AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC ISSUED BY NATIONAL WEATHER SERVICE WILMINGTON NC 1117 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/... WEAK SHORTWAVE LIFTING OUT OF FL THIS AFTERNOON WILL TAP INTO TROPICAL MOISTURE PLUME OVER THE SOUTHEASTERN CONUS...GENERATING SHOWERS AND THUNDERSTORMS. INLAND AREAS MAY END UP WITH LIMITED COVERAGE AS CURRENT TRACK OF SHORTWAVE IS SUGGESTIVE OF THE FEATURE HUGGING THE COAST. WEAK DEFORMATION ZONE EXTENDING FROM CENTRAL ALABAMA...THROUGH NORTHERN GEORGIA AND INTO WESTERN SOUTH CAROLINA WILL LIKELY BE ANOTHER WITH WIDESPREAD CONVECTION. SOME OF THIS ACTIVITY MAY END UP MOVING INTO WESTERN PARTS OF THE FORECAST AREA...BUT OVERALL BEST PRECIP CHANCES WILL BE ALONG THE COAST TODAY. HEAVY RAIN WILL BE A CONCERN WITH PRECIPITABLE WATER VALUES FROM 12Z CHS SOUNDING AND FORECAST SOUNDINGS WELL OVER 2 INCHES. DO NOT ANTICIPATE WIDESPREAD FLOODING...BUT LOCALIZED URBAN FLOODING IS POSSIBLE WHEN/IF STORMS MOVE ACROSS PRONE URBANE AREAS. 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 /15Z 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... GRADIENT WILL TIGHTEN UP LATER TODAY AS BERMUDA HIGH CONTINUES TO RIDGE IN WHILE SEVERAL WEAK WAVES LIFT NORTHEAST ALONG THE COAST. SEAS CURRENTLY BETWEEN 3 AND 4 FT WILL BUILD CLOSE TO 5 FT...WITH 6 FT BEYOND 20 NM AS SOUTHWEST FLOW INCREASES TO CLOSE TO 20 KT LATER TODAY. LOW LEVEL JET BETWEEN 20 AND 25 KT TONIGHT WILL TRANSLATE TO THE SURFACE AS FREQUENT GUSTS OF 20+ KT. SCA CONTINUES FOR OUTER GEORGIA WATERS 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. && $$