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Area forecast discussion 
National Weather Service Jackson Kentucky
955 am EDT Friday Sep 19 2014

issued at 955 am EDT Friday Sep 19 2014

All is quiet this morning with a beautiful morning ongoing. Last of
the fog should burn off over the next hour or so. No significant
changes except to refine precipitation chances based on latest hi res
model guidance. This was only to trim some areas out of the threat
for showers this afternoon. Otherwise...current forecast seems on

Update issued at 740 am EDT Friday Sep 19 2014

Hourly grids have been updated based on recent satellite imagery and
observations. This led to very little change...just a freshening up
of the hourly temperature and dewpoint curves over the next few hours.
Valley fog across the southern and southeastern counties has likely
already begun to lift and should dissipate by around 9 am. The 6z
GFS and NAM suggested the potential for a stray shower across the
southeastern near the Virginia or WV border. The model consensus seems to
indicate the highest chances for an isolated shower from Harlan
County northeast to Pike County and possibly into the next tier of
counties to the north.


Short term...(today through saturday)
issued at 355 am EDT Friday Sep 19 2014

Through tonight...upper level ridging currently centered over the
plains states will build east into the lower Ohio Valley region today
and into tonight. Meanwhile a weak upper low/trough of low pressure
will remain across the southeastern Continental U.S.. further to the northwest a
series of shortwaves is expected to lead to an upper level trough
working into the Great Lakes region by the end of the period. At the
surface...high pressure currently centered over Quebec and extending
southwest into the Ohio Valley region will move east southeast to near
Cape Cod this evening and then off the northeast US coast tonight and
into Saturday. As the high moves inverted trough is
expected to develop across the region today and then shift west and
weaken tonight. To the east of the crest of the Appalachians...a
ridge of high pressure is expected to extend southwest from this surface
high into the Appalachians generally along or just to the east of the
Blue Ridge mountains later today through early on Saturday. This will
result in a rather tight pressure gradient...rather briefly this
evening into the overnight hours across the higher terrain near the
Virginia border.

On Saturday this ridge will weaken as the upper level trough
approaches the lower Ohio Valley as the ridge retreats west and
builds toward the northern rockies. A surface cold front will also
approach the lower Ohio Valley region at the end of the period.

Once early morning valley fog dissipates...a general warming trend
is expected through Saturday as the high departs to the east. Some
moisture should be drawn west around the departing high leading to
cumulus development across the southeastern part of the County Warning Area form midday
into the afternoon. Some of this may become deep enough for a few
isolated showers below the middle level cap. The NAM is generally the
most aggressive with this among the operational models. The end of the
the 5z hrrr run generally keeps the activity south of the region
through 20z.

Diurnal cumulus should dissipate this evening...but models keep the layer
near 800 to 850 mb rather moist tonight. Some stratocu near the level
will be possible tonight. Patchy valley fog should still
develop...especially north of the Virginia border counties. Meanwhile
during the evening when the pressure gradient is highest near the Virginia
border and a period of sustained winds of 10 to 15 miles per hour is
possible...especially across the exposed ridgetops such as The
Flatwoods area of Pike County...portions of the crest of Pine
Mountains and Black Mountains. Most locations will experience lighter
winds...with valleys further northwest likely decoupled. Higher
anticipated dewpoints...a larger pressure gradient and the potential
for a few clouds should bring warmer min T tonight. South to
eventually southwest flow will bring warmer air into the region on
Saturday. Outside of the high terrain...maximum temperatures should reach the
low to middle 80s. Precipitation chances associated with the next system
should hold off until the long term period.

Long term...(saturday night through thursday)
issued at 307 am EDT Friday Sep 19 2014

The extended period will start off on 0z Sunday with a deepening
trough in the longwave pattern across the Dakotas. This will quickly
move southeastward across the upper Great Lakes by Sunday
morning...quickly pushing lowering heights into the Ohio River
valley throughout the day. At the surface...a cold frontal boundary
will push southeast towards Kentucky as well...and reach the Ohio River just
after 0z Sunday. Models are finally coming into a much better
agreement for timing of the precipitation accompanying the front...with
probability of precipitation expected to move into the northwest part of the County Warning Area as early as 12z
Sunday...then quickly spread across the remaining County Warning Area during the
afternoon...before exiting southeast of the region between 0 and 6z Monday.
Latest forecast soundings are still only supporting marginal
instability for the precipitation accompanying this front...though it has
improved slightly from run to run over the last several days. Will
continue to support idea for some scattered thunderstorms during the
day Sunday...with the best chance around and just after 18z...then
dropping off quickly as a low level inversion sets up after 0z
Monday and winds quickly turn more nearly behind the frontal passage.

Southerly winds leading up to this frontal passage will bring enough
warm air advection to keep temperatures near the 80 degree mark for during the day Sunday. the front quickly departs Sunday evening/night...Kentucky
will find itself on the backside of the upper level troughing
pattern...with strong northwest flow bringing much cooler Canadian air into
the region. As high pressure takes hold...dry and sunny skies will
prevail. Yet high temperatures on Monday are only expected to make it into
the low 70s thanks to this Canadian air mass. Tuesday will be upper level ridging finally moves in overhead and
lessons the pressure gradient/strongest nwrly winds. Airmass
modification will slowly allow temperatures to rise throughout the
remainder of the extended...however we likely won't see temperatures hit
above the 80 degree mark until at least next Friday.


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 745 am EDT Friday Sep 19 2014

Aside from mainly valley fog lifting and dissipating through about 13z...
VFR should prevail during most of the period in all locations. The
exceptions to this is the IFR or MVFR fog in a few spots initially
improving to VFR...possible MVFR in any showers that develop between
17z and 23z...and mainly valley fog late in the period where MVFR or
IFR is possible. For the fog late in the period...sjs and sme appear
to have the highest chance of dropping to IFR among the taf sites.


Jkl watches/warnings/advisories...


long term...jmw

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