-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 151748
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
148 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 PM THIS EVENING/...
-- Changed Discussion --
QUIET WEATHER CONDITIONS WILL PERSIST OVER SOUTHEAST SOUTH CAROLINA
AND SOUTHEAST GEORGIA THIS AFTERNOON. TEMPS WILL CONTINUE TO WARM AS
MID LVL RIDGING PEAKS OVER THE SOUTHEASTERN UNITED STATES WHILE
WEST/SOUTHWEST SFC WINDS OCCUR ALONG THE NORTHERN EDGE OF SFC HIGH
PRESSURE CENTERED OVER NORTHERN FLORIDA. 1000-850MB THICKNESS
VALUES ALONG WITH SUNNY SKIES FAVOR OVERALL HIGH TEMPS IN THE
MID/UPPER 80S OVER ALL INLAND LOCATIONS. TEMPS WILL BE COOLER
ALONG THE COAST AS A SEABREEZE SHIFTS INLAND...AROUND 80 DEGREES.
WINDS WILL CONTINUE TO GUST BETWEEN 20-25 MPH THIS AFTERNOON AS
THE PRESSURE GRADIENT TIGHTENS BETWEEN LOW PRESSURE TO OUR NORTH
AND HIGH PRESSURE TO THE SOUTH. WIND GUSTS WILL BE HIGHEST OVER
NORTHERN SC ZONES WHERE THE PRESSURE GRADIENT AND SEABREEZE ARE
STRONGEST. WINDS WILL THEN BEGIN TO RELAX THIS EVENING WITH
DIURNAL HEAT LOSS.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
A MILD NIGHT ON THE WAY AS ENOUGH GRADIENT FORECAST TO KEEP THE
LOWER LEVELS STIRRED N OF I-16...ALSO SURFACE DEW POINTS WILL BE
CLOSER TO 60 DEGREES MANY AREAS. LOWS 60-65 ACROSS THE AREA WITH
PERIODS OF HIGH CLOUDINESS AT TIMES.

THURSDAY...UPPER RIDGING WILL HAVE DAMPENED ACROSS THE EAST COAST
AHEAD OF A WEAK SHORTWAVE TROUGH APPROACHING FROM THE WEST. THE
LATEST RUNS OF THE ECMWF AND GFS MODELS SHOW VARYING DEGREES OF
SHORTWAVE ENERGY MOVING DOWNSTREAM OF THE BROAD TROUGH AXIS...YET
BOTH SOLUTIONS SHOW LITTLE TO NO PRECIPITATION POTENTIAL ON
THURSDAY. THE LACK OF SHOWER/THUNDERSTORM DEVELOPMENT IS LIKELY THE
RESULT OF RELATIVELY DRY AIR IN THE LOW LEVELS AND RESIDUAL
SUBSIDENCE WITH THE TROUGH AXIS STILL TO THE WEST. THUS WILL KEEP
RAIN CHANCES BELOW 15 PERCENT THROUGH THURSDAY NIGHT...WHILE
INDICATING AN INCREASE IN SKY COVER. HIGH TEMPERATURES WILL RISE
WELL ABOVE SEASONAL NORMALS...REACHING THE UPPER 80S AWAY FROM THE
LOCALLY COOLER COASTLINE.

FRIDAY...WEAK SHORTWAVE ENERGY WILL CONTINUE TO TRACK ACROSS THE
SOUTHEAST STATES AS THE UPPER TROUGH SHIFTS TOWARD THE COASTLINE.
CONSIDERING THE LOSS OF UPPER RIDGING...AS WELL AS EVIDENCE OF A
WEAK INLAND SURFACE TROUGH AND INCREASED DEEP LAYER
MOISTURE...LATEST THINKING IS THAT AN ISOLATED SHOWER/THUNDERSTORM
COULD DEVELOP ALONG AND INLAND OF THE SEABREEZE DURING THE
AFTERNOON/EARLY EVENING HOURS. WILL INDICATE SLIGHT CHANCE POPS
FROM 15Z TO 02Z ACCORDINGLY. MODEL GUIDANCE STILL SUGGESTS THAT
TEMPERATURES WILL RISE INTO THE UPPER 80S INLAND OF THE
SEABREEZE...AND WITH THICKNESS VALUES EVEN WARMER THAN
GUIDANCE...WILL CONTINUE WITH ABOVE NORMAL HIGH TEMPERATURES
FRIDAY AFTERNOON.

SATURDAY...THE UPPER LEVEL PATTERN WILL REMAIN RATHER WEAK INTO
THE WEEKEND...SUGGESTING LITTLE TO NO SUBSIDENCE AS SOME ENERGY
ALOFT COULD STILL SHIFT INTO THE REGION. THE SURFACE PATTERN WILL
BECOME A BIT MORE ILL DEFINED...WITH ATLANTIC HIGH PRESSURE
MAINTAINING SOME CONTROL OF THE COASTAL REGIONS AND A WEAKER
PRESSURE PATTERN FOUND FARTHER INLAND. NUMERICAL MODEL SOLUTIONS
ARE IN MUCH BETTER AGREEMENT IN INDICATING SEABREEZE INDUCED
DIURNAL SHOWERS/THUNDERSTORMS SATURDAY AFTERNOON UNDER IMPROVED
MOISTURE PROFILES ACROSS THE AREA. WILL THUS ADVERTISE SLIGHTLY
HIGHER RAIN POTENTIAL IN THE CHANCE CATEGORY AWAY FROM THE
IMMEDIATE COAST MAINLY DURING THE AFTERNOON HOURS...WITH ANY
ISOLATED TO SCATTERED THUNDERSTORMS LIKELY MOVING INLAND TOWARD
SUNSET. TEMPERATURES WILL PEAK IN THE UPPER 80S AWAY FROM THE
COASTLINE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
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 /18Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
THE MARINE FORECAST REMAINS ON TRACK THIS AFTERNOON AS ATLANTIC HIGH
PRESSURE MAINTAINS A HOLD OVER THE WATERS. SOUTH WINDS WILL
GRADUALLY INCREASE THIS AFTERNOON AS THE PRESSURE GRADIENT TIGHTENS
BETWEEN A TROUGH OVER THE MIDLANDS AND ATLANTIC HIGH PRESSURE
SLIDING TO THE EAST. WINDS WILL REMAIN NEAR 15-20 KNOTS ALONG THE
CHARLESTON COUNTY COASTLINE CLOSEST TO AN INLAND MOVING SEABREEZE
CIRCULATION. WINDS MAY APPROACH SMALL CRAFT ADVISORY CONDITIONS IN
THE CHS HARBOR AND ALONG SOME CHARLESTON COUNTY BEACHES BUT THE
EVENT DURATION APPEARS TOO SMALL AND MARGINAL TO INCLUDE ANY
HEADLINES THROUGH THIS EVENING. SEAS WILL RANGE FROM 2-3 FT OVER
MOST WATERS. OCCASIONAL 4 FT SEAS MAY OCCUR OVER NORTHERN SC WATERS
BEYOND 15 NM FROM THE COAST.

TONIGHT...WINDS WILL REMAIN CLOSE TO 20 KT AT FOLLY BEACH AND FROM
GRAYS REEF TO THE SAVANNAH BUOY THIS EVENING AS CONDITIONS LOOK
FAVORABLE FOR WARM SEASON NOCTURNAL SURGES IN THE 00Z-06Z TIME
FRAME. SEAS WILL AVERAGE BETWEEN 2-4 FT.

THURSDAY THROUGH SUNDAY...ATLANTIC HIGH PRESSURE WILL CONTROL THE
PATTERN ACROSS THE MARINE ZONES THROUGH THE WEEKEND...ALLOWING
SOUTHERLY FLOW TO GENERALLY PREVAIL. WIND SPEEDS COULD PEAK IN THE
15 TO 20 KT RANGE ON THURSDAY...BEFORE AVERAGING 10 TO 15 KT
FRIDAY THROUGH SUNDAY. THERE COULD BE LOCAL SURGES WITH THE
SEABREEZE EACH AFTERNOON...HOWEVER SMALL CRAFT ADVISORIES ARE NOT
EXPECTED THROUGH THE PERIOD. WAVE HEIGHTS WILL RANGE FROM 2 TO 4
FT...HIGHEST IN THE OUTER WATERS.
-- End Changed Discussion --

&&

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

&&

$$

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