100
FXUS62 KCHS 211851
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
251 PM EDT MON SEP 21 2026
WHAT HAS CHANGED
ALL SECTIONS HAVE BEEN UPDATED.
KEY MESSAGES
- 1) DAILY THUNDERSTORMS ARE EXPECTED ACROSS SOUTHEAST GEORGIA
AND SOUTHEAST SOUTH CAROLINA TODAY WITH RAIN CHANCES
INCREASING TUESDAY INTO WEDNESDAY.
- 2) A COLD FRONT COULD BRING A THREAT OF STRONG THUNDERSTORMS
WEDNESDAY AFTERNOON, AND WILL BE FOLLOWED BY COOLER WEATHER
AND GUSTY WINDS.
DISCUSSION
KEY MESSAGE 1: DAILY THUNDERSTORMS ARE EXPECTED ACROSS SOUTHEAST
GEORGIA AND SOUTHEAST SOUTH CAROLINA TODAY WITH RAIN CHANCES
INCREASING TUESDAY INTO WEDNESDAY.
TODAY AND TONIGHT: LITTLE CHANGE IN THE OVERALL PATTERN HAS OCCURRED
DURING THE PAST 24 HOURS IN REGARDS TO AN UPPER LOW MEANDERING OVER
FLORIDA AND DEEP MOISTURE ADVECTING ACROSS THE LOCAL AREA WITH PWATS
NEAR 2 INCHES. HOWEVER, A WEAK FORCING SETUP SHOULD LIMIT CONVECTIVE
ACTIVITY MORESO THAN THE PREVIOUS DAY TO A FEW SHOWERS AND/OR
THUNDERSTORMS ALONG AN INLAND MOVING SEABREEZE DURING PEAK HEATING
HOURS. AN ISOLATED STRONG THUNDERSTORM WITH GUSTY WINDS IS
POSSIBLE, BUT THE THREAT FOR SEVERE WEATHER REMAINS LOW. ACTIVITY
COULD LINGER INTO EARLY EVENING HOURS, BUT SHOULD DISSIPATE
WITHIN A FEW HOURS OF SUNSET. LOCATIONS THAT SEE RAINFALL TODAY
WILL BE MORE AT RISK FOR PATCHY TO AREAS OF FOG LATE TONIGHT,
ESPECIALLY INLAND FOR A FEW HOURS PRIOR TO AND AROUND DAYBREAK.
TUESDAY: THE AFOREMENTIONED UPPER LOW ACROSS FLORIDA WILL BEGIN TO
DRIFT NORTH ACROSS THE SOUTHEAST UNITED STATES, LIKELY TO BRING
HIGHER CHANCES OF SHOWERS/THUNDERSTORMS LOCALLY DESPITE TRENDING
WEAKER WELL IN ADVANCE OF A LONGWAVE TROUGH MAKING WAY ACROSS THE
MIDWEST. THE UPTICK IN FORCING ALONG WITH MODEST INSTABILITY AND
RESIDING 2+ INCH PWATS COULD SUPPORT A FEW STRONGER THUNDERSTORMS
DURING MID-LATE AFTERNOON INTO EARLY EVENING HOURS, PERHAPS WITH
SOME ENHANCEMENT ALONG/NEAR A SEABREEZE. LOCALIZED HEAVY RAINFALL
AND MINOR FLOODING ISSUES ARE ALSO POSSIBLE. HOWEVER, THE OVERALL
SEVERE WEATHER THREAT SHOULD BE ON THE LOWER END.
KEY MESSAGE 2: A COLD FRONT COULD BRING A THREAT OF STRONG THUNDERSTORMS
WEDNESDAY AFTERNOON, AND WILL BE FOLLOWED BY COOLER WEATHER AND GUSTY
WINDS.
THE PREVIOUSLY MENTIONED UPPER LOW IS ANTICIPATED TO SHIFT NORTH-
NORTHEAST OF THE LOCAL AREA, BECOMING PHASED WITH A LONGWAVE TROUGH
SHIFTING ACROSS THE MID-ATLANTIC AND NORTHEAST STATES MID-WEEK. A
NOTABLE COLD FRONT IS PROGGED TO PUSH SOUTH INTO THE LOCAL AS THE
MID-UPPER LVL PATTERN SUPPORTS DIGGING OF THE LONGWAVE TROUGH ACROSS
THE SOUTHEAST. TIMING OF FROPA WILL REMAIN KEY IN REGARDS TO THE
OVERALL THREAT FOR STRONGER AND/OR MARGINALLY SEVERE THUNDERSTORMS
WEDNESDAY. ALTHOUGH LATEST TRENDS SUGGEST COLD FROPA BEGINNING LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING, THERE COULD BE SUFFICIENT TIME
FOR STRONG SFC HEATING TO OCCUR WITHIN A DEEPLY MOIST ENVIRONMENT
ACROSS SOUTHEAST GEORGIA WEDNESDAY AFTERNOON, LEADING TO A GREATER
RISK FOR STRONGER AND/OR MARGINALLY SEVERE THUNDERSTORMS PRIOR TO
SUNSET.
FOLLOWING THE FRONT, AN INLAND WEDGE WILL SET UP ACROSS THE
CAROLINAS AND GEORGIA, FAVORING COOL AND DRIER CONDITIONS LOCALLY
WITHIN A NORTH-NORTHEAST FLOW DURING THE SECOND HALF OF THE WEEK.
COLD AIR ADVECTION AND A TIGHTENING PRESSURE GRADIENT SHOULD LEAD
TO BREEZY CONDITIONS POST FROPA WEDNESDAY AND THURSDAY, WITH
SOME ENHANCEMENT POSSIBLE NEAR COASTAL AREAS. IN GENERAL, HIGHS
TEMPS IN THE MID-UPPER 70S TO LOWER 80S FOR SOUTHEAST SC AND
LOW/MID 80S FOR SOUTHEAST GA ARE MOST PROBABLE INTO LATE WEEK.
AVIATION /18Z MONDAY THROUGH SATURDAY/
TEMPO MVFR CONDITIONS ARE POSSIBLE WITH SHOWERS/THUNDERSTORMS FOR
THE NEXT HOUR OR TWO AT SAV BEFORE A SEABREEZE SHIFTS FURTHER
INLAND. THE RISK FOR SHOWERS/THUNDERSTORMS REMAINS LESS AT CHS/JZI
EARLY THIS AFTERNOON, BUT CAN'T BE RULED OUT COMPLETELY. OTHERWISE,
VFR CONDITIONS ARE LIKELY AT ALL TERMINALS LATE AFTERNOON THROUGH A
BULK OF THE NIGHT. HOWEVER, LOWER CLOUDS AND FOG COULD RETURN ACROSS
THE AREA, WITH GREATER CHANCES OCCURRING AT SAV. PREVAILING MVFR
CONDITIONS HAVE BEEN INTRODUCED FROM 10-14Z TUESDAY AT SAV, BUT
IFR OR LOWER CIGS/VSBYS ARE POSSIBLE WITHIN A FEW HOURS OF
DAYBREAK. VFR CONDITIONS SHOULD THEN PREVAIL MID-LATE MORNING AT
ALL TERMINALS PRIOR TO SHOWERS/THUNDERSTORMS DEVELOPING ACROSS
THE AREA BY EARLY TUESDAY AFTERNOON. PROB30 GROUPS FOR THUNDERSTORMS
AND MVFR CONDITIONS HAVE BEEN INTRODUCED AT ALL TERMINALS, STARTING
AT 15Z AT JZI, 16Z AT CHS AND 17Z TUESDAY AT SAV.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTION CHANCES INCREASE
TUESDAY INTO WEDNESDAY AT ALL TERMINALS WITH A SHOWERS AND
THUNDERSTORMS AND A BUILDING WEDGE POST FROPA TUESDAY NIGHT
INTO WEDNESDAY. GUSTY NORTH-NORTHEAST WINDS ARE LIKELY TO FOLLOW
AT ALL TERMINALS WEDNESDAY INTO THURSDAY AS WELL.
MARINE
THROUGH TUESDAY: A DECAYING SURFACE HIGH PRESSURE AHEAD OF A SLOWLY
APPROACHING COLD FRONT WILL CONTINUE THE BENIGN MARINE WEATHER
CONDITIONS ACROSS OUR LOCAL WATERS. PERIODIC SHOWERS AND
THUNDERSTORMS DURING THIS TIME MAY BE CAPABLE OF GUSTY WINDS AND
FREQUENT LIGHTNING.
WEDNESDAY-FRIDAY: A COLD FRONT WILL BE PUSHING THROUGH ON WEDNESDAY,
WITH A STRONG SURGE IN NORTHEASTERLY FLOW AS THE PINCHED PRESSURE
GRADIENT (AKA THE WEDGE) SETS UP. BREEZY RAMP UP DURING THE EVENING
HOURS, WITH WIND GUSTS IN EXCESS OF 25 KNOTS HAVE 60-90% CHANCES, SO
SMALL CRAFT ADVISORIES ARE ANTICIPATED. THERE IS ALSO A LOW CHANCE
(20-30%) FOR GALES TO DEVELOP ON THURSDAY, FOR THE ZONES 20+NM
OFFSHORE. IN ADDITION, WAVE HEIGHTS OF 5-7 FT WILL LIKELY ACCOMPANY
THE BREEZY WINDS FOR AREAS 15+ NM AWAY FROM THE COAST THURSDAY
MORNING THROUGH FRIDAY EVENING BEFORE WINDS BEGIN TO WEAKEN.
SATURDAY: THE WEDGE CONTINUES TO WEAKEN, FURTHER DECREASING THE WIND
STRENGTH THROUGHOUT THE DAY. SEAS WILL REMAIN UNSETTLED, WITH
OFFSHORE ZONES (20+NM OFFSHORE) SEEING 6FT+ WAVES CONTINUING INTO
THE EVENING HOURS BEFORE DECREASING BELOW 6 FT.
COASTAL FLOODING: AS A FULL MOON APPROACHES ON 9/26, BREEZY
NORTHEAST WINDS WEDNESDAY EVENING INTO FRIDAY MAY RESULT IN SOME
COASTAL FLOODING ISSUES AS TIDAL DEPARTURES RISE. WE WILL NEED TO
KEEP AN EYE ON THE POTENTIAL STARTING AS EARLY AS WEDNESDAY
AFTERNOON FOR COASTAL CHARLESTON AND COLLETON COUNTIES, EXPANDING
SOUTHWARDS TO INCLUDE THE REMAINDER OF THE SE SC COAST INTO SE GA
THURSDAY AFTERNOON/EVENING.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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