252
FXUS62 KCHS 182346
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
746 PM EDT TUE AUG 18 2026
WHAT HAS CHANGED
THE AVIATION SECTION HAS BEEN UPDATED FOR THE 00Z TAF.
KEY MESSAGES
- 1) HEAT WILL REMAIN A CONCERN INTO LATE WEEK.
- 2) AFTERNOON AND EVENING THUNDERSTORM COVERAGE WILL REMAIN
ISOLATED THROUGH THURSDAY. AN INCREASE IN THUNDERSTORM
COVERAGE IS EXPECTED FRIDAY THROUGH THE WEEKEND.
DISCUSSION
KEY MESSAGE 1: HEAT WILL REMAIN A CONCERN TODAY LATE WEEK.
WEDNESDAY INTO FRIDAY: THE RIDGING ALOFT WILL BEGIN TO WEAKEN
SLOWLY STARTING ON WEDNESDAY. THIS WILL ALLOW FOR CONVECTION TO
INCREASE IN COVERAGE EACH AFTERNOON. HEAT INDEX VALUES ARE STILL
FORECAST TO REACH HEAT ADVISORY CRITERIA (>108) ALONG THE
COASTAL CORRIDOR WHERE DEW POINTS WILL BE HIGHEST. A HEAT
ADVISORY HAS BEEN ISSUED FROM 11 AM TO 8 PM WEDNESDAY FOR THE
COASTAL COUNTIES. ADDITIONAL HEAT ADVISORIES WILL LIKELY BE
REQUIRED THURSDAY AND POSSIBLY AGAIN ON FRIDAY. CONVECTIVE
COVERAGE WILL INCREASE INTO FRIDAY AS A SHORTWAVE TROUGH ALOFT
MOVES THROUGH THE MID-ATLANTIC STATES. FRIDAY COULD SEE THE
GREATEST COVERAGE OF SHOWERS AND THUNDERSTORMS, POSSIBLY
HINDERING TEMPERATURES FROM REACHING THEIR PEAK VALUES AND
NEGATING THE NEED FOR ANY HEAT HEADLINES.
KEY MESSAGE 2: AFTERNOON AND EVENING THUNDERSTORM COVERAGE WILL
REMAIN ISOLATED THROUGH THURSDAY. AN INCREASE IN THUNDERSTORM
COVERAGE IS EXPECTED FRIDAY THROUGH THE WEEKEND.
THIS EVENING: THE BACKGROUND SYNOPTIC-SCALE SETUP FEATURES A
FRONT THAT MOSTLY STRETCHES FROM WEST TO EAST SITUATED NORTH OF
THE FORECAST AREA. THIS IS DRIVING WEST TO WEST-NORTHWEST
SURFACE FLOW ACROSS THE AREA, WHICH WILL FORCE THE SEA BREEZE TO
BE PINNED VERY CLOSE TO THE COAST. GIVEN THAT WE ARE DEVOID OF
ANY FORCING MECHANISM FOR CONVECTION OTHER THAN DIFFERENTIAL
SURFACE HEATING AND THE SEA BREEZE, THE ENVIRONMENT DOESN'T
SUPPORT MUCH IN THE WAY OF COVERAGE. THIS IS WELL SUPPORTED BY
THE HI-RES MODEL RUNS AS WELL AS THE 18/12Z HREF, ALL OF WHICH
SHOW LITTLE TO DIURNAL CONVECTION. BUT, IF A STORM OR TWO CAN
GET GOING THERE WILL BE A LOW RISK OF A STRONG TO MARGINALLY
SEVERE STORM.
WEDNESDAY AND THURSDAY: A SIMILAR ENVIRONMENT IS EXPECTED EACH
DAY FAVORING ISOLATED TO SCATTERED CONVECTIVE COVERAGE AT MOST.
WE WILL STILL BE DETACHED FROM ANY MEANINGFUL FORCING SO WE WILL
CONTINUE TO BE DEPENDENT ON SURFACE HEATING AND CONVERGENCE
ALONG THE SEA BREEZE. THE TYPICAL SUMMERTIME RULES APPLY IN THAT
ANY STORM THAT DEVELOPS COULD BECOME MARGINALLY SEVERE, PRODUCE
LOCALLY HEAVY RAINFALL, AND ALSO FREQUENT LIGHTNING.
FRIDAY THROUGH THE WEEKEND: THE EXPECTATION REMAINS THAT THE
PATTERN WILL BECOME MORE ACTIVE AS WE MOVE INTO THE WEEKEND. A
SLOW MOVING FRONT IS EXPECTED TO SETTLE INTO THE AREA AND HELP
PROVIDE MORE OF A TRIGGERING AND FOCUSING MECHANISM FOR
THUNDERSTORM DEVELOPMENT. WITH CONTINUED ELEVATED PRECIPITABLE
WATER VALUES, THIS INCREASE IN COVERAGE SHOULD BRING THE
POTENTIAL FOR LOCALLY HEAVY RAINFALL AND SEVERAL ROUNDS OF
THUNDERSTORMS ACROSS THE FORECAST AREA EACH DAY.
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
19/00Z TAF DISCUSSION: VFR CONDITIONS ARE EXPECTED TO PREVAIL
THROUGH 00Z THURSDAY. AN ISOLATED SHOWER OR THUNDERSTORM COULD
DEVELOP LATE WEDNESDAY AFTERNOON OR EVENING, MAINLY NEAR THE
END OF THE CURRENT TAF PERIOD. HOWEVER, THE LIKELIHOOD OF ANY
STORMS APPEARS TO BE LOW OVERALL, THUS THERE WILL BE NO MENTION
IN THE TAF.
EXTENDED AVIATION OUTLOOK: PREVAILING VFR THROUGH THURSDAY.
AFTERNOON SHOWERS AND THUNDERSTORMS COULD BRING BRIEF FLIGHT
RESTRICTIONS STARTING FRIDAY.
MARINE
THROUGH TONIGHT: SOUTHWEST FLOW WILL PREVAIL THIS EVENING,
TURNING MORE WESTERLY THROUGH THE LATE NIGHT HOURS. WINDS SHOULD
MOSTLY TOP OUT IN THE 10-15 KNOT RANGE THIS EVENING,
DIMINISHING MORE TO BE 5-10 KNOTS LATE TONIGHT. SEAS ARE
EXPECTED TO AVERAGE 2-3 FEET.
WEDNESDAY THROUGH SUNDAY: OVERALL, A PRETTY TYPICAL SUMMERTIME
PATTERN IS EXPECTED TO PREVAIL ACROSS THE LOCAL WATERS THROUGH
THE WEEKEND. WINDS WILL LOCALLY SURGE WITH THE SEA BREEZE EACH
DAY, MOSTLY INTO THE 10-15 KNOT RANGE AND PERHAPS A FEW GUSTS UP
TO 20 KNOTS. OVER THE WEEKEND THERE COULD BE SOME SUPPORT FOR
MORE 15-20 KNOT SOUTHWEST FLOW THANKS TO A BIT MORE GRADIENT.
BUT, OVERALL CONDITIONS ACROSS THE LOCAL WATERS SHOULD REMAIN
BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH THE PERIOD.
CLIMATE
RECORD HIGH TEMPERATURES:
AUGUST 18:
KCXM: 97/1995 **TIED
AUGUST 19:
KCHS: 98/1983
KCXM: 98/1895
KSAV: 99/1900
AUGUST 20:
KCHS: 97/2005
KSAV: 102/1900
AUGUST 21:
KCHS: 100/1983
KSAV: 101/1902
RECORD HIGH MINIMUM TEMPERATURES:
AUGUST 18:
KCHS: 80/2017
KCXM: 82/2017
KSAV: 78/2010
AUGUST 19:
KCHS: 79/2010
KCXM: 83/2021
KSAV: 79/1878
AUGUST 20:
KCHS: 78/2017
KCXM: 82/2017
AUGUST 21:
KCHS: 79/2010
KCXM: 82/2023
KSAV: 80/1902
AUGUST 22:
KCHS: 79/2023
KCXM: 82/2014
KSAV: 79/1902
AUGUST 23:
KCXM: 81/2019
KSAV: 78/2016
CHS WATCHES/WARNINGS/ADVISORIES
GA...HEAT ADVISORY FROM 11 AM TO 8 PM EDT WEDNESDAY FOR GAZ217>219-
239>241.
SC...HEAT ADVISORY FROM 11 AM TO 8 PM EDT WEDNESDAY FOR SCZ148>152.
MARINE...NONE.
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