Summerville, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

928
FXUS62 KCHS 151800
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
200 PM EDT Fri Aug 15 2025

.SYNOPSIS...
A weak cold front nearby today will pass through the region on
Saturday. High pressure will then build over the area through
much of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
This Afternoon: Aloft, the region will remain along the northern
periphery of a ridge extending across the western Atlantic to the
Gulf while h5 shortwave energy associated with a mid-lvl trough
slowly approaches from the northwest late day. The trough should
nudge a sfc front southward into Southeast South Carolina as
cyclogenesis initiates off the North Carolina Coast, providing a
forcing mechanism for few/scattered shower and thunderstorm activity
locally across Southeast South Carolina and eventually Southeast
Georgia today. Latest radar trends hint at the potential for a more
confined area of higher precip coverage across the Tri-County Area
and far southern Southeast South Carolina, perhaps as the frontal
feature/h5 shortwave energy begins to interact with a sea breeze
circulation in an environment displaying weak shear, but higher
instability (SBCAPE around 4000-4500 J/kg) and ample moisture (PWATs
near 2.25 inches). A few stronger thunderstorms are possible with
gusty winds and frequent cloud-to-ground lightning across this area,
although a limited risk is also present across the coastal corridor
into Southeast Georgia where the axis of highest instability and the
sea breeze circulation reside. An isolated/brief severe thunderstorm
can not be ruled out in the most favorable zone of convergence
(Southeast South Carolina) mid-late afternoon. Storm motion should
be a bit slower than the previous day, suggesting an uptick in minor
flooding concerns during heavy downpours as well, but the overall
coverage of precip appears to limit conditions supportive for flash
flooding.

Outside of convection, a hot/muggy day is expected with temps
peaking in the low-mid 90s away from the coast (warmest across
Southeast Georgia). These temperatures combined with sfc dewpts
mixing out to the mid-upper 70s inland, but holding into the upper
70s/around 80 along the coastal corridor, support heat index values
in the 100-105 range well inland, a short duration/limited event for
heat index values touching 107-108 across the Tri-County Area
near/ahead of a sea breeze and arriving convection, and heat index
values in the 106-111 across coastal areas of far southern Southeast
South Carolina and Southeast Georgia, where a Heat Advisory remains
effective through 6 PM this evening.

Tonight: Aloft, the region remains along the northern periphery of
the ridge with weak h5 shortwave energy nudging across the local
area and to the north. The sfc front should stall across/near the
local area during the night, which could prolong few to scattered
showers and/or thunderstorms during evening hours, but convection
should generally wane/decrease by late evening and/or become more
focused across coastal waters by midnight as the bulk of higher
instability remains offshore. Low temps should only dip into the mid
70s inland to upper 70s near the coast.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Shortwave energy will move into the upper ridge on Saturday,
forming a notable weakness over the Southeast. A weak cold
front will drop into the area during the day, stalling over or
just south of the area before dissipating Sunday. A very moist
airmass will be over the area with PWATs as high as 2.3" in the
afternoon. 0-6 km flow will be less than 10 kt, so storm motions
will be quite slow. Numerous showers and thunderstorms are
expected to develop during the day, particularly during the
afternoon when instability is greater. Southeast Georgia may see
slightly greater overall coverage given the model consensus that
the cold front will be positioned in that area during the hours
of peak heating. However, conditions are favorable for just
about any location to see several rounds of showers or
thunderstorms. Locally heavy rainfall will be possible.

A deep layered ridge will build across the region Sunday into
Monday. Overall convective coverage should be reduced due to
mid-level subsidence. There will be a noticeable drop in
humidity with dewpoints in the lower 70s instead of upper 70s.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
High pressure will prevail through Wednesday, then an upper
trough could approach on Thursday. Hurricane Erin is expected to
pass the area well offshore on Wednesday. Although no rain or
wind is expected from this system, its outer wind field could
help enhance the weak cold air damming regime over the area,
keeping temps a bit cooler and reducing convective coverage.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
CHS/JZI: Showers and/or thunderstorms will likely bring periods of
MVFR conditions at CHS/JZI this afternoon, mainly in the 17-23Z
timeframe. A brief episode of lower vsbys and gusty winds are
possible when a thunderstorm directly impacts the terminal. VFR
conditions are then expected to prevail from 23Z Friday to 18Z
Saturday, although a nearby front could lead to showers or
thunderstorms near the terminals starting around 16Z Saturday.
Future TAFs will likely need to introduce TSRA groups at CHS/JZI
Saturday afternoon.

SAV: VFR conditions will likely prevail through 18Z Saturday.
However, brief MVFR conditions are possible with thunderstorms this
afternoon. VCTS has been maintained between 20-23Z to account for
uncertainty today. A front should be nearby Saturday, leading to
shower and/or thunderstorm activity near the terminal starting
around 16Z Saturday. Future TAFs will likely need to introduce TSRA
groups Saturday afternoon.

Extended Aviation Outlook: Brief flight restrictions possible
at all terminals with afternoon showers/thunderstorms.

&&

.MARINE...
This Afternoon and Tonight: The pressure gradient will remain rather
weak across local waters, favoring winds/seas that remain well below
Small Craft Advisory levels through the night. In general, southerly
winds will top out in the 10-15 kt range the rest of the day,
highest near the coast and across the Charleston Harbor where a sea
breeze circulation occurs, then weaken and turn more offshore as a
front stalls across and/or nearby local waters overnight. Seas will
generally range between 2-3 ft the rest of the day, then 1-2 ft
during the night.

Thunderstorms are anticipated to shift offshore and/or develop
across local waters late day, but should occur mostly during the
night. A few thunderstorms could be strong with wind gusts >34 kt,
frequent cloud-to-water lightning and reduced vsbys in moderate to
heavy rainfall.

High pressure will prevail over the local waters through early
next week. Winds/seas should remain well below advisory through
Sunday. A decent NE gradient will develop for the brunt of next
week as Hurricane Erin passes well east of the waters while
surface high pressure remains over land areas. Winds will
generally stay below advisory criteria, though we could have a
robust afternoon sea breeze on several days, potentially pushing
gusts to 25 kt in Charleston Harbor.

The much more significant effect from Hurricane Erin will be
large, long-period swells spreading into the waters late Monday,
continuing through Thursday. 6 ft seas expected to move into the
offshore GA waters late Monday night, then into all nearshore
waters during the day Tuesday. We`ll definitely need Small Craft
Advisories for seas during this time, continuing for much of
next week.

Additional impacts from the large swells will be frequent,
strong rip currents, high surf, and beach erosion, especially
since tides will be higher than usual accompanying the large
breakers.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory until 6 PM EDT this evening for GAZ101-116>119-
     137>141.
SC...Heat Advisory until 6 PM EDT this evening for SCZ047-048-051.
MARINE...None.

&&

$$

NEAR TERM...DPB
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...DPB/JRL
MARINE...DPB/JRL