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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 161119
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
719 AM EDT SUN JUN 16 2013

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO RETREAT FARTHER INTO THE ATLANTIC
EARLY NEXT WEEK. A WAVE OF LOW PRESSURE AND ASSOCIATED COLD FRONT
WILL APPROACH FROM THE WEST BY THE MIDDLE OF THE WEEK...WITH THE
FRONT LIKELY STALLING OVER THE REGION THROUGH AT LEAST THE LATE
WEEK PERIOD.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE UPPER RIDGE WILL GRADUALLY BREAK DOWN TODAY AS A SERIES OF
SHORTWAVES PROPAGATE ALONG ITS NORTHERN PERIPHERY. AT THE
SURFACE...THE WESTERN FLANKS OF ATLANTIC HIGH PRESSURE WILL HOLD
STRONG WHILE THE CENTER OF THE ANTICYCLONE SLOWLY MEANDERS FARTHER
OFFSHORE. THE NET RESULT WILL BE ONE MORE DRY AND WARM DAY FOR
LOWCOUNTRY AND COASTAL EMPIRE WITH ONLY MODERATE INCREASES IN
HUMIDITY. MODEL BUFR SOUNDINGS 16/18-21Z FOR CHARLESTON...SAVANNAH
AND FORT STEWART ALL SHOW A STRONG SUBSIDENCE INVERSION BETWEEN
800-600MB HOLDING THROUGH THE DAY DESPITE TEMPERATURES RISING
INTO THE UPPER 80S. EXPECT DRY CONDITIONS TO PREVAIL AS A RESULT
ALTHOUGH A SLIGHTLY CHANCED CUMULUS FIELD WILL LIKELY ACCOMPANY
THE INLAND MOVING SEA BREEZE ITSELF. HIGHS WILL RANGE FROM AROUND
90 WELL INLAND TO THE MID 80S AT THE BEACHES. A HEALTHY CUMULUS
FIELD WILL DEVELOP BY MID-MORNING WITH CLEARING OCCURRING ACROSS
THE COASTAL COUNTIES THROUGHOUT THE AFTERNOON IN THE WAKE OF THE
SEA BREEZE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
TONIGHT...LOW-LEVEL RETURN FLOW WILL BE IN FULL SWING TONIGHT AS
HIGH PRESSURE REMAINS OFFSHORE AND A STORM SYSTEM APPROACHES FROM
THE WEST. A FEW MODELS SPIT OUT A LITTLE SHOWER ACTIVITY OVER THE
ATLANTIC WATERS AFTER MIDNIGHT...BUT THIS MAY BE A BIT AGGRESSIVE
CONSIDERING A TREND OVER DEVELOPING NOCTURNAL SHOWER/TSTM
ACTIVITY OVER THE COASTAL WATERS HAS BEEN OBSERVED SINCE LAST
FALL. SHOULD ANY SHOWER ACTIVITY DEVELOP...LOW-LEVEL TRAJECTORIES
COULD FAVOR CHARLESTON COUNTY FOR ANY POTENTIAL MEASURABLE
RAINFALL. PLAN TO KEEP POPS WELL BELOW MENTIONABLE THRESHOLDS.
DIURNAL CUMULUS WILL QUICKLY DISSIPATE THIS EVENING WITH THE LOSS
OF INSOLATION...BUT MID/HIGH LEVEL CLOUDINESS WILL STEADILY
INCREASE FROM LATE EVENING ON. MOSTLY CLEAR SKIES WILL BECOME
MOSTLY CLOUDY LATE WITH LOWS RANGING THE UPPER 60S WELL INLAND TO
THE MID 70S AT THE BEACHES. IT WILL BE NOTICEABLY MORE HUMID AS
DEWPOINTS CLIMB BACK INTO THE UPPER 60S/LOWER 70S.

MONDAY...DEEP LAYER RIDGING WILL CONTINUE TO BREAK DOWN AND ALLOW
SHORTWAVE ENERGY TO SLIP EASTWARD WITHIN A MORE PROGRESSIVE ZONAL
FLOW ALOFT. WITH ATLANTIC HIGH PRESSURE STEADILY RETREATING...A
SURFACE TROUGH WILL EVENTUALLY TAKE SHAPE UPSTREAM OF THE FORECAST
AREA. WEAKENING SUBSIDENCE AND INCREASING DEEP MOISTURE WITHIN
THE TRANSITIONING PATTERN WILL SUPPORT MORE TYPICAL CONVECTIVE
DEVELOPMENT FOR THE REGION. HAVE INTRODUCED THUNDERSTORM CHANCES
GENERALLY ALONG AND INLAND OF THE SEABREEZE BY EARLY MONDAY
AFTERNOON. NUMERICAL MODEL CONSENSUS THEN INDICATES CONVECTION
LINGERING INTO THE OVERNIGHT HOURS ASSISTED BY SOME UPPER LEVEL
SUPPORT FROM THE SERIES OF SHORTWAVES...AS WELL AS FROM A SUBTLE
WARM FRONTAL FEATURE LIFTING NORTH AHEAD OF A STRENGTHENING WAVE
OF LOW PRESSURE TO THE WEST. HIGH TEMPERATURES WILL ONCE AGAIN
REACH SEASONAL NORMALS IN THE UPPER 80S TO LOWER 90S AWAY FROM THE
LOCALLY COOLER COASTLINE.

TUESDAY...MODEL SOLUTIONS DEPICT VARYING DEGREES OF STRENGTH IN
THE WAVE OF LOW PRESSURE DEVELOPING ALONG A COLD FRONT EMBEDDED
WITHIN THE UPSTREAM SURFACE TROUGH. IN GENERAL...FORECAST
GUIDANCE SHOWS THE SURFACE WAVE TRACKING FROM SOUTHWEST TO
NORTHEAST ALONG THE BOUNDARY...GUIDED BY AN AMPLIFIED SHORTWAVE
SWINGING TOWARD THE EAST COAST. THIS SCENARIO COULD HAVE THE
CENTER OF THE WAVE SHIFTING THROUGH THE UPSTATE SOUTH CAROLINA
REGION INTO THE CAROLINA COASTLINE BY TUESDAY NIGHT. THE FRONT
WILL LIKELY REMAIN JUST TO THE NORTH/NORTHWEST OF THE FORECAST
AREA AT THIS POINT...WITH BEST CONVECTIVE COVERAGE INITIALLY
FOUND ACROSS THE NORTHERN AND INLAND ZONES CLOSEST TO FRONTAL
CONVERGENCE AND SHORTWAVE ENERGY. HAVE INDICATED THUNDERSTORM
CHANCES PEAKING NEAR 50 PERCENT FOR THE FAR NORTHWEST TIER
COUNTIES TRENDING DOWN INTO THE 20 TO 30 PERCENT RANGE TOWARD THE
COAST. CONSIDERING SYNOPTIC LEVEL SUPPORT...ORGANIZED CONVECTIVE
ACTIVITY IS POSSIBLE...MAINLY AS UPSTREAM THUNDERSTORMS ATTEMPT
TO DRIFT SOUTHEAST INTO THE FORECAST AREA AS THE DAY PROGRESSES.
BEST FORCING ALOFT LOOKS TO REMAIN TO THE NORTH...EXCEPT FOR A 20
TO 30 KT LOW LEVEL JET DEVELOPING OVERNIGHT. THERMODYNAMICS STILL
APPEAR A BIT UNIMPRESSIVE...AND THUS PREFER NOT TO MENTION SEVERE
POTENTIAL IN THE HAZARDOUS WEATHER OUTLOOK AT THIS TIME. WILL
CONTINUE TO FORECAST HIGHEST TEMPERATURES FOR THE PERIOD ON TUESDAY
AFTERNOON...AS THE WARMING EFFECTS OF SOME PRE-FRONTAL COMPRESSION
ALLOW TEMPERATURES TO REACH THE LOWER 90S AWAY FORM THE COAST
DESPITE ABUNDANT CLOUD COVER.

WEDNESDAY...THE SURFACE WAVE OF LOW PRESSURE WILL SHIFT OFF THE
NORTH CAROLINA COASTLINE DURING THE MORNING HOURS...WHILE THE
WEAKENING FRONT BECOMES PARALLEL TO FLOW ALOFT AND STALLS OVER OR
NEAR THE FORECAST AREA. THERE IS SOME UNCERTAINTY WHETHER THE
FRONT WILL SET UP JUST SOUTH OF THE ALTAMAHA RIVER OR STRUGGLE TO
PROCEED PAST THE CENTRAL PORTION OF THE FORECAST AREA. THE
LOCATION OF THE FRONT WILL DICTATE CONVECTIVE COVERAGE...AND
PREFER TO MAINTAIN PERSISTENCE BY LEANING TOWARD THE SLOWER ECMWF
SOLUTION. WILL ADVERTISE SOLID CHANCE POPS OVER ALL OF SOUTHEAST
SOUTH CAROLINA AND SOUTHEAST GEORGIA THROUGH AT LEAST WEDNESDAY
AFTERNOON...ESPECIALLY AS THE STRONGEST IN THE SERIES OF
PROGRESSIVE SHORTWAVES SWEEPS THE EAST COAST.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
WITH THE CENTER OF UPPER LEVEL RIDGING REMAINING WELL WEST OF THE
REGION THROUGH THE PERIOD...THE PATTERN ALOFT WILL BE SOMEWHAT ILL
DEFINED AND PROGRESSIVE INTO AT LEAST LATE WEEK. THUS EXPECT
UNSETTLED CONDITIONS TO PERSIST INTO THE EXTENDED FORECAST
PERIOD...WITH FORECAST DETAILS QUITE UNCERTAIN DUE TO MODEL
INCONSISTENCIES. THE LINGERING FRONT ALONG THE SOUTHERN BORDER OF
THE FORECAST AREA...WHEN COMBINED WITH WEAK SHORTWAVE ENERGY
EMBEDDED WITHIN UPPER TROUGHING...WILL MAINTAIN DEEP MOISTURE AND
CONVERGENCE TO SUPPORT THUNDERSTORM CHANCES EACH DAY. MEDIUM RANGE
MODELS DO SUGGEST THAT THE SURFACE PATTERN WILL EVENTUALLY SETTLE
TOWARD HIGH PRESSURE TO THE NORTH AND A COASTAL TROUGH DEVELOPING
ALONG THE PERSISTENT FRONT TO THE SOUTH AND EAST. HIGH
TEMPERATURES WILL VARY LITTLE EACH AFTERNOON...REACHING THE UPPER
80S TO AROUND 90 DEGREES AWAY FROM THE LOCALLY COOLER COASTLINE.

&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
VFR.

EXTENDED AVIATION...PERIODIC FLIGHT RESTRICTIONS POSSIBLE LATER
MONDAY THROUGH WEDNESDAY IN ASSOCIATION WITH THE RETURN OF
CONVECTION.

&&

.MARINE...
THROUGH TONIGHT...SOUTHERLY WIND REGIME WILL PERSIST THROUGH
TONIGHT AS ATLANTIC HIGH PRESSURE REMAINS CENTERED OFFSHORE. WINDS
WILL BE NO HIGHER THAN 10-15 KT WITH SEAS 2-4 FT THROUGH THE
PERIOD.

MONDAY AND TUESDAY...SOUTHERLY FLOW WILL PREVAIL INTO THE EARLY
WEEK PERIOD. EXPECT A BRIEF SURGE BY TUESDAY AS THE GRADIENT
TIGHTENS BETWEEN AN APPROACHING COLD FRONT UPSTREAM AND HIGH
PRESSURE RETREATING FARTHER INTO THE ATLANTIC. WIND SPEEDS WILL
INCREASE INTO THE 15 TO 20 KT RANGE ON TUESDAY...WITH SEAS
BUILDING FROM 2 TO 5 FT NEARSHORE UP TO POTENTIALLY 5 TO 6 FT
BEYOND 20 NM. SMALL CRAFT ADVISORIES ARE NOT ANTICIPATED AT THIS
TIME FOR THE NEARSHORE WATERS...AND THERE IS ONLY A SMALL CHANCE
FOR MARGINAL ADVISORIES IN THE OUTER WATERS IF 6 FT SEAS BECOME
MORE LIKELY.

WEDNESDAY AND THURSDAY...THE APPROACHING FRONT WILL LIKELY STALL
NEAR THE COASTAL WATERS BY MID WEEK. UNCERTAINTY IN THE EXACT
LOCATION OF THE LINGERING BOUNDARY LENDS LOWER CONFIDENCE TO WIND
DIRECTION DETAILS. AT THIS POINT...WILL INDICATE SOUTHERLY WINDS
VEERING AROUND TO THE NORTH BY THURSDAY AS THE FRONT DRIFTS INTO
THE REGION. SPEEDS LOOK TO REMAIN 15 KT OR LESS WITHIN A WEAK
PRESSURE GRADIENT.

&&

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

&&

$$

ST/WMS