405
FXUS62 KCHS 131809
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
209 PM EDT SAT SEP 13 2025
SYNOPSIS
HIGH PRESSURE WILL EXTEND ACROSS THE REGION INTO NEXT WEEK.
WEAK LOW PRESSURE COULD DEVELOP OFFSHORE BY MONDAY BEFORE
MOVING FARTHER OUT INTO THE ATLANTIC BY MID NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
SATELLITE WATER VAPOR INDICATED A MID-LEVEL LOW OFF THE COAST OF GA,
SEEN AS NOTCH IN THE MOISTURE PLUME OVER THE ATLANTIC WATERS. NORTH
OF THE H5 LOW, A STREAM OF CIRRUS CLOUDS SHOULD REMAIN ACROSS
THE SC LOWCOUNTRY THROUGH THE REST OF THE DAY AND OVERNIGHT. AT
THE SFC, THE FORECAST AREA WILL REMAIN BETWEEN A SFC RIDGE
CENTERED OVER THE FOOTHILLS OF THE CAROLINAS AND BROAD LOW
PRESSURE OVER THE GULF STREAM. THIS PATTERN WILL SUPPORT
NORTHEAST WINDS AROUND 10 MPH THROUGH TONIGHT. GIVEN COOL
THICKNESSES AND THIN CLOUD COVER, MIN TEMPERATURES ARE FORECAST
TO RANGE FROM THE UPPER 50S INLAND TO THE MID TO UPPER 60S ALONG
THE COAST.
SHORT TERM /SUNDAY THROUGH TUESDAY/
THE SHARP UPPER TROUGH ALIGNED ALONG THE SOUTHEAST U.S. COAST IS
FORECAST TO GRADUALLY CUT OFF INTO AN UPPER-LEVEL CYCLONE MONDAY AS
THE FEATURE BECOMES INCREASINGLY DETACHED FROM THE MAIN BELT OF THE
WESTERLIES. AS THE UPPER LOW BECOME INCREASINGLY BETTER DEFINED,
THERE IS A CHANCE THAT WEAK SURFACE CYCLOGENESIS COULD OCCUR
SOMEWHERE OFF THE SOUTH CAROLINA COAST ALONG THE PRONOUNCED COASTAL
TROUGH NOTED WELL OFFSHORE. WHERE THE NON-TROPICAL SURFACE LOW WILL
TRACK AND ITS STRENGTH IS VERY MUCH UNCERTAIN AS MUCH WILL BE
DEPENDENT ON EXACTLY WHERE THE UPPER LOW FORMS IN RESPONSE TO
UPSTREAM RIDGING OVER THE OHIO VALLEY AND GREAT LAKES REGIONS. MOST
OF THE GFS AND ECMWF ENSEMBLE MEMBERS SHOW A MUCH WEAKER SYSTEM
COMPARED THEIR OPERATIONAL COUNTERPARTS WITH ONLY A FEW MEMBERS
SHOWING A WELL-DEFINED CYCLONE, MORE SO WITH THE ECMWF MEMBERS.
FOR SENSIBLE WEATHER, A WEDGE OF DRY HIGH PRESSURE WILL REMAIN PLACE
WITH THE GREATER CHANCES FOR ANY MEASURABLE RAINFALL HOLDING WELL
OFFSHORE WITH THE COASTAL TROUGH. A ROUGE LOW-TOPPED SHOWER OR TWO
MOVING ONSHORE CAN NOT BE COMPLETELY RULED OUT ALONG PARTS OF THE
GEORGIA COAST WHERE LOW-LEVEL STEERING TRAJECTORIES ARE THE MOST
FAVORABLE DUE TO THE ORIENTATION OF THE COASTLINE, BUT DRY
CONDITIONS WILL GENERALLY PREVAIL ACROSS THE SOUTH CAROLINA
LOWCOUNTRY INTO SOUTHEAST GEORGIA. FOR MONDAY, THIS PART OF THE
FORECAST WILL BE HEAVILY INFLUENCED BY ANY POTENTIAL SURFACE LOW
THAT DEVELOPS OFFSHORE. GIVEN THE ONGOING UNCERTAINTY HERE, THERE
WAS NO REASON TO DEVIATE FROM THE 13/01Z NBM WHICH SHOWS NET
MOISTURE VALUES INCREASING SLIGHTLY ACROSS THE COAST WITH RAIN
CHANCES INCREASING EVER SO SLIGHTLY, ESPECIALLY OVER THE SOUTH
CAROLINA LOWCOUNTRY ALONG/EAST OF I-95. POPS WILL RANGE FROM 20-30%
EAST OF I-95 (HIGHEST CHARLESTON TRI-COUNTY) WITH 10% OR LESS
ELSEWHERE. HIGHS WILL GENERALLY REMAIN THE LOWER-MID 80S THROUGH THE
PERIOD WITH SOME UPPER 80S CREEPING IN ACROSS FAR INTERIOR SOUTHEAST
GEORGIA BY MONDAY. LOWS WILL DROP IN THE LOWER-MID 60S INLAND WITH
UPPER 60S/LOWER 70S AT THE BEACHES EACH NIGHT. A FEW MORE SHELTERED
SPOTS COULD DROP INTO THE UPPER 50S, ALTHOUGH THESE INSTANCES SHOULD
REMAIN FAIRLY ISOLATED.
LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/
MOSTLY QUIET CONDITIONS WILL PERSIST THROUGH MUCH OF THE UPCOMING
WEEK AS THE UPPER LOW ACROSS THE CAROLINAS GRADUALLY WEAKENS AND
EJECTS OUT TO THE NORTHEAST BY WEDNESDAY. THE INLAND HIGH PRESSURE
WEDGE IS FORECAST TO STRENGTHEN AS RIDGING BUILDS IN BEHIND THE
DEPARTING UPPER LOW. ANY MEANINGFUL CHANCE FOR MEASURABLE RAINFALL
WILL GENERALLY REMAIN CONFINED TO THE COASTAL WATERS AND ESPECIALLY
NEAR THE WEST WALL OF THE GULF STREAM. HIGH TEMPERATURES WILL WARM
THROUGH THE PERIOD, PEAKING IN THE UPPER 80S/LOWER 90S THURSDAY AND
FRIDAY. OVERNIGHT LOWS WILL FOLLOW A SIMILAR PATTERN WITH LOWS
DROPPING INTO THE 60S AWAY FROM THE BEACHES EACH NIGHT.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
18Z TAFS: VFR. AT THE SFC, THE TERMINALS WILL REMAIN BETWEEN A
SFC RIDGE CENTERED OVER THE FOOTHILLS OF THE CAROLINAS AND BROAD
LOW PRESSURE OVER THE GULF STREAM. THIS PATTERN WILL SUPPORT
GUSTY NORTHEAST WINDS THROUGH THE REST OF THIS AFTERNOON,
SETTLING TO 5 TO 10 KTS THIS EVENING AND TONIGHT. NORTHEAST
WINDS MAY DEVELOP GUSTS INTO THE TEENS BY MID-MORNING SUNDAY.
EXTENDED AVIATION FORECAST: THERE ARE NO HIGH CONFIDENCE
CONCERNS.
MARINE
TODAY AND TONIGHT: NORTHEAST WINDS HAVE STARTED TO COME UP ACROSS
ALL WATERS THIS MORNING WITH BUOY 41008 NOW GUSTING TO 25 KT. AS
SUCH, THE SMALL CRAFT ADVISORY IS NOW IN EFFECT FOR ALL ATLANTIC
WATERS. CHARLESTON HARBOR REMAINS OUT OF THE ADVISORY AT THIS TIME.
A WEAK SURFACE LOW IS FORECAST TO FORM WELL OFF THE COAST OF SC THIS
AFTERNOON, BUT IT WILL HAVE THE AFFECT OF TIGHTENING THE PRESSURE
GRADIENT ACROSS THE OPEN ATLANTIC WATERS. THE OFFSHORE GA WATERS
BEYOND 20 NM COULD HAVE GUSTS APPROACHING GALE (AROUND 30 KT).
SUNDAY THROUGH THURSDAY: PINCHED GRADIENT CONDITIONS BETWEEN INLAND
HIGH PRESSURE AND A COASTAL TROUGH OFFSHORE LOOK TO HOLD THROUGH MUCH
OF THE WEEK. THERE IS A CHANCE THAT WEAK LOW PRESSURE COULD DEVELOP
OFFSHORE BY MONDAY, BUT ITS STRENGTHEN AND TRACK ARE HIGHLY
UNCERTAIN. ANY LOW THAT FORMS COULD HAVE A LOCAL IMPACT, BUT TO WHAT
DEGREE REMAINS UNKNOWN. FOR NOW, NORTHEAST WIND AND WIND GUSTS AS
WELL AS SEAS WILL REMAIN VERY NEAR SMALL CRAFT ADVISORY CONDITIONS
FOR ALL BUT THE CHARLESTON HARBOR THROUGH THE WEEK AND THE END TIMES
OF THE VARIOUS ADVISORIES THAT ARE ALREADY IN EFFECT HAVE BEEN
ADJUSTED TO REFLECT THIS. WINDS AND WIND GUSTS MAY FLIRT WITH
ADVISORY LEVELS IN THE CHARLESTON HARBOR, ESPECIALLY NEAR THE HARBOR
ENTRANCE, BUT CONFIDENCE IS TOO LOW TO HOIST ANY ADVISORY FLAGS JUST
YET.
RIP CURRENTS: THE COMBINATION OF PERSISTENT NORTHEAST WINDS,
ASTRONOMICAL FACTORS, AND ELEVATED SWELL WILL YIELD A HIGH RISK
OF RIP CURRENTS AT ALL AREA BEACHES FOR THE AFTERNOON.
FOR SUNDAY, GUSTY NORTHEAST WINDS WILL PERSIST WITHIN PINCHED
GRADIENT CONDITIONS. GUSTY NORTHEAST WINDS COUPLED WITH 4-5 FT
SWELLS WITH 8 SEC PERIODS WILL A CONTINUED HIGH RISK FOR RIP
CURRENTS ALONG THE GEORGIA BEACHES AND A MODERATE RISK FOR THE SOUTH
CAROLINA BEACHES.
TIDES/COASTAL FLOODING
TOTAL WATER LEVELS WILL REMAIN ELEVATED THROUGH THE MIDDLE OF NEXT
FROM LARGE TIDAL DEPARTURES DUE TO A PINCHED PRESSURE GRADIENT WITH
ELEVATED NORTHEAST WINDS. THE POTENTIAL FOR COASTAL FLOODING WILL
CONTINUE THOUGH THROUGH THE WEEKEND, ESPECIALLY FOR COASTAL PORTIONS
OF CHARLESTON AND COLLETON COUNTIES.
CHS WATCHES/WARNINGS/ADVISORIES
GA...HIGH RISK FOR RIP CURRENTS THROUGH SUNDAY EVENING FOR GAZ117-119-
139-141.
SC...HIGH RISK FOR RIP CURRENTS UNTIL 8 PM EDT THIS EVENING FOR
SCZ048>051.
COASTAL FLOOD ADVISORY UNTIL 3 PM EDT THIS AFTERNOON FOR
SCZ049-050.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR AMZ350-352.
SMALL CRAFT ADVISORY UNTIL 2 AM EDT MONDAY FOR AMZ354.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT TUESDAY FOR AMZ374.
NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...HAINES
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