000 FXUS62 KCHS 080742 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 342 AM EDT MON SEP 8 2008 .SYNOPSIS... HIGH PRES WILL CONTINUE BUILDING TO THE NE AS TROPICAL CYCLONE IKE REMAINS WELL S OF THE AREA THROUGH MON. A COASTAL TROUGH IS EXPECTED TO TIGHTEN LATER THIS WEEK AND FOCUS MOISTURE CONVERGENCE ACROSS THE REGION. HIGH PRES WILL RETURN BY THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 00Z ANALYSIS SHOWED US AN EXPANSIVE AND DEEP ATLC RIDGE RIDGE AXIS THROUGH OUR REGION. SOUTHERN SOUTH CAROLINA AND SE GEORGIA WILL REMAIN BETWEEN SURFACE HIGH PRES MOVING OFF THE MID ATLC COAST AND THE NORTHERN GRADIENT FRINGES OF THE WEST TRACKING TROPICAL CYCLONE IKE OVER CUBA TODAY. OUTSIDE OF THE SEA BREEZE TODAY...THE ONLY REAL UPPER LEVEL FORCING WE CAN FIND IS A REGION OF UPPER DIFLUENCE OVER GEORGIA AND THE CAROLINAS TO START THE DAY. THIS STRETCHING ZONE WAS PARTIALLY RESPONSIBLE FOR YSTDYS TSTMS JUST N OF OUR AREA AND THE ONGOING STORMS OFF THE OUTER BANKS. MODELS SUGGEST THAT THIS DIFLUENT UPPER PATTERN WILL WEAKEN DURING THE DAY. WE PAINTED A COUPLE AREAS OF AFTERNOON CONVECTION CLOSER TO THE ALTAMAHA AND OVER OUR NW TIER NW OF BEAUFORT AND CHARLESTON SIMILAR TO THE SCHEME YSTDY. WE THINK FOR MOST AREAS TODAY...SHOWERS AND TSTMS WILL BE RELATIVELY HARD TO COME BY. HIGHS WILL BE LESS THAN SUNDAY BY SEVERAL DEGREES THANKS TO A MORE ONSHORE FLOW AND FASTER SEA BREEZE EVOLUTION TODAY. LOW LEVEL THICKNESS VALUES ARE ALSO 3-5 DEGREES LOWER THIS AFTERNOON. && .SHORT TERM /TONIGHT/... SKIES WILL START OFF CLEAR TO PARTLY CLOUDY WITH DRY CONDITIONS MOST LOCATIONS. LATER TONIGHT...RICH LOW LEVEL MOISTURE FLUX AND UPSLOPE SHOULD BEGIN TO FORM STRATUS. NAM ALSO SUGGESTS A REGION OF FOG MAY DEVELOP BETWEEN THE MIDLANDS AND I-95. FOR NOW WE HAVE NOT INDICATED FOG IN THE ZONE FORECAST...BUT THIS POTENTIAL WILL NEED TO BE RE-EVALUATED FOR INLAND ZONES LATER TODAY. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... AS ATLANTIC HIGH PRESSURE SINKS SOUTH ON TUE...A WEAK SURFACE TROUGH WILL FORM INLAND. THIS SHOULD ACT AS AN INITIAL TRIGGER FOR SOME SHOWERS AND THUNDERSTORMS...MAINLY DURING THE AFTERNOON. WARM MID-LEVELS WILL LIMIT INSTABILITY SO MOSTLY SHOWERS WITH A FEW THUNDERSTORMS CAN BE EXPECTED. MOISTURE REALLY CRANKS INTO THE AREA STARTING WED AS THE CIRCULATION OF TROPICAL CYCLONE IKE ENHANCES DEEP-LAYER MOISTURE ADVECTION FROM THE SOUTHWEST ATLANTIC. PRECIPITABLE WATER VALUES APPROACHING 2.40 INCHES ARE POSSIBLE OVER SOUTHEAST GA WED AFTERNOON. MEANWHILE ANOTHER HIGH PRESSURE SYSTEM WILL SHIFT OFF THE NORTHEAST COAST PUSHING A BACKDOOR FRONT INTO THE AREA DURING THE DAY WED. STRONG MOIST ADVECTION NEAR THE 302K THETA SURFACE WILL INCREASE ISENTROPIC LIFT WHICH SHOULD PRODUCE SCATTERED SHOWERS. ISOLATED THUNDERSTORMS ARE POSSIBLE WHERE THE SUN BREAKS OUT...MAINLY OVER SOUTHEAST GA. CONSIDERABLE MOISTURE SHOULD SPREAD ACROSS THE ENTIRE AREA BY THU WITH PW/S ABOVE 2.25 INCHES. A RAINY DAY STILL LOOKS ON TAP DUE TO AN EXPECTED DEVELOPING COASTAL TROUGH...STALLED FRONTAL BOUNDARY...WEAK UPPER DIVERGENCE AND DEEP MOISTURE. THERE EXISTS A HEAVY RAINFALL POTENTIAL GIVEN THE EXPECTED CELL MOTIONS LESS THAN 10 KT AND HIGH PRECIPITATION EFFICIENCY. BY LATE FRI THE HIGH SHOULD SINK SOUTHEAST WHILE RIDGING SLOWLY WEST...DISSIPATING THE FRONT AND BRINGING WEAK SUBSIDENCE AND SLIGHTLY DRIER AIR. HOWEVER ISOLATED TO SCATTERED AFTERNOON AND EVENING SHOWERS AND STORMS WILL BE EXPECTED THROUGH THE WEEKEND MAINLY ASSOCIATED WITH CONVERGENCE ALONG THE SEABREEZE. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... OUTSIDE OF MVFR VSBYS IN FOG PRIOR TO AND SHORTLY AFTER DAWN TODAY...EXPECT MAINLY VFR CONDITIONS TO PREVAIL THROUGH THIS EVENING. INCREASING LOW-LEVEL MOISTURE...CLEAR SKIES AND LIGHT BACKING SURFACE WINDS SUGGEST MOSTLY GROUND FOG IS LIKELY AT BOTH TERMINALS LATE TONIGHT. FORECAST SOUNDINGS SUGGEST LOW-LEVEL MOISTURE REMAINS SHALLOW...SO EXPECT ONLY MVFR VISIBILITIES IN THE 09-13Z TIME FRAME. EXTENDED AVIATION OUTLOOK...MVFR OR LOWER CEILINGS POSSIBLE WED THROUGH THU NIGHT IN ASSOCIATION WITH A STALLED FRONTAL BOUNDARY. VSBYS MAY ALSO DROP TO MVFR IN OCCASIONAL SHOWERS. OTHERWISE VFR CONDITIONS OUTSIDE SCATTERED CONVECTION. && .MARINE... OUR COASTAL ARENA IS DOMINATED BY THE LONG PERIOD SWELL OF TROPICAL CYCLONE IKE THIS MORNING. SINCE A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS IS ALREADY IN EFFECT FOR OUR GEORGIA WATERS 20-60 NM...WE SEE NO REASON TO CHANGE PERSISTENCE ON FORECAST WAVE HEIGHTS THIS MORNING THROUGH TONIGHT AND WE WILL CONTINUE THE ADVISORY IN THIS LEG. AN ONSHORE FLOW INCREASING INTO THE 10-15 KT RANGE IS EXPECTED LATER TODAY AND TONIGHT. RECENT SPECTRAL DENSITY PLOTS FOR BUOY 41004 INDICATES THERE IS ENOUGH SWELL ENERGY TO MAKE A ROUGH PASSAGE FOR SMALL CRAFT THROUGH AREA SOUNDS AND INLETS TODAY...ESPECIALLY AROUND LOW TIDES AND WE WILL ISSUE A MARINE WEATHER STATEMENT ADDRESSING THIS HAZARD. SOME 6 FT SEAS COULD PERSIST OVER OUTER WATERS INTO THU AS A RESULT OF LONG-PERIOD SWELL EMANATING FROM HURRICANE IKE. ESE WINDS TUE EXPECTED TO TURN ENE LATE WED THROUGH THU AFTER A FRONT DROPS THROUGH THE WATERS. WINDS WILL LIKELY SURGE DURING THIS TIME BUT THE GRADIENT STILL LOOKS LIKE IT WILL REMAIN WEAK ENOUGH TO PRECLUDE ANY ADVISORIES. ONSHORE FLOW SHOULD RETURN FRI THROUGH THE WEEKEND WITH ATLANTIC HIGH PRESSURE RETAKING CONTROL. RIP CURRENTS...RECENT SWELL PERIODS HAVE BEEN 16 SECONDS AT BUOYS 41008 AND 41004. A LONGER SWELL PERIOD PUTS US UP INTO THE HIGH RISK CATEGORY VIA OUR LOCAL RISK EVALUATION METHOD. IN LIGHT OF STRONG RIP CURRENTS REPORTED OFF OF JACKSONVILLE BEACH YSTDY AND RECENT TRENDS...WE WILL INDEED GO WITH A HIGH RISK TODAY. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM EDT THURSDAY FOR AMZ374. && $$ JRL