AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
727 AM EDT FRI JUL 8 2011

.SYNOPSIS...
DEEPER MOISTURE WILL GRADUALLY INCREASE OVER THE REGION THROUGH
TONIGHT AS WEAK LOW PRES ALONG THE GULF COAST PERSISTS. A WEAK COLD
FRONT WILL MOVE INTO THE AREA OVER THE WEEKEND...THEN MOVE THROUGH
AND DISSIPATE BY MON. ANOTHER FRONT WILL APPROACH FROM THE N BY
THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
THROUGH MID MORNING...SCATTERED SHOWERS AND A FEW TSTMS SHOULD
CONTINUE TO FLOURISH ALONG AND E OF I-95 IN SOUTH CAROLINA AS
DEEPER MOISTURE CONVERGES IN THE LOW LEVELS AND WEAK VORT LOBE
OVER SE GEORGIA SHEARS IN A GENERAL REGION OF UPPER DEFORMATION.
IT IS IN SE GEORGIA THAT THE 06Z GFS SEEMS TO BE INITIALIZING WELL
WITH THE CONVECTIVE RAINS THAT HAVE DEVELOPED TO THE SW OF
SAVANNAH. WE HAVE UPDATED OUR PRODUCTS TO EXPAND SOME POPS A BIT
WESTWARD TO ACCOUNT FOR RECENT RADAR TRENDS.

BY MIDDAY...ATTENTION IS EXPECTED TO TURN TO DIURNAL DEVELOPMENT OF
SCATTERED TO NUMEROUS SHOWERS AND TSTMS OVER MUCH OF THE SOUTHERN
HALF OF GEORGIA AS THE WEAK VORT OVER N FLORIDA INTERACTS WITH
DEEP MOISTURE AND VARIOUS MESOSCALE BOUNDARIES. WE SHOW AFTERNOON
POPS BECOMING LIKELY ALONG AND S OF I-16 IN GEORGIA. SLOW
MOVEMENTS AND CELL MERGERS SUGGEST A LOCALLY HEAVY RAINFALL
POTENTIAL. IN SOUTH CAROLINA THIS AFTERNOON...IT LOOKS TRICKY AS
THE REGION WILL HAVE HIGH PWATS BUT POSSIBLY SOME RESIDUAL
SUBSIDENCE IN THE WAKE OF THE FIRST OFFSHORE LEAD WAVE AND AN
APPROACHING UPSTREAM SHORT WAVE HEADED FOR THE MID ATLC REGION.
CONVECTION UPSTREAM IN THE MIDLANDS AND UPSTATE LOOKS TO HAVE A
POTENTIAL TO ORGANIZE LATE DAY AND POSSIBLY BECOME SEVERE. THIS
PLACES OUR SOUTH CAROLINA INLAND AREAS BETWEEN THE SYSTEMS. WE
MAINTAINED SOME LOWER END CHANCE POPS LATE DAY BUT WOULD NOT BE
SURPRISED IF CONVECTION ENDS UP RATHER SPARSE IN SPOTS.

CLOUDS ARE A BIT TRICKY TODAY BUT WE MAINTAINED SOME LOWER TO MID
90S AGAIN...WARMEST WELL INLAND. SW WINDS WILL PICK UP LATER IN
THE AFTERNOON.

TONIGHT...CONVECTION IN SE GEORGIA SHOULD WANE AFTER A DIURNAL
LATE DAY/EARLY EVENING MAX BUT STILL ENOUGH EVIDENCE TO KEEP SOME
LOW POPS GOING MUCH OF THE OVERNIGHT. IN SOUTH CAROLINA...BOUNDARIES
FROM UPSTREAM TSTMS MAY INTERACT WITH OTHER BOUNDARIES AND FIRE SOME
SHOWERS AND STORMS AT ANY POINT OVERNIGHT. COASTAL RAIN CHANCES
ALSO MAY INCREASE AFTER MIDNIGHT AS THE MID LEVEL VORT MAX EASES
OFF THE SE GEORGIA COAST AND DEEP MOIST CONVERGENCE BECOMES ENHANCED.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
I HAVE DISCOUNTED THE 00Z NAM THIS MORNING AS SURFACE LOW SEEMS WAY
OVERDONE. I PREFER THE GLOBAL MODEL SOLUTIONS OF A SLOW MOVING FRONT
INTO THE AREA LATER IN THE WEEKEND...THEN GRADUALLY DISSIPATING
EARLY NEXT WEEK.

SATURDAY...THE ATMOSPHERE SHOULD BE STOKED WITH DEEP MOISTURE.
PWATS WILL BE 2 TO 3 SDS ABOVE NORMAL WITH ABSOLUTE VALUES IN EXCESS
OF 2 INCHES. THERE WILL BE MORE CLOUDS AROUND ON SATURDAY AS
SOUTHERN END OF MID LATITUDE TROF MEETS UP WITH REMNANTS OF THE
UPPER LOW OVER THE GULF OF MEXICO TO GIVE A SLIGHTLY ENHANCED
SOUTHWESTERLY JET OVERHEAD...TRANSPORTING A FAIR AMOUNT OF CIRRUS
INTO THE AREA. THIS WILL KEEP TEMPS A DEGREE OR TWO BELOW
AVERAGE...BUT HIGH DEW POINTS WILL KEEP THE APPARENT TEMPERATURE
ELEVATED. I WENT WITH JUST SLIGHTLY ABOVE NORMAL POPS...WITH
ACTIVITY EXTENDING INTO THE EVENING HOURS AWAY FROM THE COAST AS
PRE-FRONTAL TROF DROPS INTO THE AREA FROM THE NORTHWEST.

SUNDAY WE WILL SEE SOME SUBTLE DIFFERENCES AS WEAKENING FRONT MOVES
INTO THE NORTHERN FA. THERE WILL STILL BE PLENTY OF DEEP
MOISTURE...BUT UPPER LEVEL WINDS WILL SLACKEN BACK OFF AS HEIGHTS
BEGIN TO REBUILD...MEANING LESS CLOUD COVER. TEMPS WILL BE BACK TO
A TOUCH ABOVE NORMAL BY SUNDAY AFTERNOON...BUT DYING FRONT IN THE
AREA WILL SUPPORT ANOTHER ROUND OF AFTERNOON AND EVENING CONVECTION.
BEST CHANCES FOR THUNDERSTORMS WILL BE ALONG THE SEA BREEZE AS WELL
AS THE WEAKENING BOUNDARY.

ON MONDAY...THE FRONT WILL ESSENTIALLY HAVE DISSIPATED...ALTHOUGH A
VERY WEAK SURFACE TROF AND MID LEVEL SHEAR ZONE IS EXPECTED TO HANG
AROUND. PWS WILL DROP BACK BELOW 2 INCHES WITH A LITTLE MID LEVEL
DRYING FROM THE RIDGE BUILDING NORTH OF THE AREA...BUT CONVECTIVE
TEMPS WILL BE EASILY REACHED IN THE AFTERNOON DUE TO PLENTIFUL
SUNSHINE...SO AT LEAST A SLIGHT CHANCE OF THUNDERSTORMS IS EXPECTED.

ALSO...WITH HIGHER TEMPS IN THE AFTERNOON AND DEW POINTS REMAINING
REASONABLY HIGH...HEAT INDICES MAY START TO APPROACH ADVISORY
LEVELS. THIS WILL HAVE TO BE WATCHED.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
TUESDAY LOOKS QUITE SIMILAR TO MONDAY AS WIDELY SCATTERED AFTERNOON
AND EVENING CONVECTION IS EXPECTED...BUT LOTS OF SUNSHINE WILL ALLOW
TEMPS TO RISE WELL INTO THE 90S AWAY FROM THE COAST WITH HEAT
INDICES INTO THE MID 100S.

THE SECOND HALF OF THE WEEK IS MORE COMPLICATED. GFS HAS SHIFTED
SIGNIFICANTLY FROM ITS SOLUTION 24 HOURS. NOW..INSTEAD OF HOLDING UP
THE NEXT COLD FRONT NORTH OF THE AREA...IT PLOWS IT THROUGH MID WEEK
AND BRINGS IN A SIGNIFICANTLY DRIER AIR MASS FOR THURSDAY AND
FRIDAY. I HAVE ONLY NUDGED THE FORECAST SLIGHTLY IN THAT DIRECTION
DUE TO THE LACK OF CONTINUITY...PLUS THE FACT THAT YESTERDAYS ECMWF
HAS BACKED OF ITS FRONTAL PASSAGE BY A DAY.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
KCHS...CONVECTION AROUND DAWN LIKELY TO DIMINISH SOMEWHAT TOWARD
LATE MORNING AS MOISTURE CONVERGENCE IN THE LOWER LEVEL WEAKENS.
MVFR CIGS LIKELY TO SCATTER OUT THIS AFTERNOON WITH STILL SOME
RISK OF CB ALONG THE RESULTANT SEA BREEZE. AFTER MIDNIGHT TONIGHT
THERE IS A RENEWED RISK FOR CONVECTION WITH INCREASING LOW LEVEL
MOIST CONVERGENCE...WE HAVE INTRODUCED CB MENTIONS POST 06Z/09.

KSAV...NO SIGNIFICANT CHANGES ON 12Z TAF RELEASE...MAINLY VFR
WITH BRIEF MVFR CIGS POSSIBLE THIS MORNING AS CUMULUS FIELDS
EXPAND WHEN HEATING COMMENCES THANKS TO THE DEEPER MOISTURE.
CB MENTIONS REMAIN INTACT FOR THIS AFTERNOON WITH LOW CONFIDENCE
ON BOTH TIMING AND COVERAGE OF TSTMS AT THIS POINT. MAINLY VFR
CONDITIONS TONIGHT WITH FOG RATHER UNLIKELY DUE TO SOME STRONGER
LOW LEVEL WIND FIELDS.

EXTENDED AVIATION...AS IS USUALLY THE CASE IN MID SUMMER...THE BEST
CHANCE FOR MVFR/IFR CIGS/VSBYS IS WITH THE CHANCES OF AFTERNOON AND
EVENING CONVECTION NEAR THE TERMINALS. ALSO...WITH WINDS EXPECTED TO
GET VERY LIGHT ON MONDAY AND TUESDAY MORNINGS...THERE COULD BE A
COUPLE OF HOURS OF BR AROUND SUNRISE EACH DAY.

&&

.MARINE...
THE LOW LEVEL PRES GRADIENT IS EXPECTED TO PINCH BETWEEN ATLC
HIGH PRES AND WAVES OF LOW PRES ACROSS THE NE GULF OF MEXICO AND
THE MID ATLC REGION TODAY INTO TONIGHT. SEAS WERE ALREADY ELEVATED
WITH NEAR 3 FT CLOSE TO SHORE AND 4-6 FT WELL OFFSHORE...HIGHEST
NEAR THE EDISTO BUOY E OF CHARLESTON. SSW FLOW SHOULD EBB SOMEWHAT
LATER THIS MORNING AND THEN BECOME SW AND INCREASE TO 15 TO 20 KT
LATE TODAY. THE BEST WAVE ACTION WILL LIKELY END UP ALONG THE
SOUTH CAROLINA COAST THROUGH TONIGHT AND WE WILL NEED TO WATCH FOR
A PERIOD OF SCA CONDITIONS OVERNIGHT AS THE LOW LEVEL JET PEAKS.

OVER OUR OUTER GEORGIA WATERS FROM 40-60 NM...WE HAVE ISSUED
AN ADVISORY FOR TONIGHT AS SEAS WILL BE NEAR 6 FT AND SW WINDS
FREQUENTLY GUST TO 25 KT.

RIP CURRENTS...SE SWELLS WILL INCREASE TODAY AND THIS WILL
CONTRIBUTE TO AN ENHANCED RISK FOR RIP CURRENTS FOR ALL OF OUR
BEACHES.

WINDS WILL STAY UP ON SATURDAY IN THE 15 TO 20 KNOT RANGE...MAYBE A
BIT STRONGER IN THE EARLY MORNING HOURS IN THE CHARLESTON COUNTY
WATERS...BUT WILL START TO DIMINISH AS THE FRONT WEAKENS SATURDAY
NIGHT AND SUNDAY. GRADIENT WILL BE PRETTY SLACK ON MONDAY AND
TUESDAY WITH LIGHT WINDS GENERALLY OUT OF THE SOUTH AND
SOUTHWEST...TURNING ONSHORE NEAR THE COAST IN THE AFTERNOON AND
EVENING. WINDS MAY PICK UP SOME AGAIN ON WEDNESDAY AHEAD OF THE NEXT
FRONT.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT
     SATURDAY FOR AMZ374.

&&

$$