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Area Forecast Discussion

963
FXUS62 KGSP 280858
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
458 AM EDT SAT MAY 28 2016

.SYNOPSIS...
After a dry day today, 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.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 445 AM EDT, patchy dense fog has been added to the French
Broad Valley through daybreak, otherwise the forecast remains on
track. A Bermuda high pressure ridge will remain in place across the
forecast area today through tonight as the circulation of Tropical
Depression Two slowly approaches the South Carolina coast. A dry day
should result for most locations with just a few cumulus developing
along with slowly increasing high clouds from the coast. Any
isolated showers or thunderstorms should be confined to the Smokies
vicinity in slightly better low level convergence and instability,
and also to locations well east of I-77 toward sundown. Max temps
should run about one category above climatology this afternoon.

The latest GFS is very aggressive in bringing TD 2 moisture inland
across the piedmont of the Carolinas tonight, while most of the
other solutions are a bit more reserved. It seems that the nose of
the Bermuda ridge extending westward over the southern Appalachians
may block the path to the west and keep the tropical/subtropical
system nearer the coast through tonight. In fact, the circulation of
TD 2 already seems to be sharpening up the blocking ridge a bit
early this morning. Will thus back slightly off PoPs for tonight but
still keep solid chances of showers over mainly the Interstate 77
corridor. Expect mild mid 60s mins in most areas east of the
mountains as clouds increase from the coast.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 300 AM Saturday...By Sunday morning the models are beginning
to diverge on the track of the tropical system. The GFS continues to
be the most NW inland with the track...taking the center onshore by
18z. The 00z ECMWF has just come in similar to the GFS in this
regard...but is a little stronger and starts drifting it to the east
faster than the GFS. The 00z NAM looks similar to previous runs in
keeping the low stalled offshore for several days just SE of
Charleston. With all this said...it looks like the bulk of tropical
rain should stay south and east of the CWFA. The best shot at some
rain from this system will be early Sunday...as a possible rain band
of sorts pivots westward into the I-77 corridor. Interestingly...if
this happens it may keep the Charlotte area more stable for the race
in the evening...as the rain moves out. But confidence on convection
coverage Sunday is still below average. I will go with low-end
likely Pops ACRS the NC piedmont and eastern Upstate...and mainly
mid CHC to slight CHC west. Temps will range from slightly below
normal east to a couple categories above normal west.

Sunday night thru Monday night...with the latest guidance in better
agreement on the tropical low drifting to the east...it looks like
PoPs should trend downward. So I will go with CHC PoP along the Blue
Ridge and slight CHC elsewhere Monday AFTN...generally waning in the
evening. Temps will be one or two categories above normal.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 315 AM Saturday...During the medium range...an upper level
trough will progress across the Midwest and deepen. This will
increase the steering flow across the Mid Atlantic and should carry
out any remnants of the tropical system to the NE Wed-Thu. A cold
front will accompany the approaching trough and both the 00z runs of
the GFS and the ECMWF agree should reach the Appalachians by late
Friday. Moisture will be increasing ahead of the front such that
there should be decent coverage of AFTN SHWRS and TSTMS on
Thursday...and even better coverage on Friday. So I will FCST a
gradual increasing PoP trend thru the medium range with solid CHC
Piedmont to low-end likely Mtn PoPs by Friday. Temps will continue
to be near or slightly above normal thru the period.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
At KCLT, dry air pushing westward from the coast will permit little
more than spotty cirrus through the first half of the TAF cycle.
Moisture will start to increase the latter half of the period with a
small chance of showers wrapping westward toward the I-77 corridor
from the coastal tropical/subtropical system. Will keep conditions
VFR throughout and confine any VCSH mention until after 01Z. Light
southeast winds today will toggle ENE or NE this evening as the
ridge blocking the path of the tropical system sharpens up.

Elsewhere, crossover temperatures for fog development could be met
through daybreak as lingering VFR cloud cover slowly scatters or
moves west. LIFR to VLIFR fog and clouds have already formed in the
French Broad Valley and will be carried as a TEMPO through 13Z.
Otherwise, the mountain and foothill TAF sites will remain dry
through the period with slowly increasing mid and high clouds this
evening. Expect mainly light southeast surface winds, possibly
toggling ENE in the foothills late in the period.

Outlook: Uncertainty remains over the westward reach of tropical
moisture associated with Tropical Depression Two Sunday through
early next week. KCLT will see the closest approach of any deeper
moisture. Otherwise, patchy fog chances continue at KAVL each
morning, with scattered afternoon/evening SHRA/TSRA increasing into
early next week.

Confidence Table...

            09-15Z        15-21Z        21-03Z        03-06Z
KCLT       High 100%     High 100%     High 100%     High  97%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       Low   48%     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...HG
NEAR TERM...HG
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...HG



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