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Area Forecast Discussion

FXUS62 KGSP 280559

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
159 AM 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 145 AM EDT, 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 with just a few cumulus developing along
with slowly increasing high clouds. 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.


At 230 PM Friday, on Saturday evening an upper ridge will extend
from the atlantic ocean to the mid atlantic states, while an upper
trough will be over the eastern plains, and an upper low will be
near the southern SC coast. The models move this upper low slowly
inland over SC on Sunday, while the upper trough progresses to the
wester Great Lakes, and the upper ridge progresses over New England.
By Monday the low weakens near the SC and NC border, while the
upper trough deamplifies over the easter Great Lakes, and the ridge
downstream reaches the eastern Canada.

At the surface, on Saturday evening the models show a surface low
ostensibly associated with tropical development approaching the SC
coast approaching, with associated moisture moving inland over the
Carolinas. The models differ on the movement of the low into Sunday,
and therefore the amount of moisture reaching the western Carolinas
and northeast Georgia. At this point the bulk of precipitation is
expected to be near the SC coast, but uncertainty remains on inland
amounts. Model soundings vary on the amount of instability over our
area on Sunday and Monday, depending on how moist the atmosphere
becomes. Temperatures should exhibit a reduced diurnal range if
moisture can indeed spread inland over our area.


At 230 PM Friday, on Monday evening, an upper low will be weakening
near the SC and NC border. The models have disagreed on the precise
location of a an associated surface low over either SC or NC, but
now appear to move this system off the southern NC coast on Tuesday,
where it dissipated on Thursday.

By Friday an upper ridge progressing to the east coast deamplifies,
while a cold front approaches from the northwest, preceded by
sufficient moisture to support widespread precipitation.
Precipitation amounts are currently forecast to be rather limited
west of the coastal Carolinas, however if the surface low can reach
far enough inland, and linger there, rainfall totals could be

Temperatures may exhibit a reduced diurnal range if moisture lingers
over the area, otherwise they would run near normal under nearly
zonal upper level flow.


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. The best chance of fog will be in the mountain valleys
with another round of IFR fog and low clouds likely at KAVL after
08z. 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 morning fog chances continue at KAVL
each morning, with scattered afternoon/evening SHRA/TSRA increasing
into early next week.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High 100%     High 100%     High 100%     High  98%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       Low   55%     High  89%     High 100%     High 100%
KHKY       High  97%     High  97%     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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