836
FXUS62 KCHS 190522
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
122 AM EDT Thu Sep 19 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 THIS MORNING/...
Mid-level circulation center is now across the mid-Atlantic
region with drier mid level air wrapping around the western and
southern side down through Georgia. Earlier shower activity has
pretty much ended and leftover debris cloud continues to slowly
fade in time. Quiet weather is anticipated through the balance
of the night. That said, recent CAM guidance solutions want to
kick off some additional shower activity overnight in the tri-
county vicinity into the Atlantic. Discounting that idea for
now.

Meanwhile, with clearing skies, light/calm winds...risk for fog
and stratus will increase particularly where there was decent
rainfall Wednesday afternoon (essentially along the I-95
corridor). HREF highest fog probabilities favor southeast
Georgia, especially south of I-16 where strongest drying
aloft/clearing skies will be found. A Dense Fog Advisory is
certainly possible toward morning.

Lows tonight will range from the mid-upper 60s inland to the
lower 70s at the beaches and Downtown Charleston.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM 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 Wednesday: 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 /05Z THURSDAY THROUGH MONDAY/...
19/06z TAF Discussion:
KCHS/KSAV/KJZI: There is a risk for fog and stratus development
overnight as wet grounds from earlier rainfall combine with
clearing skies and light winds. The best fog/stratus parameters
look to occur across interior Southeast Georgia where KSAV will
likely be on the eastern periphery of the lowest vsbys. For now,
cigs were limited to MVFR with a TEMPO group from 10-13z for IFR
cigs just above alternate minimums with MVFR vsbys. Lower
conditions are possible with amendments likely toward morning.

For KCHS, fog/stratus looks a bit more marginal although it is
located close to where heavier rains fell earlier. VFR was
maintained, but with a TEMPO group for MVFR cigs with scattered
clouds at 600 ft between 10-13z. Light MVFR fog was also included
between 10z-13z. At KJZI, VFR was continued as fog/stratus
looks to remain west of the terminal. Some light fog could occur
as winds go light and skies clear, but no meaningful reductions
in vsbys are expected at this time.

Extended Aviation Outlook: VFR. No significant weather expected.

&&

.MARINE...
Tonight: Southerly flow early evening will veer to the west and
northwest late tonight towards daybreak. Speeds generally
remain less than 10 knots with seas 1 to 3 ft nearshore waters
out 20 NM and 3-4 feet over the Georgia offshore waters out
20-60 NM.

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.

&&

.TIDES/COASTAL FLOODING...
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.

The astronomical high tides start to lower Saturday and Sunday, 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...None.
MARINE...None.

&&

$$