779
FXUS62 KCHS 202332
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
732 PM EDT MON JUL 20 2026
WHAT HAS CHANGED
ALL SECTIONS HAVE BEEN UPDATED.
KEY MESSAGES
- 1) SMOKE FROM THE HORSE ISLAND WILDFIRE WILL IMPACT NORTHEAST
BERKELEY COUNTY TONIGHT INTO TUESDAY.
- 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 MAY BRING GREATER RAINFALL CHANCES
LATE THIS WEEK THROUGH THIS WEEKEND.
DISCUSSION
KEY MESSAGE 1: SMOKE FROM THE HORSE ISLAND WILDFIRE WILL IMPACT
NORTHEAST BERKELEY COUNTY TONIGHT INTO TUESDAY.
A DENSE SMOKE ADVISORY HAS BEEN REQUESTED BY THE U.S. FOREST SERVICE
FOR NORTHEAST PORTIONS OF BERKELEY COUNTY IN RESPONSE TO THE HORSE
ISLAND WILDFIRE. SMOKE IN THE VICINITY OF THE FIRE IS SIGNIFICANT
AND CONDITIONS WILL DETERIORATE OVERNIGHT AS THE NOCTURNAL INVERSION
DEVELOPS. THE LATEST HYSPLIT OUTPUT SHOWS THE WORST OF THE SMOKE
WILL REMAIN ACROSS NORTHEAST BERKELEY COUNTY AND EXTEND ACROSS
THE SANTEE RIVER INTO A SMALL AREA OF SOUTHWEST GEORGETOWN
COUNTY. 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 TUESDAY
ALTHOUGH VISIBILITIES SHOULD IMPROVE SOME BY MID-MORNING AS
DISPERSION INCREASES AND MIXING HEIGHTS RISE. ANOTHER DENSE
SMOKE ADVISORY MAY BE NEEDED TUESDAY NIGHT AS SMOKE SETTLES
DURING THE OVERNIGHT HOURS.
KEY MESSAGE 2: HOT AND HUMID CONDITIONS ACROSS COASTAL SOUTH
CAROLINA AND GEORGIA THROUGH MID-WEEK. HEAT ADVISORIES COULD BE
NEEDED.
THE FORECAST AREA WILL REMAIN OF THE EDGE OF A H5 RIDGE CENTERED OFF
THE SOUTHEAST U.S. COAST. SFC HIGH PRESSURE OVER THE WESTERN
ATLANTIC WILL PROVIDE THE REGION WITH SOUTH WINDS TUESDAY AND
WEDNESDAY, WITH OCCASIONAL GUSTS DURING THE AFTERNOON. THIS PATTERN
SHOULD SUPPORT HOT DAYTIME TEMPERATURES, WITH HIGHS GENERALLY IN THE
MID 90S. AFTERNOON DEWPOINTS MAY RANGE IN THE MID TO UPPER 70S,
ESPECIALLY AFTER THE PASSAGE OF THE SEA BREEZE. HEAT INDEX VALUES
MAY PEAK BETWEEN 105 TO 109 DEGREES RIGHT ALONG THE COAST. IT IS
POSSIBLE THAT A HEAT ADVISORY COULD BE NEEDED.
LOW TEMPERATURES ARE FORECAST TO RANGE IN THE UPPER 70S, WITH VALUES
AROUND 80 DEGREES ALONG THE COAST. THE MILD LOW TEMPERATURES COULD
CHALLENGE SOME RECORD HIGH LOW TEMPERATURES THIS WEEK, SEE CLIMATE
SECTION BELOW.
KEY MESSAGE 3: A SLOW-MOVING COLD FRONT MAY BRING GREATER RAINFALL
CHANCES LATE THIS WEEK THROUGH THIS WEEKEND.
RECENT RUNS OF THE GFS AND ECMWF INDICATE THAT A COLD FRONT MAY
REACH THE FORECAST AREA BY EARLY THURSDAY. GUIDANCE INDICATES THAT
THE FRONT WILL SLOW AS IT APPROACHES THE COAST, THEN POSSIBLY REMAIN
NEARLY STATIONARY THROUGH THIS WEEKEND. AT H5, A BROAD TROUGH IS
FORECAST TO SETTLE OVER THE EAST COAST, POSSIBLY AMPLIFYING INTO
SUNDAY. FORECAST SOUNDINGS INDICATE VERY MOIST CONDITIONS ACROSS THE
REGION, WITH PW VALUES POSSIBLY RANGING BETWEEN 2.2 TO 2.4 INCHES ON
SATURDAY. GIVEN THE DEEP MOISTURE, SYNOPTIC SCALE FORCING, AND
PERIODS OF MODERATE INSTABILITY, THE FORECAST WILL FEATURE AT LEAST
LIKELY POPS. THE EXCESSIVE RAINFALL OUTLOOKS WEDNESDAY THROUGH
FRIDAY INDICATES A MARGINAL RISK FOR THE AREA.
AVIATION /00Z TUESDAY THROUGH SATURDAY/
21/00Z AVIATION DISCUSSION:
KCHS/KJZI/KSAV: VFR THROUGH 22/00Z.
EXTENDED AVIATION OUTLOOK: PREVAILING VFR THROUGH MID- WEEK.
CHANCES OF FLIGHT RESTRICTIONS INCREASE LATER THIS WEEK WITH A
GREATER COVERAGE OF SHOWERS/THUNDERSTORMS.
MARINE
TODAY AND TONIGHT: THE GRADIENT WILL REMAIN PINCHED BETWEEN
HIGH PRESSURE CENTERED OFFSHORE AND AN INLAND TROUGH. SOUTH TO
SOUTHWEST WINDS COULD GUST UP TO 20 KT, BUT SHOULD REMAIN BELOW
SMALL CRAFT ADVISORY CRITERIA. WITH LITTLE TO NO SWELL ENERGY,
SEAS WILL RANGE FROM 2 TO 3 FT THROUGH THE EVENING, BEFORE
INCREASING TO 3 TO 4 FT OVERNIGHT.
TUESDAY THROUGH FRIDAY: 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 ON TUESDAY, WITH GUSTY CONDITIONS
EXPECTED ACROSS THE MARINE ZONES INTO WEDNESDAY NIGHT. IN ADDITION,
SEAS WILL BUILD ON TUESDAY, WITH 6 FT SEA COMMON ACROSS THE WATERS
TUESDAY NIGHT IN WEDNESDAY MORNING. A SMALL CRAFT ADVISORY IS IN
EFFECT FROM TUESDAY AFTERNOON TO WEDNESDAY NIGHT. AS A COLD FRONT
APPROACHES THE REGION ON THURSDAY AND REMAINS INTO FRIDAY, THE
PRESSURE GRADIENT ACROSS THE REGION WILL WEAKEN. THURSDAY AND
FRIDAY, WINDS ARE FORECAST TO REMAIN FROM THE SOUTH BETWEEN 15 TO 20
KTS WITH SEAS AROUND 3 FT.
RIP CURRENTS: A MODERATE RISK OF RIP CURRENTS IS IN EFFECT FOR THE
SC AND GA BEACHES THROUGH WEDNESDAY, GIVEN ENHANCED WINDS ALONG THE
COASTLINE AND WAVE PERIODS UP TO 6 SECONDS. BREAKERS MAY EXCEED 4 FT
ON WEDNESDAY, WITH WAVE PERIODS BETWEEN 6 TO 7 SECONDS. IT IS
POSSIBLE THAT A PORTION OF THE SC COAST MAY NEED A HIGH RISK IF
SWELL WAVES OR WIND SPEEDS INCREASE FROM THE CURRENT FORECAST.
CLIMATE
RECORD HIGH MINIMUM TEMPERATURES:
JULY 20:
KCHS: 79/2025
KCXM: 83/2000
KSAV: 79/1942
JULY 21:
KCHS: 80/1986
KCXM: 83/1998
JULY 22:
KCHS: 81/2011
KCXM: 83/2011
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...DENSE SMOKE ADVISORY UNTIL 10 AM EDT TUESDAY FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY FROM NOON TUESDAY TO 5 AM EDT THURSDAY
FOR AMZ360-362.
SMALL CRAFT ADVISORY FROM 2 PM TUESDAY TO MIDNIGHT EDT
WEDNESDAY NIGHT FOR AMZ364-384.
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