National Weather Service Weather Forecast Office

Area Forecast Discussion

806
FXUS62 KCHS 190536
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
136 AM EDT WED JUN 19 2013

.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE NORTHWEST TONIGHT...THEN
SLOWLY PROGRESS THROUGH THE AREA WEDNESDAY AND THURSDAY. HIGH
PRESSURE WILL THEN BUILD FROM THE NORTH INTO THE WEEKEND AND
SETTLE OVER THE ATLANTIC EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
OVERNIGHT WE LOWERED POPS TO SLIGHT CHANCE MOST AREAS AS THE
ATMOSPHERE LOADS UP FOR ANOTHER BUSY DIURNAL DAY COMING UP.
WE MAINTAINED SOME SLIGHTLY HIGHER POPS ALONG COASTAL SOUTH
CAROLINA AS MOISTURE ADVECTION WAS ON AN UPTICK EARLY THIS MORNING.
PARTLY TO MOSTLY CLOUDY SKIES WILL PERSIST WITH TEMPS SLOWLY
FALLING THROUGH THE 70S OVERNIGHT. WE BUMPED UP WINDS A TAD ALONG
THE SOUTH CAROLINA COAST WHERE A LOW LEVEL JET WAS ONGOING.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
WEDNESDAY AND THURSDAY...A COLD FRONT WILL SLOWLY SHIFT OVER
SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA BY WEDNESDAY MORNING
BEFORE GRADUALLY STALLING SOUTH OF THE REGION BY THURSDAY. AS THIS
OCCURS...PWATS NEAR 2.0 INCHES ALONG WITH MID LVL FORCING FROM AN H5
SHORTWAVE SHOULD FAVOR PERIODS OF SHOWERS/THUNDERSTORMS THROUGH MUCH
OF WEDNESDAY...ESPECIALLY ALONG/NEAR THE PASSING COLD FRONT. HAVE
THEREFORE INCREASED POPS TO 50-60 WEDNESDAY AFTERNOON MAINLY ALONG
COASTAL LOCATIONS IN SOUTHEAST GEORGIA CLOSER TO THE FRONT. AT THIS
TIME...CLOUD COVER WILL REMAIN A LIMITING FACTOR FOR STRONGER
THUNDERSTORMS TO DEVELOP OVER THE REGION. HOWEVER...WEAK WIND FIELDS
WILL LIKELY RESULT IN SLOW STORM MOTIONS THAT MAY CONTRIBUTE TO
HEAVY RAINFALL DURING A FEW THUNDERSTORMS.

A GRADUAL DECREASE IN OVERALL POPS SHOULD THEN OCCUR FROM NORTH TO
SOUTH WEDNESDAY NIGHT INTO THURSDAY AS THE FRONT SLOWLY SLIPS TO THE
SOUTH OF THE FORECAST AREA...BUT HAVE MAINTAINED A MENTION OF PRECIP
OVER ALL LOCATIONS THROUGH THURSDAY NIGHT...WITH 20 POPS OVER INLAND
SOUTH CAROLINA TO 30-40 POPS OVER LOCATIONS SOUTH OF INTERSTATE 16
IN GEORGIA. OVERALL HIGH TEMPS ARE EXPECTED TO PEAK IN THE MID/UPPER
80S OVER MOST LOCATIONS WEDNESDAY AND THURSDAY...WITH SLIGHTLY COOLER
TEMPS IN THE MID 80S OVER SOUTH CAROLINA BEHIND THE FRONT. OVERNIGHT
LOWS ARE EXPECTED TO BE IN THE UPPER 60S TO LOWER 70S.

FRIDAY...SURFACE HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE
NORTH...WITH THE PATTERN EVENTUALLY TRANSITIONING INTO AN INLAND
WEDGE/COASTAL TROUGH TYPE SCENARIO. A FEW MODELS INDICATE A WEAK
WAVE/SFC LOW DEVELOPING ALONG THE STALLED FRONT JUST OFFSHORE LATE
MORNING/EARLY AFTERNOON BEFORE DRIFTING ONSHORE DURING THE EVENING.
A SLIGHT CHANCE TO CHANCE OF SHOWERS AND/OR THUNDERSTORMS WILL
THEREFORE BE MAINTAINED IN THE CURRENT FORECAST...WITH HIGHEST
CHANCES OVER SOUTHEAST GEORGIA COUNTIES. OVERALL HIGH TEMPS SHOULD
REMAIN IN THE MID/UPPER 80S WITH SLIGHTLY COOLER TEMPS ALONG COASTAL
COUNTIES AND THE TRI COUNTY AREA DUE TO ENHANCED CLOUD COVER AND
HIGH PRESSURE NUDGING IN FROM THE NORTH.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A WEAK INLAND WEDGE/COASTAL TROUGH PATTERN WILL PERSIST INTO
SATURDAY...BEFORE THE TROUGH DAMPENS BY SUNDAY AS HIGH PRESSURE
SETTLES OVER THE ATLANTIC. THE FORECAST AREA WILL THEN REMAIN
ALONG THE WESTERN PERIPHERY OF THE ATLANTIC HIGH PRESSURE INTO
EARLY NEXT WEEK. SHOWER/THUNDERSTORM CHANCES WILL RANGE FROM
AROUND 20 TO 30 PERCENT EACH AFTERNOON AND EARLY EVENING...BEFORE
DIMINISHING OVERNIGHT AS MORE TYPICAL FOR EARLY SUMMER. THE
INITIALLY WEAK AND ILL DEFINED UPPER LEVEL PATTERN WILL TRANSITION
INTO BROAD RIDGING ALOFT...SUPPORTING A GRADUAL WARMING TREND
THROUGH THE PERIOD. HIGH TEMPERATURES AROUND 90 DEGREES AWAY FROM
THE COASTLINE SATURDAY AND SUNDAY WILL WARM INTO THE LOWER 90S BY
MONDAY AND TUESDAY.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
OVERNIGHT...CHANCES GOOD THAT BOTH TERMINALS SEE A CONTINUATION
OF VFR CONDITIONS BUT CANNOT RULE OUT SOME MVFR CIGS DEVELOPING
TOWARD DAYBREAK. SPOTTY SHOWERS ARE ALSO POSSIBLE. CONVECTIVE
RAINS EXPECTED TO FIRE UP AND SWEEP THROUGH THE COASTAL CORRIDOR
ALONG AND AHEAD OF A COLD FRONT. WE HAVE TIMING SHOWERS AND TSTMS
FROM 17Z-21Z AT THIS POINT AND RAINS COULD EVEN LINGER INTO THE
EVENING HOURS BEFORE DIMINISHING. MVFR OR BRIEF IFR CONDITIONS
MAY ACCOMPANY HEAVIER DOWNPOURS. WILL ALSO MONITOR FOR MVFR OR
LOWER CIGS IN THE WAKE OF THE FRONT AT KCHS AFTER SUNSET.

&&

.MARINE...
TONIGHT...THE PRESSURE GRADIENT IS CONTINUING TO TIGHTEN BETWEEN
THE STRONG SUB-TROPICAL ATLANTIC RIDGE TO THE SE AND AN UPSTREAM
COLD FRONT TO THE NW. THE PACKING OF THE ISOBARS WILL BECOME
GREATEST EARLY TONIGHT BETWEEN THE COLD FRONT AND ATLANTIC
HIGH...AS GEOSTROPHIC WINDS CLIMB TO 25-30 KT. THIS IS SUPPORTIVE
OF A MARGINAL SCA ACROSS OUR OUTER GA WATERS FOR SOME 5-6 FOOTERS
AND FREQUENT GUSTS OF 25 KT. THE OTHER WATERS LOOK TO REMAIN JUST
BELOW ANY HEADLINE CONDITIONS...WITH WINDS PEAKING AT 15 OR 20 KT
AND SEAS AT 3-5 FT.

WEDNESDAY THROUGH SATURDAY...WINDS/SEAS ARE EXPECTED TO REMAIN BELOW
SMALL CRAFT ADVISORY CRITERIA AS A COLD FRONT SHIFTS OVER THE
COASTAL WATERS WEDNESDAY BEFORE STALLING NEAR/OVER SOUTHERN GA
WATERS ON THURSDAY. AS THE FRONT SLOWLY SHIFTS SOUTH...SOUTHERLY
WINDS WILL VEER BEHIND THE FRONT AND EVENTUALLY BECOME
NORTHEAST/EAST THURSDAY. HIGH PRESSURE WILL THEN BUILD FROM THE
NORTH OVER THE WATERS INTO EARLY FRIDAY...WITH WIND SPEEDS
APPROACHING 15-20 KT OVER NORTHERN SC WATERS AND SEAS BUILDING TO
3-4 FT. ENHANCED EAST/NORTHEAST FLOW MAY CONTINUE INTO SATURDAY
AS A COASTAL TROUGH DEVELOPS OFFSHORE AND GRADUALLY SHIFTS OVER
LAND.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EDT EARLY THIS MORNING FOR
     AMZ374.

&&

$$

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