633
FXUS62 KCHS 192330
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
730 PM EDT Tue Aug 19 2025

.SYNOPSIS...
Weak high pressure will build into the region early this week
as Hurricane Erin passes well offshore through the middle of
the week. The pattern may become more unsettled again late week
and into this weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
The mid-levels will consist of a ridge to the west and Hurricane Erin
to the southeast. At the surface, High pressure will be to our
west with Erin well to our southeast. This is keeping decent
moisture across our area with PWATs ~2". Models have convection
through this evening. The severe threat is low, but locally
heavy rainfall is possible. The overnight should be dry. Lows
will be in the low to mid 70s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Upper level ridging weakens slightly as Hurricane Erin makes
its closest approach to the coast on Wednesday, though still
remaining roughly 500 miles out to sea. Rain bands associated
with Erin will therefore most likely remain off to the near-
shore Atlantic waters, though areas along the coast have a 30%
chance for seeing a shower/storm throughout the day. Otherwise,
expect semi-breezy northerly winds sustained near 10 mph with
gusts into the teens to lower 20s, strongest along the coast,
with temperatures remaining seasonal in the upper 80s to mid
90s. Dewpoints look to remain in the lower 70s, keeping max heat
index values largely in the 90s.

On Thursday, Erin will be moving off to our northeast while a
weak surface high pressure develops over southern Georgia. As
this happens, winds will be swinging from northerly to west-
northwesterly before decreasing throughout the afternoon hours.
May see a round of scattered showers and thunderstorms at about
a 30% chance, though weak upper level ridging will act to keep
coverage fairly scattered. Afternoon highs in the lower to upper
90s expected, with heat index values highest along the coast to
near 100.

Overnight into Friday, weak shortwaves move into the flow
overhead while a surface high pressure over the Great Lakes
region which is sending a weak cold front through the region
overnight. Both of these features will allow for chances for
showers and thunderstorms to expand in areal coverage throughout
the day on Friday. With the weak cold front through the area to
the south and chances for rain throughout the day, temperatures
will be a touch cooler in the mid 80s to lower 90s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Chances for showers and thunderstorms continue into the
weekend, as additional weak shortwaves continue to move across
the region and the front remains situated to our south. There is
decent consensus for a weak low pressure to develop along the
front and into the near- shore Atlantic waters on Saturday and
Sunday, with greatest rain chances on Saturday. Ensemble
situational awareness tables (ESATs) indicate PWATs rise back up
to near 2 inches by Saturday, remaining near 2 inches through
Sunday, just shy of the 90th percentile of climatology
indicating a very moist atmosphere. NBM probabilities for an
inch are highest just south of the South Carolina/Georgia,
border at around 60%, dropping to 30% up to the I-26 corridor
and also remaining near 30% along the Altamaha River. Thus,
locally heavy rainfall does look to become possible again on
Saturday, possibly lingering into Sunday.

After some cooler temperatures over the weekend in the 80s and
lower 90s, temperatures warm back up to normal in the lower 90s
area-wide next week.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Prior to the 0Z TAFs, isolated showers and thunderstorms were
passing in the vicinity of KCHS and KSAV. These storms should
drift inland and outside the vicinity of the terminals by 1Z.
North-northeast winds should remain light late this evening into
late tonight. During the pre-dawn hours, northeast winds should
strengthen between 5 to 10 kts. During the daylight hours,
winds show remain from the northeast, increasing to around 10
kts, gusts into the teens expected at KJZI. Simulated satellite
products indicates that the terminals will remain under BKN
cirrus sourced from Hurricane Erin after sunrise Wednesday.

Extended Aviation Forecast: Brief flight restrictions possible at
KCHS/KJZI/KSAV with afternoon showers and/or thunderstorms.

&&

.MARINE...
Through Tonight: The coastal waters will be between High
pressure inland and the broader circulation around Hurricane
Erin offshore. This will cause winds to gradually strengthen, with
gusts up to 25 kt by sunrise Wednesday. Likewise, seas will
build as long period swell originating from Erin will continue
to move through our waters. The highest seas will be at sunrise
Wednesday. Small Craft Advisories remain in effect for all of
our waters, except Charleston Harbor.

Wednesday and Thursday: As the swell from Hurricane Erin
continues to mix into the marine zones, seas will build to 7 to
10 ft with some 12 footers possible across the outer nearshore
waters (10 to 13 ft across the outer Georgia waters) as Erin
reaches its closest proximity on Wednesday afternoon. This swell
from Erin will be on tap through Friday and will cause a long
period of dangerous surf and rip currents. Along with the swell,
strong north-northeasterly winds will increase to 20 to 25 kts
with gusts up to 30 kts by Wednesday morning and continue
through most of Thursday.

Hazardous seas will maintain Small Craft Advisories through at
least Friday, although seas should start subsiding as Erin pulls
away from the region.

Friday through Sunday: Expect the swell to slowly back off as
winds switch to east-southeasterly at 10 to 15 kts. Periodic
showers and thunderstorms are possible throughout the weekend.

Rip Currents/High Surf: The combination of increasing northeast
winds along the coast and impressive long period swell
associated with Erin will create ideal conditions for dangerous
conditions within the surf zone, both for the rest of today and
for Wednesday. A High Risk of rip currents is in effect for all
beaches today and again on Wednesday. There is also the
potential for large breaking waves of 5 feet or higher, with
chances increasing through the day and remaining high through
Thursday. A High Surf Advisory is in effect for the entire
southeast SC/GA coastline through Thursday.

&&

.TIDES/COASTAL FLOODING...
Increasing northeast winds and impressive swells associated with
Hurricane Erin passing well offshore will result in higher tidal
levels through at least Thursday. Minor to moderate coastal flooding
is expected with the evening high tide cycles, beginning with this
evenings high tide. The highest chance for moderate coastal flooding
will come Wednesday and Thursday at the Charleston Harbor tide
gauge, though the reasonable worst case scenario does peak into
major on Wednesday evening. At Fort Pulaski, the highest chance for
minor flooding is on Wednesday evening, though guidance currently
keeps the water level just shy of minor flood stage. Coastal Flood
Advisories will almost certainly be needed each evening for portions
of the coast.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents through Wednesday evening for GAZ117-119-
     139-141.
     High Surf Advisory until 8 PM EDT Thursday for GAZ117-119-139-
     141.
SC...High Risk for Rip Currents through Wednesday evening for SCZ048>051.
     High Surf Advisory until 8 PM EDT Thursday for SCZ048>051.
MARINE...Small Craft Advisory until 2 PM EDT Friday for AMZ350-352-354.
     Small Craft Advisory until 8 AM EDT Saturday for AMZ374.

&&

$$

NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...