666
FXUS62 KCHS 211917
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
317 PM EDT TUE JUL 21 2026
WHAT HAS CHANGED
ALL SECTIONS HAVE BEEN UPDATED.
KEY MESSAGES
- 1) SMOKE FROM THE HORSE ISLAND WILDFIRE WILL IMPACT PORTIONS
OF BERKELEY COUNTY TONIGHT INTO WEDNESDAY.
- 2) HOT AND HUMID CONDITIONS ACROSS COASTAL SOUTH CAROLINA AND
GEORGIA THROUGH MID-WEEK. HEAT ADVISORIES COULD BE NEEDED.
- 3) A SLOW-MOVING COLD FRONT WILL BRING INCREASING CHANCES FOR
SHOWERS AND THUNDERSTORMS LATE THIS WEEK THROUGH THE WEEKEND,
WITH THE POTENTIAL FOR LOCALLY HEAVY RAINFALL.
DISCUSSION
KEY MESSAGE 1: SMOKE FROM THE HORSE ISLAND WILDFIRE WILL IMPACT
PORTIONS OF BERKELEY COUNTY TONIGHT INTO WEDNESDAY.
THE HORSE ISLAND WILDFIRE NEAR SHULERVILLE, SC HAS INCREASED TO 1200
ACRES. A DENSE SMOKE ADVISORY HAS BEEN REQUESTED BY THE U.S. FOREST
SERVICE FOR PORTIONS OF BERKELEY COUNTY IN RESPONSE TO THE WILDFIRE
SMOKE. THE LATEST HYSPLIT OUTPUT SHOWS THE WORST OF THE SMOKE WILL
REMAIN ACROSS BERKELEY COUNTY, BETWEEN JAMESTOWN AND THE CHARLESTON
BORDER, EXTENDING NORTHEAST ACROSS THE SANTEE RIVER INTO PORTIONS OF
GEORGETOWN AND WILLIAMSBURG COUNTIES. VISIBILITIES MAY DROP BELOW 1
MILE AT TIMES OVERNIGHT, ESPECIALLY ALONG PARTS OF HIGHWAY 45. ROAD
CLOSURES ARE POSSIBLE. SMOKE WILL LIKELY REMAIN AN ISSUE INTO
WEDNESDAY ALTHOUGH VISIBILITIES SHOULD IMPROVE SOME BY MID-MORNING
AS DISPERSION INCREASES AND MIXING HEIGHTS RISE.
KEY MESSAGE 2: HOT AND HUMID CONDITIONS ACROSS COASTAL SOUTH
CAROLINA AND GEORGIA THROUGH MID-WEEK. HEAT ADVISORIES COULD BE
NEEDED.
HOT AND HUMID CONDITIONS ARE EXPECTED TO CONTINUE OVER THE NEXT 48
TO 72 HOURS AS THE FORECAST AREA REMAINS ON THE WESTERN PERIPHERY OF
THE UPPER RIDGE. OVERALL HEAT INDICES HAVE COME DOWN A BIT COMPARED
TO THE LAST FEW FORECASTS. THIS IS LIKELY A RESULT OF THE MOISTURE
FROM NOW TROPICAL STORM BERTHA REMAINING INCREASING FURTHER SOUTH
AND WEST AND THE RIDGE BEING A LITTLE STRONGER. WITH DECREASED
MOISTURE COMPARED TO PREVIOUS FORECASTS, DEWPOINTS ARE NOW EXPECTED
TO MIX INTO THE LOW 70S ACROSS INLAND AREAS KEEPING HEAT INDICES IN
THE 100 TO 105 RANGE FOR MOST OF THE AREA TODAY AND WEDNESDAY. WHILE
THESE VALUES WILL STILL MAKE THINGS RATHER UNCOMFORTABLE THEY ARE
NOT QUITE HEAT ADVISORY CRITERIA. CLOSER TO THE COAST, CONDITIONS
WILL BE DETERMINED BY THE MOVEMENT OF THE AFTERNOON SEABREEZE. AS IT
MOVES SLOWLY INLAND EACH AFTERNOON, DEWPOINTS WILL SURGE INTO THE
UPPER 70S BEHIND THE BOUNDARY LEADING TO HEAT INDICES IN THE 105 TO
108 RANGE. HOWEVER, THIS WILL LIKELY ONLY BE FOR A COUPLE HOURS
DURING THE LATE AFTERNOONS LEADING TO LOWER CONFIDENCE IN REACHING
ADVISORY CRITERIA. ON TOP OF THE SHORTER DURATION, ISOLATED SHOWERS
AND THUNDERSTORMS DURING THE EARLY AFTERNOON MAY LIMIT HOW HOT
TEMPERATURES GET DURING THE AFTERNOON LEADING TO INCREASED
UNCERTAINTY. AS A RESULT WE HAVE CONTINUED TO HOLD OFF ON AN HEAT
ADVISORIES FOR COASTAL AREAS.
DESPITE NOT HAVING ANY HEAT ADVISORIES, CONDITIONS WILL STILL REMAIN
RATHER UNCOMFORTABLE AND WITH DEWPOINTS IN THE UPPER 70S OVERNIGHT
VERY LITTLE RELIEF WILL OCCUR EACH NIGHT. GIVEN WE HAVE SET RECORD
HIGH MINIMUM TEMPERATURES THE LAST FEW NIGHTS, CONTINUED HEAT STRESS
THROUGH THE MIDDLE OF THE WEEK CAN BE DANGEROUS TO VULNERABLE
COMMUNITIES INCLUDING ELDERLY AND THOSE WHO DO NOT HAVE ACCESS TO
ADEQUATE COOLING. THE EXTREME HEAT IS EXPECTED TO COME TO AN END BY
THE END OF THE WEEK AS INCREASING RAIN CHANCES ARRIVE WITH A SLOW
MOVING FRONT.
KEY MESSAGE 3: A SLOW-MOVING COLD FRONT WILL BRING INCREASING
CHANCES FOR SHOWERS AND THUNDERSTORMS LATE THIS WEEK THROUGH THE
WEEKEND, WITH THE POTENTIAL FOR LOCALLY HEAVY RAINFALL.
AS A MID-LEVEL TROUGH SETTLES OVER THE EASTERN CONUS ON WEDNESDAY,
AN ASSOCIATED COLD FRONT WILL SLOWLY APPROACH THE REGION, REACHING
THE AREA ON THURSDAY BEFORE STALLING THROUGH THE END OF THE WEEK.
THIS PATTERN WILL SUPPORT NUMEROUS SHOWERS AND THUNDERSTORMS FROM
FRIDAY THROUGH SUNDAY. FORECAST SOUNDINGS CONTINUE TO INDICATE A
VERY MOIST AIRMASS, WITH PWAT VALUES INCREASING TO AROUND 2.2 INCHES
ON FRIDAY AND UP TO 2.4 INCHES THIS WEEKEND. THESE CONDITIONS WILL
FAVOR EFFICIENT RAINFALL PRODUCTION AND INCREASE THE POTENTIAL FOR
LOCALIZED FLOODING. WHILE MOST FLOODING IMPACTS ARE EXPECTED TO
REMAIN MINOR, REPEATED HEAVY DOWNPOURS OVER URBAN AREAS SUCH AS THE
CHARLESTON OR SAVANNAH METRO AREAS COULD WARRANT FLOOD ADVISORIES OR
EVEN FLASH FLOOD WARNINGS.
ALTHOUGH STILL QUITE FAR AWAY AND SUBJECT TO CHANGE, RAINFALL TOTALS
OF A COUPLE OF INCHES ARE POSSIBLE FROM FRIDAY THROUGH SUNDAY. THE
HIGHEST AMOUNTS (~3-4 INCHES) ARE POSSIBLE IN PROXIMITY TO THE
STALLED FRONTAL BOUNDARY, WHICH AT THIS TIME LOOKS TO BE THE
LOWCOUNTRY. LOCALLY HIGHER TOTALS WILL BE POSSIBLE WHERE
THUNDERSTORMS REPEATEDLY MOVE OVER THE SAME LOCATIONS.
AVIATION /19Z TUESDAY THROUGH SUNDAY/
18Z TAFS: VFR GENERALLY EXPECTED ACROSS THE TERMINALS THROUGH THE
TAF PERIOD. THUNDERSTORMS MAY DEVELOP OVER SOUTHERN GA LATE THIS
AFTERNOON INTO THIS EVENING. THESE THUNDERSTORMS MAY PASS NEAR OR
OVER KSAV BETWEEN 20 TO 24Z, HIGHLIGHTED WITH A TEMPO. GUSTY SOUTH
WINDS MAY PERSIST THROUGH THE REST OF THE DAYLIGHT HOURS. ONCE
MIXING BEGINS WEDNESDAY MORNING, SW WINDS MAY DEVELOP GUSTS TO
AROUND 20 KTS.
EXTENDED AVIATION OUTLOOK: CHANCES OF FLIGHT RESTRICTIONS INCREASE
LATER THIS WEEK WITH A GREATER COVERAGE OF SHOWERS/THUNDERSTORMS.
MARINE
TONIGHT: THE PRESSURE GRADIENT WILL TIGHTEN ACROSS THE COASTAL
WATERS AS A COLD FRONT APPROACHES FROM THE NORTH AND A EAST-WEST SFC
RIDGE REMAINS TO THE SOUTH. THIS PATTERN SHOULD SUPPORT INCREASING
SOUTH WINDS TONIGHT, WITH GUSTY CONDITIONS EXPECTED ACROSS THE
MARINE ZONES INTO WEDNESDAY NIGHT. IN ADDITION, SEAS WILL BUILD
TONIGHT, WITH 5 TO 6 FT SEA COMMON ACROSS THE WATERS INTO WEDNESDAY
MORNING. A SMALL CRAFT ADVISORY ARE IN EFFECT FOR ALL MARINE ZONES,
INCLUDING THE CHARLESTON HARBOR.
WEDNESDAY THROUGH SUNDAY: BREEZY SOUTH TO SOUTHEASTERLY WINDS AHEAD
OF AN APPROACHING COLD FRONT WILL MAINTAIN HAZARDOUS MARINE
CONDITIONS THROUGH WEDNESDAY. AS THE FRONT STALLS NEAR THE AREA
THURSDAY AND THE PRESSURE GRADIENT RELAXES, WINDS AND SEAS WILL
STEADILY DIMINISH, WITH ALL SMALL CRAFT ADVISORIES EXPECTED TO END
BY THURSDAY MORNING. BENIGN MARINE CONDITIONS SHOULD THEN PREVAIL
THROUGH SUNDAY.
RIP CURRENTS: A MODERATE RISK OF RIP CURRENTS IS EXPECTED TO
CONTINUE ALONG THE SOUTH CAROLINA AND GEORGIA BEACHES WEDNESDAY AND
THURSDAY. ON WEDNESDAY, INCREASING SOUTH TO SOUTH-SOUTHWEST WINDS
WILL SUPPORT BREAKERS OF 3 TO 4 FT, WITH OCCASIONAL BREAKERS ABOVE 4
FT POSSIBLE AND DOMINANT WAVE PERIODS OF 6 SECONDS. ALTHOUGH SURF IS
EXPECTED TO SUBSIDE SOMEWHAT ON THURSDAY, A LONGER-PERIOD SWELL OF
AROUND 8 SECONDS SHOULD CONTINUE TO SUPPORT DANGEROUS RIP CURRENTS.
IF SURF HEIGHTS OR WIND SPEEDS TREND HIGHER THAN CURRENTLY FORECAST
ON WEDNESDAY, PORTIONS OF THE SC/GA COAST COULD REQUIRE AN UPGRADE
TO A HIGH RISK.
CLIMATE
RECORD HIGH TEMPERATURES:
JULY 27:
KSAV: 100/2010
RECORD HIGH MINIMUM TEMPERATURES:
JULY 21:
KCHS: 80/1986
KCXM: 83/1998
KSAV: 81/1942
JULY 22:
KCHS: 81/2011
KCXM: 83/2011
JULY 23:
KCHS: 80/1991
KCXM: 83/1952
JULY 24:
KCHS: 81/2024
KCXM: 84/1952
JULY 25:
KCHS: 80/2011
KCXM: 82/2016
KSAV: 80/1893
JULY 26:
KCHS: 78/2025
JULY 27:
KSAV: 80/1885
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...DENSE SMOKE ADVISORY FROM 8 PM THIS EVENING TO 10 AM EDT
WEDNESDAY FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT WEDNESDAY FOR AMZ340.
SMALL CRAFT ADVISORY UNTIL 5 AM EDT THURSDAY FOR AMZ360-362.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT WEDNESDAY NIGHT FOR
AMZ364-384.
BRS/NED
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