Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 290725

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
325 AM EDT FRI JUL 29 2016

Broad surface high pressure will linger over the Southeast, while a
surface low tracks along a stationary front across the Mid-Atlantic.
This front will sag south into our area this weekend and linger
through the next week.


As of 300 AM EDT Friday:  Western Atlantic subtropical ridging
finally starts to flatten out today thanks to falling H5
heights consequent of an approaching longwave trof.  At the
surface, weakening high pressure looks to prevail across much
of the southeast while a lee trof sets east of the Appalachians.
Guidance RH fields indicate modest moisture in the low/mid levels
of the atm, backed up by latest nam fcst soundings which exhibit
rather deep/moist profiles amidst poor mid level lapse rates.
These conditions will be favorable for isolated/scattered showers
and thunderstorms across the fthills/piedmont, with slightly better
chances over the mtns.  Given the a fore mentioned lapse rates,
think most thunderstorms will struggle to become strong to severe,
however a few cannot be ruled out, thus will mentioned such in
the HWO with the primary threats being gusty/damaging winds and
frequent lightning.  Pwats are somewhat elevated, however modest
unidirectional low/mid level flow should allow for enough storm
motion to prohibit any widespread flooding concerns.

Given the flattening ridge and falling heights aloft, as well as
partly to mostly cloudy skies at times this afternoon, guidance
favors max temps around a degree or two lower than that of yesterday
on average.  The only exception to that will perhaps be over the
central/western Upstate into northeast GA where maxes will be
around a degree or two warmer.  HI`s will once again approach the
100 degree mark south of I85, with the highest levels likely over
the lakelands as well as the lower NC piedmont region, however
all remaining below heat advisory criteria.  Convective coverage
will once again decrease into the late evening hours as heating
is lost, thus pops are allowed to taper from east/west, keeping
slight chances over the mtns through the overnight.


As of 215 AM Friday...subtropical ridge over the SE US breaks down
over the short range. A weak upper low moving into the Great Lakes
pushing a weak trough over the area. A short wave moving through the
trough on Sunday deepens the trough over the area. At the surface,
lee trough remains over the area both days providing low level
forcing for convection. The mountains have the best chance of
convection on Saturday. Chance increases all areas Sunday with
increasing moisture leading to more instability and the
strengthening trough leading to better forcing. Although instability
increases into the moderate range by Sunday, DCAPE is forecast to be
significantly lower than earlier this week. Cannot rule out an
isolated severe storm however. Temps will remain above normal each
day, but heat index values should remain below heat advisory level.


As of 320 AM upper level trough remains over the eastern
CONUS through much of the period, but the axis of the trough slides
eastward by the end of the period as ridging builds over the MS
valley. At the surface, a weak quasi-stationary boundary will remain
draped over our area through most of the period, but dissipates on
Thursday. This surface boundary provide a focus for showers and
thunderstorms over the area. This combined with the upper trough
will lead to convection that is slightly enhanced over the normal
diurnal summertime trend. Despite the boundary washing out and the
weakening upper trough, lee trough at the surface and some upslope
flow will prevent keep diurnal convection over the area on Thursday.
Above normal temps at the beginning of the period drop to near
normal by the end.


At KCLT:  VFR through the period aside for any restrictions
associated with aftn/evng tsra on Friday.  Initialized taf with
modest sw flow under few high cirrus, however wouldn`t be suprised
if a few mid clouds advected downstream of the mtns near daybreak,
thus did favor such.  Otherwise, expecting diurnal heating to
gradually improved instability over the NC piedmont, possibly
overcoming deep layer subsidence late in the afternoon, therefore
opted for a tsra prob30 amidst low vfr cu into early evening before
any convection wains and/or advects east.  Winds on Friday will
remain out of the wsw, generally around 6-10kts.

Elsewhere:  VFR through the period at all sites aside for possible
mvfr fog/cigs at KAVL around daybreak, as well as any restrictions
associated with tsra on Friday.  Few mid/high clouds to prevail
through morning before heating builds on Friday yielding increased
tsra coverage amidst low vfr cu, thus prob30s where included at
all sites.  Winds looks to remain in the 6-10kts range, with some
low end gusting possible at the SC sites, especially at KAND.

Outlook: Broad troffing to move across the east/central CONUS
through the weekend into next week.  Moisture in the low/mid
levels combined with a series of impulses working through the mean
flow aloft will yield continued/increased chances for shra/tsra
into/through the start of the new work week.  As such, restrictions
associated with shra/tsra are possible, as well as early morning

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  83%     High  93%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:




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