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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 180754
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
354 AM EDT TUE JUN 18 2013

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO RETREAT FARTHER INTO THE ATLANTIC
EARLY THIS WEEK. A COLD FRONT WILL APPROACH FROM THE NORTHWEST
TUESDAY...THEN SLOWLY PROGRESS THROUGH THE AREA WEDNESDAY AND
THURSDAY. HIGH PRESSURE WILL THEN BUILD FROM THE NORTH INTO THE
WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
THROUGH SUNRISE...A STRONG CLUSTER OF TSTMS WHICH MOVED THROUGH
THE CHARLESTON METRO AREA AROUND 3 AM IS PUSHING STEADILY
OFFSHORE. ONCE THIS ACTIVITY MOVES INTO THE ATLANTIC...EXPECT
RELATIVELY QUIET CONDITIONS THROUGH SUNRISE. SATELLITE SHOWS SOME
CLEARING OCCURRING ACROSS SOUTHEAST GEORGIA WHICH COULD WORK
FARTHER UP ALONG THE LOWER SOUTH CAROLINA COAST OVER THE NEXT FEW
HOURS. CLOUD SEE SOME PATCHES OF LOW CLOUDS AND FOG FORM GIVEN THE
LIGHT WIND FIELDS THAT ARE IN PLACE.

TODAY...IT LOOKS TO BE ANOTHER ACTIVE DAY FOR SHOWERS/TSTMS. MODELS
ARE SIMILAR IN SHOWING ANOTHER POTENT SHORTWAVE TRAVERSING
SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA THIS AFTERNOON AS
INSOLATION PEAKS. SOME FILTERED SUNSHINE THIS MORNING SHOULD ALLOW
TEMPERATURES TO RISE QUICKLY...REACHING THE UPPER 80S TO LOWER 90S
AWAY FROM THE BEACHES BY EARLY AFTERNOON. THE RESULTANT SEA
BREEZE AS WELL AS LINGERING CONVECTIVE OUTFLOWS AND POSSIBLY SOME
DIFFERENTIAL HEATING BOUNDARIES WILL SERVE AS THE PRIMARY FOCI FOR
CONVECTIVE DEVELOPMENT. GENERALLY FOLLOWED THE 4KM WRF/S
CONVECTIVE SOLUTION TO CONSTRUCT HOURLY POPS WHICH MATCHES FAIRLY
WELL WITH THE LATEST H3R. GIVEN THAT...WILL GO WITH A 50-70 POP
REGIME TODAY...WITH THE HIGHEST GRIDDED POPS ALIGNED NORTH OF A
METTER-BEAUFORT-CHARLESTON LINE. LOCALLY HEAVY RAINFALL IS
POSSIBLE WITH PWATS 1.8 TO 2.0 INCHES AND AN ISOLATED SEVERE
TSTM OR TWO CAN NOT BE COMPLETELY RULED OUT...ESPECIALLY WHERE
UPDRAFTS ARE ENHANCED DUE TO MESOSCALE BOUNDARY INTERACTIONS.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
-- Changed Discussion --
TONIGHT...SHOWER/TSTM ACTIVITY WILL LINGER INTO THE NIGHT AS A
COLD FRONT MEANDERS CLOSER TO THE REGION. THE FRONT LOOKS TO
REMAIN TO THE WEST PRIOR TO SUNRISE...KEEPING THE AREA WELL WITHIN
THE WARM SECTOR. WEAK IMPULSES/VORTICITY LOBES WILL LIKELY KEEP
AT LEAST SCATTERED ACTIVITY GOING FOR MUCH OF THE NIGHT...ALTHOUGH
IDENTIFYING THE AREAS WHERE POCKETS OF CONVECTION WILL OCCUR IS
PROVING DIFFICULT. WILL KEEP CHANCE POPS GOING ALL NIGHT. LOWS
WILL RANGE FROM THE LOWER 70S INLAND TO THE MID 70S AT THE COAST.

WEDNESDAY...THE WAVE OF LOW PRESSURE RIDING ALONG THE COLD FRONT
WILL HAVE SHIFTED OFF THE MID ATLANTIC COASTLINE BY
DAYBREAK...WHILE THE MAIN SHORTWAVE RAPIDLY PROGRESSES TOWARD THE
EAST COAST AND PUSHES THE FRONT INTO THE FORECAST AREA. THE
COMBINATION OF UPPER LEVEL FORCING WITH FRONTAL CONVERGENCE WILL
SUPPORT SOLID THUNDERSTORM CHANCES UP TO 50 PERCENT DURING THE
DAYTIME HOURS...BEFORE THE FRONT SLIPS FARTHER SOUTH/SOUTHEAST AND
PULLS DEEPEST MOISTURE TOWARD THE ALTAMAHA RIVER AFTER SUNSET.
HIGHER RAIN CHANCES WERE CONSIDERED...YET FAIRLY SIGNIFICANT
TIMING DISCREPANCIES REGARDING THE PROGRESSION OF THE FRONT IS
EVIDENT BETWEEN MODELS...LENDING SOME UNCERTAINTY TO COVERAGE
DETAILS. WILL TREND CONVECTIVE POTENTIAL DOWNWARD FROM NORTH TO
SOUTH OVERNIGHT...WHILE STILL MAINTAINING 20 TO 30 PERCENT POPS
THROUGH THE PRE DAWN HOURS ON THURSDAY. INSTABILITY WILL BE
COMPROMISED BY PERSISTENT CLOUD COVER...AND WITH UNIMPRESSIVE WIND
PROFILES...THE MAIN HAZARD FROM THE STRONGEST CONVECTION WILL BE
HEAVY DOWNPOURS DUE TO SLOW STORM MOTION.

THURSDAY AND FRIDAY...THE FRONT IS EXPECTED TO STALL NEAR THE
SOUTHERN BORDER OF THE FORECAST AREA AS IT BECOMES PARALLEL TO THE
FLOW ALOFT LATE IN THE WEEK. SURFACE HIGH PRESSURE WILL BUILD
INTO THE REGION FROM THE NORTH...WITH THE PATTERN EVENTUALLY
TRANSITIONING INTO AN INLAND WEDGE/COASTAL TROUGH TYPE SCENARIO.
EXPECT BEST CONVECTIVE COVERAGE TO BE FOUND ALONG AND SOUTH OF THE
STALLED FRONT DURING THE DAYTIME HOURS...WITH SHOWER/THUNDERSTORM
ACTIVITY SHIFTING MORE TOWARD THE COAST AND OFFSHORE EACH NIGHT
WITHIN COASTAL TROUGH CONVERGENCE.

HIGH TEMPERATURES EACH DAY WILL GENERALLY RANGE FROM THE UPPER 80S
NORTH TO AROUND 90 DEGREES SOUTH...WITH LOCALLY COOLER CONDITIONS
ALONG THE COASTLINE. OVERNIGHT LOWS WILL TREND A FEW DEGREES
COOLER THAN EARLIER IN THE WEEK...RANGING FROM THE UPPER 60S
INLAND TO LOWER 70S COAST.
-- End Changed Discussion --

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
TSTMS WILL MOVE ACROSS THE KCHS TERMINAL 06-08Z BRINGING GUSTY
WINDS AND LOCALIZED IFR VSBYS. THE NEAR TERM RISK FOR TSTMS SHOULD
END BY 08Z WITH A RETURN TO VFR CONDITIONS. VFR WILL DOMINATE AT
KSAV THROUGH SUNRISE WITH THE BULK OF THE TSTMS ACTIVITY PASSING
TO THE NORTH OF THAT TERMINAL. HIGH RESOLUTION MODELS SHOW ANOTHER
BATCH OF SHOWERS/TSTMS MOVING ACROSS THE COASTAL CORRIDOR BY LATE
MORNING AFTERNOON AS A POTENT SHORTWAVE PUSHES THROUGH. WILL
CARRY TEMPO GROUPS FOR 4SM TSRA BR BKN040CB FROM 18-21Z AT KCHS
AND 16-19Z AT KSAV TO COVER. ADJUSTMENTS WILL MOST CERTAINLY BE
NEEDED AS THE MORNING PROGRESSES.

EXTENDED AVIATION...PERIODIC FLIGHT RESTRICTIONS TUESDAY THROUGH
THURSDAY IN ASSOCIATION WITH SCATTERED TO NUMEROUS
SHRA/TSRA...MAINLY DURING THE AFTERNOON HOURS.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
TODAY...SOUTHERLY FLOW REGIME WILL REMAIN IN TACT. WINDS WILL
GENERALLY REMAIN 10-15 KT WITH SEAS 2-4 FT NEARSHORE WATERS AND
4-5 FT OFFSHORE WATERS.

TONIGHT...WINDS WILL PICK UP SLIGHTLY AS A COLD FRONT APPROACHES
FROM THE WEST. WINDS LOOK TO PEAK 15-20 KT OVER THE GEORGIA
OFFSHORE WATERS AND THE CHARLESTON COUNTY COASTAL WATERS WITH 15
KT ELSEWHERE OUTSIDE OF THE CHARLESTON HARBOR. SEAS WILL REMAIN
2-4 FT NEARSHORE AND 4-5 FT GEORGIA OFFSHORE WATERS...BUT MAY
FLIRT WITH 6 FT AT TIMES ABOUT 15 NM EAST OF THE CHARLESTON COUNTY
COAST. SITUATION LOOKS TO MARGINAL FOR A SECOND PERIOD SMALL CRAFT
ADVISORY...SO WILL DEFER ANY ADVISORY DECISION TO THE NEXT
FORECAST SHIFT.

WEDNESDAY THROUGH SATURDAY...A COLD FRONT WILL SLIP INTO THE
COASTAL WATERS WEDNESDAY AND LIKELY STALL NEAR THE GEORGIA MARINE
ZONES THURSDAY. SOUTHERLY WINDS EARLY WEDNESDAY WILL THUS BECOME
EAST/NORTHEAST WEDNESDAY NIGHT INTO THURSDAY BEHIND THE DESCENDING
FRONT. A BRIEF SURGE IN NORTHEAST FLOW IS POSSIBLE THURSDAY
AFTERNOON...AS HIGH PRESSURE RAPIDLY BUILDS FROM THE NORTH AND
BRIEFLY TIGHTENS THE GRADIENT. WIND SPEEDS COULD INCREASE TO 15 TO
20 KT OVER PORTIONS OF THE WATERS AT THAT TIME...YET CONDITIONS
WILL REMAIN BELOW SMALL CRAFT ADVISORY CONDITIONS. MODERATE
EAST/NORTHEAST FLOW WILL CONTINUE INTO FRIDAY WITHIN A COASTAL
TROUGH TYPE PATTERN...BEFORE WINDS BECOME LIGHTER ON SATURDAY AS
THE CENTER OF HIGH PRESSURE SHIFTS OFFSHORE.
-- End Changed Discussion --

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

$$

ST/WMS