668
FXUS62 KCHS 281000
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
600 AM EDT FRI MAR 28 2025
SYNOPSIS
DRY, HIGH PRESSURE WILL PREVAIL THROUGH SATURDAY, THEN RAIN AND
THUNDERSTORM CHANCES INCREASE INTO SUNDAY AND MONDAY FOLLOWED
BY A STRONG COLD FRONT MONDAY EVENING.
NEAR TERM /THROUGH TONIGHT/
NO MAJOR CHANGES WERE NEEDED FOR THE SUNRISE UPDATE.
TODAY: THE NORTHWEST FLOW REGIME THAT HAS BEEN IN PLACE FOR THE
PAST SEVERAL DAYS WILL RAPIDLY BREAKDOWN TODAY AS SUBTROPICAL
RIDGING BUILDS ACROSS THE DEEP SOUTH AND SOUTHEAST U.S. AHEAD OF
THE SOUTHERN STREAM STORM SYSTEM MOVING ACROSS TEXAS. HIGH
PRESSURE OFF THE NORTH CAROLINA OUTER BANKS THIS MORNING WILL
STRENGTHEN WHILE SHIFTING FARTHER OFFSHORE. THE LOCAL AREA WILL
BE POSITIONED ALONG THE WESTERN FLANKS OF THE HIGH WHICH WILL
ALLOW FOR CONSIDERABLY HIGHER DEWPOINTS AND RH TO PREVAIL. THIS
WILL HELP TEMPER THE OVERALL FIRE DANGER THIS AFTERNOON,
ALTHOUGH IT WILL REMAIN SOMEWHAT ELEVATED GIVEN THE ONGOING
D0-D1 DROUGHT CONDITIONS AND CRITICALLY DRY FUELS THAT ARE IN
PLACE.
A SUBTLE COASTAL TROUGH NEAR THE WEST WALL OF THE GULF STREAM
THIS MORNING WILL WORK STEADILY INLAND THIS AFTERNOON AS IT
BECOMES ABSORBED IN THE SOUTHERLY SYNOPTIC FLOW. A FEW SHOWERS
COULD BE GENERATED OFF THE LOWER SOUTH CAROLINA COAST NEAR THE
HEAD OF THE COASTAL TROUGH, BUT ANY ISOLATED ACTIVITY THAT FORMS
SHOULD LARGELY REMAIN OFFSHORE SANS A BRIEF SPRINKLE OR TWO
THAT COULD BRUSH PARTS OF THE MIDDLE TO UPPER CHARLESTON COUNTY
COAST.
DESPITE THE LOSS OF WARMING CONTRIBUTIONS FROM DOWNSLOPE
TRAJECTORIES IN THE LEE OF THE BLUE RIDGE/SOUTHERN
APPALACHIANS, LOW-LEVEL THICKNESS AND 850 HPA TEMPERATURES WILL
RISE THROUGH THE DAY AS MID-LEVEL HEIGHTS BUILD. HIGHS LOOK TO
PEAK IN THE UPPER 70S/LOWER 80S AWAY FROM THE IMMEDIATE COAST
WITH MID-UPPER 60S AT THE BEACHES. THE COMBINATION OF CIRRUS
ALOFT AND SOME DEVELOPING CUMULUS/STRATO-CUMULUS WILL YIELD
PARTLY CLOUDY TO PARTLY SUNNY SKIES.
TONIGHT: THE WESTWARD EXTENSION OF ATLANTIC HIGH PRESSURE
CENTERED WELL OFFSHORE WILL REMAIN ACROSS THE SOUTHEAST U.S.
TONIGHT AS SUBTROPICAL RIDGING HOLDS ALOFT. EXTENSIVE CIRRUS
WILL SPREAD ACROSS THE REGION AS THE SOUTHERN STREAM STORM
SYSTEM OVER TEXAS BEGINS TO WEAKEN AND EJECT OUT ACROSS THE
LOWER MISSISSIPPI VALLEY. A NORTHWEST-SOUTHEAST ORIENTED
SHORTWAVE WILL APPROACH FROM THE SOUTHWEST OVERNIGHT. THERE ARE
SIGNALS THAT THIS FEATURE COULD GENERATE A BAND OF LIGHT
SPRINKLES AS IT APPROACHES SOUTHEAST GEORGIA AFTER MIDNIGHT.
WHILE MEASURABLE RAINFALL IS NOT EXPECTED, A FEW SPOTS COULD SEE
A FEW DROPS FALL PRIOR TO DAYBREAK. LOWS TONIGHT WILL RANGE
FROM THE LOWER-MID 50S INLAND TO THE LOWER 60S AT THE BEACHES
AND DOWNTOWN CHARLESTON.
SHORT TERM /SATURDAY THROUGH MONDAY/
AS THE SURFACE HIGH PRESSURE CONTINUES TO MOVE OUT INTO THE
ATLANTIC, A SHALLOW MOIST LAYER NEAR 850MB LOOKS TO BUILD ACROSS
THE AREA THROUGHOUT THE DAY. IN COMBINATION WITH PERIODIC WARM-
AIR ADVECTION IN THE MID-LEVELS ALONG WITH WEAK SCATTERED
SHORTWAVES, THIS WILL RESULT IN PARTLY TO MOSTLY CLOUDY SKIES
THROUGHOUT THE DAY. SOME GUIDANCE IS STARTING TO HINT THAT THERE
MAY BE ENOUGH MOISTURE TO SQUEEZE OUT SOME ISOLATED SHOWERS,
BUT THE LACK OF LOW- LEVEL MOISTURE CURRENTLY LOOKS TO PREVENT
ANY SHOWERS FROM REACHING THE GROUND. OTHERWISE, CLOUDS WILL
KEEP TEMPERATURES A SHADE COOLER IN THE MID 70S TO LOWER 80S
INLAND, DOWN TO THE LOWER 70S ALONG THE COAST. THE SEA-BREEZE
LOOKS TO MOVE ONSHORE BY THE EARLY AFTERNOON HOURS, WITH WINDS
DECREASING INTO THE EVENING HOURS.
OVERNIGHT INTO SUNDAY, WE REMAIN UNDER WEST-SOUTHWESTERLY FLOW
ALOFT CONTINUING TO ADVECT WEAK SHORTWAVES ACROSS THE AREA. LOW-
LEVEL MOISTURE WILL BE INCREASING LEADING TO CHANCES FOR
RAINFALL BUILDING THROUGHOUT THE DAY. PRECIPITABLE WATER (PWAT)
VALUES APPROACH/EXCEED 1.5" BY THE AFTERNOON HOURS, THOUGH
WITHOUT STRONG FORCING AND RATHER WEAK INSTABILITY (<500 J/KG)
RAINFALL AMOUNTS WILL REMAIN ON THE LIGHTER SIDE. 24 HOUR
RAINFALL PROBABILITIES FROM THE NBM FOR 0.10" (0.25") INCHES ARE
IN THE 40S (20S) NEAR THE CHARLESTON TRI- COUNTY REGION, RISING
INTO THE MID 50S (30S) 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, WE WILL BE OBSERVING THE EXPECTED REMNANTS OF A
MESOSCALE CONVECTIVE SYSTEM (MCS) OUT AHEAD OF AN APPROACHING
COLD FRONT MOVE TOWARDS THE AREA THROUGHOUT THE DAY. THIS MAY
END UP BEING THE MAIN CHANCES FOR RAIN LATE IN THE DAY AS MODEL
DETAILS REMAIN UNCLEAR, BUT THERE IS ALSO A CHANCE FOR DIURNALLY
DRIVEN THUNDERSTORMS OUT AHEAD OF THE MAIN LINE IN THE
EARLY/MID AFTERNOON HOURS IF THEY ARE ABLE TO BREAK THROUGH THE
CAP AS SURFACE TEMPERATURES BREAK INTO THE UPPER 70S TO MID 80S.
WITH EXPECTED CAPE VALUES NEAR/ABOVE 1000 J/KG, HIGHER IN THE
MORE AGGRESSIVE MODEL SOLUTIONS, SEVERE THUNDERSTORMS CAN'T BE
RULED OUT AT THIS TIME. LIMITING FACTORS INCLUDE LOWER SHEAR
VALUES (25 - 30 KNOTS), ALONG WITH CLOUD COVERAGE OUT AHEAD OF
THE EXPECTED MCS. SPC AND THE CSU MACHINE LEARNING PAGE CONTINUE
TO SHOW CHANCES FOR SEVERE WEATHER, THOUGH THE ECMWF EFI IS
LESS CONVINCED GIVEN THE LACK OF SHEAR. GIVEN THE CONFLICTING
GUIDANCE, CONFIDENCE IN SEVERE WEATHER IS LOW AT THIS TIME.
LONG TERM /MONDAY NIGHT THROUGH THURSDAY/
THE AFOREMENTIONED MCS/LINE OF SHOWERS AND THUNDERSTORMS WILL
BE PUSHING ACROSS THE AREA OVERNIGHT INTO TUESDAY, AS THE
SURFACE COLD FRONT AND MAIN UPPER LEVEL TROUGH AXIS MOVES ACROSS
THE REGION. NBM 24 HOUR RAINFALL PROBABILITIES FOR 0.10"
(0.25") ARE IN THE 60S (40S) NEAR THE CHARLESTON TRI-COUNTY
REGION, FALLING INTO THE MID 40S (30S) ACROSS OUR FAR SOUTHERN
SOUTHEASTERN GEORGIA COUNTIES. DESPITE THE FRONTAL PASSAGE
(FROPA) TEMPERATURES ARE EXPECTED TO REBOUND BACK UP INTO THE
UPPER 70S TO LOWER 80S.
DETERMINISTIC AND ENSEMBLE GUIDANCE BEGIN TO DIVERGE IN TIMING
OF ADDITIONAL SHORTWAVES THAT MOVE THROUGH THE ZONAL FLOW, WHICH
RESULTS IN NUMEROUS PERIODS WHERE THE NBM HAS ADDED LOW CHANCES
FOR RAIN (~20%). EXPECT THIS TO BE REFINED WITH FURTHER MODEL
RUNS. OTHERWISE, WARM TEMPERATURES ARE EXPECTED TO CONTINUE INTO
THE END OF THE WEEK.
AVIATION /10Z FRIDAY THROUGH TUESDAY/
28/12Z TAF DISCUSSION:
KCHS/KJZI/KSAV: VFR WILL PREVAIL AT ALL TERMINALS, GUSTY WINDS
WILL DEVELOP BY LATE MORNING AND PERSIST THROUGH SUNSET. GUSTS
AS HIGH AS 18-20 KT COULD OCCUR.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS ARE POSSIBLE
SATURDAY NIGHT THROUGH MONDAY EVENING, MAINLY DUE TO LOW
CEILINGS. A LINE OF THUNDERSTORMS COULD MOVE THROUGH MONDAY
AFTERNOON OR EVENING, POTENTIALLY LINGERING INTO THE OVERNIGHT
HOURS.
MARINE
TODAY: EAST TO NORTHEAST WINDS WILL GRADUALLY VEER SOUTHEAST
THIS AFTERNOON AS A COASTAL TROUGH MOVES ONSHORE AND ATLANTIC
HIGH PRESSURE EXTENDS INTO THE REGION. SPEEDS WILL HOLD 10 KT OR
LESS, ALTHOUGH IT WILL LIKELY BE A BIT MORE ENHANCED, CLOSER TO
15 KT WITH GUSTS TO 20 KT, IN THE CHARLESTON HARBOR FOR A PERIOD
THIS AFTERNOON. SEAS WILL AVERAGE 1-3 FT WITHIN 20 NM AND 2-4 FT
OVER THE GEORGIA OFFSHORE WATERS OUT 20-60 NM.
TONIGHT: A MORE ESTABLISHED SOUTHERLY FLOW WILL DOMINATE TONIGHT
AS ATLANTIC HIGH PRESSURE HOLDS WELL OFFSHORE. SPEEDS WILL HOLD
5-10 KT WITHIN 20 NM AND WILL INCREASE TO 10-15 KT OVER THE
GEORGIA OFFSHORE WATERS AFTER MIDNIGHT. SEAS WILL BUILD 2-4 FT
NEARSHORE WATERS AND 4-5 FT OVER THE GEORGIA OFFSHORE WATERS.
SATURDAY AND SUNDAY: HIGH PRESSURE WILL KEEP WINDS OUT OF THE
SOUTHEAST THROUGHOUT THE WEEKEND. SATURDAY IS EXPECTED TO BE
PARTLY TO MOSTLY CLOUDY, WITH LOW CHANCES (<15%) FOR ISOLATED
RAIN SHOWERS. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE
EXPECTED TO DEVELOP OVERNIGHT INTO SUNDAY, LIKELY CONTINUING OFF
AND ON THROUGHOUT THE DAY. 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 IS TOO LOW TO ISSUE
AT THIS TIME.
MONDAY: BREEZY SOUTHEAST GRADIENT WINDS OUT AHEAD OF AN
APPROACHING COLD FRONT LOOK TO REMAIN JUST BELOW SMALL CRAFT
CRITERIA ON THE WIND SIDE, THOUGH CHANCES FOR 6 FOOT WAVES
CONTINUE IN THE OFFSHORE GA WATERS. 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. MAY CONTINUE TO
SEE SOME ISOLATED SHOWERS THROUGHOUT THE DAY ON TUESDAY (20%
CHANCES), WITH VARYING WINDS 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.
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.
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