996
FXUS62 KCHS 071029
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
629 AM EDT FRI AUG 7 2026
WHAT HAS CHANGED
ALL KEY MESSAGES AND SECTIONS WERE UPDATED.
KEY MESSAGES
- 1) ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS TODAY WITH
INCREASING RAIN CHANCES AT THE COAST EARLY SATURDAY MORNING.
- 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.
DISCUSSION
KEY MESSAGE 1: ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
TODAY WITH INCREASING RAIN CHANCES AT THE COAST EARLY SATURDAY
MORNING.
A DEEP ONSHORE FLOW REGIME WILL HOLD THROUGH TONIGHT WITH THE
REGION POSITIONED ALONG THE WESTERN FRINGES OF THE BERMUDA-
AZORES HIGH. SOME NOCTURNAL SHOWER/TSTM ACTIVITY IS EXPECTED TO
DEVELOP OFFSHORE THROUGH DAYBREAK, WHICH MAY MAKE A RUN FOR THE
BEACHES, PARTICULARLY ALONG THE LOWER SOUTH CAROLINA COAST.
GOES-E TOTAL PRECIPITABLE WATER PRODUCTS ARE HIGHLIGHTING A
LARGE AREA OF DRIER AIR CHARACTERIZED BY PWATS <2" LURKING JUST
OFFSHORE. THE LATEST RAP SHOWS PWATS FALLING THROUGH DAY AS THIS
DRIER AIRMASS PUSHES ONSHORE, BUT SURFACE DEWPOINTS STILL LOOK
TO REMAIN NEAR CLIMATOLOGICAL NORMALS FOR EARLY AUGUST (LOWER-
MID 70S) AIDED BY THE FLOW OFF THE ATLANTIC. STILL, NET
MOISTURE VALUES WILL BE CONSIDERABLY LOWER COMPARED TO THE PAST
FEW DAYS WHICH WILL TEND TO LIMIT CONVECTION SOMEWHAT,
ESPECIALLY WITH A FAIRLY PROGRESSIVE SEA BREEZE EXPECTED TO MOVE
INLAND THROUGH THE AFTERNOON. POPS TODAY WERE LIMITED TO 20-40%,
HIGHEST INTERIOR SOUTHEAST SOUTH CAROLINA, AND IS CONSISTENT
WITH THE 07/01Z NBM. MODIFIED SOUNDINGS DO SHOW ELEVATED DCAPES
WHICH COULD YIELD A RISK STRONG OR LOCALLY DAMAGING WIND GUSTS
WITH ANY TSTMS THAT FORM. HIGHS WILL WARM INTO THE LOWER 90S
AWAY FROM THE BEACHES WITH HEAT INDICES PEAKING 100-105.
DEEP MOISTURE WILL BEGIN TO SURGE FROM THE SOUTH TONIGHT AS THE
UPPER RIDGES WEAKENS AND RETROGRADES FARTHER OFFSHORE AND A
BROAD MID-LEVEL WEAKNESS TO THE WEST NUDGES EAST. THIS WILL
GENERALLY RESULT IN AN UPTICK IN MARINE-BASED NOCTURAL
CONVECTION OVERNIGHT INTO EARLY SATURDAY, BUT THERE ARE MIXED
SIGNALS ON EXACTLY HOW MUCH COVERAGE WILL OCCUR AS DAYBREAK
APPROACHES. MOISTURE CONVERGENCE DOES NOT LOOK OVERLY STRONG
GIVEN THE FAIRLY WEAK WIND FIELDS NOTED BOTH ALOFT AND AT THE
SURFACE, SO SUSPECT SOME OF THE MORE RELIABLE CAMS ARE LIKELY
TOO AGGRESSIVE IN THE AMOUNT OF CONVECTION THAT WILL FORM OVER
THE ATLANTIC LATE. GIVEN THE UNCERTAINTIES, OPTED TO MAINTAINED
OUTPUT FROM THE NBM, WHICH HIGHLIGHTS POPS AS HIGH AS 40-60% AT
THE COAST LATE. ADJUSTMENTS MAY BE NEEDED IN LATER FORECAST
CYCLE UPDATES AS ADDITIONAL DATA AND MODEL OUTPUT ARE RECEIVED.
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.
AS THE PATTERN WITH DEEP HIGH PRESSURE OVER THE WESTERN
ATLANTIC AND EASTERN SEABOARD CONTINUES, DAILY SCATTERED
CONVECTION CHANCES WILL REMAIN POSSIBLE. HIGH-RES CONVECTION
ALLOWING MODELS CONTINUE TO SUGGEST THAT SATURDAY WILL START OFF
WITH MORNING SHOWERS AND THUNDERSTORMS AS A SHORTWAVE MOVES
ONSHORE, WITH ADDITIONAL DEVELOPMENT POSSIBLE ON ANY REMNANT
OUTFLOW BOUNDARIES THROUGHOUT THE AFTERNOON HOURS. PWATS NEAR 2
INCHES ARE EXPECTED THROUGHOUT THE DAY, WITH FORECAST SOUNDING
PROFILES SHOWING LONG AND SKINNY CAPE PROFILES, BOTH INDICATING
LOCALLY HEAVY RAINFALL WILL BE POSSIBLE. REFS AND HREF WOULD
BOTH SUGGEST SCATTERED 50-70% CHANCES FOR AN INCH IN A 6 HOUR
PERIOD, WITH SCATTERED 30-50% CHANCES FOR 2 INCHES IN A 6 HOUR
PERIOD. DIFFICULT TO NARROW DOWN AREAS MOST PRONE TO THE HEAVY
RAINFALL THREAT GIVEN THE SCATTERED NATURE OF THE CONVECTION,
WITH WPC INDICATING A LEVEL 1 OUT OF 4 (MARGINAL) RISK OF FLASH
FLOODING ACROSS THE REGION. GIVEN 1000-2000 J/KG OF SBCAPE AN
ISOLATED RISK FOR SEVERE WEATHER CAN'T BE ENTIRELY RULED OUT,
WITH THE RATHER WEAK 10 KNOTS OF 0-6KM BULK SHEAR SUGGESTING
STORMS WILL REMAIN PULSE-LIKE. GIVEN THE HIGH WATER LOADING
POTENTIAL AND ~500 J/KG OF DCAPE, STRONG WIND GUSTS WOULD BE THE
PRIMARY RISK.
FOR SUNDAY INTO NEXT WEEK, SHOWERS AND THUNDERSTORMS WILL BE
PRIMARILY DRIVEN BY THE EXPECTED AFTERNOON SEA-BREEZES AND
OUTFLOW BOUNDARIES. GIVEN SIMILAR ENVIRONMENTAL CONDITIONS EACH
DAY, LOCALLY HEAVY RAINFALL AND AN ISOLATED STRONG-SEVERE
THUNDERSTORM WILL BE POSSIBLE SUNDAY AND INTO NEXT WEEK.
AS FOR TEMPERATURES, SATURDAY IS LOOKING TO BE A TOUCH COOLER
GIVEN THE EARLIER START TO SHOWERS AND THUNDERSTORMS, WITH HIGHS
IN THE MID 80S TO LOWER 90S. SUNDAY INTO NEXT WEEK WILL LIKELY
SEE HIGH TEMPERATURES IN THE LOWER TO MID 90S, LIKELY GETTING
CLOSER TO THE MID 90S BY TUESDAY. WILL HAVE TO SEE HOW THE
DEWPOINT TEMPERATURE FORECAST TRENDS, AS AREAS ALONG THE COAST
CURRENTLY HAVE HEAT INDEX VALUES PEAKING INTO THE UPPER 100S ON
MONDAY AND TUESDAY, WHICH WOULD NECESSITATE HEAT ADVISORIES
BEING POSTED.
AVIATION /10Z FRIDAY THROUGH TUESDAY/
07/12Z TAFS:
KCHS/KJZI/KSAV: THERE ARE NO MAJOR CONCERNS FOR TODAY. ISOLATED
SHOWERS WILL MEANDER NEAR THE TERMINALS THROUGH MID-MORNING.
VCSH WAS HIGHLIGHTED TO ACCOUNT FOR THIS. THIS AFTERNOON, THE
RISK FOR TSTMS LOOK TO REMAIN WEST OF THE TERMINALS WITH THE SEA
BREEZE PASSING THROUGH A BIT EARLIER THAN NORMAL. THE RISK FOR
SHOWERS/TSTMS WILL INCREASE ALONG THE COAST BY DAYBREAK SATURDAY
AS A SURGE OF TROPICAL MOISTURE PUSHES ONSHORE. THE RISK THROUGH
12Z IS HIGHEST AT KSAV. VCSH WAS NOTED AFTER 09Z TO TREND FOR
NOW.
EXTENDED AVIATION OUTLOOK: PERIODIC FLIGHT RESTRICTIONS ARE
EXPECTED IN SHOWERS AND THUNDERSTORMS THROUGH EARLY NEXT WEEK.
LOCALLY HEAVY RAINFALL MAY PRODUCE BRIEF IFR OR LOWER VISIBILITY
RESTRICTIONS.
MARINE
THROUGH TONIGHT: SOUTHEAST WINDS 15 KT OR LESS WILL PERSIST INTO
TONIGHT WITH THE REGION LOCATED ALONG THE WESTERN FLANKS OF
ATLANTIC HIGH PRESSURE. SEAS 2-3 FT TODAY WILL BUILD TO 3-5 FT
TONIGHT.
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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