Special Weather Statement, NWS Charleston, SC

Area Forecast Discussion
National Weather Service Charleston SC
707 PM EDT SAT AUG 20 2016

.SYNOPSIS...
A trough of low pressure will persist inland into Sunday. A cold
front will move south through the area early Monday and dissipate
Tuesday. High pressure will build from the north behind the front
and prevail into next weekend.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Scattered showers and thunderstorms this evening will diminish in
coverage and intensity over the next few hours with mostly dry
conditions expected overnight. Any lingering convective debris
clouds should gradually thin through the night and southwest/west
flow will prevail. Low temperatures generally in the mid to upper
70s, except near 80 at the coast.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday: Mid-level heights increase slightly this period ahead of
shortwave energy digging across the Great Lakes into the Ohio
Valley. Rain chances will be low with a dry, deep westerly flow
keeping the sea breeze circulation pinned until very late in the
day. This combined with poor mid-level lapse rates and decreased
surface based instability will support pops below normal for
mid/late August. 20% pops look reasonable for most areas with 30%
along portions of the lower South Carolina coast where low-level
convergence will be locally enhanced with the resultant. It is
very possible that little, if any, meaningful convective activity
could occur and pops may be need to be lowered even more in
subsequent updates. Highs will range from the upper 90s across the
interior to the lower 90s at the beaches. Any lingering convection
will quickly diminish after sunset with dry conditions prevailing
overnight. Lows will range from the mid 70s inland to around 80 at
the beaches and Downtown Charleston.

Monday: A backdoor cold front will drop south through the area
Monday morning and stall out across southern Georgia during the
afternoon as it become intermingled with the sea breeze
circulation. Although a somewhat cleaner/drier airmass will ooze
into parts of Southern South Carolina behind the front, a
significant airmass change is not expected across Southeast
Georgia where conditions will favor isolated-scattered showers/tstms
within a moderately unstable atmosphere. The best rain chances
will occur south of I-16 and closer to the Georgia coast where
low-level convergence will be maximized along the cold front/sea
breeze intersection. 20-40% pops look on track for Southeast
Georgia with pops below mentionable thresholds across most of
Southeast South Carolina. Highs will range from the lower 90s
along the I-26 corridor to the mid 90s across Southeast Georgia
with cooler conditions at the beaches. Although isolated
convection could linger through sunset across the far southern
counties, mostly dry conditions are expected Monday Night. Could
see isolated, low-topped showers move inland from off the
Atlantic after midnight and affect portions of coastal McIntosh
county, however confidence in this scenario is rather low this
far out.

Tuesday: Frontal remnants will gradually dissipate across southern
Georgia during the day, but will remain the primary focus for
isolated-scattered shower/tstm development during peak heating.
A dry/stable airmass across Southeast South Carolina should
inhibit convective development north of the Savannah River with
pops south of the Savannah River ranging from 20-40%, highest
along the Altamaha River. Highs will top out in the lower 90s away
from the beaches, possibly a bit cooler north of the I-26
corridor.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
High pressure will prevail through this period. Through late week,
the high will provide a continued respite from the relentless heat
and humidity of recent weeks. Highs in the upper 80s to lower 90s
will be accompanied by dewpoints in the 60s north of I-16 and not
far above 70F farther south. Tuesday and/or Wednesday night,
temperatures could even dip into the upper 60s at some
inland/northern locations. The relatively dry/capped environment
will remain hostile for deep/moist convection, and POPs are limited
to isolated/scattered showers which could push onshore into far
southern counties. Next weekend, a transition to highs in the
lower/mid 90s and increasing dewpoints/greater instability could
support an increased chance for afternoon/evening showers/
thunderstorms.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
VFR conditions are expected for the most part. Scattered showers
and thunderstorms are expected across the area through this
evening but there is a low risk of direct impacts at KCHS/KSAV.

Extended Aviation Outlook: Thunderstorms could produce brief flight
restrictions at both terminals Sunday afternoon/evening and at KSAV
Monday-Tuesday PM. Otherwise, VFR.

&&

.MARINE...
Tonight: Assuming that convective outflow from evening storms don't
disrupt the prevailing synoptic setup, southwest to westerly flow
will persist through the night mainly around 15 knots. There could
be periods of 15-20 knots, but conditions are expected to remain
below Small Craft Advisory thresholds. Seas will range 2-3 feet,
with some 4 footers possible in the outer reaches of the outer
waters.

Sunday through Thursday: Southwest winds as high as 15-20 kt are
expected Sunday/Sunday evening ahead of an approaching cold front.
Winds will veer to the northeast and east Monday as a cold front
drops south. In the wake of the front, high pressure will build
into the region and will provide east/northeast winds mainly 15
kt or less through late week. Seas will average 2-3 ft most areas
Sunday through Tuesday, although 4 ft seas could occasionally
develop over waters beyond 20 nm during this period. The long
fetch/duration of east/northeast winds should push seas to 3-5 ft
Wednesday/Thursday and there is a low probability for 6 ft seas to
push into water beyond 20 nm mid to late week.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

SYNOPSIS...
NEAR TERM...RJB
SHORT TERM...ST
LONG TERM...SPR
AVIATION...RJB/ST
MARINE...BSH/ST