Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 240025

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
825 PM EDT MON MAY 23 2016

Dry high pressure builds into our region from the Mississippi
and Ohio valleys for the first half of the week as low pressure
lingers over the Mid-Atlantic. A moist southerly flow develops in
the middle of the week, which will lead to warmer temperatures
and mainly afternoon chances of showers and thunderstorms each
day into the weekend.


At 8:15 PM Monday...An upper level low pressure system continues to
spin off the coast of North Carolina and Virginia, while spokes of
energy rotate around its western flank. Pockets of cloudiness were
noted on satellite, mid level clouds in our western forecast area,
and lower level clouds northern and eastern sections. We would
expect the western mid level clouds to dissipate through the
evening, while some cloudiness (upstream to the north) may clip
parts of our northern and eastern areas overnight. Therefore, we
have made adjustments in the cloud department.

The potential for diurnal showers, in a cool and more unstable
environment, has ended. We have followed short term guide in the
temperature department, and also in the placement of patchy fog.

For Tuesday, the fcst remains dry with a few cu possible, however
with less overall density as soundings exhibit a dryer llv layer
than that of today.  Likewise, mid level temperatures will be warmer
amidst rising heights as the upper ridge settles in.
Temperatures through the period will warm with overnight lows near
normal, leading into afternoon highs topping out a few degrees above
normal for Tuesday.


As of 130 PM Monday...The upper pattern will dominate the sensible
wx through the short-term period as deep layered ridging slowly
crosses east. Soundings indicate a strong subs inver developing
Wed...which will effectively limit the convec potential to the nc
mtns as llvl moist flux remains weak. Will continue the isol pop
mention late Wed across the mtns with fair wx cu and ci anticipated
across the non/mtns. The Atl ridge backs off slightly Thu and this
will allow a bit better moisture transport as llvl winds align more
sw/ly. With max temps remaining above normal...the increase in Td/s
shud enable at least moderate levels of SBCAPE based on a GFS/NAM
blend. Pops are more expansive Thu...but will mainly cover the mtns
and nc fhills. The flow through the column remains very weak...thus
storms that develop will be thermally cyclic and unorganized. The
main stg/svr threat from the deeper tstms will be large hail with a
couple lower-end microbursts possible.


As of 2 PM Monday, Upper heights rise into the weekend as the ridge
builds over the East and broad trofiness lingers over the Western
half of the nation.  Meanwhile, a wave of low pressure initially
over the Bahamas Thursday night and Friday will drift north toward
SC through the weekend.  This feature was originally displayed just
on GFS but now other models are showing it as well with some timing
differences. However, the GFS solution for development is considered
a low possibility. The inverted wave should remain weak as it drifts
toward the SC coast.

Waves of low pressure will track from near TX to the Great Lakes
then east over the top of the ridge. High CAPEs and other factors in
organized SVR threats will stay out over the plains and Miss Valley
areas. Models have generally low CAPE over the western Carolinas and
NE GA Friday PM...only 500 or less on GFS for NC mtns. A little
better instability on Saturday although the GFS has the tropical
low east of Savannah at 00Z Sunday. For Sunday and Monday, the GFS
and ECMWF have differences based on the advancement of the tropical
low across the mid Atlantic on the GFS as it has the low crossing
central NC at 18Z Monday. The ECMWF has a tropical low reaching the
GA coast at 12Z Wed which is after our current forecast period.
Our low level wind flow is forecast to be from a general southerly
direction Friday and Saturday, light and variable Sunday then based
on ECMWF will be from the east early next week.

Max Temps well into the 80s Friday and Saturday then cooling to 70s
mtns and lower to mid 80s Piedmont by Monday. Min Temps in the 60s.


At KCLT and elsewhere: A variety of clouds, and at varying levels,
still remain across pockets of our forecast area. We still expect
VFR through the period at all sites aside for KAVL/KHKY where valley
fog will likely occur once again given, persistence of low level
moisture, and winds becoming weak to calm at the surface.

More specifically, guidance favors (but appears overdone)continued
low level moisture advection overnight as moisture wraps around the
primary east coast upper low, therefore all tafs feature only
few/sct lower vfr clouds. Although some drying looks probable on
Tuesday morning, all tafs feature continued few vfr clouds through
the morning, before some lower afternoon cumulus bubbles up.

Winds should be trending to light and variable, or calm, as the
night wears on. The flow will continue to veer Tuesday with winds
taking on a more southerly flow.

Outlook: Mainly VFR conditions will prevail through the week, but
patchy morning fog chance continues at KAVL. Scattered afternoon
SHRA/TSRA may return Wednesday, with daily coverage increasing
Thursday and Friday.

Confidence Table...

            00-06Z        06-12Z        12-18Z        18-00Z
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  88%     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:




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