000 FXUS62 KCHS 042059 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 459 PM EDT FRI JUL 4 2008 .SYNOPSIS... HIGH PRESSURE WILL REMAIN ANCHORED OVER THE ATLANTIC THROUGH NEXT WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... ISOLATED STRONG TO SEVERE THUNDERSTORMS HAVE INITIATED ALONG AND INLAND OF THE SEABREEZE LATE THIS AFTERNOON. WHILE BEACHES WILL LIKELY REMAIN DRY FOR THE REMAINDER OF THE AFTERNOON AND EVENING...AREAS AWAY FROM THE COASTLINE WILL BE AT RISK FOR THUNDERSTORM DEVELOPMENT INTO THE EARLY EVENING. ANY THUNDERSTORM COULD BECOME SEVERE...WITH LARGE HAIL AND DAMAGING WINDS. WILL MAINTAIN CHANCE POPS FOR FAR INLAND COUNTIES...WITH SLIGHT CHANCE POPS ELSEWHERE. BOTH GFS AND NAM SUGGEST THAT SHOWER/THUNDERSTORM ACTIVITY COULD PERSIST FOR A FEW HOURS AFTER SUNSET. HAVE MAINTAINED ONLY A SMALL AREA OF SLIGHT CHANCE POPS ACROSS THE FAR INLAND COUNTIES...FROM APPROXIMATELY ALLENDALE SOUTHWARD TO TATTNALL. ALSO CONTINUE TO INDICATE SLIGHT CHANCE POPS ACROSS THE OUTER WATERS...WHERE NOCTURNAL INSTABILITY AND CONVERGENCE COULD INITIATE THUNDERSTORM ACTIVITY. CONDITIONS OVERNIGHT WILL BE WARM AND HUMID...WITH LOW TEMPERATURES IN THE LOWER 70S AWAY FROM THE COAST. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... A SURFACE TROUGH INLAND WILL BE STRENGTHENING ON SATURDAY...WHILE AN UPPER LEVEL TROUGH AMPLIFIES ACROSS THE OHIO AND TENNESSEE VALLEYS. SEABREEZE WILL BE THE MAIN FORCING MECHANISM AGAIN ON SATURDAY AFTERNOON...HOWEVER GRADUALLY INCREASING MOISTURE PROFILE AND CONVERGENCE WITHIN THE INLAND SURFACE TROUGH COULD ALLOW DIURNAL CONVECTION TO BECOME MORE WIDESPREAD THAN WHAT IS SEEN TODAY. HAVE THEREFORE MAINTAINED CHANCE POPS ACROSS THE ENTIRE FORECAST AREA FOR SATURDAY AFTERNOON. SHORTWAVE ENERGY WILL BE ROTATING WITHIN THE SOUTHWEST FLOW AROUND THE BASE OF THE UPPER TROUGH AND INTO THE CAROLINAS SATURDAY NIGHT. THIS UPPER LEVEL SUPPORT MAY BE ABLE TO KEEP CONVECTION GOING PAST SUNSET...ESPECIALLY IN THE VICINITY OF SEABREEZE AND OUTFLOW BOUNDARY INTERACTIONS. HAVE THEREFORE CONTINUED TO MENTION SLIGHT CHANCE POPS UNTIL JUST AFTER MIDNIGHT. DECIDED TO REMOVE POPS AFTER ABOUT 07Z...AS CLIMATOLOGICALLY UNFAVORABLE NIGHTTIME CONDITIONS SHOULD DIMINISH REMAINING SHOWERS/THUNDERSTORMS. TEMPERATURES ON SATURDAY WILL BE AROUND SEASONAL NORMS...WITH HIGHS IN THE LOWER TO MID 90S INLAND AND LOWS DROPPING INTO THE LOWER 70S. && .LONG TERM /SUNDAY THROUGH FRIDAY/... SUNDAY THROUGH MONDAY NIGHT...THE AREA WILL BE SANDWICHED BETWEEN THE WESTERN FLANKS OF BROAD ATLANTIC HIGH PRESSURE AND A PRONOUNCED MID-LEVEL SHORTWAVE EXTENDING SOUTH FROM THE OHIO VALLEY. SPOKES OF VORTICITY EJECTING OUT AHEAD OF THE MAIN SHORTWAVE COUPLED WITH MODEST SURFACE BASED INSTABILITY AND LOW- LEVEL CONVERGENCE WILL PROMOTE THE DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS EACH DAY AHEAD OF THE SEA BREEZE. TYPICAL SUMMER-TIME PULSE SEVERE THUNDERSTORMS WILL BE POSSIBLE WITH DAMAGING WINDS...LOCALLY HEAVY RAINFALL AND CLOUD TO GROUND LIGHTNING STRIKES BEING THE MAIN HAZARDS. WILL CONTINUE WITH CHANCE POPS OF 40-50 PERCENT DURING THIS TIME BUT FUTURE SHIFTS MAY NEED TO EVENTUALLY RAISE THEM UP INTO THE LIKELY CATEGORY SUNDAY AFTERNOON ACROSS INTERIOR SOUTHEAST SOUTH CAROLINA AS BOUNDARY INTERACTIONS FROM STORMS OVER THE MIDLANDS COULD ENHANCE LOW-LEVEL CONVERGENCE IN THAT AREA. THE GREATER CHANCES FOR SHOWERS AND THUNDERSTORMS IS FORECAST TO SHIFT INTO INTERIOR SOUTHEAST GEORGIA MONDAY AFTERNOON AS THE BERMUDA HIGH RIDGES FARTHER WEST INTO SOUTHEAST SOUTH CAROLINA AND THE STRONGEST LOW- LEVEL CONVERGENCE NUDGES SOUTH OF THE INTERSTATE 16 CORRIDOR. HIGHS WILL BE IN THE LOWER 90S WITH LOWS IN THE LOWER TO MID 70S. WEDNESDAY THROUGH FRIDAY...THE BERMUDA HIGH WILL BUILD FARTHER WEST INTO THE SOUTHEAST U.S. DURING THIS TIME. A TYPICAL EARLY SUMMER CONVECTIVE PATTERN WILL ENSUE WITH SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED EACH DAY AHEAD OF THE SEA BREEZE. VARIOUS DEGREES CONVECTIVE ORGANIZATION CAN BE EXPECTED THROUGH THE PERIOD BUT WILL BE HEAVILY DEPENDANT ON MESOSCALE BOUNDARY INTERACTIONS. TEMPERATURES WILL BE NEAR NORMAL. HEAT INDICES COULD ALSO APPROACH HEAT ADVISORY CRITERIA IN A NUMBER OF LOCATIONS THROUGH THE PERIOD. && .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/... VFR CONDITIONS ARE EXPECTED TO PREVAIL FOR KCHS AND KSAV THROUGH THE NEXT 24 HOUR PERIOD. HAVE KEPT CB GROUPS IN BOTH TAFS DUE TO CONVECTIVE DEVELOPMENT ALONG THE SEABREEZE THIS AFTERNOON. MOST OF THE ACTIVITY WILL BE FURTHER INLAND BY 20Z...LEAVING 13 KT WINDS IN THE WAKE OF THE SEABREEZE. ALTHOUGH CLEARING SKIES AND LIGHT WINDS ARE EXPECTED LATE TONIGHT...HAVE NOT INCLUDED ANY FOG POTENTIAL IN EITHER TAF DUE TO LOW CROSS-OVER TEMPERATURES AND LOW CONFIDENCE. TIMING OF CONVECTION FOR SATURDAY WILL BE EVALUATED AT THE NEXT TAF PERIOD. EXTENDED AVIATION OUTLOOK...MVFR CONDITIONS OR LOWER ARE POSSIBLE EACH AFTERNOON WITHIN SHOWERS AND THUNDERSTORMS. && .MARINE... THE COASTAL WATERS WILL REMAIN ON THE WESTERN PERIPHERY OF ATLANTIC HIGH PRESSURE THROUGH SATURDAY. MODERATE SOUTH TO SOUTHWEST FLOW WILL CONTINUE...WITH WIND SPEEDS MAINLY AT OR BELOW 15 KT. BRIEF INCREASES CAN BE EXPECTED OVERNIGHT WITHIN TYPICAL NOCTURNAL SURGING...AS WELL AS DURING SATURDAY AFTERNOON SEABREEZE DEVELOPMENT ALONG THE COAST. SEAS WILL REMAIN IN THE 2 TO 4 FT RANGE...HIGHEST OUTER WATERS. SUNDAY THROUGH WEDNESDAY...SOUTHERLY FLOW REGIME WILL DOMINATE THROUGH THE PERIOD WITH THE AREA REMAINING ON THE WESTERN FLANKS OF ATLANTIC HIGH PRESSURE. TYPICAL DIURNAL SURGES CAN BE EXPECTED THROUGH THE PERIOD...PARTICULARLY ALONG THE SEA BREEZE. && .TIDES/COASTAL FLOODING... WILL CONTINUE TO WATCH ELEVATED TIDES THE NEXT COUPLE OF NIGHTS DUE TO LINGERING ASTRONOMICAL INFLUENCES...HOWEVER DO NOT ANTICIPATE SHALLOW COASTAL FLOODING ADVISORY CRITERIA WILL BE MET AT THIS TIME. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$