Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS62 KGSP 271048

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
648 AM 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 645 AM EDT, brief patchy dense fog has been added to the
mountain valleys around daybreak, otherwise the forecast remains on
track. 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. Mountain SBCAPE values
should again rise into the 1000 to 1500 J/Kg range this afternoon.
The severe potential will be relatively low but weak steering flow
will likely produce some heavy rainers. 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, a FEW VFR clouds have lingered around 6 to 7 kft through
daybreak. Scattered bases will lower with heating and convective
cloud development through the day. Brief cigs will be possible at
times, but SCT conditions are expected on average. The cumulus will
thin with the loss of heating through evening. Precipitation chances
appear small given some capping aloft and the lack of a significant
trigger. Light south to southeast flow will briefly pick up from the
SSW with mixing today, but with speeds generally less than 10 kt.

Elsewhere, brief IFR fog may continue for an hour or two past
daybreak at KAVL and in the other mountain valleys, but this this
lift and scatter quickly. Otherwise, SCT to BKN VFR clouds at 6 to 7
kft will be predominant through the period, with some lowering today
with heating and convective cloud development. The best chance of
thunderstorms this afternoon will be near KAVL with southeast
upslope flow and wind convergence. KHKY will also see a small
afternoon chance. Will keep the Upstate TAFs dry for now given just
a bit more capping and less of a trigger, but isolated nearby
convection will be possible from mid to late afternoon. Clouds will
thin and scatter through evening as deeper drying pushes in from the
east. Expect mainly southerly flow through the period at less than
10 kt. Another round of IFR restrictions is quite possible in the
mountain valleys tonight with drying at mid and upper levels.

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...

            10-16Z        16-22Z        22-04Z        04-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  91%     High 100%     High 100%     High 100%
KHKY       Low   50%     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:




AVIATION...HG is the U.S. government's official web portal to all federal, state and local government web resources and services.