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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