279
FXUS62 KCHS 201111
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
711 AM EDT Sun Sep 20 2026

.WHAT HAS CHANGED...
Aviation section has been updated to reflect 12z aviation
forecast.

&&

.KEY MESSAGES...
- 1) Daily thunderstorms are expected across southeast Georgia
 and southeast South Carolina this weekend and into early next
 week. An increase in rain chances is expected by the middle of
 next week, with cooler temperatures thereafter.

&&

.DISCUSSION...
KEY MESSAGE 1: Daily thunderstorms are expected across
southeast Georgia and southeast South Carolina this weekend and
into early next week. An increase in rain chances is expected by
the middle of next week, with cooler temperatures thereafter.

Sunday through Monday: Continued unsettled afternoons are
expected as an upper level low over the Florida peninsula
meanders around the next 48 hours. At the surface a weak
boundary has slipped south of the area and is expected to slowly
wash out. With very little upper forcing, storms will likely be
more confined to any remnant boundaries and the slowly advancing
seabreeze each afternoon. With the location of the upper low,
continued moisture will stream up over the area as PWATS linger
in the 2 inch range. Expect isolated to scattered storms to
develop both this afternoon and Monday afternoon along the slow
advancing seabreeze and work south with time. Overall,
instability continues to remain meager and with very little
deep layer shear strong to severe storms should be limited.
While this means a stronger storm cannot be ruled out, not
really expecting a widespread risk. With PWATS around 2 inches
and slow moving storms a low end heavy rainfall threat cannot be
ruled out with any storms.

Tuesday through the end of the week: Convective coverage and
rain chances will increase Tuesday into Wednesday as a cold
front approaches from the north. Deep moisture, with PWATS
exceeding 2 inches, will create a threat of locally heavy
rainfall during this period. In regards to the severe weather
potential, guidance targets late Tuesday night for the initial
push of the front, which should keep the severe weather threat
low due to unfavorable overnight timing. However, a secondary,
reinforcing cold front is timed to move across the region on
Wednesday. Prior to the arrival of cooler air, dew points in the
lower 70s and afternoon heating could build sufficient
instability to support strong thunderstorms Wednesday afternoon,
primarily across Southeast Georgia. Though, much of this will
depend on the evolution of the front moving through Tuesday
night.

Behind the cold front, noticeably cooler air is expected for the
latter half of the week and into the following weekend. Highs in the
upper 70s to low 80s for southeast SC and low to mid 80s for
southeast GA look probable at this time, which would be a few
degrees below normal for late September.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
LIFR to VFR conditions have developed across the area as a low
stratus deck and patchy fog has overspread much of the area.
Conditions should prevail for the next hour or two especially
at KSAV where fog has set in this morning. VFR conditions should
return by mid-morning as light and variable winds slowly
increase out of the northeast before turning more easterly with
the passage of the seabreeze. Scattered showers and
thunderstorms will be possible once again this afternoon
resulting in possible reductions at all TAF sites. Storms should
diminish during the early evening as winds relax once again and
instances of low ceilings and fog likely develop once again
across interior portions of the area after midnight.

Extended Aviation Outlook: The main potential for sub-VFR
conditions will come from afternoon and evening showers and
thunderstorms each day. The best chance of showers and
thunderstorms is expected to come Tuesday into Wednesday.

&&

.MARINE...
Sunday: Very quiet conditions will continue across the
local waters. Light northeasterly flow will continue through
the day before turning more easterly overnight. Seas are
expected to average around 2 ft. A few showers/thunderstorms are
possible along the GA coast this evening, potentially producing
gusty winds and frequent lightning.


Monday through Friday: Conditions across the local waters will
remain quiet through Monday night with northeast or east flow
generally no more than 10 knots. However, this will change during
the middle of the week as a cold front pushes through. This will
result in a strong surge of northeast flow beginning Wednesday and
potentially continuing through Friday. There are increasing
probabilities of gusts into the 25-30 knot range with seas building
to 5-6 ft as well. Small Craft Advisories will likely be needed for
most of the local waters, including the Charleston Harbor. Also of
note, rounds of thunderstorms will be possible at times ahead of the
front which could bring the potential for strong wind gusts and
frequent lightning.

&&

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

&&

$$

Black/BRS