing skies from west to east throughout
the day as temperatures warm back to near normal, topping out
generally in the mid 70s. Surface ridging will then be in control
once again Monday night into Tuesday, leading to another
ridge/valley temperature split ranging from the mid-upper 40s in
valleys and low 50s on ridgetops. Continued increasing heights and
plenty of solar insolation will propel highs into the upper 70s to
lower 80s Tuesday afternoon.

An unsettled pattern will then return for midweek through the end of
the week and likely into the upcoming weekend. Flow aloft will back
southwesterly in response to cyclonic flow developing from central
Canada through the Intermountain West. Subsequent increasing warmth
and moisture will lead to a more favorable thermodynamic environment
supportive of convective development. While the thermodynamics
should be conducive for showers and thunderstorms, dynamical
prospects may be lacking as the core of any upper forcing may lift
north well west of the Commonwealth. This will in turn keep a nearly
stationary frontal boundary west of the region through much if not
all of the upcoming week, furthermore decreasing the chances for
seeing any appreciable forcing locally. Nonetheless, scattered
thunderstorms certainly look possible in the warm sector whenever
forcing becomes realized, rather from passing upper perturbations or
at least along the higher terrain. High temperatures in the lower
80s and lows in the lower 60s look likely by midweek into the


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

The clearing form the west and northwest has led to improvement in
CIGS to VFR as far southeast as JKL and SJS. However, dense fog
has developed or been reported at least at times at SME and SYM
with some indefinite ceilings. As clearing continues to move into
to the remainder of the area, additional areas of dense fog should
develop. At this time, dense fog is expected to also affect LOZ,
JKL, and SYM at least briefly by 11Z. For now, we expect that
drier air moving into the northwest should lead to improvement or
at least limit dense fog at SYM. Improvement to VFR should occur
in all locations 12z to 14z, however, daytime heating should
steepened lapse rates and lead to redevelopment of a substantial
CU field by 17Z along with the threat of some instability
showers at SYM, SJS, and JKL. Winds will be generally be out of
the west-northwest through the forecast period, averaging 10 kt
or less.


.JKL Watches/Warnings/Advisories...
Dense Fog Advisory until 9 AM EDT this morning for KYZ068-069-



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