249
FXUS62 KCHS 291458
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1058 AM EDT SAT MAR 29 2025
SYNOPSIS
DRY, HIGH PRESSURE WILL PREVAIL THROUGH TODAY, THEN RAIN AND
THUNDERSTORM CHANCES INCREASE INTO SUNDAY AND MONDAY FOLLOWED
BY A STRONG COLD FRONT MONDAY EVENING. A FRONT COULD LINGER
NEARBY MID-WEEK, BEFORE STRONGER HIGH PRESSURE PREVAILS LATE
NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
TODAY: ALOFT, H5 SHORTWAVE ENERGY SHOULD BEGIN TO RIPPLE ACROSS THE
REGION LATE DAY ALONG THE NORTHEASTERN EDGE OF A BROAD RIDGE AXIS
PLACED WELL OFFSHORE. AT THE SFC, WEAK COASTAL TROUGHING SHOULD
SLOWLY TRACK ALONG THE WESTERN PERIPHERY OF THE ATLANTIC HIGH,
PERHAPS SPAWNING A FEW SHOWERS ACROSS COASTAL WATERS THAT ATTEMPT TO
REACH COASTAL AREAS LATER THIS AFTERNOON. UNTIL THEN, RADAR RETURNS
CONTINUE ACROSS PORTIONS OF SOUTHEAST GEORGIA LATE THIS MORNING, BUT
ACTIVITY WILL LIKELY NOT RESULT IN PRECIP REACHING THE SFC AS MOST
GUIDANCE SUGGESTS DEEPER MOISTURE TO BE LACKING (PWATS AROUND 1.0
INCH) AND LOCAL SOUNDINGS SHOWING A DEEP POCKET OF MID-LVL DRY AIR
PERSISTING FOR A BULK OF THE DAY. AT THIS TIME, DRY CONDITIONS
REMAIN IN THE FORECAST FOR ALL ZONES, BUT AN ISOLATED SHOWER CAN NOT
BE RULED OUT COMPLETELY DURING PEAK HEATING THIS AFTERNOON. WARM AIR
ADVECTION, PARTLY TO MOSTLY SUNNY SKIES, AND 1000-850 MB THICKNESSES
REMAIN SUPPORTIVE OF MAX TEMPS IN THE UPPER 70S TO AROUND 80 DEGREES
INLAND. AN ONSHORE WIND SHOULD LIMIT TEMPS TO THE LOW-MID 70S CLOSER
AT THE BEACHES.
TONIGHT: SUBTLE IMPULSES MOVE THROUGH ALOFT, WHILE SURFACE HIGH
PRESSURE WEAKENS ACROSS THE AREA. THE PWAT CLIMBS TO NEAR OR
GREATER THAN 1.5 INCHES, SO THAT AND SOME FORCING FROM THE
IMPULSES, MIGHT BE ABLE TO GENERATE A FEW SHOWERS. BUT WITH THE
LACK OF ANY INSTABILITY, AND THE MODEL CONSENSUS THAT WE STAY
RAINFREE, WE HAVE NO POPS GREATER THAN 14% IN THE LATEST
FORECAST. A CONTINUED DEEP SOUTHERLY FLOW AND AT LEAST SOME
CLOUD COVER WILL YIELD LOWS DOWN IN THE UPPER 50S AND LOWER 60S.
ALTHOUGH WITH LIGHT OR CALM WINDS, PLUS THE POTENTIAL FOR LESS
CLOUD COVER, LOWS COULD BE SEVERAL DEGREES COOLER.
SHORT TERM /SUNDAY THROUGH TUESDAY/
ANOTHER WARM DAY IS EXPECTED FOR SUNDAY, WITH HIGHS IN THE UPPER 70S
TO LOWER 80S. THROUGHOUT THE DAY, WE REMAIN UNDER WEST-SOUTHWESTERLY
FLOW ALOFT WHICH WILL CONTINUE TO ADVECT WEAK SHORTWAVES ACROSS THE
AREA, ALONG WITH BROAD WARM-AIR ADVECTION (WAA) IN THE MID-LEVELS.
COMBINED WITH THE INCREASING LOW-LEVEL MOISTURE (PRECIPITABLE WATER
(PWAT) VALUES APPROACH/EXCEED 1.5"), WE'LL SEE CHANCES (30-70%) FOR
SCATTERED SHOWER AND ISOLATED THUNDERSTORMS THROUGH MOST OF THE DAY,
WITH HIGHEST CHANCES ACROSS INLAND SOUTHEAST GEORGIA COUNTIES.
BIGGEST AREA OF UNCERTAINTY ARE FOR THOSE FROM BEAUFORT AND UP
TOWARDS THE CHARLESTON TRI-COUNTY REGION, AS SOME OF THE HIGHER
RESOLUTION GUIDANCE IS SHOWING A WEAK 850MB HIGH PRESSURE DEVELOPING
JUST OFF THE COAST, WHICH WOULD ACT TO BLOCK SHOWERS/STORMS FOR
THOSE AREAS THROUGHOUT THE DAY. HOWEVER, THROUGHOUT THE EVENING
HOURS THE HIGH WEAKENS/SHIFTS NORTHEASTWARDS, ALLOWING FOR RAIN
CHANCES TO SHIFT NORTHEASTWARDS OVERSPREADING THE TRI-COUNTY REGION.
RAINFALL AMOUNTS REMAIN ON THE LOWER SIDE, CONSIDERING THERE ISN'T
STRONG FORCING AND INSTABILITY REMAINS ON THE WEAKER SIDE (<1000
J/KG). 24 HOUR RAINFALL PROBABILITIES FROM THE NBM FOR 0.10" (0.25")
INCHES ARE IN THE 40S (30S) NEAR THE CHARLESTON TRI-COUNTY REGION,
RISING INTO THE MID 70S (50S) ACROSS THE INLAND GEORGIA COUNTIES.
CHANCES FOR RAINFALL DECREASE INTO THE OVERNIGHT HOURS AS THE MOSTLY
DIURNALLY DRIVEN SHOWERS RUN OUT OF INSTABILITY.
FOR MONDAY, THE REGION REMAINS IN THE WARM-SECTOR WELL OUT AHEAD OF
AN ADVANCING COLD FRONT, WITH A LINE OF SHOWERS AND THUNDERSTORMS
OUT AHEAD OF THE FRONT. THIS WILL RESULT IN EVEN WARMER TEMPERATURES
(UPPER 70S TO MID 80S) AS INSTABILITY DEVELOPS ACROSS THE REGION,
PEAKING IN THE 1000-2000 J/KG RANGE WITH DECENT SHEAR OF 30-40
KNOTS. DOWNDRAFT CAPE VALUES UP TO NEAR 1000 J/KG ARE ALSO BEING
SHOWN, WHICH COMBINED WITH LOW-LEVEL LAPSE RATES NEAR 7 DEG C/KM
WOULD SUGGEST STRONG/DAMAGING WINDS BEING THE PRIMARY THREAT WITH
THE STRONGEST THUNDERSTORMS. WHILE DIURNALLY DRIVEN THUNDERSTORMS
CAN'T BE RULED OUT, THE 00Z GUIDANCE SUITE WOULD SUGGEST DIURNALLY
DRIVEN STORMS WOULD STRUGGLE TO REALIZE THE MUCAPE, AND WOULD THUS
REMAIN ON THE WEAKER SIDE. THE 00Z MODELS ALSO SHOW THE
AFOREMENTIONED LINE OF SHOWERS AND THUNDERSTORMS BECOMING MORE
BROKEN AS THEY APPROACH FROM THE NORTHWEST DURING THE LATE
AFTERNOON/EARLY EVENING HOURS, LEADING TO LESS INSTABILITY BEING
AVAILABLE TO THEM. SO WHILE IT IS LARGELY TIMING DEPENDENT, THERE IS
A CONDITIONAL RISK OF SEVERE WEATHER, WITH SPC CONTINUING TO PLACE A
LEVEL 2 OUT OF 5 RISK FOR SEVERE WEATHER. THE CIPS ANALOGUE PAGE IS
LESS CONVINCED OF THE SEVERE WEATHER THREAT, WHICH WOULD SUGGEST
HISTORICALLY THIS SETUP ENDS UP NOT PRODUCING SEVERE WEATHER, THOUGH
MACHINE LEARNING TECHNIQUES CONTINUE TO SHOW CHANCES FOR SEVERE
WEATHER EXISTS.
SOMETIME IN THE EVENING AND OVERNIGHT HOURS THE AFOREMENTIONED LINE
OF SHOWERS AND THUNDERSTORMS PUSHES THROUGH THE REGION, WITH THE
COLD FRONT CLEARING THE AREA INTO THE EAST BY TUESDAY MORNING. 24
HOUR RAINFALL PROBABILITIES FROM THE NBM FOR 0.10" (0.25") INCHES
ARE IN THE 80S (MID 40S) ALONG THE COASTAL REGIONS, RISING INTO THE
UPPER 80S TO LOWER 90S (MID 60S) ACROSS THE INLAND AREAS. A SURFACE
HIGH PRESSURE BUILDS IN FROM THE NORTH, WITH UPPER LEVEL RIDGING
TAKING PLACE ALOFT. HIGHS ARE A TOUCH COOLER, THOUGH STILL IN THE
UPPER 70S TO LOWER 80S.
LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/
THE LONG TERM CONTINUES TO REMAIN LARGELY WARM AND DRY AS A STRONG
UPPER LEVEL RIDGE SETS UP JUST OFF TO OUR SOUTH, THOUGH GIVEN THE
SOUTHWESTERLY FLOW ALOFT AND PERIODIC WARM-AIR ADVECTION IN THE MID
LEVELS, CAN'T RULE OUT A COUPLE STRAY SHOWERS THROUGH THE MIDDLE OF
THE WEEK. ENSEMBLE SITUATIONAL AWARENESS TABLES SHOW THE STRONG
UPPER LEVEL RIDGE WILL LIKELY PRODUCE ABNORMALLY HIGH SURFACE
TEMPERATURES, WITH THE DETERMINISTIC NBM COMING IN CLOSE TO THE
25TH PERCENTILE OF AVAILABLE GUIDANCE. COLLABORATED TO RAISE
TEMPERATURES WEDNESDAY THROUGH FRIDAY TO BE CLOSER TO THE 50TH
PERCENTILE, WHICH RESULTS IN LOWER 90S BECOMING POSSIBLE ACROSS
OUR INLAND SOUTHEASTERN GEORGIA AND SOUTH CAROLINA COUNTIES, AND
LOWER TO MID 80S ALONG THE COAST. THE RANGE BETWEEN THE 50TH
AND 90TH PERCENTILE DOES SHRINK, THOUGH THERE IS ROOM FOR A
COUPLE MORE DEGREES TO BE ADDED TO THE FORECAST SHOULD MODEL
AGREEMENT INCREASE.
AVIATION /15Z SATURDAY THROUGH WEDNESDAY/
KCHS/KJZI/KSAV: VFR WILL PREVAIL THROUGH 06Z SUNDAY. S-SE WINDS
WILL GET A BIT GUSTY THIS AFTERNOON DURING PEAK HEATING AND THE
PASSAGE OF THE SEA BREEZE.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS ARE POSSIBLE SUNDAY
MORNING AND AGAIN SUNDAY NIGHT INTO MONDAY, MAINLY DUE TO LOW
CEILINGS. A LINE OF THUNDERSTORMS IS EXPECTED TO MOVE THROUGH MONDAY
AFTERNOON OR EVENING, POTENTIALLY LINGERING INTO THE OVERNIGHT HOURS
INTO EARLY TUESDAY.
MARINE
TODAY: HIGH PRESSURE CENTERED NEAR BERMUDA AND ITS ASSOCIATED
RIDGE AXIS WILL STRETCH ATOP THE LOCAL MARINE COMMUNITY, GENERATING
SE AND S WINDS NO HIGHER THAN 10-15 KT. WITH A "BOOST" FROM THE
SEA BREEZE, THERE COULD BE A FEW HIGHER GUSTS NEAR THE IMMEDIATE
COAST AND IN CHARLESTON HARBOR DURING THE AFTERNOON. SEAS REACH
AS LARGE AS 3-4 FT WITHIN 20 NM, AND UP TO 4-5 FT ON THE OUTER
GEORGIA WATERS, RESULTING FROM A MIX OF WIND WAVES AND SWELLS,
ALTHOUGH THERE IS A RISK FOR 6 FT SEAS ALONG THE OUTER STRETCH
OF OUTER GEORGIA WATERS LATE DAY.
TONIGHT: THE AREA IS SITUATED ALONG THE WESTERN SIDE OF ATLANTIC
HIGH PRESSURE, KEEPING SE WINDS AT OR BELOW 10 OR 15 KT
THROUGHOUT. SEAS COULD BUILD A BIT FURTHER, DEPENDING UPON HOW
MUCH SWELL ENERGY OCCURS, AND 6 FOOTERS LOOK TO MOVE INTO THE
WATERS BEYOND 40 NM OFF THE GEORGIA COAST. THIS COULD PROMPT A
SMALL CRAFT ADVISORY FOR THE OUTER GEORGIA WATERS AT A LATER
TIME. BUT IT STILL LOOKS TOO MARGINAL TO ISSUE AN ADVISORY WITH
THE LATEST FORECAST PRODUCTS. MAYBE A FEW LATE NIGHT SHOWERS
CAN OCCUR NEAR THE GULF STREAM.
SUNDAY: WHILE HIGH PRESSURE WILL KEEP WINDS OUT OF THE SOUTHEAST
THROUGHOUT THE DAY, SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE
EXPECTED TO INCREASE IN COVERAGE INTO THE AFTERNOON HOURS. GIVEN THE
INCREASED WINDS AND FETCH LENGTHS IN THE OUTER WATERS, CAN'T RULE
OUT NEEDING A SMALL CRAFT ADVISORY FOR THE OFFSHORE WATERS FROM
SAVANNAH GA TO ALTAMAHA SOUND GA DUE TO 6 FOOT WAVES, BUT CONFIDENCE
REMAINS TOO LOW TO ISSUE AT THIS TIME. OVERNIGHT INTO MONDAY, SOME
GUIDANCE IS HINTING AT SEA-FOG DEVELOPING ALONG THE COAST AND
PUSHING ASHORE. HOWEVER, GIVEN THE BREEZY WINDS WE HAVE LEFT
MENTION OUT OF THE FORECAST FOR THE TIME BEING.
MONDAY/TUESDAY: BREEZY SOUTHEAST GRADIENT WINDS OUT AHEAD OF AN
APPROACHING COLD FRONT CONTINUE TO REMAIN JUST BELOW SMALL CRAFT
CRITERIA ON THE WIND SIDE, THOUGH CHANCES FOR 6 FOOT WAVES CONTINUE
IN THE OFFSHORE GA WATERS. MORNING/AFTERNOON SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ARE POSSIBLE, THOUGH THE BETTER CHANCES
ARRIVE AS A BROKEN LINE OF SHOWERS AND THUNDERSTORMS IS EXPECTED TO
PUSH THROUGH OVERNIGHT INTO TUESDAY MORNING. WINDS WILL BE STARTING
OUT OF THE WEST DURING THE MORNING, VEERING TO THE NORTH-
NORTHEAST IN THE AFTERNOON, AND CONTINUING TO VEER TO THE EAST
INTO THE EVENING HOURS.
WEDNESDAY: SURFACE HIGH PRESSURE BUILDS IN FROM THE NORTH, RESULTING
IN EAST WINDS BECOMING SOUTHEASTERLY. MAY SEE SOME ISOLATED SHOWERS
DEVELOP IN THE OFFSHORE WATERS, THOUGH CONFIDENCE IS LOW AT THIS
TIME.
EQUIPMENT
THE KCLX RADAR REMAINS OFFLINE FOR DOME MAINTENANCE THROUGH
APRIL 1, 2025. RADAR DATA WILL NOT BE AVAILABLE DURING THIS
TIME. USERS ARE URGED TO USE ADJACENT WSR-88D SITES WHICH ALSO
COVER MUCH OF SOUTHEAST SOUTH CAROLINA, SOUTHEAST GEORGIA AND
THE ADJACENT COASTAL WATERS. THESE INCLUDE:
KCAE - COLUMBIA, SC
KLTX - WILMINGTON, NC
KJAX - JACKSONVILLE, FL
KVAX - MOODY AFB, GA
KJGX - ROBBINS AFB, GA
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...DPB
SHORT TERM...
LONG TERM...
AVIATION...DPB
MARINE...DPB
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