Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 271746

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
146 PM EDT FRI MAY 27 2016

Moist southerly flow will lead to continued warm temperatures and
mainly afternoon chances of showers and thunderstorms today. After a
dry day on Saturday, a period of cooler and wetter weather may
develop late in the weekend through early next week as Atlantic low
pressure moves toward the South Carolina coast.


As of 11am EDT Friday.  Forecast in pretty good shape.  Showers and
thunderstorms are anticipated this afternoon over higher terrain in
response to diurnal heating and southerly upslope flow.  Storms are
expected to be well below severe limits with marginal CAPE to 250
j/kg and negligible wind shear.  The need for upslope flow should
confine activity almost exclusively to higher terrain areas.
Currently, light showers over the mountains of far western North
Carolina and northeast Georgia are in line with expectations.  HRRR
and UCAR CAM ensemble both have a good handle on the current
situation with realistic development that peaks around 2pm and
declines near sunset.

A 500 mb ridge will persist over the southeast through the near term
period, but with weak low pressure development off the FL coast
north of the Bahamas. Under the high pressure over our area, mainly
mountain convection is expected today with showers triggering in and
near the southern mountains in upslope flow this morning and then
better ridge top showers and thunderstorms this afternoon with
heating and low level wind convergence. Will feature fairly solid
precipitation chances over the mountains and taper these off quickly
farther east. Maxes will be about a category above climo again today
under partly cloudy skies.

A band of dry mid level air should work inland from the coast
tonight. Any lingering evening PoPs over the mountains should taper
off fairly quickly. Mins will remain above climo, but with better
radiating conditions developing over the lower piedmont late in the


As of 300 AM Friday...The latest operational models are in good
agreement on a tropical disturbance (which as of this writing has an
80% chance of becoming a named storm within 48 hours per NHC)
drifting NW toward the SC coast on Saturday. The SFC low pressure
center looks to be not far SW of Charleston by 00z Sunday. How
strong the system will get is still it looks to take
a while for it to organize. In any case, there should be a ring of
subsidence around the system and over our area during the day. so
saturday looks like a dry and warm day for the most part. Highs a
couple categories above normal.

Saturday night and Sunday...models start to diverge on the handling
of the tropical system...with the GFS bringing the center into
southern SC and stalling out...while the ECMWF make a right turn and
drift toward the NE across the coastal plain. The stalls the low
offshore thru F84 hours. With all that said...there should be a
general increase in moisture...especially across the I-77 corridor
Sunday. I will forecast generally chance PoPs for Sunday...with some
low-end likely east of Charlotte. Temps will feature above normal
lows and near normal highs.


As of 315 AM Friday...There is still a lot of uncertainty on where
the tropical system will go early in the medium range. The 00z ECMWF
has just come in holding onto a track that stays close to the coast
in eastern SC/NC. While the GFS drifts the low inland across SC,
then stalls it just north of Savannah, GA. This results in the GFS
being much more unsettled than the ECMWF from Monday thru Wednesday.
By Thursday, the ECMWF brings a weak cold front in from the NW,
while the GFS still has the front back over the MS valley. They both
show increasing PoP though. The GFS because of remnant tropical
moisture and the ECMWF because of the front. So I went with the
Superblend PoPs...which are slightly above climo Monday-Wednesday.
Then high-end chance to low-end likely on Thursday. Temps will
continue to be near or slightly above normal for highs and well
above normal for lows within the moist regime.


At kclt...high-res model guidance is fairly consistent and
reasonable in its depiction of convective showers forming well
northwest of the aerodrome over higher terrain and moving northward
on prevailing winds...thus have left mention of showers out of the
TAF.  General flow pattern has the area on the west side of upper
and lower anticyclonic flow with weak flow at all levels, a pattern
that will persist through the next 24 hours as central CONUS trough
makes gradual eastward progress.   surface winds will be VRB to
8kts, southeasterly when not VRB.

Elsewhere... General flow has the area on the west side of a broad
lower and upper trough, with light generally southeasterly surface
winds.  Afternoon heating and upslope flow is creating areas of
convective showers over higher terrain.  These showers are moving
northward in prevailing flow and should not affect locations outside
of the mountains.  Only an occasional lightning strike is expected
with these showers due to their shallow nature.  Low-level flow is
weak enough that BL moisture weakens on saturday, with a reduction
in shower potential.  In mountain areas receiving rainfall today,
fog will again be possible in the morning.

Outlook: Mainly VFR conditions will prevail through the period, but
patchy morning fog chances continue at KAVL. Scattered afternoon
SHRA/TSRA coverage will return on Sunday, with increasing chances
into early next week.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
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%     Med   71%
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:




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