411
FXUS62 KCHS 020517
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1217 AM EST TUE DEC 2 2025
SYNOPSIS
A STORM SYSTEM WILL PASS THROUGH THE REGION LATE TODAY BRINGING
MUCH NEEDED RAINFALL TO COASTAL SOUTH CAROLINA AND GEORGIA.
HIGH PRESSURE THEN RETURNS FOR THE MIDDLE OF THIS WEEK BEFORE
THE NEXT FRONTAL SYSTEM IMPACTS THE AREA FRIDAY INTO THE
WEEKEND.
NEAR TERM /UNTIL 6 AM THIS MORNING/
UPDATE TO ISSUE A COASTAL FLOOD ADVISORY FOR THE UPCOMING 5 AM
HIGH TIDE FOR CHARLESTON AND COASTAL COLLETON COUNTIES.
EARLY THIS EVENING: SURFACE ANALYSIS SHOWS A NICE SYNOPTIC
SETUP WITH COLD AIR DAMMING ENTRENCHED ACROSS GA AND THE
CAROLINAS ASSOCIATED WITH THE PARENT HIGH CENTERED ACROSS NEW
ENGLAND. A SHARPENING COASTAL TROUGH SITS OFFSHORE WITH AN
ORGANIZING SURFACE LOW IN THE NORTH-CENTRAL GULF ALONG A NEARLY
STATIONARY BOUNDARY THAT STRETCHES ACROSS NORTH FL. ALOFT,
SATELLITE IMAGERY SHOWS A WELL DEFINED SHORTWAVE ACROSS THE
CENTRAL CONUS AND A NICE FEED OF DEEP MOISTURE INTO THE
SOUTHEAST WITHIN THE WEST-SOUTHWEST FLOW. OVERNIGHT, THIS
SHORTWAVE WILL PRESS TO THE EAST WHILE LIFTING INTO THE OH
VALLEY WHILE THE UPPER LEVEL JET STRENGTHENS, ESPECIALLY THE
STREAK ACROSS THE EASTERN GREAT LAKES. A NOTABLE SLUG OF
DIVERGENCE IN THE RIGHT ENTRANCE REGION OF THE STRENGTHENING JET
WILL TRACK THROUGH THE SOUTHEAST COINCIDENT WITH PRECIPITABLE
WATER VALUES SURGING INTO THE 1.5-1.7" RANGE BY SUNRISE TUESDAY
(LIKELY NEAR A DAILY MAX ACCORDING TO THE SPC SOUNDING CLIMO).
IN RESPONSE TO THE FORCING ALOFT, THE AFOREMENTIONED SURFACE LOW
WILL DEEPEN A BIT AND TRACK TO THE NORTHEAST AND WILL LIKELY BE
SITUATED NEAR THE AL/GA/FL STATE LINE AROUND SUNRISE TUESDAY.
AS STRENGTHENING FORCING AND DEEPENING MOISTURE SPREAD INTO THE
AREA THIS EVENING, STRATIFORM RAIN IS EXPECTED TO BEGIN ACROSS
SOUTHEAST GA BY THE LATE EVENING AND BEGIN GETTING INTO
SOUTHEAST SC AFTER MIDNIGHT. THE COVERAGE OF RAIN WILL THEN
STEADILY INCREASE THROUGH THE REST OF THE NIGHT SUCH THAT THE
ENTIRE FORECAST AREA SHOULD BE COVERED BY SUNRISE TUESDAY.
RAINFALL INTENSITY SHOULD REMAIN GENERALLY LIGHT THROUGH THE
OVERNIGHT, THOUGH THERE COULD BE SOME EMBEDDED POCKETS OF
MODERATE RAIN. THROUGH THE OVERNIGHT HOURS, RAINFALL AMOUNTS
WILL MOSTLY PEAK IN THE 0.25-0.50" RANGE FOR MOST OF THE AREA,
THOUGH A STREAK OVER HEAVIER AMOUNTS APPROACHING OR EVEN
EXCEEDING 0.75" WILL BE POSSIBLE ACROSS THE FAR INLAND TIER
INCLUDING JENKINS, CANDLER, SCREVEN, BULLOCH, AND ALLENDALE
COUNTIES. IT WILL BE A CHILLY AND SOMEWHAT UNPLEASANT OVERNIGHT
PERIOD WITH TEMPERATURES FALLING INTO THE LOW TO MID 40S INLAND
AND THE UPPER 40S TO LOW 50S ALONG THE COAST, COMBINED WITH
PERSISTENT NORTHEAST WIND OF 5-10 MPH AND INCREASING COVERAGE OF
RAIN.
SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/
TUESDAY: ALOFT, A TROUGH EXTENDING ACROSS THE GREAT LAKES TO
THE DEEP SOUTH WILL ADVANCE EAST, LIKELY REACHING THE ATLANTIC
SEABOARD BY LATE DAY/EARLY EVENING. AT THE SFC, LOW PRESSURE
DEVELOPING AND POSITIONED NEAR A FRONT IN THE NORTHERN GULF IS
ANTICIPATED TO TRACK EAST-NORTHEAST ACROSS THE REGION,
ENCOUNTERING A CAD PRIOR TO SHIFTING OFF THE COAST LATE DAY.
STRONG ISENTROPIC LIFT AND DEEP MOISTURE (PWATS NEAR 1.7 INCHES)
RUNNING OVER THE CAD IN ADDITION TO FORCING ASSOCIATED WITH A
STRONG H25 JET CORE, H5 VORT ENERGY AND A PASSING FRONT WILL
CONTINUE TO FAVOR NUMEROUS/WIDESPREAD RAIN AND SHOWER ACTIVITY
ACROSS SOUTHEAST GEORGIA AND SOUTHEAST SOUTH CAROLINA DURING
MORNING INTO AFTERNOON HOURS, WITH WEAK INSTABILITY ALSO
SUGGESTING A FEW RUMBLES OF THUNDER BEING POSSIBLE, ALTHOUGH
PRIMARILY WELL SOUTH AND NEAR THE SOUTHEAST GEORGIA COAST WHERE
SFC TEMPS ARE WARMEST.
THE BULK OF GUIDANCE SUGGESTS GREATEST RAINFALL AMOUNTS OCCUR
WELL INLAND, GENERALLY AROUND AN INCH ALONG A STRETCH FROM
TATTNALL COUNTY, GA AND NORTH-NORTHEAST TO BERKELEY COUNTY.
CLOSER TO THE COAST, ADDITIONAL RAINFALL AMOUNTS AROUND 0.5 INCH
ARE FORECAST DURING MORNING INTO EARLY AFTERNOON HOURS,
IMPLYING GREATEST FORCING AND PERHAPS LOW PRESSURE TRACK TO
OCCUR INLAND WHILE THE CAD HOLDS IN PLACE. REGARDLESS OF LOW
TRACK, THESE RAINS SHOULD BE QUITE BENEFICIAL TO THE REGION
GIVEN ONGOING DROUGHT CONDITIONS, WHILE LOWER RAINFALL RATES
ALSO LIMIT CONCERN FOR FLOODING. THE EXCEPTION COULD BE WITH THE
EARLY MORNING HIGH TIDE CYCLE ALONG THE SOUTHEAST SOUTH
CAROLINA COAST SHOULD RAINFALL OCCUR DURING ELEVATED TIDE LEVELS
(SEE COASTAL FLOODING SECTION BELOW).
THE LOCAL AREA WILL LIKELY EXPERIENCE A WIDE RANGE OF TEMPS
GIVEN THE SETUP. FOR LOCATIONS WELL INLAND, WIDESPREAD CLOUDS
AND RAIN/SHOWERS COULD LIMIT AFTERNOON HIGHS TO THE MID-UPPER
50S. CLOSER TO THE COAST, SFC WINDS HAVE A GREATER CHANCE OF
BECOMING SOUTHERLY IN ADVANCE OF THE FRONT, ALLOWING AFTERNOON
HIGHS TO PEAK IN THE MID 60S ALONG COASTAL SOUTH CAROLINA TO
UPPER 60S/AROUND 70 ALONG COASTAL GEORGIA AND PERHAPS SOUTH OF
I-16 ACROSS SOUTHEAST GEORGIA. DRY AND COOLER HIGH PRESSURE
BUILDS ACROSS THE REGION DURING THE NIGHT POST FROPA, FAVORING
LOWS IN THE MID 30S INLAND TO LOW-MID 40S NEAR THE COAST.
WEDNESDAY AND THURSDAY: HIGH PRESSURE CENTERED ACROSS THE OHIO
RIVER VALLEY WILL SPREAD ACROSS THE MID-ATLANTIC AND SOUTHEAST
STATES MID- WEEK, FAVORING DRY AND COOLER CONDITIONS ACROSS THE
LOCAL AREA WEDNESDAY, PRIOR TO WEAK AIRMASS MODIFICATION ON
THURSDAY. IN GENERAL, HIGH TEMPS SHOULD RANGE BETWEEN THE MID-
UPPER 50S WITH A FEW TEMPS AROUND 60 DEGREES ACROSS SOUTHEAST
GEORGIA WEDNESDAY AFTERNOON, FOLLOWED BY HIGHS IN THE UPPER 50S
INLAND TO LOW-MID 60S CLOSER TO THE COAST THURSDAY AFTERNOON.
LOWS COULD REACH THE FREEZING MARK WELL INLAND WEDNESDAY NIGHT
(LOWER 30S), BUT STAY WARMER ALONG THE COAST (LOW-MID 40S).
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
ALOFT, THE LOCAL AREA SHOULD REMAIN UNDER A MOSTLY ZONAL FLOW
BETWEEN A BROAD TROUGH EXTENDING ACROSS THE NORTHERN UNITED
STATES AND A BROAD RIDGE ACROSS THE GULF AND ATLANTIC. AT THE
SFC, ANOTHER LOW PRESSURE SYSTEM DEVELOPS ACROSS THE NORTHERN
GULF, ALTHOUGH APPEARS WEAKER AND MORE PROGRESSIVE LATE WEEK,
SUGGESTING A LIGHTER AND SLIGHTLY SHORTER RAINFALL EVENT
COMPARED TO EARLY WEEK, BUT STILL SUFFICIENT TO PRODUCE NUMEROUS
TO WIDESPREAD RAIN/SHOWERS FRIDAY AFTERNOON/EVENING AND
POSSIBLY THROUGH SATURDAY MORNING, BEFORE THE SYSTEM AND/OR
FRONT SHIFTS OFFSHORE LATE DAY. DRY HIGH PRESSURE RETURNS POST
FROPA SUNDAY, WITH HIGHS REMAINING BELOW NORMAL, GENERALLY IN
THE UPPER 50S INLAND TO LOWER 60S ACROSS COASTAL AREAS.
AVIATION /06Z TUESDAY THROUGH SATURDAY/
PRIOR TO THE 6Z TAFS, KCLX DETECTED WIDESPREAD RAIN ADVANCING
NORTH ACROSS SE GA, ACCOMPANIED BY IFR CEILINGS. THE RAINFALL
AND IFR CEILINGS SHOULD REACH KCHS AND KJZI BY 7Z. COLD AIR
DAMMING WILL BE REINFORCED BY THE WIDESPREAD RAIN FALL THIS
MORNING, SUPPORTING NORTH-NORTHEAST WINDS AND IFR CONDITIONS
THROUGH MID-DAY. IN ADDITION, STRENGTHENING LLVL JET AND
DIRECTIONAL SHEAR SHOULD YIELD LLWS AT EACH TERMINAL THIS
MORNING. A PERIOD OF HEAVIER RAINFALL RATES SHOULD PASS OVER
THE TERMINALS THIS MORNING AFTER SUNRISE, REDUCING VISIBILITY
DOWN TO 2SM AT TIMES, HIGHLIGHTED WITH TEMPOS FROM 12-17Z.
RAINFALL IS TIMED TO SHIFT EAST OF THE TERMINALS DURING THE MID
TO LATE AFTERNOON HOURS AS THE FRONT SWEEPS EAST. IN THE WAKE OF
THE FRONT, WINDS WILL SHIFT FROM THE NORTHWEST AND CLOUD BASES
WILL GRADUALLY LIFT, IMPROVING TO MVFR BY THIS EVENING.
EXTENDED AVIATION OUTLOOK: VFR CONDITIONS RETURN AT ALL
TERMINALS TUESDAY NIGHT INTO WEDNESDAY AND THURSDAY WITH HIGH
PRESSURE DOMINATING THE WEATHER PATTERN, BEFORE CHANCES FOR
FLIGHT RESTRICTIONS RETURN AT ALL TERMINALS WITH THE NEXT
FRONT/LOW PRESSURE SYSTEM BRINGING RAIN AND/OR SHOWERS TO ALL
TERMINALS FRIDAY.
MARINE
TONIGHT: A WEDGE OF HIGH PRESSURE SHOULD WEAKEN TONIGHT AS AN
AREA OF LOW PRESSURE MOVES OVER THE REGION. THIS WILL ALLOW
NORTHEAST WINDS INITIALLY TO BECOME SOUTHERLY LATE TONIGHT.
GUSTS IN THE LOW 20 KT RANGE THIS AFTERNOON WILL BRIEFLY COME
DOWN LATER THIS EVENING, BEFORE BEGINNING TO RAMP BACK UP NEAR
DAYBREAK. WAVE HEIGHTS WILL ALSO INCREASE LATE TONIGHT, WITH 6
FT SEAS DEVELOPING OVER THE SC NEARSHORE AND OUTER GA WATERS
DURING THE PRE-DAWN HOURS. THE WIND AND SEA CONDITIONS WILL BE
HIGHLIGHTED WITH SMALL CRAFT ADVISORIES FOR THESE ZONES.
A LOW PRESSURE SYSTEM WILL APPROACH LOCAL WATERS FROM THE WEST-
SOUTHWEST ON TUESDAY WITH A CAD SLOW TO WEAKEN AND RESULTING IN
A SLIGHTLY PINCHED GRADIENT. SOUTHERLY WINDS GUSTING UP TO
25-30 KT OUTSIDE THE CHARLESTON HARBOR AND BEYOND GEORGIA
NEARSHORE WATERS ARE POSSIBLE. SEAS SHOULD ALSO BUILD UP TO 6-8
FT DURING THIS TIMEFRAME, SUPPORTING THE CONTINUATION OF SMALL
CRAFT ADVISORIES ACROSS NEARSHORE SC WATERS AND OUTER GEORGIA
WATERS LATE DAY INTO THE EVENING ON TUESDAY. WINDS WILL REMAIN
MOSTLY OFFSHORE AND WEAKEN HEADING INTO WEDNESDAY AS HIGH
PRESSURE SPREADS ACROSS THE REGION. EXPECT WINDS/SEAS TO REMAIN
WELL BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH LATE WEEK,
WITH ONLY A SLIGHT UPTICK IN WINDS AND SEAS ASSOCIATED WITH THE
ARRIVAL OF THE NEXT LOW PRESSURE SYSTEM.
TIDES/COASTAL FLOODING
UPCOMING 5 AM HIGH TIDE CYCLE: CURRENT TIDAL TRENDS AT THE
CHARLESTON HARBOR TIDE GAGE INDICATE THAT THE TIDE DEPARTURE HAS
STEADILY INCREASED SINCE THE AFTERNOON HIGH TIDE AND IS NOW UP
TO 1 FT AS WE APPROACH THE ~10:30 PM LOW TIDE. THE TUESDAY
MORNING HIGH TIDE IS AT ~5 AM AND THE ASTRONOMICAL TIDE IS 6.23
FT MLLW, MEANING WE WOULD NEED TO SEE AT LEAST A 0.77 FT
DEPARTURE TO REACH THE MINOR COASTAL FLOODING THRESHOLD OF 7 FT
MLLW. OVER THE NEXT 6-8 HOURS, NORTHEAST FLOW ALONG THE COAST
WILL CONTINUE BUT IS EXPECTED TO DIMINISH IN STRENGTH AS AN
ELONGATED AREA OF LOW PRESSURE STRETCHES ALONG THE COAST AND THE
PRESSURE GRADIENT RELAXES. THOUGH WIND SPEEDS WILL COME DOWN, WE
SHOULD SEE THE AMBIENT PRESSURE DECREASE BY 7-9 MB WHICH SHOULD
COUNTER THE LOSS OF WIND FORCE. ALL THIS TO SAY, WE THINK A
DEPARTURE OF A LITTLE LESS THAN 1 FT IS LIKELY AROUND THE TIME
OF HIGH TIDE AND THE FORECAST IS FOR A PEAK TIDE VALUE OF
7.0-7.2 FT MLLW. A COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR
CHARLESTON AND COASTAL COLLETON COUNTIES.
ASTRONOMICAL TIDES WILL THEN CONTINUE TO RISE WITH THE MORNING
HIGH TIDE CYCLES THROUGH FRIDAY AND REMAIN ELEVATED THROUGH THE
WEEKEND. COASTAL FLOOD ADVISORIES WILL LIKELY BE NEEDED FOR
MORNING HIGH TIDE CYCLES, PRIMARILY AT CHARLESTON HARBOR
(CHARLESTON AND COASTAL COLLETON COUNTIES) THROUGH LATE WEEK.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...COASTAL FLOOD ADVISORY UNTIL 7 AM EST THIS MORNING FOR SCZ049-
050.
MARINE...SMALL CRAFT ADVISORY FROM 4 AM EARLY THIS MORNING TO 1 AM EST
WEDNESDAY FOR AMZ350-374.
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 7 PM EST THIS
EVENING FOR AMZ352.
NEAR TERM...BSH
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...NED
MARINE...DPB/ETM
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