Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 272349
Area Forecast Discussion
National Weather Service Charleston SC
749 PM EDT SAT AUG 27 2016
High pressure centered to the north will prevail into Monday. Weak
low pressure will approach the North Carolina Outer Banks early
next week then dissipate.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
This evening: Other than a persistent band of broken showers that
has pushed onshore across Tybee Island and points further inland,
radar imagery is quiet. Many areas are experiencing clear skies
and this will prevail for much of the night. The overall pattern
will change little, and through the night low level flow will
gradually become more northeasterly. We could still see some
isolated shower activity across the Georgia coastal waters and
along the Georgia coast, but overall a quiet night. Stratocumulus
is progged to expand closer to sunrise, but will have little
impact on the sensible weather. Forecast lows are in the low to
mid 70s inland, upper 70s along the coast.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
It is becoming increasingly likely that the tropical wave
approaching south Florida will only have peripheral impacts on
the area as it tracks into the eastern or central Gulf of Mexico
over the coming days. Weak low pressure which developed near
Bermuda last night is on track to approach the North Carolina
Outer Banks Monday into Tuesday as the supporting upper trough it
gradually moves onshore along the Southeast U.S. coast. The low is
being monitored for possible tropical cyclone development by NHC,
but the combination of dry air and increasing wind shear over the
coming days should limit its development. No direct influences
from this system are expected this far south.
The risk for scattered showers/tstms will persist Sunday into
Tuesday as the upper trough retrogrades to the west beneath the
upper level anticyclone which has been the dominate feature across
the region for the past several days. The various models continue
to have a hard time resolving both QPF and precip fields for the
next several days, likely due to extensive subsidence/dry air that
is in place across the Southeast. This is well represented in the
latest MEN output which shows a large spread in daily pops with
the various ensemble members. Will limit pops to 20-40% each day
to account for this uncertainty with the risk for showers/tstms
initiating near the coast mid-late morning, then moving inland
each afternoon. Locally higher pops may eventually be needed as
periods 2 through 6 gradually enter the temporal domains of the
higher resolution, mesoscale models. There will be a continued
risk for nocturnal showers moving inland from off the Atlantic and
impacting the coastal counties through the period. Highs will
range from the lower-mid 90s to mid-upper 80s the coast with
overnight lows ranging from the lower 70s well inland to around 80
at the beaches.
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
There is still some uncertainty through mid week regarding the
potential for low pressure to develop and track close to the area.
Nonetheless, troughing will prevail into late week with rain
chances near normal. Temperatures should be a bit above normal
through at least Thursday before falling closer to normal by
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
VFR conditions are expected to prevail. Stratocumulus from the
adjacent coastal waters will expand inland starting around sunrise
on Sunday, and there is a low end chance that we could see a brief
period of MVFR level ceilings. Better coverage of showers and
thunderstorms is expected on Sunday, but confidence in direct
impact at the terminals is too low to include in the forecast.
Extended Aviation Outlook: Scattered showers/tstms are possible
This Evening and Tonight: High pressure will dominate most
waters, especially off the coast of South Carolina. However,
east/northeast winds will continue to gust up to 15-20 kt this
evening before slowly improving during the overnight period.
Strongest winds will occur over southern Georgia waters where the
pressure gradient is slightly enhanced and the 1000mb geostrophic
flow is highest. Although winds will steadily decrease later
tonight, seas will remain between 3-5 ft due to long period swell
from the east/southeast. Seas will be highest in waters beyond
20 nm from the coast.
Sunday through Wednesday: Weak low pressure will approach the
Outer Banks through mid-week before weakening. This pattern will
favor mainly east/northeast winds 15 kt or less with periods of
occasionally higher winds, mainly during the afternoon hours.
Seas will average 2-4 ft nearshore waters and as high as 4-5 ft
offshore waters through the week. Both winds and seas look to
remain just below Small Craft Advisory thresholds; however, rough
continues will linger near entrances to bays, rivers, inlets and
harbors due to long period swells impacting the waters.
Rip currents: Given what the observed rip currents today and
swell periods forecast to only increase Sunday, a high rip current
risk will be issued for all beaches. Some guidance shows periods
reaching as high as 15-17 seconds at times at buoys 41008 and
41004, but NWPS Gerling-Hanson plots closer to the beaches would
suggest some of this swell energy will dampen as it approaches the
Long period swells up near 15 seconds are expected to
impact the coast through early next week. Thus an enhanced risk
Tides remain elevated due to ongoing east/northeast winds, long
period swell energy and influences from the approaching new moon.
The latest extratropical surge guidance suggests afternoon high
tides through mid-week will be very close to levels which will
produce shallow coastal flooding, especially along the lower South
Carolina Coast. Coastal Flood Advisories may eventually be needed
for some areas.
GA...High Risk for Rip Currents from Sunday morning through Sunday
evening for GAZ117-119-139-141.
SC...High Risk for Rip Currents from Sunday morning through Sunday
evening for SCZ048>051.