Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 231835
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
235 PM EDT TUE AUG 23 2016

.SYNOPSIS...
High pressure will persist over the region through midweek allowing
temperatures to climb back above normal. Another weak cold front will
approach the Western Carolinas from the northwest toward the end of
the work week, with high pressure building back to our north in the
front`s wake. Rain chances will remain below normal through the
weekend, with maximum temperatures above average through early next
week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 150 PM: The CWFA remains under an easterly flow regime
associated with sfc high pressure centered over the Chesapeake Bay
region. A strong subsidence inversion was evident from the 12z KGSO
sounding, and as expected this is keeping deep convection suppressed
over most of the area. The inversion is substantially weaker to
our south and west, however, and a few showers have occurred over
NE GA since late morning. This activity may continue to percolate
thru the heat of the aftn, but RAP profiles suggest the inversion
strengthens rapidly going north and east, and is likely too strong
to overcome beyond the Savannah River counties of SC.

Tonight looks like it will play out similarly to last night, with
a weak southeasterly flow developing some patchy stratocu toward
daybreak. The NAM, which verified reasonably well w.r.t. cloud cover
this morning, depicts moisture being even deeper Wed morning, so
cloud cover is expected to be more widespread. Some fog is expected
in the mountain valleys, especially if/where cloud cover does not
develop. Min temps should be a little warmer in the presence of
modified air and more cloud cover.

As the high slips further offshore, the subsidence inversion will
weaken; we`ll continue to see moisture rebound. Accordingly
a consensus of various model guidance supports a return of
mentionable PoPs over the mountains. Further east lapse rates
remain just too weak. No appreciable threat of severe weather
exists given modest wind and moisture profiles. Lent slightly
more weight to bias-corrected temps given that we will again see
elevated dewpoints; this supports max temps rising a degree or
two above Tuesday`s values.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 215 PM EDT Tuesday...it looks like the Southeast will be
dominated by a mid/upper level anticyclone through the late part of
the week. This will support surface high pressure ridging back from
off the east coast on Thursday and will keep a weak cold front at
bay to our N on Friday. The models suggest low level moisture, which
is unimpressive to begin with, should mix out each day. This will be
a limiting factor and should preclude any deep convection east of
the Blue Ridge through the period. Across the mountains, we should
be able to generate a few showers both days and the fcst might be
overly-optimistic with patches of 30 pct in the afternoon. The
chances of anything significant are small. Temps will be close to
normal on Thursday and then maybe a category or so above normal
Friday.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
As of 230 PM EDT Tuesday...the extended period begins 12Z Saturday
morning with the southeast still under the influence of a
substantial upper ridge, with a surface high moving over the
northeastern CONUS. This will keep max temperatures across the
entire forecast area well above average, and precip chances well
below average for the weekend. The ridge will be relatively slow to
erode, so the only sensible pops will be confined to the higher
terrain through the weekend and early next week. By late Monday,
though, guidance does suggest modest height falls may start to
occur, so the forecast features a slight decrease in max temps to
just a degree or two above average by Tuesday. Guidance diverges
significantly after that, however, with the GFS increasing moisture
early next week as another frontal boundary approaches the southern
Appalachians (no tropical low to speak of), and the ECMWF
maintaining the development of a tropical low in the Bahamas/Gulf of
Mexico. Development of the system is uncertain at best right now,
and this model divergence currently has little impact over the
forecast through next Tuesday, so model trends will simply be
watched over the next few cycles. Overall, there were few sensible
weather changes from the previous guidance package.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: An area of high pressure centered over
the Mid-Atlantic will reinforce easterly to southeasterly flow
over the terminals into Wednesday. Initially some sites (including
KCLT) will see ENE winds, but as that high drifts east, winds will
veer. SCT diurnal cumulus will cover much of the area today, but
subsidence inversion aloft will suppress convection. Overnight,
some guidance (namely NAM/WRF family) brings a moist layer into
SW NC and NW SC. This is a deeper layer than was progged for this
morning, when SCT-BKN low VFR stratocu developed. On that accord,
some MVFR cigs are expected tonight at KAVL and KAND, possibly
slightly further east as well. KAVL and other mountain valley sites
could also see some fog develop particularly if the low clouds are
not as widespread as expected. Expect slightly better convective
chances Wednesday over the mtns, but not until after 18z.

Outlook: A deep ridge will remain in place over the Southeast thru
the weekend, keeping afternoon SHRA/TSRA chances below normal each
day, and generally confined to the mountains. However, sfc moisture
will gradually return, and morning vsby restrictions will become
increasingly likely during this time.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High  93%     High  88%
KAVL       High 100%     High  97%     High  82%     Med   75%
KHKY       High 100%     High 100%     High  83%     High  88%
KGMU       High 100%     High 100%     High  88%     High  87%
KAND       High 100%     High 100%     High  83%     Med   75%

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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...LEV
NEAR TERM...Wimberley
SHORT TERM...PM
LONG TERM...LEV
AVIATION...Wimberley


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