545
FXUS62 KCHS 181944
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
344 PM EDT Wed Sep 18 2024

.SYNOPSIS...
Weak high pressure will develop over the region on Thursday.
The area of high pressure is expected to gradually strengthen
through early next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Mid level low over the Carolinas this afternoon will slowly drift
eastward tonight, with the associated trough axis becoming oriented
along the East Coast by around daybreak Thursday. At the
surface, a weak boundary will also push east, and eventually
offshore overnight. Highest coverage of showers/thunderstorms
will be late this afternoon and evening then activity will
largely decrease with loss of heating. However with some
moisture and upper forcing lingering, a few showers could
percolate overnight, especially over South Carolina. Otherwise,
latest guidance hints at fog developing late towards morning
particularly over southeast Georgia. Included mention of patchy
fog. Lows should average in the upper 60s to lower 70s.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
Thursday: Short term guidance indicates that the forecast area will
remain under a broad H5 longwave trough. At the sfc, a weak ridge
should build across the western and central Carolinas as a broad
trough remains over the Coastal Plain. As temperatures warm into the
mid to upper 80s, a very weak sea sea breeze is forecast to develop
during the early afternoon, but should remain over the coastal
counties through late afternoon. There should be enough instability
during the heat of the afternoon to support isolated to scattered
showers with isolated thunderstorms along the coast. Any convection
should dissipated by the mid-evening hours.

Friday: The axis of the mid-level trough should ripple east over the
western Atlantic as strong ridge centered over TX starts to build
east. GFS indicates that a short wave is expected to track from
north to south across the forecast area during the afternoon. As
temperatures reach the mid to upper 80s over dewpoints in the 70s,
weak instability should develop across the region. The combination
of the shortwave passage and weak instability may support isolated
convection along the coast during the afternoon.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Saturday and Sunday, the forecast area will become dominated by weak
sfc high pressure as a H5 ridge builds across the Deep South and
Southeast U.S. Forecast soundings indicate that the environment will
remain generally dry with a significant inversion at H75. The
forecast will indicate dry conditions each day. High temperatures
should favor values in the upper 80s, with low 90s possible across
inland GA on Sunday.

Monday through mid-week, long term guidance indicates that the H5
ridge will shift east across the northern Gulf coast and FL. H5
heights should increase across the forecast area, limiting any
instability across the forecast area. The forecast will feature dry
weather through early next week. High temperatures are forecast to
remain in the mid to upper 80s on Monday, then mid 80s expected
through the rest of the forecast period.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
Prevailing VFR through 18z Thursday, although brief flight
restrictions are possible in showers and maybe a couple
thunderstorms this afternoon and evening. Shower coverage will
slowly diminish late evening and overnight. Towards Thursday
morning, there are some indications that fog/low clouds could
develop. Showed hints of this in the TAF but did not have high
enough confidence to include prevailing restrictions.

Extended Aviation Outlook: VFR. No significant weather expected.

&&

.MARINE...
Tonight: Southerly flow late this afternoon and early evening
will veer to the west and northwest late tonight towards
daybreak. Speeds generally remain less than 10 knots with seas 2
to 4 feet.

Thursday through Sunday: Building high pressure should result in
winds between 10-15 kts with sea generally between 2-4 ft. No
headlines expected during this period.

Rip Currents: The combination of a lingering swell around 2 ft
at 9 seconds and high astronomical tides from the full moon will
lead to a Moderate Risk of rip currents for all of our beaches
today.

&&

.TIDES/COASTAL FLOODING...
Given high astronomical tides and latest tidal departures, minor
coastal flooding is expected along the Charleston and Colleton
county coasts with the evening high tide cycle. A Coastal Flood
Advisory has been issued for 7-11 PM with tide levels expected
to peak between 7.3-7.5 ft MLLW. Further south and along the
Georgia coast, current forecast has tides peaking just shy of
minor flooding criteria (9.5 ft MLLW in Fort Pulaski), so no
advisory has been issued. Will continue to monitor trends.

Positive tidal anomalies along with high astronomical tides from the
full moon will lead to elevated tides for the rest of this week and
through the weekend. Coastal Flood Advisories will probably be
needed for both the morning and evening high tides through Friday
for both Charleston Harbor and Fort Pulaski.

Saturday and Sunday, the astronomical high tides start to lower but
the morning high tides will likely be elevated enough to still
require Coastal Flood Advisories (especially for Charleston and
coastal Colleton Counties). More uncertainty exists for Fort
Pulaski.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Coastal Flood Advisory from 7 PM to 11 PM EDT this evening for
     SCZ049-050.
MARINE...None.

&&

$$

NEAR TERM...ETM
SHORT TERM...NED
LONG TERM...NED
AVIATION...ETM/NED
MARINE...ETM/NED