Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 252007
Area Forecast Discussion
National Weather Service Charleston SC
407 PM EDT THU AUG 25 2016
High pressure will prevail into the weekend. A weak surface trough
will develop over the region by late weekend and will persist
through the middle of next week.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Isolated showers over the coastal waters will dissipate this
evening as convergence weakens. High pressure and an unseasonably
dry airmass will prevail. PWATs will generally remain at or below
1.5" and this combined with broad subsidence will maintain dry
conditions. Light winds and mostly clear skies should allow
temperatures to drop into the upper 60s inland and the lower 70s
near the coast.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Friday: A large mid/upper lvl ridge of high pressure will prevail
over the Southeast late week, generally favoring rain-free
conditions over all locations while subsidence occurs and pwats
remain at or below 1.0 inch for most of the area. In general, high
temps should peak in the low/mid 90s. Overnight lows will range in
the lower 70s inland to mid/upper 70s near the coast Friday night.
Saturday and Sunday: Very little change is anticipated in the
overall pattern this weekend into early next week. However, models
continue to suggest that the mid/upper ridge of high pressure
responsible for dry weather over the Southeast will nudge further
north/northeast as a trough of low pressure begins to develop over
the region late Sunday. The setup should allow a more direct onshore
flow and increasing levels of moisture to advect over the region
from the Atlantic. Given sufficient sfc heating each day, expect at
least slight chances of showers/thunderstorms during peak diurnal
heating each day. However, the best chance of precip will likely
remain in southern Georgia counties on Saturday, before increasing
coverage in Southeast Georgia and Southeast South Carolina on
Sunday, mainly due to a more active seabreeze. Overall, high temps
are expected to range in the low to mid 90s away from the coast each
day. Overnight lows will range in the low/mid 70s away from the
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Independent of the development of a tropical entity that evolves
from a disturbance located near Hispaniola and moving WNW toward the
Florida peninsula, a shift to deep-layered troughing should
translate to a greater chance for showers/thunderstorms during this
period, especially during the Tuesday through Thursday time frame.
After another day with high temps in the lower/mid 90s Monday, the
greater potential for clouds/precipitation is reflected in near
normal temperatures in the upper 80s/lower 90s Wednesday and
Thursday. Lows should range in the mid 70s inland to around 80 along
the coast through this period.
As of Thursday afternoon, the National Hurricane Center indicated a
70 percent chance for tropical development within a zone from north
of Hispaniola to southern Florida within 5 days, and guidance
generally agrees that a tropical system will be located in the
vicinity of south Florida later this weekend. Thereafter, guidance
has generally trended toward a solution which turns the tropical
system toward the north, either over the Gulf of Mexico or near the
western Florida coast, perhaps carrying low pressure over land and
across our area with a threat of heavy rain and potentially severe
weather for mid to late week. However, due in part to the uncertain
rate of weakening of the deep-layered ridge currently over the area
and a highly uncertain tropical cyclone track/intensity forecast
beyond this weekend, the latest forecast does not explicitly account
for any impacts from a recurving tropical cyclone next week.
.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
Extended Aviation Outlook: VFR conditions are expected at both CHS
and SAV terminals.
High pressure over the northern Atlantic will maintain E winds
5-10 kt tonight. Seas will range from 2-3 ft within 20 nm and 3-4
ft in AMZ374.
Friday through Tuesday: High pressure will dominate the coastal
waters through Saturday, before giving way to a weak trough of low
pressure advancing into the area this weekend. The setup will favor
east/northeast winds between 10-15 kts with gusts as high as 20 kts
in offshore Georgia waters into early next week, before winds become
more east/southeast in response to low pressure entering the area.
Seas will slowly build from 2-4 ft to 3-5 ft this weekend into early
next week. There is a chance that offshore Hurricane Gaston could
push a long period swell as high as 6 feet into waters beyond 20 nm
early next week.
Rip currents: Persistent onshore winds and a small long period swell
could begin to produce an elevated risk of rip currents this weekend.
A larger and longer period swell produced by Hurricane Gaston could
begin to reach the coast early next week and this could set the
stage for stronger/more frequent rip currents.
Tides have been running above extratropical surge guidance but have
remained just below Coastal Flood Advisory levels for the past
couple of days. This scenario will likely repeat around the times of
the afternoon high tides through this weekend as E/NE winds prevail.
There is a chance that the influence of the Sept. 1 new moon and
a larger swell produced by offshore Hurricane Gaston could combine
to push evening high tides past Coastal Flood Advisory levels next