952
FXUS62 KCHS 161834
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
234 PM EDT Sat Aug 16 2025

.SYNOPSIS...
A weak cold front will push south of the area today. High
pressure then builds into the region as Hurricane Erin passes
well offshore to the east through the coming week.

&&

.NEAR TERM /THROUGH TONIGHT/...
This Afternoon: Aloft, weak troughing and associated h5 vort energy
will drift south across the Southeast United States just north of
weak ridging across Florida and the Gulf. The mid-lvl trough will
help nudge a weak sfc front across Southeast Georgia south of the
Altamaha River by late day, promoting scattered/numerous showers and
thunderstorms within a weakly sheared, but high instability/moisture
environment marked by SBCAPE around 3500-5000 J/kg and PWATs around
2.25-2.40 inches. Much like the previous day, convection should peak
in intensity and coverage mid-late afternoon. A few stronger
thunderstorms are possible across Southeast South Carolina and/or
Southeast Georgia, but the bulk of stronger activity should
transition to Southeast Georgia as an outflow boundary arrives from
the north and interacts with a sea breeze closer to the sfc front.
An isolated/brief severe thunderstorm can not be ruled out in the
most favorable zone of moisture convergence and forcing near an east-
west sfc instability axis extending from the nearby Atlantic into
Southeast Georgia zones, mainly along and south of I-16 heading into
the later part of the afternoon. Given slow storm motion and deep
moisture residing across the local area, there remains a risk for at
least minor flooding across most areas today, and flash flooding
during locally heavy downpours produced by thunderstorms across
coastal Southeast South Carolina into much of Southeast Georgia,
especially if boundary collisions promote longer duration precip
across urban areas.

Outside of convection, a more typical hot/muggy summer day is
expected with temps peaking 1-2 degrees lower than yesterday,
generally in the upper 80s near the beaches to lower 90s inland
(warmest across Southeast Georgia). These temperatures combined with
sfc dewpts mixing out into the mid 70s inland to mid-upper 70s along
the coastal corridor, support heat index values in the 100-105 range
prior to convection today, falling short of Heat Advisory Criteria.

Tonight: Aloft, weak troughing/h5 vort energy continues to shift
south during the evening and overnight, nudging a sfc front further
south of the region. Shower/thunderstorm activity will likely be
ongoing across Southern Southeast South Carolina into Southeast
Georgia, but should trend more south towards the Altamaha River
and/or offshore by early-mid evening, eventually ending across land
zones as instability wanes and/or the environment is worked over.
Other than the potential for a few coastal showers and/or isolated
thunderstorm along the immediate Georgia coast overnight, most areas
are anticipated to remain dry by around midnight. Latest guidance
indicates ample moisture and lower condensation pressure deficits
late night, suggesting some potential for patchy fog prior to
sunrise. However, much depends on where showers/thunderstorms have
occurred during the day/evening and if clouds limit the potential,
thus fog remains out of the latest forecast. Overnight lows should
generally range in the low 70s inland to mid-upper 70s closer to the
coast.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
The forecast area will largely remain on the eastern periphery of a
mid level ridge early next week. A relatively weak pressure pattern
will exist at the surface, with a subtle trough axis eventually
being replaced by high pressure. By Tuesday, Hurricane Erin will
begin lifting well off the Southeast coast (with its center forecast
to be some 600 miles offshore). Highest coverage of showers and
thunderstorms is expected on Sunday, especially over southeast
Georgia where deepest moisture and some mid level energy will
reside. Monday and Tuesday should be much less active than previous
days with only a 20% PoP highlighted on Tuesday. High temperatures
largely stay in the low to mid 90s and heat indices peaking 100-103
in most spots. Lows will average in the low to mid 70s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Hurricane Erin is expected to pass well off the Carolina coast on
Wednesday, continuing to lift away from the region on Thursday. As
this occurs, a cold front is expected to sink into the area and
possibly linger in the vicinity late in the week. Only isolated
showers and thunderstorms are possible on Wednesday, then rain
chances will increase late week as 2+ inch Pwats return and the
aforementioned front and shortwave energy provide a potential focus
for convective development. Temperatures will be within a few
degrees of normal.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
CHS/JZI: Showers and/or thunderstorms will likely bring periods or
TEMPO MVFR conditions this afternoon, mainly in the 18-21Z
timeframe. A brief episode of lower vsbys and gusty winds to 20-25
kt is possible when a thunderstorm directly impacts the terminal.
VFR conditions are then expected to prevail from 23Z Saturday to 18Z
Sunday.

SAV: TEMPO MVFR conditions are possible with thunderstorms between
18-20Z this afternoon, before TEMPO MVFR/IFR conditions occur
between 20-23Z mid-late afternoon due to showers/thunderstorms
impacting the terminal. A brief episode of of lower vsbys and gusty
winds are possible when a thunderstorm directly impacts the
terminal. VFR conditions are then expected to prevail from 00Z
Sunday to 18Z Sunday. However, there are some hints of lower vsbys
at the terminal tonight due to patchy fog. Confidence is too low to
include in the latest TAF issuance.

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

&&

.MARINE...
This Afternoon and Tonight: A rather diffuse front will remain
nearby, leading to a weak pressure gradient across local waters for
the remainder of the day and through the night. In general, easterly
winds around 10-15 kt or less are expected for the day, highest near
the coast where a sea breeze circulation resides. Overnight, winds
are expected to turn more north-northeast and become 10 kt or less
outside shower/thunderstorm activity.

Thunderstorms are anticipated to shift offshore across local waters
mid-late afternoon into the evening, some of which could be strong
with wind gusts >34 kt, frequent cloud-to-water lightning and
reduced vsbys in moderate to heavy rainfall. Additional
thunderstorms are also possible overnight, especially away from the
coast after midnight.

Sunday through Thursday: Relatively benign marine conditions to
start the week with northeast to east winds around 10 knots or less
and seas 2-3 feet. Seas will begin building later Monday into mid-
week as Hurricane Erin is forecast to pass well off the Southeast
coast. Small Craft Advisories are expected for all coastal waters
outside of the Charleston Harbor as early as Monday night, but more
likely beginning on Tuesday due to seas. Hazardous seas will
maintain Advisories through much, if not the remainder, of the
period, although they should start subsiding on Thursday as Erin
pulls away from the region.

Rip Currents/High Surf: A period of dangerous beach conditions is
expected next week as Hurricane Erin passes well offshore.
Increasing long period swell will result in an enhanced risk of rip
currents at all area beaches, beginning Monday and continuing
through much of the week. A Moderate Risk is currently forecast for
Monday. In addition, large breaking waves are expected and a High
Surf Advisory could be needed towards mid week.

&&

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

&&

$$

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