Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 210519
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
119 AM EDT MON APR 21 2014

.SYNOPSIS...
LOW PRESSURE WELL OFF THE CAROLINA COAST WILL CONTINUE TO DEPART TO
THE NORTHEAST OVERNIGHT. OTHERWISE...HIGH PRESSURE WILL BUILD OVER
THE REGION INTO TUESDAY...BEFORE A WEAKENING COLD FRONT MOVES ACROSS
THE AREA TUESDAY NIGHT. HIGH PRESSURE WILL THEN PREVAIL THROUGH
LATE WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
LOW PRESSURE PILED ATOP ONE ANOTHER FROM THE SURFACE THROUGH THE
TROPOPAUSE OVER THE ATLANTIC NEAR 33N AND 75W WILL CONTINUE TO
EXIT FURTHER OUT TO SEA AS SHORT WAVE RIDGING ARRIVES FROM THE
WEST BY LATE TONIGHT. MEANWHILE...A FAIRLY STRONG HIGH PRESSURE
WEDGE EAST OF THE APPALACHIANS WILL HOLD IN PLACE. BUT GIVEN THAT
THE ATLANTIC CYCLONE WILL DROP A FEW MORE MILLIBARS THE ASSOCIATED
CYCLONIC CIRCULATION WILL EXTEND BACK TO THE WEST AND WILL COVER
MUCH OF THE REGION. THIS ALONG WITH A 2-3C NOCTURNAL INVERSION TO
FORM AND TRAPPING MOISTURE UNDERNEATH INDICATES THAT CLOUD COVER
WILL BE SLUGGISH IN DIMINISHING ALONG SE SOUTH CAROLINA. OVER SE
GEORGIA...CLOUDS HAVE DIMINISHED SIGNIFICANTLY IN THE PAST HOUR
AND THIS TREND MAY CONTINUE.

WE LOWERED MIN TEMPS IN SOME AREAS TO THE W OF I-95...OTHERWISE
CHANGES WERE MINOR OUTSIDE OF INITIAL/SHORT TERM CLOUD COVERAGE
TRENDS.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY/...
MONDAY...LOW PRESSURE WELL OFF THE CAROLINA COAST WILL CONTINUE TO
DEPART TO THE NORTHEAST AS UPPER LEVEL RIDGING BUILDS EAST OVER THE
REGION AND HIGH PRESSURE AT THE SURFACE APPROACHES FROM THE WEST.
MODEL SOUNDINGS INDICATE THAT MOISTURE WILL REMAIN TRAPPED BENEATH
AN INVERSION TO START THE DAY...LIKELY RESULTING IN PARTLY TO MOSTLY
CLOUDY SKIES...BUT THEN CLEARING SHOULD TAKE PLACE IN THE LATE
MORNING AND AFTERNOON. DESPITE THE NORTHERLY FLOW...AFTERNOON
SUNSHINE COMBINED WITH RISING HEIGHTS ALOFT WILL RESULT IN
TEMPERATURES REACHING HIGHS IN THE MID TO UPPER 70S AWAY FROM THE
IMMEDIATE COAST.

MONDAY NIGHT...SURFACE HIGH PRESSURE WILL SETTLE OVER THE NORTHERN
GULF OF MEXICO...SETTING UP A WEAK RETURN FLOW ACROSS THE AREA.
DESPITE LIGHT WINDS...RADIATIONAL COOLING WILL BE LIMITED BY
INCREASING HIGH CLOUDS AS AN UPPER LEVEL JET SHIFTS OVER THE REGION.
LOWS SHOULD RANGE FROM AROUND 50 ACROSS INLAND SOUTHEAST SOUTH
CAROLINA TO THE LOWER AND MID 50S ELSEWHERE.

TUESDAY AND TUESDAY NIGHT...A MID AND UPPER LEVEL SHORT WAVE TROUGH
WILL MOVE ACROSS THE AREA TUESDAY AFTERNOON...FOLLOWED BY THE
PASSAGE OF A WEAK COLD FRONT FROM THE NORTHWEST OR NORTH TUESDAY
NIGHT. CLOUD COVER WILL BE ON THE INCREASE WITH THE APPROACH OF THE
UPPER TROUGH ON TUESDAY AND THE FORECAST WILL INDICATE A SLIGHT
CHANCE OF SHOWERS IN THE AFTERNOON INLAND FROM THE COAST. THEN...THE
POTENTIAL FOR SHOWERS INCREASES INTO THE CHANCE CATEGORY MAINLY
NORTH OF THE SAVANNAH RIVER TUESDAY EVENING...WITH A SLIGHT CHANCE
ELSEWHERE...AHEAD OF THE ACTUAL COLD FRONT. SURFACE BASED
INSTABILITY...WITH CAPE VALUES AS HIGH AS 500-900 J/KG AND LI/S DOWN
TO -2 OR -3...COULD SUPPORT SOME THUNDERSTORMS AHEAD OF THE FRONT AS
WELL. THE PRECIPITATION WILL END LATE EVENING OR DURING THE EARLY
OVERNIGHT HOURS AS THE FRONT PASSES. THE FLOW ALOFT WILL BECOME
DOWNSLOPE AS THE UPPER TROUGH MOVES THROUGH...AND COMBINED WITH SOME
COMPRESSIONAL HEATING AHEAD OF THE COLD FRONT WILL DRIVE
TEMPERATURES WELL INTO THE LOWER 80S FOR HIGHS AWAY FROM THE
IMMEDIATE COAST.

WEDNESDAY...HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE
NORTHWEST WITH MOSTLY SUNNY SKIES ACROSS THE AREA. TEMPERATURES WILL
BE A BIT COOLER BEHIND THE FRONT...WITH HIGHS IN THE UPPER 70S TO
LOWER 80S IN MOST AREAS.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD OVER THE SOUTHEAST
THROUGH THURSDAY SUPPORTING RAIN-FREE CONDITIONS AND HIGH
TEMPERATURES RANGING FROM THE UPPER 70S TO LOWER 80S THURSDAY. AS A
SURFACE RIDGE OF HIGH PRESSURE SHIFTS OFFSHORE FRIDAY THROUGH
SUNDAY...TEMPERATURES IN THE LOWER TO MID 80S WILL BE COMMON AWAY
FROM THE IMMEDIATE COAST. WITH MODERATE INSTABILITY EXPECTED FRIDAY
AND SATURDAY...INCLUDED A SLIGHT CHANCE FOR AFTERNOON THUNDERSTORMS.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
KCHS...PERIODIC MVFR CIGS AROUND THE TERMINAL AT 06Z INITIALIZATION
TIME. BORDERLINE MVFR CIGS MAY LINGER AT TIMES PRIOR TO DAYBREAK
BUT OVERALL...VFR CONDITIONS WILL PREVAIL TODAY AND TONIGHT AS
CLOUDS SCATTERED OUT IN THE WAKE OF THE OFFSHORE LOW. N WINDS MAY
BE GUSTY AT TIMES MID MORNING TO EARLY AFTERNOON.

KSAV...4-5 KFT CIGS MAY BACK IN OVERNIGHT BUT MVFR CIGS APPEAR
UNLIKELY OVERNIGHT. VFR TODAY AND TONIGHT WITH OCCASIONAL WIND
GUSTS 15-19 KT FROM THE N DURING THE LATE MORNING HOURS.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED TO CONTINUE
INTO TUESDAY. THERE IS A SMALL CHANCE OF SOME IFR/MVFR CONDITIONS IN
CONVECTION LATE TUESDAY OR TUESDAY NIGHT...WITH CONDITIONS IMPROVING
BACK TO VFR BY WEDNESDAY.

&&

.MARINE...
OVERNIGHT...ALTHOUGH LOW PRESSURE EAST OF THE WATERS WILL CONTINUE
TO PULL FURTHER INTO THE ATLANTIC THROUGH THE NIGHT...IT/S CENTRAL
PRESSURE WILL DROP A FEW MORE MILLIBARS AS A HIGH PRESSURE WEDGE
REMAINS POSITIONED INLAND OVER THE SE. THE RESULTING PRESSURE
GRADIENT BETWEEN THESE TWO FEATURES WILL REMAIN PACKED...WITH THE
END RESULT THAT THE ONGOING SMALL CRAFT ADVISORIES WILL CONTINUE
FOR NORTHERLY WINDS OF 20-25 KT. WE TOYED WITH THE IDEA OF
DROPPING THE SCA FOR CHARLESTON HARBOR...BUT AS COOL ADVECTION
DEVELOPS WE ANTICIPATE THAT THE WINDS WILL RISE AGAIN OVER AMZ330.
SEAS WILL BE HELD IN CHECK SOMEWHAT BY THE OFFSHORE FETCH...BUT
GIVEN THAT UNDER THE WIND WAVES THERE IS ALSO SOME SWELL
ENERGY...COMBINED SEAS WILL BE AS HIGH AS 4-6 FT WITHIN 20 NM AND
7-10 FT FURTHER OUT. IN CHARLESTON HARBOR WAVES WILL BE 1-2
FT...EVEN A FOOT OR SO HIGHER AT THE JETTIES.

WINDS AND SEAS WILL DIMINISH MONDAY AND MONDAY NIGHT AS COASTAL
LOW PRESSURE DEPARTS TO THE NORTHEAST AND HIGH PRESSURE BUILDS
FROM THE WEST. SMALL CRAFT ADVISORIES WILL PERSIST INTO MONDAY
MORNING FOR THE CHARLESTON COUNTY COASTAL WATERS AND THROUGH
MONDAY NIGHT FOR THE OUTER GA WATERS FOR LINGERING 6 FT SEAS. A
SOUTHWEST FLOW WILL STRENGTHEN TUESDAY AND TUESDAY EVENING AHEAD
OF AN APPROACHING COLD FRONT...WITH SPEEDS PEAKING AROUND 15 KT.
THE FRONT WILL MOVE OFFSHORE TUESDAY NIGHT...FOLLOWED BY HIGH
PRESSURE AND CONDITIONS BELOW SMALL CRAFT ADVISORY LEVELS THROUGH
THE REST OF THE WEEK.

&&


.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR
     AMZ330-352-354.
     SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR AMZ350.
     SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR AMZ374.

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...JAQ
LONG TERM...MTE
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...






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