Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 281745

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
145 PM EDT SAT MAY 28 2016

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.


As of 1100 AM Saturday: Main changes with this update were to slow
down the increasing sky cover and then make minor tweaks for
PoPs/T/Td through the late morning and early afternoon hours. Not
enough changes for any real wording differences in the zone
forecast. Otherwise, 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.


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 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 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 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 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.


As of 315 AM Saturday...During the medium 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.


At KCLT: VFR this afternoon and the first part of the overnight
period but with increasing high clouds as the cirrus from TD2
continues to spread inland. Winds will flirt around E but in general
should be mainly ESE until close to 06z, when approaching surface
low swings wind around to NE. Expect MVFR cigs to build in about
this time with increasing chances for -SHRA so have introduced VCSH.
Went prevailing -SHRA by 09z with solid MVFR cigs and in-and-out
MVFR vsbys, depending on where the rain is at the time. Winds
continue backing to the N and pick up after 12z to 10-12kt or so as
-SHRA chances increase. Introduced PROB30 TSRA after 15z on Sunday.

Elsewhere: Other TAF sites will be farther away from impacts from
TD2 or whatever it will be at the time, but overall should see a
similar pattern with increasing high clouds through the period. Did
introduce MVFR cigs and -SHRA at 15z for KHKY, and included PROB30
TSRA everywhere by 15z Sunday for all but KAND. KAVL might well see
another period of crashing vsby/cigs in the morning, but with high
clouds over the area have only reduced vsby to 2SM.

Outlook: Uncertainty remains over the westward reach of tropical
moisture associated with TD2 through the day Sunday and into early
next week as the surface low spins slowly up the SC and then NC
coast. KCLT will continue to have the best chance of lingering
SHRA/TSRA. Otherwise, patchy fog chances continue at KAVL each
morning, with scattered afternoon/evening SHRA/TSRA increasing into
early next week.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High 100%     High 100%     Low   57%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     Med   66%
KHKY       High 100%     High 100%     High 100%     Med   66%
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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