266
FXUS62 KCHS 060322
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1122 PM EDT Sat Jul 5 2025

.SYNOPSIS...
Tropical Storm Chantal is forecast to approach the South
Carolina coast tonight and move onshore Sunday morning. High
pressure will rebuild into the area next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Late this evening: Quick update following the 11pm advisory for
Chantal and coordination with WPC regarding rainfall for the
overnight. The forecast track for Chantal continues to shift to
the east which will also take the axis of heaviest rain further
east as well. This combined with radar imagery and short term
model guidance supporting considerably lower rainfall amounts,
we have updated QPF for the overnight. Additional rainfall
amounts should mostly be limited to the Charleston Tri-County
region and primarily eastern Berkeley and upper Charleston
counties. Expect additional rainfall amounts of no more than
0.25-0.50" for this area, except along the Santee River where
localized amounts of up to an inch will be possible.
Accordingly, WPC has updated the Excessive Rainfall Outlook
through Sunday morning to only include far upper Charleston
County in the Marginal Risk area.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday: The latest NHC forecast has Tropical Storm Chantal
making landfall by Sunday 12Z/8AM EDT near the mouth of the
South Santee River, weakening to a Tropical Depression as it
moves across southwestern South Carolina. This will continue
chances for scattered showers showers, expanding southwards into
southeast Georgia throughout the morning as the TD continues to
weaken. While the threat has decreased slightly now that we`re
dependent on wrap around moisture making it around the surface
low, precipitable water values of 2-2.5 inches combined with
repeated/training storms will continue the threat of locally
heavy rainfall. Otherwise, aside from areas in northern
Charleston county where winds will be a touch stronger due to
proximity to the weakening TS, expect winds to swing around from
west-northwesterly to south-southwesterly throughout the day,
with gusts into the teens. Highs in the mid 80s to lower 90s are
expected, with partly to mostly cloudy skies throughout the
day.

Monday and Tuesday: As weak ridging occurs aloft, the remnants
of Chantal will continue to lose influence over the area. In
addition to the expected daily sea-breeze, some weak shortwaves
propagating through the southwesterly flow in the lower-levels
will keep chances for low pops in the afternoon hours. While
shear remains weak and there is a lack of strong forcing,
chances for severe weather remain low, though given 1000-2000
J/kg of CAPE the chances are non-zero. Max temperatures for
Monday are in the mid 90s, rising into the mid to upper 90s on
Tuesday, with heat index values getting closer to the Heat
Advisory criteria of 108 deg F.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Weak flow within subtle ridging aloft will persist along with
no discernible synoptic features. The forecast will be dominated
by a typical summertime sea breeze pattern, with scattered
showers and thunderstorms possible each day especially in the
afternoon and early evening when instability is maximized. Highs
are forecast to creep back up to the mid 90s inland of the
coast, with heat indices in the lower to mid 100s.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
The 00z TAF period begins with VFR conditions in place, though
there are more showers developing around KCHS and KJZI. Perhaps
the biggest forecast challenge concerns the potential for low
stratus to develop and spread across the area, as suggested by
model guidance. Chance for flight restrictions due to stratus
are highest at KCHS and KJZI, and will likely dip into the IFR
range. For KCHS and KJZI, the TAF`s depict MVFR ceilings by 03z
and IFR by 06z. For KSAV, the arrival should be later and we
held off until 12z there. Periodic showers through the night
could also bring some short-lived reductions in visibilities
with moderate or even heavy rain. Stratus could linger through
much of the morning on Sunday, but should start to lift and
scatter as the center of Chantal gets north of the area. Thanks
to the passage of Chantal, winds will gradually turn more
northerly, then northwesterly and then southwesterly. Though
shower and thunderstorm potential should be limited by late
morning there could be isolated showers and thunderstorms along
the coast by mid to late afternoon.

Extended Aviation Outlook: Brief ceiling/vsby restrictions
possible through Wednesday due to scattered showers and
thunderstorms.

&&

.MARINE...
Tonight, the pressure gradient between Chantal and high
pressure ridged across the western Carolinas will peak this
afternoon, then may gradually decrease into the overnight hours.
NHC track and wind forecast for Chantal indicates that a band
of strong winds around the system`s center will approach the
northern Charleston County coast late tonight, bringing another
round of stronger winds closer to the track line. Please see
NHC`s latest advisory.

Tropical Storm Warnings are in effect for the SC nearshore
waters with a Tropical Storm Watch across the CHS Harbor. SC
nearshore waters should see NE winds 25-30 kt with gusts 40 kts
through late tonight. As Chantal tracks over the northern
Charleston County nearshore waters, winds around the center may
strengthen with gusts around 45 kts. As a result of the strong
winds, seas will build through the near term, reaching 8-10 ft
across the Charleston nearshore waters after midnight.
Elsewhere, conditions will remain with solid Small Craft
Advisory conditions, featuring gusts around 30 kts and seas 6 to
7 ft. Wave heights within the CHS Harbor between 1 to 3 ft.

Sunday through Thursday: Conditions will drastically improve on
Sunday as the flow briefly becomes offshore with the tropical
system located to the north. Winds will then settle into a SW
flow by Monday as high pressure rebuilds. Seas will remain
elevated across the Charleston County nearshore waters Sunday
before lowering to 3-4 ft by Monday. Elsewhere, seas 3-4 ft will
decrease to 2-3 ft by Monday night. No marine
concerns/headlines expected beyond Sunday.

Rip Currents: A Moderate Risk for rip currents exists for all
area beaches on Sunday due to residual swell, decreasing back to
Low Risk on Monday.

High Surf: Building northeast winds will push seas off the
Charleston County coast to 5-8 ft with local NWPS output showing
breaking waves of 4-6 ft occurring by this afternoon and
continuing through the night along parts of the Charleston
County beaches. The beaches of most concern are Kiawah Island,
Folly Beach, Sullivans Island and Dewees Island. A High Surf
Advisory has been posted from 2 PM today until 8 AM Sunday.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Tropical Storm Watch for SCZ050.
     High Surf Advisory until 8 AM EDT Sunday for SCZ050.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for AMZ330.
     Tropical Storm Watch for AMZ330.
     Tropical Storm Warning for AMZ350-352.
     Small Craft Advisory until 6 AM EDT Sunday for AMZ354-374.

&&

$$

NEAR TERM...BSH
SHORT TERM...APT
LONG TERM...APT
AVIATION...BSH
MARINE...APT/NED