518
FXUS62 KCHS 190608
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
208 AM 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 TONIGHT/...
Today: Aloft, not much change to the pattern as the forecast
area sits in the area between the ridge to the west and Erin to
the southeast. At the surface, the forecast area will be
situated between the periphery of the circulation around Erin
and high pressure ridging down the East Coast. Overall, the
expectation is for a more active day than we saw on Monday. This
uptick in convective coverage will be fueled by a narrow zone
of precipitable water values up to 2 inches that will extend
down from eastern NC, through the SC Pee Dee region, and across
inland portions of the Lowcountry and southeast GA. The
background flow will primarily be northeasterly, but the sea
breeze should provide sufficient convergence for convective
initiation. We should see showers and storms start developing
along the coast in the noon-2pm time period, then see the focus
steadily shift inland through the rest of the afternoon and into
the early evening. Though the convective coverage isn`t
expected to be too extensive, there will be potential for some
locally heavy rainfall along the corridor that extends from
around Moncks Corner, to Summerville, to Walterboro, to Hampton,
and to the Statesboro area. Most places will see less than half
an inch of rain, but this there could be isolated amounts in
this corridor of 1- 2 inches. Temperatures are expected to be a
few degrees less today across southeast SC, with most places
topping out around 90. Southeast GA should see another day of
low to mid 90s. Heat index values should mostly top out around
100, with a corridor along the coastal corridor where low 100`s
are likely.

Tonight: Convection from the afternoon should gradually shift
inland and diminish through the evening. Then for the late night
hours, the area should be dry. Lows are forecast to range from
the low to mid 70s.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
While located on the eastern periphery of this mid-lvl ridge,
drier air will continue to be advected into the region and allow
for a less active Wednesday and Thursday with PoPS kept ~30%
(highest along the immediate coastline). Simultaneously,
powerful Hurricane Erin will pass well offshore (nearly 500
miles) to the east of the region on Wednesday and Thursday. Even
though Erin will likely remain well offshore, we will still
experience impacts from the system. This large swell associated
with Erin will continue to slowly work itself across the marine
waters and allow for dangerous surf and rip currents through at
least Friday (see marine section below). Heading into Friday,
mid-lvl trough swings eastward towards the region and drops a
cold front across the region. This will allow for a surge of
moisture to return. Expect scattered to numerous showers on
Friday afternoon with PoPs in the 60-75% range (highest across
SE Georgia). Highs will be near normal as temperatures are
expected to reach into the low to mid 90s on Wednesday and
Thursday. However, as this cold front drops across the region,
expect highs to be in the mid to upper 80s across SE South
Carolina and low 90s across SE Georgia. Lows will be slightly
above normal with temperatures only dropping into the low to mid
70s inland and then mid to upper 70s along the coastline.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Hurricane Erin will continue to move north-northeastward across
the Atlantic and become further and further away from the
region throughout the period. This aforementioned cold front
could potentially stall across the region through the weekend. A
good amount of moisture will linger along with the front and
allow scattered to numerous showers and thunderstorms to develop
each afternoon/evening (with the highest chances on Saturday).
Temperatures finally cool off a bit this weekend as highs will
only reach into the mid to upper 80s. However on Monday and
Tuesday, temperatures will go back to near normal for this time
of the year.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
The 06z TAF period begins with VFR conditions at KCHS, KJZI,
and KSAV. The main forecast challenge concerns thunderstorm
chances this afternoon. Thunderstorms should start developing in
the early afternoon hours along the coast and then steadily
shift inland into the evening. Current thinking is that the
window of potential thunderstorm impacts will be earliest at
KJZI (17-20z), then a bit later for KCHS (19-22z) and KSAV
(20-23z). A brief period of MVFR or IFR conditions will be
possible during this thunderstorm time window. Otherwise, VFR.

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

&&

.MARINE...
Today through tonight: The local waters will gradually start to
get increasingly pinched between the broader circulation around
Erin and high pressure inland. During the daytime hours, winds
will mostly be northeasterly and should gradually increase to
become 15-20 knots by late afternoon. Overnight, winds will
continue to gradually strengthen, nearing a solid 20 knots with
gusts up to 25 knots by sunrise Wednesday. Increasing seas will
be the most impactful aspect, as long period swell driven by
Erin will continue to increase. By late today seas are expected
to be 4-7 feet across the nearshore waters and 7-10 feet in the
outer waters. Then by sunrise Wednesday, guidance supports 5-9
feet across the nearshore waters and 8-11 feet across the outer
waters. Small Craft Advisories remain in effect for all waters,
excluding Charleston Harbor.

Wednesday and Thursday: As the swell from Hurricane Erin
continues to mix into the marine zones, seas will build to 8 to
10 ft with some 12 footers possible across the nearshore waters
(10 to 14 ft across the outer Georgia waters) as Erin reaches
its closest proximity by 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 Advisories through at least
Friday, although seas should start subsiding as Erin pulls away
from the region.

Friday through Sunday: As Hurricane Erin moves north-
northeastward and pulls further away, expect the swell to slowly
back off as winds switch to east-southeasterly at 10 to 15 kts.

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. A High Risk of rip currents is
in effect for all beaches today and again on Wednesday. Also,
the potential for large breaking waves of 5 feet or higher will
increase through the day and a High Surf Advisory is in effect
for the entire southeast SC/GA coastline through Thursday.

&&

.TIDES/COASTAL FLOODING...
Increasing northeast winds and impressive swell 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 today. The best chance for moderate coastal flooding
will come Wednesday and Thursday at the Charleston Harbor tide
gauge. Coastal Flood Advisories will almost certainly be needed
each evening for much/all of the coast.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents from 8 AM EDT this morning through this
     evening for GAZ117-119-139-141.
     High Surf Advisory from 8 AM this morning to 8 PM EDT Thursday
     for GAZ117-119-139-141.
SC...High Risk for Rip Currents from 8 AM EDT this morning through this
     evening for SCZ048>051.
     High Surf Advisory from 8 AM this morning to 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...BSH
SHORT TERM...Dennis
LONG TERM...Dennis
AVIATION...BSH/Dennis
MARINE...BSH/Dennis