-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 152002
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
402 PM EDT WED MAY 15 2013

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL EXTEND ACROSS THE REGION THIS WEEK.
RAIN CHANCES WILL INCREASE OVER THE WEEKEND AS UPPER LEVEL ENERGY
MOVES OVER THE AREA...WITH A COLD FRONT APPROACHING FROM THE WEST
BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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QUIET WEATHER CONDITIONS WILL PERSIST THROUGH THE EVENING AND
OVERNIGHT PERIOD AS A TROUGH OF LOW PRESSURE PASSES THROUGH THE
NORTHEASTERN UNITED STATES AND INTO THE ATLANTIC WHILE SFC HIGH
PRESSURE GRADUALLY EXPANDS OVER THE FORECAST AREA FROM THE SOUTH.
WINDS WILL HAVE A TOUGH TIME DECOUPLING OVERNIGHT AS THIS PROCESS
OCCURS MAINLY DUE TO AN ENHANCED PRESSURE GRADIENT POSITIONED
BETWEEN THE TWO WEATHER FEATURES...ESPECIALLY OVER THE TRI COUNTY
AREA. HIGH CIRRUS SHOULD THEN DEVELOP TO OUR WEST AND SHIFT OVER THE
FORECAST AREA LATE TONIGHT AS MID/UPPER LVL MOISTURE INCREASE ALONG
THE NOSE OF AN H25 JET PUSHING INTO THE REGION. GIVEN THE INCREASING
HIGH CLOUD OVERNIGHT AND LACK OF STRONG RADIATIONAL COOLING...LOW
TEMPS WILL LIKELY BE WARMER THAN THE PREVIOUS NIGHT...IN THE LOW
TO MID 60S.
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&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
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THURSDAY...FAIRLY QUIET WEATHER DAY EXPECTED ON THURSDAY. SURFACE
HIGH PRESSURE WILL REMAIN OFF THE SOUTHEAST COAST...WITH A WEAK
TROUGH INLAND. ALOFT...A BROAD UPPER TROUGH WILL APPROACH FROM THE
WEST...WITH ASSOCIATED VORT ENERGY FORECAST TO CROSS THROUGH THE
AREA. THIS WILL MAINLY RESULT IN AN INCREASE IN MID AND HIGH LEVEL
CLOUDS AS MODELS REMAIN CONSISTENT IN KEEPING THE FORECAST AREA
PRECIP-FREE. DESPITE INCREASING CLOUD COVER...THICKNESS VALUES ONCE
AGAIN SUPPORT HIGH TEMPS A FEW DEGREES ABOVE NORMAL...IN THE MIDDLE
AND UPPER 80S. LOWS WILL BE IN THE LOWER AND MIDDLE 60S.

FRIDAY...THE INLAND SURFACE TROUGH WILL BECOME LESS DEFINED...AND
THE FORECAST AREA WILL BE MAINLY UNDER THE INFLUENCE OF HIGH
PRESSURE OFFSHORE. MODELS CONTINUE TO HINT AT POSSIBLE CONVECTION
FIRING OFF THE SEA BREEZE IN THE AFTERNOON...WITH BEST CHANCES AWAY
FROM THE COAST. NO MORE THAN LOW END SLIGHT CHANCES ARE WARRANTED AT
THIS TIME AS COVERAGE SHOULD REMAIN ISOLATED. POPS WILL DIMINISH
AFTER SUNSET WITH LOSS OF INSOLATION.

SATURDAY...A WEAK PRESSURE PATTERN WILL BE IN PLACE...BOTH ALOFT AND
AT THE SURFACE WITH SOME UPPER LEVEL ENERGY STILL APPARENT. MODELS
ARE BIT MORE AGGRESSIVE SHOWING DIURNALLY DRIVEN PRECIP DEVELOPING
ONCE AGAIN IN THE AFTERNOON....THUS HAVE MAINTAINED CHANCE POPS
INLAND AND SLIGHT CHANCE POPS ALONG THE COAST. CONVECTIVE PARAMETERS
CURRENTLY ARE NOT ALL THAT IMPRESSIVE WITH WEAK MID LEVEL LAPSE
RATES AND WEAK SHEAR...SO SEVERE POTENTIAL IS LOW.
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
WEAK UPPER LEVEL RIDGING WILL PREVAIL ACROSS THE SOUTHEAST STATES
INTO EARLY NEXT WEEK...DEFLECTING A PROGRESSIVE SHORTWAVE TO THE
NORTHWEST SUNDAY INTO MONDAY. ATLANTIC HIGH PRESSURE WILL CONTINUE
TO BE THE MAIN FEATURE AT THE SURFACE...AND WITH LITTLE CHANGE IN
THE PATTERN UNTIL AS LATE AS WEDNESDAY...EXPECT SHOWER/THUNDERSTORM
POTENTIAL TO MAINLY BE DRIVEN BY TYPICAL DIURNAL HEATING/INSTABILITY
AND SEABREEZE FORCING. WILL THUS CONTINUE TO ADVERTISE ISOLATED TO
SCATTERED THUNDERSTORM DEVELOPMENT SUNDAY THROUGH WEDNESDAY DURING
THE CLIMATOLOGICALLY FAVORED AFTERNOON AND EARLY EVENING HOURS.
HIGH TEMPERATURES EACH AFTERNOON WILL RISE INTO THE UPPER 80S
INLAND...TO THE LOW 80S RIGHT ALONG THE COAST BEHIND THE
SEABREEZE. THE NEXT MAJOR SYNOPTIC FEATURE WILL BE AN UPPER TROUGH
AND ASSOCIATED COLD FRONT APPROACHING FROM THE WEST BY LATE TUESDAY
INTO WEDNESDAY.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
VFR CONDITIONS WILL PREVAIL AT BOTH CHS AND SAV TERMINALS THROUGH
18Z THURSDAY. SOUTHWEST WINDS WILL GUST BETWEEN 15-20 KT AT TIMES
BETWEEN 18Z TO 23Z THIS AFTERNOON WITH AN INLAND MOVING
SEABREEZE...ESPECIALLY AT THE KCHS TERMINAL.

EXTENDED AVIATION OUTLOOK...VFR. ISOLATED DIURNAL CONVECTION IS
POSSIBLE OVER THE WEEKEND.

&&

.MARINE...
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TONIGHT...WINDS WILL REMAIN NEAR 20 KTS OVER SC WATERS ALONG THE
CHARLESTON COUNTY COASTLINE AS WELL AS GRAYS REEF TO THE SAVANNAH
BUOY THIS EVENING WHILE AN ENHANCED GRADIENT REMAINS BETWEEN HIGH
PRESSURE OVER THE WATERS AND LOW PRESSURE PASSING TO THE NORTH.
CONDITIONS SHOULD GRADUALLY IMPROVE AFTER MIDNIGHT ONCE THE PRESSURE
GRADIENT SLACKENS AS LOW PRESSURE SHIFTS OVER THE WESTERN ATLANTIC
TO THE NORTH WHILE HIGH PRESSURE GRADUALLY BUILDS OVER THE WATERS
FROM THE SOUTH. SEAS WILL RANGE FROM 2-3 FT OVER MOST WATERS.
OCCASIONAL 4 FT SEAS WILL OCCUR OVER NORTHERN SC WATERS BEYOND
15 NM FROM THE COAST AND OUTER GA WATERS

THURSDAY THROUGH MONDAY...ON THURSDAY SURFACE HIGH PRESSURE WILL
REMAIN CENTERED OFFSHORE EAST OF THE WATERS WITH A TROUGH INLAND.
INITIALLY THERE WILL BE SOME RESULTANT SURGE BETWEEN THE TWO WITH
WIND SPEEDS 15-20 KTS POSSIBLE...MAINLY OVER THE SC WATERS. THE
TROUGH WILL GRADUALLY BECOME LESS DEFINED THURSDAY NIGHT AND ALLOW
FOR QUIET MARINE CONDITIONS TO RETURN. OVERALL SUB-SCA CRITERIA WILL
PREVAIL THROUGH THE WEEKEND...WITH WINDS GENERALLY 10-15 KT AND SEAS
2-3 FEET...HIGHEST OVER THE OUTER WATERS.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...DPB
SHORT TERM...ECT
LONG TERM...WMS
AVIATION...DPB/ECT
MARINE...DPB/ECT