102  
FXUS62 KCHS 232151  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
551 PM EDT WED JUL 23 2025  
   
SYNOPSIS
 
 
A WEAK STATIONARY FRONT WILL REMAIN OVER OR NEAR THE AREA  
THROUGH THURSDAY, THEN DISSIPATE OVERNIGHT INTO FRIDAY. THE  
WEEKEND WILL FEATURE A RETURN OF ATLANTIC HIGH PRESSURE AND  
SURFACE TROUGHING INLAND.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
SCATTERED SHOWERS WILL LIKELY FALL OFF IN COVERAGE AFTER  
SUNSET. HOWEVER, GIVEN THE PRESENCE OF AN INVERTED TROUGH OF LOW  
PRESSURE, ALONG WITH AN AXIS OF DEEP LAYER MOISTURE AND LOW  
LEVEL CONVERGENCE, HAVE KEPT SLIGHT CHANCE TO ASTRONOMICAL TIDES  
WILL RISE WITH THE UPCOMING NEW MOON ON THURSDAY. ADDITIONALLY,  
NORTHEAST SURFACE WINDS WILL CAUSE TIDAL ANAMOLIES TO INCREASE.  
MINOR COASTAL FLOODING IS POSSIBLE AT THE CHARLESTON TIDE GAUGE  
WITH THIS EVENING'S HIGH TIDE. ELEVATED TIDES COULD PERSIST  
INTO THURSDAY. THOUGH, WINDS SHOULD VEER TO THE SOUTHEAST BY  
THEN, WHICH SHOULD LOWER TIDAL ANOMALIES. CHANCE POPS MUCH OF  
THE NIGHT.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/
 
 
WHILE THE REMNANTS OF THE INVERTED TROUGH WILL CONTINUE CHANCES FOR  
SHOWERS AND THUNDERSTORMS INTO THE MORNING HOURS, MID-LEVEL RIDGING  
CENTERED OVER THE REGION WILL BE PUSHING RAINFALL INLAND THROUGHOUT  
THE AFTERNOON. MAJORITY OF THIS ACTIVITY WILL BE DRIVEN BY THE  
EXPECTED SEA-BREEZE, WHICH WILL LIKELY BE PUSHING ASHORE EARLIER  
THAN USUAL GIVEN THE INVERTED TROUGH THAT IS PUSHING INLAND  
THROUGHOUT THE DAY. WITH PWATS REMAINING AOA 2 INCHES, THE MAIN  
THREAT STORMS WILL CARRY IS CHANCES FOR HEAVY RAIN AND BREEZY WINDS,  
THOUGH AN ISOLATED SEVERE STORMS CANNOT BE RULED OUT GIVEN 1000-1500  
J/KG OF CAPE. THE SIMILAR CLOUD COVERAGE TO TODAY WILL RESULT IN  
SIMILAR TEMPERATURES, WITH AFTERNOON HIGHS IN THE LOWER TO MID 90S.  
 
OVERNIGHT INTO FRIDAY, THE ATLANTIC SURFACE HIGH PRESSURE  
STRENGTHENS AS THE MID-LEVEL RIDGE ALSO STRENGTHENS, WITH MAX  
TEMPERATURES DURING THE AFTERNOON ON FRIDAY RISING INTO THE MID 90S  
TO LOWER 100S AS A RESULT. THE NBM CONTINUES TO SHOW DEWPOINTS IN  
THE MID 70S TO LOWER 80S, AND IS THUS RESULTING IN FORECAST HEAT  
INDEX VALUES IN THE MID 100S TO LOWER 110S. NOT SURE WE'LL GET DEW  
POINTS UP THAT HIGH, ESPECIALLY DURING PEAK MIXING, SO WE'LL HAVE TO  
SEE IF WE END UP NEEDING A HEAT ADVISORY AS WE GET CLOSER TO FRIDAY.  
AN AFTERNOON SEA-BREEZE MAY AGAIN POP-UP SCATTERED SHOWERS AND  
THUNDERSTORMS, AND WITH 1000-1500 J/KG OF CAPE AGAIN ISOLATED SEVERE  
THUNDERSTORMS CANNOT BE RULED OUT.  
 
THE RIDGE ALOFT CONTINUES TO STRENGTHEN INTO SATURDAY. THE ECMWF  
EXTREME FORECAST INDEX (EFI) AND SHIFT OF TAILS (SOT) NOW SHOWS SOT  
VALUES OF 0 (INDICATING THAT AT LEAST 10% OF THE ENSEMBLE MEMBERS  
ARE FORECASTING ABOVE MODEL CLIMATE), WHICH IS VERIFIED ON THE ESAT  
TABLES. NBM PROBABILITIES ARE SHOWING NON-ZERO CHANCES FOR REACHING  
100 DEGREES F, WHILE THE DETERMINISTIC NBM IS COMING INTO THE MID 90  
TO 100 DEGREES. AGAIN, IN COMBINATION WITH FORECAST DEWPOINTS IN THE  
MID TO UPPER 70S, HEAT INDEX VALUES ARE FORECAST TO RISE INTO THE  
MID 100S TO MID 110S ON SATURDAY, WHICH WILL HAVE TO BE MONITORED  
FOR HEAT HEADLINES.  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
 
 
HEAT WAVE CONTINUES SUNDAY INTO MONDAY AS THE RIDGE REMAINS PARKED  
ACROSS THE SOUTHEASTERN CONUS. THE ECMWF EXTREME FORECAST INDEX  
(EFI) AND SHIFT OF TAILS (SOT) SHOWS THAT SOTS ARE STARTING TO  
POPULATE SOME 0'S AND 1'S FOR SUNDAY AND MONDAY, WITH EFI VALUES  
ABOVE 80% ACROSS THE REGION. THIS SHOWS THAT THE ENSEMBLE IS  
EXPECTING UNUSUALLY WARM WEATHER, WHILE THE EFI OF 1 WOULD INDICATE  
THAT ALL ENSEMBLE MEMBERS ARE FORECASTING ABOVE MODEL CLIMATE. NBM  
CURRENTLY HAS HIGHS ON SUNDAY AND MONDAY IN THE UPPER 90S TO LOWER  
100S, WITH HEAT INDEX VALUES IN THE MID 100S TO 110S.  
 

 
   
AVIATION /22Z WEDNESDAY THROUGH MONDAY/
 
 
24/00Z TAF DISCUSSION:  
KCHS/KJZI: SHOWER ACTIVITY IS EXPECTED TO PICK UP AROUND BOTH  
TERMINALS LATE TONIGHT AS THE COASTAL FRONT OFFSHORE TICKS  
CLOSER TO THE COAST. A CORRIDOR OF ISENTROPIC ASCENT WILL LIKELY  
SPARK OFF THIS ACTIVITY. IT IS UNCLEAR HOW FAR INLAND THIS  
ACTIVITY WILL GET. FOR NOW, VCSH WAS HIGHLIGHTED ROUGHLY 04-09Z  
WITH A TEMPO FOR MVFR VSBYS AT KJZI WHERE IMPACTS ARE THE MOST  
LIKELY. SHOWERS SHOULD MOSTLY CONCENTRATE INLAND OF THE  
TERMINALS DURING THE DAY THURSDAY.  
 
KSAV: VFR FOR MUCH OF THE PERIOD. THERE IS A RISK FOR SOME  
SHOWER ACTIVITY TO POP NEAR THE TERMINAL AS DAYBREAK APPROACHES  
AND THE COASTAL FRONT OFFSHORE NEARS, BUT CONFIDENCE FOR IMPACTS  
IS TOO LOW TO JUSTIFY ANYTHING MORE THAN VCSH FROM 10-15Z FOR  
NOW. SHOWERS SHOULD MOSTLY CONCENTRATE INLAND OF THE TERMINAL  
DURING THE DAY THURSDAY.  
 
EXTENDED AVIATION OUTLOOK: EXPECT BRIEF FLIGHT RESTRICTIONS EACH  
AFTERNOON/EVENING DUE TO SHOWERS/THUNDERSTORMS, MAINLY THROUGH  
FRIDAY.  
 

 
   
MARINE
 
 
THROUGH TONIGHT: AN INVERTED TROUGH OF LOW PRESSURE, CURRENTLY  
OVER THE WATERS, WILL MOVE WESTWARD ACROSS THE LAND AREAS  
OVERNIGHT. NORTHEAST WINDS OF 10-15 KNOTS, WILL VEER TO  
SOUTHERLY LATER TONIGHT AS THE TROUGH MOVES WESTWARD. WINDS  
WILL CONTINUE TO GUST TO NEAR 20 KNOTS CLOSER TO THE COAST  
THROUGH THE REST OF THIS AFTERNOON, BUT SHOULD THEN DECREASE  
AFTER SUNSET AS THE PRESSURE GRADIENT DECREASES. SCATTERED TO  
NUMEROUS SHOWERS LIKELY TO DEVELOP AGAIN LATER TONIGHT. SEAS 2  
TO 3 FEET.  
 
THURSDAY THROUGH SUNDAY: WAVE HEIGHTS OF 2 TO 3 FEET EXPECTED,  
WITH OTHERWISE NO MARINE CONCERNS IN THE EXTENDED WITH 50% OR  
GREATER CONFIDENCE.  
 

 
   
TIDES/COASTAL FLOODING
 
 
THE COASTAL FLOOD ADVISORY HAS BEEN EXTENDED SOUTH TO INCLUDE  
THE REMAINDER OF THE LOWER SOUTH CAROLIAN COAST INTO MUCH OF  
COASTAL GEORGIA. BASED ON TIDE TRENDS, TIDE LEVELS IN THE  
CHARLESTON HARBOR ARE EXPECTED TO PEAK 7.5-7.7 FT (MODERATE)  
WITH 9.4-9.6 FT (MINOR) AT FORT PULASKI.  
 
ELEVATED TIDES COULD PERSIST INTO THURSDAY. THOUGH, WINDS  
SHOULD VEER TO THE SOUTHEAST BY THEN, WHICH SHOULD LOWER TIDAL  
ANOMALIES.  
 

 
   
CLIMATE
 
 
RECORD HIGH TEMPERATURES:  
 
JULY 27:  
KCHS: 100/2005  
KSAV: 100/2010  
 
RECORD HIGH MINIMUM TEMPERATURES:  
 
JULY 26:  
KCHS: 78/2012  
KCXM: 82/2023  
 
JULY 27:  
KCHS: 80/2014  
KSAV: 80/1885  
 
JULY 28:  
KCHS: 80/2016  
KCXM: 83/1999  
KSAV: 81/1878  
 
JULY 29:  
KCHS: 80/2016  
KSAV: 82/1878  
 

 
   
CHS WATCHES/WARNINGS/ADVISORIES
 
 
GA...COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR GAZ117-  
119-139-141.  
SC...COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR  
SCZ048>051.  
MARINE...NONE.  
 

 
 

 
 
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