Hilton Head Island, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

877
FXUS62 KCHS 090149
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
949 PM EDT Fri Aug 8 2025

.SYNOPSIS...
A front will linger south of the area this weekend, while high
pressure remains centered well to the north.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Quick update to expire the Coastal Flood Advisory.

Early this evening: Radar imagery shows pockets of showers
generally moving to the west within the low-level east to
northeast flow across the area on the periphery of the inland
high. Precipitable water values are on the rise as now the
entire coastal corridor is within an area of 2-2.25 inches.
There will continue to be sufficient low-level moisture
transport and convergence to support periodic clusters of
showers that develop and push inland through the early morning
hours. The showers should be progressive enough to prevent too
much concern for flooding issues, but if we start to see showers
training over the same areas rainfall amounts could pile up to
be an inch or more.

Of particular note is the potential highlighted by incoming hi-
res model runs that a band of heavy showers (with an embedded
isolated thunderstorm) could start to organize across the waters
late tonight and perhaps take aim at the southeast SC coast,
especially Charleston County. Model guidance would suggest that
this might not be an issue until after daybreak, but could
arrive along portions of the coast as early as 4-6 am. While
there is considerable uncertainty regarding the intensity and
placement of such a band, the HREF 3-hour rainfall probabilities
of 1 inch or more are 50-70 percent along much of the coast, and
even shows 3 inch or more probabilities of 10-30 percent. This
is certainly something to keep an eye on through the evening,
especially since it could coincide with the morning high tide
cycle (~8:30 am). We will continue to assess incoming hi-res
runs this evening and update as needed.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
A surface wedge of high pressure extending along the ridge of
the Appalachians, will support a relatively unusual August cold
air damming (CAD) setup. As a result, temperatures will remain
below normal through the weekend, with highs in the low to mid
80s under persistent cloud cover. Overnight lows will generally
hold in the low to mid 70s.

A stationary front draped across the northern Florida Peninsula
will provide a persistent focus for convection, enhanced by
deep moisture and Atlantic convergence. PWATs will remain
elevated around 2.25 inches through Monday. Scattered to
numerous showers and thunderstorms are expected each afternoon
and evening, with development likely initiating along the
inland-moving sea breeze. While instability will be sufficient
for thunderstorm development (SBCAPE peaking around 1500-2000
J/kg), weak shear and limited storm organization will prevent
any severe threat. The primary concern remains locally heavy
rainfall, especially given slow storm motions (5-10 kt). The
highest rainfall totals are expected along the coastal areas,
where storms are likely to initiate and where greater convective
coverage, particularly offshore, could enhance activity.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Upper-level ridging will gradually build overhead next week,
leading to erosion of the inland surface wedge. As the ridge
strengthens, temperatures will climb into the low to mid 90s by
Thursday. This will bring a return to a more typical summertime
pattern featuring hot, humid conditions and daily afternoon
thunderstorms. Heat index values could climb into the triple
digits by midweek.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
The 00z TAF period begins with VFR conditions in place at KCHS,
KJZI, and KSAV, but the forecast looks to be quite challenging.
There are currently showers passing near KCHS and could also
pass near KJZI and KSAV through the late evening hours. Any
showers that move across the terminal will be capable of
producing brief moderate to heavy rainfall with MVFR conditions.
Model guidance again suggests that MVFR to IFR stratus will be
an issue late tonight, but confidence isn`t quite as high as the
last couple of nights thanks to the expected increased shower
activity through the night. We have gone with prevailing MVFR
ceilings by 08z at all 3 sites, with IFR ceilings by 10z. There
is also increasing concern for a band of moderate to heavy
showers to develop and align along or near the SC coast close to
daybreak and through the mid to late morning. If this occurs, it
could disrupt the developing stratus but still produce a period
of MVFR to IFR ceilings and visibilities, especially at KCHS and
KJZI. This activity could linger through late morning or
midday, and current thinking is that VFR will prevail for the
afternoon.

Extended Aviation Outlook: Brief flight restrictions will be
possible through the weekend and into early next week with
afternoon showers/thunderstorms.

&&

.MARINE...
Tonight: Northeast flow will generally prevail through tonight
in between high pressure inland and a subtle coastal trough
offshore. Speeds will average in the 10-15 knot range, although
could be briefly higher in any shower/thunderstorm that occurs.
Seas will be 2-3 feet.

Saturday through Wednesday: Surface high pressure to the north
and well offshore will maintain east to northeast winds around
10-15 kt. Seas will range from 2 to 3 ft with no significant
marine concerns anticipated.

&&

.TIDES/COASTAL FLOODING...
Upcoming full moon (8/9) and lunar perigee (8/14), will
contribute to increasing astronomical tide values in the coming
days. At Charleston, the astronomical evening high tide will
be at or just over 6 ft MLLW with each evening high tide cycle
through Monday.

The observed high tide is expected to peak right around 7 ft
MLLW both Saturday and Sunday evening. Coastal Flood Advisories
could be needed for Charleston and coastal Colleton counties.

&&

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

&&

$$

NEAR TERM...BSH
SHORT TERM...BRS
LONG TERM...BRS
AVIATION...BRS/BSH
MARINE...BRS/ETM