189
FXUS62 KCHS 071818
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
218 PM EDT FRI AUG 7 2026
WHAT HAS CHANGED
CONFIDENCE HAS INCREASED IN THE HEAVY RAINFALL POTENTIAL
SATURDAY MORNING, ESPECIALLY ACROSS THE SE SC COASTLINE. A KEY
MESSAGE WAS ADDED FOR THE MINOR COASTAL FLOODING POTENTIAL NEXT
WEEK. ALSO, CONFIDENCE IS BEGINNING TO INCREASE IN THE
POTENTIAL FOR DANGEROUS HEAT THROUGH THE MIDDLE OF NEXT WEEK.
KEY MESSAGES
- 1) THERE IS THE POTENTIAL FOR LOCALIZED HEAVY RAINFALL EARLY
SATURDAY MORNING ACROSS THE FORECAST AREA, ESPECIALLY ALONG
THE COASTAL COUNTIES.
- 2) THE TYPICAL SUMMERTIME PATTERN WILL CONTINUE THIS WEEKEND
INTO NEXT WEEK. THE THREAT FOR ISOLATED STRONG TO SEVERE
THUNDERSTORMS AND LOCALIZED HEAVY RAINFALL WILL EXIST EACH
DAY.
- 3) MINOR COASTAL FLOODING POSSIBLE ALONG THE SOUTH CAROLINA
COAST WITH EVENING HIGH TIDE CYCLES NEXT WEEK.
DISCUSSION
KEY MESSAGE 1: THERE IS THE POTENTIAL FOR LOCALIZED HEAVY RAINFALL
EARLY SATURDAY MORNING ACROSS THE FORECAST AREA, ESPECIALLY ALONG
THE COASTAL COUNTIES.
AN INVERTED SURFACE TROUGH LOCATED OFF THE FL ATLANTIC COAST
FRIDAY AFTERNOON IS FORECAST TO MEANDER CLOSER TOWARDS THE SE
COASTLINE TONIGHT AND INTO EARLY SATURDAY MORNING. THIS FEATURE
WILL SERVE AS THE MAIN DRIVER OF POTENTIAL SHOWERS AND TSTORMS
EARLY SATURDAY MORNING, AS CONVECTION OVER THE MARINE WATERS
PUSHES ONSHORE. THE HREF IS THE MOST AGGRESSIVE OF THE CAMS,
AND FEATURES THE EARLIEST ARRIVAL TIMING WITH THE HEAVY RAIN
POTENTIAL, WITH THE 12Z HREF FROM TODAY (8/7) SHOWING THE
PROBABILITY OF >2" ALONG THE COASTAL COUNTIES AS ROUGHLY 20-30%.
THE 12Z HRRR IS SLIGHTLY SLOWER THAN THE HREF WITH BRINGING THE
CONVECTION ONSHORE, BUT STILL FEATURES THE THREAT OF HEAVY
RAINFALL. THE WEATHER PREDICTION CENTER HAS HIGHLIGHTED MOST OF
THE LOCAL FORECAST AREA IN A SLIGHT RISK FOR EXCESSIVE RAINFALL
TOMORROW (SATURDAY). GIVEN THE UNCERTAINTY REGARDING THE TIMING
THE FORECAST FEATURES THE RAW NBM, WHICH SEEMED TO BE A GOOD
AVERAGE OF THE GUIDANCE, WITH SHOWERS/TSTORMS MOVING ONSHORE
ROUGHLY IN THE 6-8AM TIMEFRAME. RAINFALL TOTALS ARE FORECAST TO
BE 0.5-1", WITH LOCALLY HIGHER AMOUNTS (HIGHEST ALONG THE
COAST).
KEY MESSAGE 2: THE TYPICAL SUMMERTIME PATTERN WILL CONTINUE THIS
WEEKEND INTO NEXT WEEK. THE THREAT FOR ISOLATED STRONG TO
SEVERE THUNDERSTORMS AND LOCALIZED HEAVY RAINFALL WILL EXIST
EACH DAY.
FOR SUNDAY AND MONDAY, HIGH PRESSURE RIDGING IN FROM OFFSHORE AND
VERY WEAK TROUGHING INLAND WILL BRING MAINLY SCATTERED, DIURNALLY
DRIVEN CONVECTION. A FEW STRONGER TO MARGINALLY SEVERE STORMS ARE
POSSIBLE EACH AFTERNOON, BUT THE OVERALL SEVERE RISK IS LOW.
ADDITIONALLY, WITH VERY LIGHT FLOW THROUGHOUT THE CLOUD LAYER, SLOW
STORM MOTIONS WILL BE THE NORM, AND LOCALLY HEAVY RAINFALL WILL
OCCUR UNDER THE STRONGEST STORMS. EXPECT HEAT INDEX VALUES TO REACH
100-105 EACH AFTERNOON, WITH SOME LOCATIONS POTENTIALLY THREATENING
THE 108 HEAT ADVISORY CRITERIA ALONG THE HWY 17/SEA BREEZE CORRIDOR
EACH AFTERNOON.
UPPER SUBSIDENCE STRENGTHENS BY THE MIDDLE OF NEXT WEEK, RESULTING
IN A MODEST REDUCTION IN AFTERNOON THUNDERSTORM COVERAGE, BUT WARMER
TEMPS AND GREATER HEAT INDEX VALUES. TUESDAY THROUGH THURSDAY
LOOK TO BRING MORE COVERAGE OF 105-110 HEAT INDEX VALUES,
ESPECIALLY CLOSER TO THE COAST. CONTINUE TO MONITOR FORECAST
UPDATES FOR THIS POTENTIAL PERIOD OF DANGEROUS HEAT.
KEY MESSAGE 3: MINOR COASTAL FLOODING POSSIBLE ALONG THE SOUTH
CAROLINA COAST WITH EVENING HIGH TIDE CYCLES NEXT WEEK.
PERIGEAN NEW MOON WILL BRING ELEVATED TIDAL RANGES NEXT WEEK. EVEN
MODEST TIDAL DEPARTURES DURING THE EVENING HIGH TIDE CYCLES MONDAY
THROUGH THURSDAY WOULD BRING TIDAL LEVELS APPROACHING OR EXCEEDING
MINOR COASTAL FLOODING THRESHOLDS. CONTINUE TO MONITOR FORECAST
UPDATES THROUGH THE WEEKEND AS THE TOTAL WATER LEVEL FORECAST GETS
REFINED.
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
PREVAILING VFR THROUGH THE REMAINDER OF THIS AFTERNOON AND INTO THIS
EVENING AT KCHS/KJZI/KSAV. SHOWERS AND TSTORMS OVER THE OFFSHORE
ATLANTIC WATERS ARE FORECAST TO PUSH ONSHORE EARLY SATURDAY MORNING.
THERE IS SOME UNCERTAINTY IN THE TIMING OF THIS PRECIPITATION SO THE
18Z TAFS ONLY FEATURE A TEMPO GROUP TO ADDRESS THIS THREAT.
RESTRICTIONS ARE LIKELY IF SHOWERS/TSTORMS IMPACT THE TERMINALS
TOMORROW MORNING, WITH THE GREATEST THREAT AT KCHS/KJZI.
EXTENDED AVIATION OUTLOOK: PERIODIC FLIGHT RESTRICTIONS ARE EXPECTED
IN SHOWERS AND THUNDERSTORMS THIS WEEK AND INTO THIS WEEKEND.
MARINE
THROUGH TONIGHT: QUIET CONDITIONS THROUGH THE REMAINDER OF THIS
AFTERNOON AND INTO TONIGHT ACROSS THE MARINE WATERS. AS AN INVERTED
TROUGH, CURRENTLY OFFSHORE OF THE ATLANTIC COAST OF FL, MEANDERS
TOWARDS THE SE COAST OVERNIGHT, SHOWERS AND THUNDERSTORMS ARE
FORECAST TO DEVELOP OVER THE MARINE WATERS. THESE SHOWERS/TSTORMS
WILL PERSIST ACROSS THE MARINE WATERS INTO SATURDAY MORNING.
SATURDAY THROUGH TUESDAY: ATLANTIC HIGH PRESSURE WILL BE THE
DOMINANT SYNOPTIC FEATURE THROUGH THE WEEKEND. LIGHT TO MODERATE
WINDS PREVAIL WITH GUSTY WINDS ALONG THE LAND/SEA INTERFACE EACH
AFTERNOON ASSOCIATED WITH THE SEA BREEZE. BE ALERT FOR THE POTENTIAL
FOR NOCTURNAL JETTING TO SET UP SUNDAY INTO EARLY NEXT WEEK, KEEPING
BREEZY CONDITIONS IN PLACE ALONG THE BEACHES OVERNIGHT. THIS FEATURE
IS TYPICALLY POORLY RESOLVED BY MODELS, BUT THE COMBINATION OF THE
WEAK SURFACE TROUGH SHIFTING INLAND WITH PERSISTENT STRONG HIGH
PRESSURE OFFSHORE AND VERY WARM WATER MAKES FOR A FAVORABLE
SETUP.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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