Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 231848

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
248 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.


A large upper low continues to rotate atop the mid Atlantic states
while a high amplitude ridge slides east across the MS river valley.
At the surface, high pressure beneath said upper ridge will migrate
east with time yielding gradually veering surface flow over the
central/southern Appalachians.  Closer to home, a modest cu field
across much of the fcst area illustrates the location of the most
unstable airmass, generally in closest proximity to the upper
cyclone where mid/upper lapse rates are steepest and boundary
layer moisture is greatest.  Thus, continued to favor low end
slight chance pops along/north of I40, with a dry fcst elsewhere.
Pops are lowered/removed after all heating is lost beyond 00z,
leading into a quiet night as the above mentioned surface/upper
ridge approaches.

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: Vfr through the period at all sites aside
for KAVL/KHKY where valley fog will likely occur once again
given persistence of llv moisture amongst weak/calm surface flow.
Otherwise, low vfr cu to persist through the day into the evening
before eroding as lapse rates flatten with heating loss.  Guidance
favors continued llv moisture advection overnight as moisture wraps
around the primary east coast upper low, therefore all tafs feature
few/sct low vfr stratus.  Although some drying looks probable on
Tuesday morning, all tafs feature continued few low vfr clouds
through the end of the taf cycle.  Northerly winds will remain
elevated with minor gusts possible this afternoon leading into a
light/calm evening as flow veers southeast thanks to a shifting
surface ridge.  Flow will continue to veer and increase out of the
south on Tuesday.

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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     Med   78%     High 100%
KHKY       High 100%     High 100%     High  88%     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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