620
FXUS62 KCHS 311114
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
714 AM EDT SUN MAY 31 2026
WHAT HAS CHANGED
ALL SECTION HAVE BEEN UPDATED.
KEY MESSAGES
- 1) LOCALLY HEAVY RAINFALL AND ISOLATED FLASH FLOODING
POSSIBLE AGAIN TODAY, ESPECIALLY ACROSS SOUTHEAST GEORGIA.
- 2) UNSETTLED WEATHER CONDITIONS PERSIST ACROSS PORTIONS OF
SOUTHEAST GEORGIA AND THE SOUTH CAROLINA LOWCOUNTRY ON MONDAY
AND TUESDAY.
- 3) ELEVATED TIDAL DEPARTURES COULD YIELD MINOR COASTAL
FLOODING TO CHARLESTON AND COLLETON COUNTY COASTLINES THIS
EVENING.
DISCUSSION
KEY MESSAGE 1: LOCALLY HEAVY RAINFALL AND ISOLATED FLASH
FLOODING POSSIBLE AGAIN TODAY, ESPECIALLY ACROSS SOUTHEAST
GEORGIA.
ANOTHER ROUND OF LOCALLY HEAVY RAINFALL WILL YIELD AN ISOLATED
FLASH FLOODING THREAT THIS AFTERNOON AND EVENING, ESPECIALLY FOR
THE SOUTHEAST GEORGIA AREA. ALOFT, WEST OR WEST-NORTHWEST FLOW
WILL PREVAIL. AT THE SURFACE, HIGH PRESSURE SOURCED BACK TO THE
GREAT LAKES REGION WILL BEGIN PUSHING IN ACROSS THE CAROLINAS
EARLY THIS MORNING. AS THE HIGH BUILDS IN, IT WILL PUSH THE VERY
SUBTLE STATIONARY BOUNDARY THAT HAS LINGERED ACROSS THE AREA
THE LAST FEW DAYS BACK TO THE SOUTH AND SOUTHWEST. MOST GUIDANCE
FAVORS THE HIGH BUILDING IN AS FAR SOUTH AS THE SAVANNAH RIVER,
ALIGNING THE BOUNDARY ACROSS SOUTH AND SOUTHEAST GA FOR THE
AFTERNOON AND EVENING HOURS. THIS WILL HAVE NOTABLE IMPLICATIONS
FOR THE POTENTIAL FOCUSING OF CONVECTION LATER TODAY.
WITH THE BOUNDARY EXPECTED TO BE ALIGNED ACROSS SOUTHEAST GA
WITHIN THE BEST CONVERGENCE ZONE ON THE PERIPHERY OF THE HIGH,
ALL COINCIDENT WITH IMPRESSIVE PRECIPITABLE WATER VALUES IN THE
2.0-2.2" RANGE, CONDITIONS WILL BE SUPPORTIVE OF VERY INTENSE
RAINFALL RATES. BUT PERHAPS THE BIGGEST CONCERN FOR HEAVY
RAINFALL WILL BE THE LIKELIHOOD OF MINIMAL STORM MOTION,
ANCHORING/BACK BUILDING OF CONVECTION AS MODEL SOUNDINGS SHOW
~20 KTS OF MID-LEVEL FLOW ATOP EASTERLY FLOW IN THE SUB-850 MB
LAYER. THEREFORE IT FOLLOWS THAT THE HREF CONTAINS 3-HOUR
PROBABILITIES OF >1" WELL INTO THE 50-70 PERCENT RANGE AND
PROBABILITIES OF >3" OF 30-50 PERCENT. THE MAIN AREA OF CONCERN
IS SOUTHEAST GA MAINLY ALONG AND SOUTH OF I-16 AND ESPECIALLY AS
YOU GET CLOSER TO THE ALTAMAHA. THIS REGION IS LOCATED WITHIN
THE WPC DAY 1 EXCESSIVE RAINFALL OUTLOOK SLIGHT RISK AREA.
CONVECTION SHOULD INITIATE AROUND MIDDAY OR THE EARLY AFTERNOON,
AND THEN PERSIST INTO THE EVENING WITH THE FOCUS GRADUALLY
SHIFTING FURTHER TO THE SOUTH WITH TIME. GIVEN THE EXCEEDINGLY
ACTIVE AND WET CONDITIONS IN THIS AREA OVER THE LAST WEEK OR SO,
ISOLATED FLASH FLOODING IS CERTAINLY A CONCERN.
KEY MESSAGE 2: UNSETTLED WEATHER CONDITIONS PERSIST ACROSS
PORTIONS OF SOUTHEAST GEORGIA AND THE SOUTH CAROLINA LOWCOUNTRY
ON MONDAY AND TUESDAY.
A STALLED FRONTAL BOUNDARY WILL CONTINUE TO LINGER ACROSS THE
SOUTHEAST COMBINED WITH A VERY MOIST AIRMASS CHARACTERIZED BY
PWAT VALUES RANGING FROM 1.5 TO 2.0 INCHES. THIS WILL KEEP THE
PATTERN RATHER UNSETTLED ON MONDAY AND TUESDAY.
MONDAY: EXPECT SHOWER AND THUNDERSTORM COVERAGE TO INCREASE
THROUGH THE LATE MORNING AND AFTERNOON ESP. ACROSS THE SOUTH
CAROLINA LOWCOUNTRY. WHILE ACTIVITY REMAINS SOMEWHAT
DISORGANIZED, SLOW CELL MOTIONS, BOUNDARY INTERACTIONS, AND
LOCALIZED TRAINING COULD STILL PRODUCE POCKETS OF HEAVY
RAINFALL. THIS WILL YIELD LOCALIZED FLOODING IN URBAN AREAS AND
LOW-LYING AREAS THROUGH THE LATE MORNING AND INTO THE EVENING.
HOWEVER, CONVECTION SHOULD GRADUALLY DIMINISH OVERNIGHT WITH
SOME LINGERING SHOWERS PERSISTING NEAR THE COASTLINE.
TUESDAY: AS A LOW PRESSURE SYSTEM TRIES TO DEVELOP OFFSHORE OF
THE SOUTH CAROLINA COASTLINE, THE AFOREMENTIONED FRONTAL
BOUNDARY WILL SETTLE FARTHER SOUTHWARD ACROSS NORTHERN FLORIDA.
THIS SET-UP WILL SHIFT THE FOCUS TO SOUTHEAST GEORGIA ON
TUESDAY, AND EXPECT SHOWERS AND THUNDERSTORM COVERAGE TO
INCREASE THROUGH THE LATE MORNING AND AFTERNOON ESP. NEAR AND
SOUTH OF I-16. THE OVERALL FLOODING THREAT APPEARS LIMITED,
HOWEVER LOCALIZED TRAINING AND REPEATED ROUNDS OF RAINFALL COULD
BE STILL POSSIBLE WHERE OUTFLOW BOUNDARIES BECOME ESTABLISHED.
COVERAGE SEEMS TO BE LITTLE LESS ACROSS THE SOUTH CAROLINA
LOWCOUNTRY COMPARED TO MONDAY AS DRY, NORTHEASTERLY FLOW BECOMES
ESTABLISHED IN THE NORTHERN ZONES OF THE CWA. SIMILAR TO
MONDAY, CONVECTION SHOULD GRADUALLY DIMINISH OVERNIGHT WITH SOME
LINGERING SHOWERS POSSIBLE NEAR THE COASTLINE.
KEY MESSAGE 3: ELEVATED TIDAL DEPARTURES COULD YIELD MINOR
COASTAL FLOODING TO CHARLESTON AND COLLETON COUNTY COASTLINES
THIS EVENING.
BREEZY EAST-NORTHEASTERLY FLOW WILL YIELD ELEVATED TIDAL
DEPARTURES FOR THIS EVENING'S HIGH TIDE (9:05PM). THE RECENT
GUIDANCE FROM PETSS10, PETSS50, AND ETSS SUGGESTS THIS EVENING'S
HIGH TIDE WILL LIKELY RANGE FROM 6.9 TO 7.2 FT MLLW AT THE
CHARLESTON HARBOR. THUS, THE FORECAST NOTES A 7.0 FT MLLW FOR
THIS EVENING'S HIGH TIDE AND THIS WILL LIKELY RESULT IN BRIEF,
SHALLOW COASTAL FLOODING IN THE USUAL PRONE FLOOD AREAS ACROSS
CHARLESTON AND COASTAL COLLETON COUNTIES. ALSO, IF SHOWERS AND
THUNDERSTORMS TRACK OVER THE REGION AROUND THE TIME OF HIGH
TIDE, THEN FLOODING COULD BE EXACERBATED. THEREFORE, THE
ISSUANCE OF A COASTAL FLOOD ADVISORY IS POSSIBLE FOR THIS
EVENING.
AVIATION /12Z SUNDAY THROUGH THURSDAY/
KCHS AND KJZI: MVFR CEILINGS HAVE ARRIVED ALONG WITH THE SURGE
OF NORTHEAST FLOW THIS MORNING. THERE IS POTENTIAL FOR CEILINGS
TO LOWER INTO THE IFR RANGE FOR A SHORT TIME PERIOD THIS
MORNING, BEFORE RETURNING TO MVFR AND LINGERING THROUGH THE DAY.
REGARDING AFTERNOON THUNDERSTORM CHANCES, THE MAIN CONCERN WILL
BE FOR AREAS FURTHER TO THE SOUTH AND SOUTHWEST SO WE HAVE KEPT
THE AFTERNOON CLEAR OF STORMS FOR NOW. A BETTER CHANCE FOR
SHOWERS AND STORMS WILL COME LATE TONIGHT, ALONG WITH CEILINGS
LOWERING TO IFR. THIS WILL PRIMARILY HAPPEN AROUND OR JUST AFTER
06Z AND CONTINUE THROUGH THE END OF THE TAF PERIOD.
KSAV: IFR CEILINGS HAVE REACHED THE TERMINAL AND WILL LIKELY
STICK AROUND FOR AT LEAST A FEW HOURS. THUNDERSTORM CHANCES ARE
EXPECTED TO RAMP UP AROUND AND JUST AFTER MIDDAY. WE HAVE
MAINTAINED A TEMPO GROUP FOR THE 18-22Z TIME PERIOD TO ACCOUNT
FOR AT LEAST MVFR CONDITIONS, THOUGH IF THE AIRPORT WERE TO TAKE
A DIRECT HIT IFR WOULD BE LIKELY WITHIN HEAVY RAINFALL REDUCING
VISIBILITIES. THE RISK OF STORMS WILL DIMINISH BY THE EARLY
EVENING. FOR THE REST OF THE PERIOD, THERE IS GOOD MODEL
AGREEMENT THAT CEILINGS WILL LOWER INTO THE IFR RANGE LATE IN
THE EVENING AND CONTINUE THROUGH THE REST OF THE NIGHT.
EXTENDED AVIATION OUTLOOK: EXPECT PERIODIC FLIGHT RESTRICTIONS
EARLY NEXT WEEK DUE TO UNSETTLED WEATHER CONDITIONS. PATCHY
OVERNIGHT FOG AND/OR STRATUS ARE ALSO POSSIBLE.
MARINE
TODAY: BREEZY EAST-NORTHEASTERLY WINDS AT 15 TO 20 KT WITH
GUSTS NEAR 30 KT POSSIBLE ACROSS THE NEARSHORE SOUTH CAROLINA
WATERS AS THE REGION BECOMES SANDWICHED BETWEEN A STALLED
FRONTAL BOUNDARY AND SURFACE HIGH PRESSURE SHIFTING OVERHEAD.
SEAS WILL ALSO INCREASE AS A SHORT-LIVED EAST-SOUTHEASTERLY
SWELL SURGES INTO THE LOCAL WATERS. EXPECT THE NEARSHORE SOUTH
CAROLINA WATERS TO PEAK TO 4 TO 6 FT IN THE AFTERNOON, WHILE THE
NEARSHORE AND OFFSHORE WATERS SOUTHEAST GEORGIA WATERS TO PEAK
3 TO 4 FT IN THE EVENING. THEREFORE, SMALL CRAFT ADVISORIES
(SCAS) HAVE BEEN MAINTAINED FOR THE NEARSHORE SOUTH CAROLINA
WATERS ON SUNDAY CONSIDERING THE ELEVATED WINDS AND SEAS. ALSO,
A SCA HAS BEEN ISSUED FOR THE CHARLESTON HARBOR AS RECENT
GUIDANCE HAS SHOWN GUSTS OF 25-26 KTS EARLY SUNDAY MORNING
THROUGH THE EARLY AFTERNOON. OPTED TO CANCEL THE SCA ACROSS THE
OUTER GEORGIA WATERS AS THE LATEST WAVE GUIDANCE HAS BACKED OFF
QUITE A BIT WITH THE STRENGTH OF THE SWELL.
MONDAY THROUGH WEDNESDAY: MODERATE NORTH-NORTHEASTERLY FLOW
WILL PERSIST ON MONDAY THROUGH TUESDAY AFTERNOON AS SEVERAL
SUBTLE DISTURBANCES EMBEDDED WITHIN SOUTHWESTERLY FLOW ALOFT
TRAVERSES ACROSS THE LOCAL WATERS. SEAS WILL RANGE FROM 2 TO 4
FT ON MONDAY, AND THEN BECOMING 3 TO 5 FT ON TUESDAY AFTERNOON.
SHIFTING THE FOCUS TO TUESDAY EVENING, THE FORECAST BECOMES
CONSIDERABLE MORE INTERESTING. AT THE BASE OF AN EAST COAST
UPPER-LVL TROUGH, A CLOSED-OFF LOW APPEARS TO SPIN UP OFFSHORE
OF THE SOUTH CAROLINA COASTLINE ON TUESDAY EVENING BEFORE SLOWLY
TRACKING OUT INTO THE MID-ATLANTIC OCEAN. THUS, THIS WILL CAUSE
FOR NORTHEASTERLY FLOW TO SURGE ON TUESDAY EVENING INTO
WEDNESDAY NIGHT. EXPECT WINDS TO RANGE FROM 20 TO 25 KT WITH
GUSTS UP 30 KT ACROSS THE NEARSHORE AND OFFSHORE SOUTH CAROLINA
AND GEORGIA WATERS. IT'S POSSIBLE TO SEE GUSTS UP 34-35 KT
ACROSS THE OFFSHORE WATERS ON WEDNESDAY MORNING. THEREFORE,
SMALL CRAFT ADVISORIES DEEM LIKELY ACROSS THE LOCAL WATERS ON
TUESDAY EVENING THOUGH WEDNESDAY NIGHT, WITH THE POTENTIAL FOR
GALE WARNINGS BEING NEEDED FOR THE OFFSHORE WATERS. STRONG EAST-
NORTHEASTERLY SWELL WILL ALSO SURGE INTO THE LOCAL WATERS
TUESDAY EVENING AND ALLOW FOR SEAS TO PEAK TO 5 TO 7 FT IN THE
NEARSHORE WATERS AND 7 TO 9 FT IN THE OFFSHORE WATERS ON
WEDNESDAY AFTERNOON. THEREAFTER, AS THE CLOSED-OFF LOW TRACKS
FURTHER OFFSHORE, MARINE CONDITIONS SHOULD GRADUALLY SUBSIDE
OVERNIGHT ON WEDNESDAY.
RIP CURRENTS: A MODERATE RISK FOR RIP CURRENTS HAS BEEN
MAINTAINED AT ALL BEACHES FOR TODAY. AND THEN, A LOW RISK IS
EXPECTED FOR MONDAY.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR AMZ340.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR AMZ360.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR AMZ362.
BSH/DENNIS
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