Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 281210
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
710 AM EST SAT FEB 28 2015

.SYNOPSIS...
HIGH PRESSURE WILL BUILD NORTH OF THE REGION THROUGH TONIGHT AND
WEDGE SOUTHWARD OVER GEORGIA AND SOUTH CAROLINA OVER THE WEEKEND
WHILE A COASTAL TROUGH DEVELOPS OFF THE SOUTHEAST COAST. A COLD
FRONT WILL MOVE IN AND STALL OVER OR JUST SOUTH OF THE AREA ON
MONDAY...THEN LIFT NORTH AS A WARM FRONT ON TUESDAY. A COLD FRONT
WILL SHIFT THROUGH THE AREA LATE WEDNESDAY INTO THURSDAY...FOLLOWED
BY COOLER HIGH PRESSURE NEXT WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
A WEAK MID LEVEL SHORT WAVE ALONG THE NORTHERN GULF COAST EARLY
THIS MORNING WAS ACCOMPANIED BY A 110 KT 250 MB JET SEGMENT. THIS
SHORT WAVE IS FORECAST TO PASS ACROSS NORTH FLORIDA TODAY...ENHANCING
THE BAROCLINIC ZONE NORTHWARD ACROSS THE PANHANDLE. IN RESPONSE TO
THIS WEAK FEATURE...MODELS PAINT INCREASING MOISTURE FLUX FROM THE
ATLC ACROSS SE GEORGIA TODAY WHILE A STRONG 1044 MB HIGH BUILDS
OVER SOUTHERN NEW ENGLAND TO THE DELMARVA. ISENTROPIC ASCENT ALONG
THE 290K AND 295K SURFACES ALONG WITH THE INCREASING LOW LEVEL
MOISTURE LOOKS SUFFICIENT TO BREAK OUT SOME SCATTERED BUT LIGHT
WARM PROCESS RAINS ACROSS SOUTH GEORGIA FROM LATE MORNING INTO THE
AFTERNOON AT THE NOSE OF THE ADVANCING MOISTURE/THETA-E GRADIENT
BETWEEN 950 MB AND 750 MB. SHOWERS WILL INITIALLY BE LIMITED DUE
TO PLENTY OF DRY AIR TO OVERCOME BUT WE LOW END CHANCE POPS ALONG
AND S OF I-16 LATE MORNING AND AFTERNOON WITH 30-50 POPS SOUTH OF
CHARLESTON BY LATER IN THE DAY...HIGHEST SOUTH OF I-16. RAINFALL
AMOUNTS ARE NOT EXPECTED TO AMOUNT TO MUCH TODAY BUT THE THICKER
CLOUDS AND DAMPNESS OVER GEORGIA ZONES LIKELY TO KEEP TEMPS IN THE
40S ALL DAY. AS THE WEDGE STRENGTHENS DURING THE DAY THE REMAINDER
OF THE FORECAST AREA COULD ALSO REMAIN IN THE 40S WITH PLENTY OF
CLOUDS...ESPECIALLY BY AFTERNOON NORTHERN ZONES. IT WILL BE BREEZY
TO WINDY ON THE BEACHES AND BARRIER ISLANDS WITH BUILDING SURF.

TONIGHT...A COASTAL TROUGH WILL TAKING ON BETTER DEFINITION OFF
THE COAST WHILE LOW LEVEL MOISTURE/COASTAL CONVERGENCE AND CONTINUED
ISENTROPIC ASCENT/WEAK UPPER DIFLUENCE KEEPING DECENT CHANCES FOR
LIGHT RAINS OVER INLAND AREAS TO THE WEST OF I-95. WE HAVE BUMPED
POPS UP TO LIKELY ALONG GEORGIA COASTAL ZONES TO ABOUT BEAUFORT
COUNTY WHERE MODELS ALL AGREE THAT CHANNELED CONVERGENCE AND
ENHANCED LOW LEVEL MOISTURE FEED WILL MAXIMIZE AT SOME POINT
OVERNIGHT. BREEZY TO WINDY CONDITIONS WILL LINGER ALONG THE
BEACHES AND BARRIER ISLANDS...DIMINISHING LATE. LOW TEMPS MOST
AREAS WILL BE AROUND 40 DEGREES.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
SUNDAY....THE AREA WILL REMAIN PRIMARILY UNDER A WEST/SOUTHWEST
ZONAL FLOW ALOFT ALONG THE NORTHERN EDGE OF A BROAD RIDGE OF HIGH
PRESSURE THAT SLOWLY BUILDS NORTH INTO EARLY NEXT WEEK. AT THE
SFC...A FAIRLY STRONG WEDGE OF HIGH PRESSURE WILL PERSIST INLAND FOR
MUCH OF THE DAY WHILE A COASTAL TROUGH SLIDES NORTH OFF THE
SOUTHEAST COAST. THE SETUP WILL FAVOR CHANCES OF SHOWERS INTO SUNDAY
EVENING WHILE ISENTROPIC ASCENT PERSISTS OVER THE AREA AND MOISTURE
CONVERGENCE IS ENHANCED WITH THE PASSING TROUGH ALONG THE SOUTH
CAROLINA COAST. HIGH TEMPS WILL BE TRICKY SUNDAY...PRIMARILY DUE TO
CLOUD COVER...SHOWERS...AND THE WEDGE INLAND. IN GENERAL...TEMPS
SHOULD RANGE IN THE MID/UPPER 40S INLAND TO LOW/MID 50S ALONG THE
COAST...WARMEST IN SOUTHEAST GEORGIA.

MODELS ARE IN FAIR AGREEMENT THAT THE WEDGE OF HIGH PRESSURE WILL
BEGIN TO BREAK DOWN SUNDAY NIGHT AS THE COASTAL TROUGH SHIFTS
FURTHER NORTH AND AWAY FROM THE AREA. SHOWERS SHOULD THEREFORE TAPER
OFF...BEGINNING IN SOUTHERN AREAS SHORTLY AFTER SUNSET. OVERNIGHT
LOWS REMAIN MORE MILD THAN THE PREVIOUS NIGHT...IN THE LOW/MID 40S
AWAY FROM THE COAST.

MONDAY...A BRIEF WARMUP SHOULD OCCUR WHILE WEAK HIGH PRESSURE
PREVAILS OVER THE AREA IN ADVANCE OF A BACKDOOR COLD FRONT THAT
APPROACHES FROM THE NORTH LATE IN THE DAY. TEMPS SHOULD PEAK IN THE
MID 60S NORTH TO LOW 70S SOUTH OF INTERSTATE 16 IN SOUTHEAST
GEORGIA. SHOWERS ARE POSSIBLE AHEAD OF THE FRONT...BUT MOISTURE WILL
NOT BE AS DEEP AS PREVIOUS DAYS...THUS LIMITING OVERALL COVERAGE.
THE FRONT SHOULD STALL NEAR THE FLORIDA/GEORGIA STATE LINE EARLY
MONDAY NIGHT...WITH PERHAPS A FEW SHOWERS IN THE OVERNIGHT PERIOD.
LOW TEMPS WILL BE NOTICEABLY MORE MILD THAN THE PREVIOUS NIGHT...IN
THE LOW/MID 50S OVER MOST AREAS.

TUESDAY...HIGH PRESSURE WILL TRY TO WEDGE SOUTHWARD INTO THE AREA
EARLY...BEFORE A STATIONARY FRONT LIFTS NORTH AS A WARM FRONT DURING
THE AFTERNOON. TEMPS WILL ONCE AGAIN BE TRICKY TO FORECAST AND WILL
BE HIGHLY DEPENDENT ON THE POSITION OF THE WARM FRONT OVER THE
COURSE OF THE DAY. CLOUD COVER AND A FEW SHOWERS WILL ALSO POSE SOME
LIMITING FACTORS ON HOW WARM CONDITIONS WILL GET DURING TYPICAL PEAK
HEATING HOURS. AT THIS TIME...HAVE TRENDED WITH SLIGHTLY COOLER
TEMPS IN THE LOW/MID 60S FOR MOST AREAS...AND MAINTAINED LOW 70S
SOUTH OF INTERSTATE 16 IN SOUTHEAST GEORGIA.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
WARMER CONDITIONS ARE EXPECTED THROUGH WEDNESDAY AS A SOUTHERLY FLOW
STRENGTHENS AHEAD OF A COLD FRONT APPROACHING FROM THE NORTHWEST.
SFC HEATING AS WELL AS SOME COMPRESSIONAL HEATING SUPPORT OVERALL
HIGH TEMPS IN THE MID/UPPER 70S WEDNESDAY AFTERNOON BEFORE THE ONSET
OF SHOWERS AHEAD OF THE APPROACHING COLD FRONT. STRONG FORCING WILL
BE ASSOCIATED WITH THE FRONT...SUPPORTING THE NEED FOR A FEW
THUNDERSTORMS OVER INLAND AREAS EARLY WEDNESDAY NIGHT. THE COLD
FRONT WILL THEN PUSH THROUGH THE AREA ON THURSDAY...WITH PERIODS OF
MODERATE SHOWERS UNTIL EARLY FRIDAY. DRY AND COOLER HIGH PRESSURE
WILL FOLLOW THE FRONT ON FRIDAY...THEN PERSIST ON SATURDAY. OVERALL
TEMPS WILL REMAIN BELOW NORMAL INTO THE WEEKEND...WITH AFTERNOON
HIGHS IN THE MID/UPPER 50S AND LOWS IN THE MID/UPPER 30S.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
GUSTY NE WINDS ARE LIKELY AT KCHS/KSAV TODAY AND EVEN INTO
TONIGHT AS THE PRESSURE GRADIENT TIGHTENS BETWEEN INLAND HIGH
PRESSURE AND A COASTAL TROUGH OFFSHORE. MODELS CAME IN FAIRLY
ROBUST FOR RAIN CHANCES LATER TODAY AGAIN ON THE 06Z RUN. WE
MAINTAINED PREVIOUS TRENDS WITH VCSH AT KSAV FROM LATE MORNING
INTO THE AFTERNOON...THEN PERHAPS PREVAILING AT SOME POINT
OVERNIGHT WITH INCREASING MOISTURE DEPTH AND SPEED CONVERGENCE
IN THE LOW LEVELS. VCSH AT KCHS LATE IN THE DAY THROUGH TONIGHT.

CIGS ARE TRICKY WITH SOME MODEL DISCREPANCIES DESPITE A COMMON
THEME OF INCREASING MOISTURE UNDER A STRENGTHENING WEDGE
INVERSION. OUR MAIN THEME WAS A GRADUAL LOWERING TODAY...MVFR
OR LOWER CIGS A GOOD BET AT KSAV AFTER MID AFTERNOON...THEN
LIKELY TONIGHT WITH IFR AFTER MIDNIGHT PER 06Z FORECAST SOUNDINGS.
KCHS WILL HANG ONTO SOME LOWER LEVEL DRIER AIR A WHILE LONGER AND
MVFR CIGS POSSIBLE LATER THIS AFTERNOON...THEN LIKELY OVERNIGHT.

EXTENDED AVIATION OUTLOOK...FLIGHT RESTRICTIONS ARE LIKELY SUNDAY
AFTERNOON/EVENING AS A WEDGE OF HIGH PRESSURE PERSISTS OVER THE
AREA. VFR CONDITIONS SHOULD THEN RETURN ON MONDAY. A BACKDOOR COLD
FRONT COULD PRODUCE ANOTHER ROUND OF FLIGHT RESTRICTIONS MONDAY
AFTERNOON/EVENING...FOLLOWED BY MORE CHANCES OF FLIGHT RESTRICTIONS
ON TUESDAY AS THE FRONT RETURNS AS AS WARM FRONT. VFR CONDITIONS
SHOULD RETURN FOR WEDNESDAY.

&&

.MARINE...
HIGH PRESSURE WILL WEDGE INLAND TODAY AND TONIGHT WHILE A COASTAL
TROUGH DEVELOPS OFF THE GEORGIA COAST. A STRONG PRESSURE GRADIENT
IS EXPECTED TO DEVELOP BETWEEN THESE TWO FEATURES...LEADING TO
DETERIORATING CONDITIONS OVER ALL MARINE WATERS. A GALE WARNING
IS IN EFFECT FOR OFFSHORE GEORGIA WATERS TODAY INTO TONIGHT WHERE
PINCHING BECOMES GREATEST ALONG THE NORTHERN EDGE OF THE COASTAL
TROUGH...AND SMALL CRAFT ADVISORIES WILL REMAIN ONGOING FOR ALL
REMAINING WATERS TODAY AND TONIGHT.

THE 00Z NAM CAME IN A BIT STRONGER WITH FORECAST WIND SPEEDS WHICH
IS A CONCERN THAT GALES MAY DEVELOP ACROSS NEAR SHORE MARINE
WATERS LATER TODAY AND ALONG THE SOUTH CAROLINA COAST THIS
EVENING. IT LOOKED BORDERLINE ENOUGH TO HOLD OFF ANY UPGRADES
TO GALE WARNINGS WITHIN 20 NM BUT WE HAVE TO WATCH TRENDS CLOSE
TODAY AS THERMAL/MOISTURE GRADIENTS ARE IN PLACE PERHAPS SUPPORTIVE
OF SMALLER SCALE ENHANCEMENTS TO NE FLOW. MODELS TYPICALLY DROP
WINDS A BIT FAST WITH THIS PARTICULAR SYNOPTIC PATTERN AND WE
TRENDED IN THIS DIRECTION WITH THE LATEST FORECAST LATER TONIGHT.
SEAS WILL BUILD TO 6 TO 8 FT NEAR SHORE WATERS AND AT LEAST 9-11
FEET OVER GEORGIA WATERS.

SUNDAY...HIGH PRESSURE WILL WEDGE INLAND ON SUNDAY WHILE A COASTAL
TROUGH LIFTS NORTH ALONG THE SOUTHEAST COAST. A STRONG PRESSURE
GRADIENT IS EXPECTED TO DEVELOP BETWEEN THESE TWO FEATURES...WITH
SMALL CRAFT ADVISORY LEVEL CONDITIONS OVER ALL NEARSHORE WATERS
THROUGH SUNDAY MORNING. WINDS/SEAS SHOULD THEN FALL BELOW SMALL
CRAFT ADVISORY LEVELS IN NEAR SHORE WATERS BY SUNDAY EVENING AS
WEAKER HIGH PRESSURE SLIDES OVER THE WATERS AND THE COASTAL TROUGH
SHIFTS NORTH OF THE AREA. LINGERING 6-7 FT SEAS WILL LIKELY KEEP
OFFSHORE GEORGIA WATERS IN A SMALL CRAFT ADVISORY TO AROUND MIDNIGHT
SUNDAY NIGHT.

MONDAY AND TUESDAY...CONDITIONS SHOULD REMAIN BELOW ADVISORY LEVELS
AS A BACKDOOR COLD FRONT STALLS OVER OR JUST SOUTH OF THE COASTAL
WATERS ON MONDAY...THEN LIFTS BACK NORTH AS A WARM FRONT ON TUESDAY.
AS THE FRONT LIFTS NORTH...DEWPTS SHOULD RISE INTO THE UPPER 50S TO
AROUND 60...POSSIBLY RESULTING IN SOME SEA FOG OVER SOUTHERN WATERS.

WEDNESDAY THROUGH FRIDAY...SEA FOG COULD BE AN ISSUE AS DEEP
MOISTURE ADVECTS OVER COOLER WATERS WEDNESDAY AND THURSDAY AHEAD OF
AN APPROACHING COLD FRONT. WINDS AND SEAS WILL ALSO GRADUALLY
INCREASE/BUILD AHEAD OF A COLD FRONT...LIKELY SUPPORTING THE NEED
FOR ADDITIONAL SMALL CRAFT ADVISORIES THAT START WEDNESDAY NIGHT AND
PERSIST INTO FRIDAY AS THE COLD FRONT SHIFTS OVER THE WATERS AND IS
FOLLOWED BY COOLER HIGH PRESSURE.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR AMZ330.
     SMALL CRAFT ADVISORY UNTIL 1 PM EST SUNDAY FOR AMZ350-352-354.
     GALE WARNING UNTIL 11 PM EST THIS EVENING FOR AMZ374.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...
MARINE...DPB


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