Area Forecast Discussion
Issued by NWS Greer, SC

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443
FXUS62 KGSP 252346
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
746 PM EDT WED MAY 25 2016

.SYNOPSIS...
High pressure will prevail over the Southeast region through most of
this week. Moist southerly flow will lead to warmer temperatures and
mainly afternoon chances of showers and thunderstorms each day
through Friday. A period of cooler and wetter weather may develop
late in the weekend as Atlantic low pressure moves toward the
coastline.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 730 PM EDT Wednesday...radar imagery shows shallow convection
widely scattered across the nrn mountains of NC. The lack of CAPE
seems to have severely limited our potential, which also means
convection should die off quickly with sunset.

Otherwise...upper ridging continues to dominate the area through
the near-term, with weakly diffluent southwesterly flow aloft.
Weakness in the upper flow will also slowly push through the area.
Surface high offshore will continue to bring a warm moist southerly
flow to the Southern Appalachians, and this combined with the upper
weakness will continue to allow moisture to pool along the eastern
slopes. Low temperatures tonight another handful of degrees warmer
than those last night with continued increasing low-level moisture.

Convection chances look a little better tomorrow as a weak upper jet
pushes through the Southeast and the dissipating southern end of a
front (if you can call it that) tries to push across the
Appalachians. With the southerly flow continuing to bring moisture
into the area, sbCAPE values are progged to be a couple hundred J/kg
higher tomorrow than today. Cannot rule out some of the convection
breaking containment and spreading across the Piedmont corresponding
with 300-500 J/kg sbCAPE, so have introduced slight chance PoPs
outside of the mountains with mid-range chances at the higher
elevations.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 200 PM EDT Wednesday: The short range fcst period kicks
off Thursday evening amidst a broad upper subtropical anticyclone
dominating the pattern for the southeast CONUS, while an H5 vortex
continues to deepen over the four corners states.  At the surface,
a western Atlantic ridge beneath the a fore mentioned H5 high
will prevail leading to south/southeasterly waa across much of
the south as cyclogenesis is underway over the western tier of the
southern Plains.  Closer to home, diurnal convection looks to be
the primary weather feature to impact northeast GA and the western
Carolinas through the period as the overall pattern doesn`t modify
all that much.  Guidance favors mtn/fthill airmass convection at
initialization, again on Friday, and to a lesser extent Saturday
per soundings that feature slightly drier llvs.  Points further
south and west will see decreased chances for said convection given
proximity to the upper ridge axis and thus subsidence.  Overall,
any hazards will most likely remain tied to the mtns/fthills where
slow storm motions could lead to isolated flash flooding associated
with any prolonged/deeper pulse convection.  Outside of the high
terrain the threats are lower in general as antecedent conditions
are less favorable for flash flooding.  All in all, the fcst will
feature similar pops each day with with pops increased over/along
the Blue Ridge, less so over the Piedmont.  Temperatures through
the period will continue to be above normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 200 PM Wednesday...No sigfnt changes were made to the ext
range fcst. The guidance continues to show a weakness in the Atl
ridge early Sun with the development of a weak tropical system
likely. The latest GFS has trended more inline with the ECMWF in
regards to the track and strength of the Atl low. It looks like the
low will be picked up by the westerlies early on leading to a
sheared and disorganized system as it approaches the coast. There
are a couple GEFS ens members bringing a very weak sfc low across
the Carolinas...but the main driver will be an H5 vort center...if
at all. So...will keep the best pops capped at high-end chance Mon
with some likelys across the se/rn upslope regions. Cloud cover and
llvl tropical theta/e increases during the period so diurnal temp
curves will hover arnd 20 F...basically highs around normal and lows
a couple cats above normal.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere...VFR through the period, outside of
thunderstorms. Some high-based stratocu over the mtns may fan out
across the Piedmont later this evening...but do not expect this to
constitute a ceiling. Wind will be light from the S to SW. Expect
another round of low VFR Cu tomorrow but with increasing moisture
probably more coverage. The convection-allowing model guidance does
not have a consensus on the development of thunderstorms in the
afternoon...but the synoptic scale guidance indicates a more
favorable environment. For now, this was included as a PROB30 at all
TAF sites in the mid/late afternoon, but fairly confident not all
places will be near a storm.

Outlook...Mainly VFR conditions will prevail through the period, but
patchy morning fog chances continue at KAVL. Scattered afternoon
SHRA/TSRA coverage will increase on Friday, with more uncertainty
into the weekend.

Confidence Table...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     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 schedule 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...SBK/Wimberley
NEAR TERM...PM/TDP
SHORT TERM...CDG
LONG TERM...SBK
AVIATION...PM



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