441
FXUS62 KCHS 200639
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
239 AM EDT MON JUL 20 2026
WHAT HAS CHANGED
A NEW KEY MESSAGE FOR SMOKE GENERATED BY THE HORSE ISLAND
WILDFIRE WAS INTRODUCED. THE AVIATION AND MARINE SECTIONS WERE
ALSO UPDATED.
KEY MESSAGES
- 1) SMOKE FROM THE HORSE ISLAND WILDFIRE WILL IMPACT NORTHEAST
BERKELEY COUNTY TONIGHT INTO MONDAY.
- 2) HOT AND HUMID CONDITIONS ARE EXPECTED ACROSS THE AREA INTO
MIDWEEK. HEAT ADVISORIES COULD BE NEEDED.
- 3) A SHIFT IN THE SYNOPTIC PATTERN WILL LIKELY BRING HIGHER
PRECIPITATION CHANCES TOWARDS THE END OF THE WEEK.
DISCUSSION
KEY MESSAGE 1: SMOKE FROM THE HORSE ISLAND WILDFIRE WILL IMPACT
NORTHEAST BERKELEY COUNTY TONIGHT INTO MONDAY.
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 EXTENDING ACROSS THE SANTEE RIVER INTO A SMALL AREA
OF SOUTHWEST GEORGETOWN COUNTY. VISIBILITIES MAY DROP BELOW 1/4
MILE AT TIMES OVERNIGHT, ESPECIALLY ALONG PARTS OF HIGHWAY 45.
ROAD CLOSURES ARE POSSIBLE. SMOKE WILL LIKELY REMAIN AN ISSUE
INTO MONDAY ALTHOUGH VISIBILITIES SHOULD IMPROVE SOME BY MID-
MORNING AS DISPERSION INCREASES AND MIXING HEIGHTS RISE. ANOTHER
DENSE SMOKE ADVISORY MAY BE NEEDED MONDAY NIGHT AS SMOKE SETTLES
DURING THE OVERNIGHT HOURS.
KEY MESSAGE 2: HOT AND HUMID CONDITIONS ARE EXPECTED ACROSS THE
AREA INTO MIDWEEK. HEAT ADVISORIES COULD BE NEEDED.
VERY LITTLE CHANGE IN THE FORECAST IS EXPECT THE NEXT COUPLE OF
DAYS AS THE HEAT AND HUMIDITY LINGERS THROUGH WEDNESDAY. THE
OVERALL PLAYERS REMAIN THE SAME ACROSS THE AREA WITH DEEP UPPER
TROUGHING ACROSS THE NORTHEAST, HIGH PRESSURE TO OUR EAST OVER
THE ATLANTIC AND A TROPICAL DEPRESSION OVER THE NORTHERN GULF.
MONDAY AND TUESDAY, WILL SEE HIGHS TOPPING OUT IN THE LOW TO
MID 90S AND DEWPOINTS ABLE TO MIX OUT INTO THE LOW 70S. THIS
SHOULD BE ENOUGH TO KEEP HEAT INDICES IN THE 100 TO 105 RANGE
AND WHILE THIS IS STILL HOT, THIS IS MORE IN LINE WITH TYPICAL
SUMMERTIME CONDITIONS FOR THE AREA. A FEW LOCATIONS MAY BE ABLE
TO CRACK 108 TO 110 ALONG THE IMMEDIATE COASTLINE ESPECIALLY
ACROSS COASTAL SOUTH CAROLINA AS THE SEABREEZE SLOWLY MOVES
INLAND. CONFIDENCE IN REACHING THOSE VALUES FOR A LONG ENOUGH
PERIOD OF TIME IS TOO LOW AT THIS TIME TO SUPPORT AN ADVISORY
FOR TOMORROW. NONETHELESS, THE DIFFERENCE BETWEEN 104/105 AND
108/109 IS NOT THAT NOTICEABLE AND THE KEY TAKEAWAY IS THAT
CONDITIONS STILL REMAIN ON THE HOTTER SIDE.
THE BIGGER QUESTIONS COME ON WEDNESDAY AS DEWPOINTS SHOULD
GRADUALLY INCREASE AS BETTER MOISTURE ARRIVES. THIS WILL BE
AIDED BY THE DEPRESSION IN THE GULF AS IT SLOWLY TRACKS
WESTWARD. THE USUAL TROUBLE AREAS BEHIND THE SEABREEZE COULD
APPROACH ADVISORY CRITERIA COME WEDNESDAY AS DEWPOINTS CLIMB
INTO THE UPPER 70S TO NEAR 80 RESULTING IN HEAT INDICES OF
AROUND 108 TO 110. THIS COULD REQUIRE HEAT ADVISORIES ACROSS
PORTIONS OF THE AREA. THE BIGGEST QUESTION FOR WEDNESDAY WILL BE
IF CONVECTIVE COVERAGE WILL BE ENOUGH TO LIMIT THE HEAT ACROSS
THE AREA. WITH BETTER MOISTURE USUALLY COMES MORE STORMS AND
MORE STORMS EARLIER IN THE DAY COULD LIMIT HOW HOT WE ARE ABLE
TO GET.
KEY MESSAGE 3: A SHIFT IN THE SYNOPTIC PATTERN WILL LIKELY BRING
HIGHER PRECIPITATION CHANCES TOWARDS THE END OF THE WEEK.
AS A LOW PRESSURE IN THE NORTHERN GULF (TD2) SLOWLY SHIFTS WESTWARD
THROUGH THE MID-WEEK, A HIGH PRESSURE WILL REMAIN CENTERED OVER THE
WESTERN ATLANTIC. SIMULTANEOUSLY, A MID-LVL TROUGH WILL SITUATE
ITSELF OVER THE EASTERN CONUS BY MID-WEEK. AT THE SURFACE, AN
ASSOCIATED COLD FRONT WILL APPROACH THE REGION ON WEDNESDAY, LIKELY
STALLING IN THE VICINITY OF THE FORECAST AREA INTO THE END OF THE
WEEK. THIS STALLED FRONT WILL LIKELY BRING INCREASED PRECIPITATION
CHANCES TO THE REGION. THE WEATHER PREDICTION CENTER (WPC) HAS THE
ENTIRE FORECAST AREA OUTLOOKED IN A MARGINAL RISK FOR EXCESSIVE
RAINFALL ON THURSDAY, WITH A SLIGHT RISK OVER NORTHERN CHARLESTON
AND BERKELEY COUNTIES.
AVIATION /06Z MONDAY THROUGH FRIDAY/
20/06Z TAFS: EXPECT VFR CONDITIONS WILL PREVAIL KCHS/KJZI/KSAV
THROUGH THE PERIOD. LIGHT SOUTHWESTERLY FLOW OVERNIGHT SHOULD
STRENGTHEN THIS AFTERNOON AS THE SEABREEZE SHIFTS INLAND BETWEEN 18-
19Z FOR KCHS/KJZI AND ~20Z FOR KSAV. AS THE SEABREEZE SHIFTS MORE
INLAND, THE WINDS SHOULD VEER OUT MORE OUT OF THE SOUTH WITH GUSTS
UP TO 20-21 KTS NOTED. GUSTS SHOULD SUBSIDE AFTER 00Z, ALTHOUGH
SUSTAINED SOUTH-SOUTHWEST WINDS AROUND 10 KTS WILL CONTINUE THROUGH
THE END OF THE PERIOD. NO MENTION OF SHOWERS AND THUNDERSTORMS AS
COVERAGE REMAINS RATHER LIMITED.
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: THE GRADIENT WILL REMAIN PINCHED BETWEEN A HIGH PRESSURE
CENTERED OFFSHORE AND THE PIEDMONT TROUGH THROUGHOUT TODAY. EXPECT
WIND SPEEDS TO RANGE FROM 10 TO 15 KTS WITH GUSTS UP TO 20 KTS.
THUS, MARINE CONDITIONS REMAIN UNDER SMALL CRAFT ADVISORY (SCA)
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: AS A MID-LVL TROUGH SLOWLY SITUATES ITSELF
ACROSS THE REGION THROUGH THE PERIOD, AN ASSOCIATED COLD FRONT WILL
APPROACH THE LOCAL WATERS ON WEDNESDAY AND THEN STALL OUT IN THE
VICINITY. THIS WILL YIELD BREEZY SOUTH-SOUTHEASTERLY FLOW ON TUESDAY
THROUGH THURSDAY. ALSO, SOUTHERLY SWELL WILL BRIEFLY SURGE INTO THE
LOCAL WATERS ON TUESDAY NIGHT AND ALLOW FOR SEAS TO INCREASE FROM 4
TO 6 FT (ESP. ACROSS THE SOUTH CAROLINA WATERS). THUS, SCAS WILL
LIKELY BE NEEDED TUESDAY THROUGH WEDNESDAY GIVEN THE ELEVATED WINDS
AND SEAS. THEREAFTER, SEAS SHOULD TAPER BACK ON WEDNESDAY AFTERNOON
THROUGH THE REST OF THE PERIOD.
RIP CURRENTS: A MODERATE RISK OF RIP CURRENTS IS IN EFFECT FOR OUR
SE GA BEACHES THROUGH THIS EVENING, GIVEN ENHANCED WINDS ALONG THE
COASTLINE AND WAVE PERIODS UP TO 6 SECONDS. A MODERATE RISK RETURNS
TO ALL AREA BEACHES ON TUESDAY AS 6 SECOND SWELL AND ENHANCED SSW/SW
WINDS DEVELOP ALONG THE ENTIRE COASTLINE.
CLIMATE
RECORD HIGH MINIMUM TEMPERATURES:
JULY 19:
KCHS: 79/1986
KCXM: 83/1986
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 THIS MORNING FOR SCZ045.
MARINE...NONE.
BLACK/DENNIS
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