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Area Forecast Discussion

313
FXUS62 KCHS 191501
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1101 AM EDT SAT APR 19 2014

.SYNOPSIS...
LOW PRESSURE WILL SHIFT OFF THE SOUTHEAST COAST LATE TODAY INTO
TONIGHT. THEN...THE LOW WILL CONTINUE TO GRADUALLY MOVE AWAY FROM
COAST SUNDAY. HIGH PRESSURE WILL BRIEFLY BUILD INTO THE REGION
MONDAY. A WEAKENING COLD FRONT WILL PUSH THROUGH THE AREA BY
WEDNESDAY... FOLLOWED BY HIGH PRESSURE AND WARMER TEMPERATURES
THROUGH LATE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
A DREARY DAY IS IN STORE AS A COMPLEX LOW PRESSURE SYSTEM MOVES
OFF THE FL/GA COAST INTO THE WESTERN ATLANTIC WHILE PRODIGIOUS
MOISTURE WRAPS AROUND THE NORTHWEST PERIPHERY. A WEAK WEDGE OF
HIGH PRESSURE WILL REMAIN ENTRENCHED ACROSS INLAND AREAS WHILE THE
SURFACE LOW TRACKS TO A POSITION OFF THE FL COAST BY EARLY THIS
EVENING. MORNING WATER VAPOR IMAGERY DEPICTS THE POWERFUL UPPER
LOW SPINNING ACROSS NORTHERN FLORIDA WITH AN ATMOSPHERIC RIVER
EXTENDING FROM THE BAHAMAS INTO EASTERN NC. A LARGE DRY SLOT
REMAINS ACROSS SC THOUGH A SECONDARY WAVE OF MID/UPPER LEVEL
MOISTURE WILL MOVE IN FROM THE SW THIS AFTERNOON.

DUE TO THE POSITION OF THE UPPER LOW SO NEAR THE AREA...THE MID
LEVELS ARE QUITE UNSTABLE. 700-500 MB LAPSE RATES EXCEED 8 C/KM
AND SHOWALTER INDICES WILL BE -4 TO -6C ACROSS SOUTHEAST GA THIS
AFTERNOON. THIS WOULD NORMALLY BE RATHER CONCERNING FOR HAIL
GROWTH. HOWEVER IT LOOKS AS THOUGH THE EXTENSIVE ISENTROPIC ASCENT
TODAY WILL MAINTAIN DENSE STRATUS AND THUS PRECLUDE THE
DEVELOPMENT OF SURFACE BASED INSTABILITY. WE STILL THINK A FEW
ELEVATED TSTMS WILL BE POSSIBLE DURING THE AFTERNOON IF SOME
POCKETS OF INSTABILITY DEVELOP. THOUGH THE PRIMARY PRECIPITATION
WILL BE AREAS OF DRIZZLE AND LIGHT RAIN SHOWERS TRAVERSING THE
AREA FROM TIME TO TIME.

LOW CLOUDS AND AREAS OF DRIZZLE/FOG LIKELY TO PERSIST INTO TONIGHT
AS THE LOW SLOWLY MOVES EAST OFF THE COAST. BREEZY CONDITIONS
EXPECTED LATER TONIGHT AS THE GRADIENT TIGHTENS.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
THE CUT-OFF UPPER LOW WILL ROLL ONLY SLOWLY EAST/NORTHEAST SUNDAY
THROUGH MONDAY...SUPPORTING ONLY GRADUAL IMPROVEMENT/LOWERING POPS.
CAPPED MAXIMUM POPS AROUND 50 PERCENT SUNDAY MORNING ACROSS NORTHERN
COASTAL COUNTIES/ADJACENT COASTAL WATERS...BUT HIGHER POPS COULD BE
REQUIRED SUNDAY DEPENDING ON THE DISTRIBUTION OF WRAP-AROUND
MOISTURE. ALSO OF NOTE...A TIGHT SURFACE PRESSURE GRADIENT BETWEEN
THE OFFSHORE LOW PRESSURE AND HIGH PRESSURE BUILDING FROM THE NORTH
WILL SUPPORT BREEZY/WINDY CONDITIONS AND BELOW-NORMAL TEMPERATURES
MAINLY IN THE 60S SUNDAY...FOLLOWED BY TEMPERATURES IN THE 70S AND
LIGHTER WINDS MONDAY.

TUESDAY...AN UPPER TROUGH AND ASSOCIATED SURFACE COLD FRONT WILL
APPROACH THE REGION FROM THE WEST/NORTHWEST. AHEAD OF THESE
FEATURES...TEMPERATURES SHOULD WARM INTO THE LOWER 80S AT MANY
LOCATIONS. DURING THE AFTERNOON/EVENING...GUIDANCE CONTINUES TO
DEPICT A BAND OF ENHANCED 850-500 MB MOISTURE PUSHING THROUGH THE
REGION. THE 19/00 UTC GFS DEPICTION OF INSTABILITY FEATURING SBCAPES
AS HIGH AS 900-1000 J/KG AND CLIMATOLOGY JUSTIFY A SLIGHT CHANCE OF
THUNDERSTORMS DURING THIS PERIOD.

LAKE WINDS...GUSTY WINDS WILL LIKELY NECESSITATE A LAKE WIND
ADVISORY SUNDAY INTO SUNDAY NIGHT.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
THE UPPER TROUGH AND ASSOCIATED SURFACE COLD FRONT WILL PUSH THROUGH
THE REGION TUESDAY NIGHT. SURFACE HIGH PRESSURE WILL THEN BUILD OVER
THE REGION FROM THE NORTH...SUPPORTING RAIN-FREE CONDITIONS AND
TEMPERATURES RANGING FROM THE THE MID 70S LOWER 80S WEDNESDAY AND
UPPER 70S TO MID 80S THURSDAY. AS THE HIGH SHIFTS OFFSHORE
FRIDAY...TEMPERATURES IN THE LOWER TO MID 80S WILL BE COMMON AWAY
FROM THE IMMEDIATE COAST.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
IFR/LIFR CIGS ACROSS THE COASTAL CORRIDOR AT DAYBREAK WITH THE
DRY SLOT ALOFT PROVIDING AN IMPETUS FOR LOW CLOUDS TO BUILD
DOWN EARLY THIS MORNING. WHERE THE CLOUDS WERE BELOW 500 FT...
LIGHT FOG REPORTED. FORECAST SOUNDINGS DO NOT PROVIDE MUCH
HOPE THAT CIGS LIFT QUICKLY OR SCATTER OUT TODAY. THERE IS
GREAT DOUBT THAT CIGS BREAK AT KCHS AND WE RETAINED IFR THROUGH
THE TAF CYCLE BUT STRONGER LOW LEVEL WINDS BY TONIGHT COULD
ALLOW CIGS TO LIFT TO LOW END MVFR. SCATTERED SHOWERS DEVELOPING
ACROSS SE GEORGIA SHOULD EXPAND TO SE SOUTH CAROLINA BY LATER
THIS AFTERNOON AND EVENING. THERE IS A CHANCE FOR TSRA LATER
TODAY BUT OVERALL POTENTIAL NOT THERE FOR TAF INCLUSIONS.

EXTENDED AVIATION OUTLOOK...FLIGHT RESTRICTIONS INTO SUNDAY. VFR
THEREAFTER. GUSTY WINDS POSSIBLE SUNDAY.

&&

.MARINE...
CONDITIONS NOT LOOKING TO IMPROVE TOO MUCH TODAY AS LOW PRES
MOVES OFF THE NE FLORIDA COAST LATE. THE GRADIENT WILL BEGIN TO
PACK AGAIN TONIGHT PRODUCING INCREASING N TO NE FLOW AND WINDS
GUSTING OVER 30 KT AGAIN...ESPECIALLY AFTER MIDNIGHT. SMALL CRAFT
ADVISORIES WILL CONTINUE ALL WATERS INCLUDING THE CHARLESTON
HARBOR THROUGH TONIGHT.

AN IMPRESSIVE SURFACE PRESSURE GRADIENT AND 35-40 KT WINDS AS LOW AS
THE 950-925 MB LAYER SUGGEST THE POTENTIAL FOR GALES OUTSIDE
CHARLESTON HARBOR SUNDAY INTO SUNDAY NIGHT. THUS...RAISED GALE
WATCHES FOR ALL ZONES OUTSIDE THE HARBOR BEGINNING 12Z SUNDAY AND
CONTINUING THROUGH SUNDAY EVENING ACROSS NEARSHORE WATERS AND
THROUGH SUNDAY NIGHT ACROSS AMZ374. SOLID SMALL CRAFT ADVISORY
CONDITIONS WILL PREVAIL ON CHARLESTON HARBOR DURING THIS PERIOD.
EXPECT A TRANSITION TO SMALL CRAFT ADVISORY CONDITIONS OUTSIDE THE
HARBOR WHEN GALES END OVERNIGHT SUNDAY NIGHT INTO MONDAY. SMALL
CRAFT ADVISORY SEAS COULD PERSIST ACROSS AMZ374 THROUGH MONDAY
NIGHT/TUESDAY MORNING.

WINDS/SEAS ARE EXPECTED TO REMAIN SMALL CRAFT ADVISORY LEVELS AHEAD
OF AN APPROACHING COLD FRONT TUESDAY. THIS FRONT WILL ADVANCE
THROUGH THE WATERS TUESDAY NIGHT...AND A PERIOD OF SMALL CRAFT
ADVISORY WINDS IS POSSIBLE ESPECIALLY ACROSS AMZ374 THROUGH
WEDNESDAY. THEN...WINDS/SEAS SHOULD REMAIN BELOW SCA LEVELS THROUGH
LATE WEEK.

RIP CURRENTS...MODERATE TO HIGH RISK TODAY...HIGHEST ALONG THE
GEORGIA COAST. AN ENHANCED RISK FOR RIP CURRENTS WILL PERSIST
THROUGH THE WEEKEND AND PERHAPS INTO EARLY NEXT WEEK.

&&

.TIDES/COASTAL FLOODING...
TIDES WILL CONTINUE TO RUN HIGH THROUGH THE WEEKEND AND COASTAL
FLOOD ADVISORIES COULD BE NEEDED DURING THE NIGHTTIME HIGH TIDE
CYCLES.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT MONDAY FOR AMZ330.
     GALE WATCH FROM SUNDAY MORNING THROUGH SUNDAY EVENING FOR
     AMZ350-352-354.
     SMALL CRAFT ADVISORY UNTIL 8 AM EDT SUNDAY FOR AMZ350-352-354-
     374.
     GALE WATCH FROM SUNDAY MORNING THROUGH LATE SUNDAY NIGHT FOR
     AMZ374.

&&

$$

SYNOPSIS...
NEAR TERM...JRL
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...
MARINE...SPR
TIDES/COASTAL FLOODING...






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