732 FXUS62 KCHS 061532 CCA AFDCHS AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE CHARLESTON SC 1044 AM EDT SUN MAY 6 2012 .SYNOPSIS... A BACKDOOR COLD FRONT WILL SINK ACROSS THE AREA THIS AFTERNOON AND THIS EVENING...BEFORE SETTLING SOUTH OF THE AREA TONIGHT. THE FRONT WILL STALL OUT AND DISSIPATE JUST TO THE SOUTH THROUGH EARLY WEEK. ANOTHER COLD FRONT IS EXPECTED TO MOVE THROUGH FROM THE NORTHWEST WEDNESDAY NIGHT FOLLOWED BY COOLER AND DRIER HIGH PRESSURE THROUGH LATE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... IT IS VERY DIFFICULT TO DISCERN THE POSITION OF THE ACTUAL BACKDOOR COLD FRONT LATE THIS MORNING WITH OUTFLOW FROM LAST NIGHT/S THUNDERSTORMS HAVING PUSHED THE LEE SIDE TROUGH WELL TO THE SOUTH. INSTABILITY...MOISTURE AND SATELLITE DIAGNOSTIC TOOLS SUGGEST THE BOUNDARY IS JUST NOW ENTERING THE CHARLESTON TRI-COUNTY AREA AND SOUTHERN MIDLANDS WITH TEMPERATURES RISING QUICKLY FROM THERE AND POINTS SOUTH. CLOUDS ARE QUICKLY FILLING IN AS THE FRONT PROPAGATES TO THE SOUTH WHILE THE SKY REMAINS CLEAR ACROSS THE LOWER SAVANNAH RIVER AREA AND ALL OF SOUTHEAST GEORGIA. THE PRIMARY CONCERNS THIS AFTERNOON CENTER ON THE CONVECTIVE POTENTIAL AND HIGH TEMPERATURES. CONVECTIVE POTENTIAL: MODIFIED 06/12Z JAX RAOB AS WELL AS THE LATEST RAP SOUNDINGS SUGGEST THE PRE-FRONTAL ENVIRONMENT WILL REMAIN CAPPED FOR MUCH OF THE DAY WITH THE CAP POSSIBLY ERODING BY LATE AFTERNOON INTO THE EVENING HOURS AS THE ELONGATED VORTICITY CENTER SPINNING OVER NORTH-CENTRAL GEORGIA DROPS TO THE SOUTH. EVEN AS THE CAP ERODES...POTENTIAL INSTABILITY REMAINS SOMEWHAT LIMITED AS DEWPOINTS MIX OUT YIELDING SBCAPE LESS THAN 2000 J/KG AND LI/S -3 TO -5C. THE VARIOUS HIGH RESOLUTION MODELS ARE LESS THAN ENTHUSIASTIC WITH THE COVERAGE OF SHOWERS/TSTMS THIS AFTERNOON WITH THE BEST POTENTIAL LIKELY REMAINING CLOSER TO THE ALTAMAHA RIVER AS A POSSIBLE PSEUDO-ORGANIZED CLUSTER OF TSTMS DROPS TO THE SOUTHEAST--BRUSHING PARTS OF EVANS...TATTNALL AND LONG COUNTIES. IT REMAINS TO BE SEEN IF THIS FEATURE WILL EXIST SO THIS COULD EASILY CHANGE AS THE DAY PROGRESSES. THE GENERAL POP TREND FROM THE EARLY MORNING FORECAST CYCLE WAS GENERALLY ON TRACK...BUT HAVE OPTED TO LOWER POPS INTO THE SLIGHT CHANCE CATEGORY FOR ALL OF SOUTHEAST SOUTH CAROLINA AND LIMIT POPS TO 40 PERCENT FOR THE COUNTIES BORDERING THE ALTAMAHA RIVER GIVEN CURRENT SHORT-TERM MODEL TRENDS. DESPITE LIMITED INSTABILITY... DCAPES REMAIN HIGH WITH VALUES APRCHG 1200 J/KG FROM THE SAVANNAH RIVER SOUTH. THEREFORE AN ISOLATED SEVERE TSTM CAN NOT BE COMPLETELY RULED OUT IN THIS AREA WITH DAMAGING WINDS BEING THE PRIMARY HAZARD. TEMPERATURES: HIGH TEMPERATURES WILL BE VERY TRICKY TODAY AS INSOLATION WILL BE CURTAILED ACROSS THE NORTH WHILE MUCH OF SOUTHEAST GEORGIA SHOULD SEE NEAR FULL SUN FOR A GOOD PORTION OF THE DAY. EXPECT HIGHS TO RANGE FROM THE UPPER 70S ACROSS NORTHERN PORTIONS OF BERKELEY COUNTY AS WELL AS UPPER CHARLESTON COUNTY TO THE LOWER 90S FROM I-16 SOUTH. COULD EVEN SEE A FEW MID 90S ALONG THE ALTAMAHA RIVER FROM REIDSVILLE TO LUDOWICI...ALTHOUGH THIS WILL NOT BE EXPLICITLY SHOW IN THE GRIDDED FORECASTS. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... THE BACKDOOR COLD FRONT WILL CONTINUE TO SINK SOUTHWARD THROUGH SOUTHERN GEORGIA AND INTO FLORIDA TONIGHT. SCATTERED SHOWERS AND THUNDERSTORMS WILL LIKELY BE ONGOING THIS EVENING ALONG AND SOUTH OF THE I-16 CORRIDOR WITH A FEW OF THEM POSSIBLY SEVERE...WITH CONVECTIVE COVERAGE DIMINISHING FARTHER NORTH BEHIND THE FRONT. PRECIPITATION SHOULD THEN BEGIN TO TAPER OFF ACROSS MUCH OF SOUTHEAST SOUTH CAROLINA OVERNIGHT...ALTHOUGH SOME ISOLATED STORMS COULD CONTINUE IN PARTS OF SOUTHEAST GEORGIA. LOWS WILL GENERALLY BE IN THE MID 60S. HIGH PRESSURE WEDGING DOWN THE COAST MONDAY INTO MONDAY NIGHT WILL SLOWLY BREAK DOWN TUESDAY AS A COLD FRONT BEGINS TO APPROACH FROM THE WEST. THE FRONT WILL BE POISED TO PUSH THROUGH THE AREA BY LATE WEDNESDAY. ALOFT...AN UPPER TROUGH OF LOW PRESSURE WILL LINGER THROUGH THE PERIOD. BEST RAIN CHANCES LOOK TO OCCUR MONDAY ACROSS SOUTHEAST GEORGIA WHERE THE DEEPEST MOISTURE WILL BE FOUND CLOSEST TO A STATIONARY FRONT. RAIN CHANCES MAINLY CONFINED TO COASTAL AREAS MONDAY NIGHT NEAR A WEAK COASTAL TROUGH...THEN INLAND TUESDAY AFTERNOON/EVENING BEFORE DIMINISHING TUESDAY NIGHT...AND INCREASING AGAIN WEDNESDAY AS THE COLD FRONT AND UPPER TROUGH APPROACH FROM THE WEST WHILE DEEPER MOISTURE AND FAVORABLE JET DYNAMICS OVERSPREAD THE AREA. TEMPERATURES WILL START OFF NEAR NORMAL MONDAY BEFORE INCREASING ABOVE NORMAL TUESDAY AND ESPECIALLY WEDNESDAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... A COLD FRONT IS EXPECTED TO MOVE THROUGH WEDNESDAY NIGHT FOLLOWED BY COOLER/DRIER HIGH PRESSURE FROM THE NORTH THROUGH LATE WEEK. AFTER WEDNESDAY NIGHT...MAINLY DRY ALTHOUGH A FEW SHOWERS ARE POSSIBLE...ESPECIALLY ACROSS SOUTHEAST GEORGIA AS ANOTHER SHORTWAVE TROUGH MOVES OFFSHORE. TEMPERATURES AT OR BELOW NORMAL THROUGH THE PERIOD. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... A BACKDOOR COLD FRONT WILL DROP THROUGH THE AREA TODAY...WITH DEEP LOW LEVEL MOISTURE EXPECTED TO SLOWLY WORK ITS WAY INTO THE AREA FROM THE NORTH IN WAKE OF THE FRONT. MODEL TIME-HEIGHT CROSS SECTIONS AND UPSTREAM OBSERVATIONS INDICATE A STRONG LIKELIHOOD OF MVFR CEILINGS DEVELOPING AT KCHS AFTER 14Z...THEN LIFTING TO VFR LEVELS FOR MUCH OF THE AFTERNOON...BEFORE LOWERING TO MVFR LEVELS AGAIN AFTER 03Z. AT KSAV...THE BEST LOW LEVEL MOISTURE APPEARS TO REMAIN NORTH OF THE TERMINAL FOR MUCH OF THE DAY...SO WILL MAINTAIN VFR CONDITIONS IN THE TAF UNTIL 05Z...WHEN THE MVFR CEILINGS ARE FINALLY EXPECTED TO ARRIVE. A PERIOD OF IFR CEILINGS ARE POSSIBLE AT BOTH TERMINALS TOWARD DAYBREAK MONDAY...BUT CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE IN THE FORECAST AT THIS TIME. SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND COULD AFFECT THE TERMINALS...THEN THE CONVECTION SHOULD CONTINUE THROUGH THE EVENING BUT MAINLY ACROSS SOUTHEAST GEORGIA. PROBABILITIES OF CONVECTION IMPACTING EITHER TERMINAL ARE STILL TOO LOW TO ADD MENTION TO THE FORECAST AT THIS TIME. EXTENDED AVIATION OUTLOOK...MVFR CIGS POSSIBLE INTO MONDAY BEHIND A COLD FRONT WITH BREEZY CONDITIONS MONDAY AFTERNOON. && .MARINE... NORTH-NORTHWEST WINDS THIS MORNING WILL VEER NORTHEAST THIS AFTERNOON AS A BACKDOOR COLD FRONT DROPS THROUGH THE WATERS. WIND SPEEDS WILL DIMINISH THIS MORNING AHEAD OF THE FRONT...BUT THEN SURGE UPWARDS OF AROUND 15 KT LATE IN THE DAY OFF THE CHARLESTON COUNTY COAST. SEAS WILL GENERALLY REMAIN IN THE 2-3 FT RANGE. TONIGHT...A NORTHEAST FLOW WILL DEVELOP THROUGHOUT THE WATERS IN WAKE OF A BACKDOOR COLD FRONT. SPEEDS SHOULD SURGE INTO THE 15-20 KT RANGE WITH SEAS BUILDING TO 3-5 FT IN RESPONSE. AS OF NOW...FORECAST CONDITIONS ARE JUST BELOW SMALL CRAFT ADVISORY CRITERIA...BUT ANY INCREASE IN WINDS AND/OR SEAS COULD REQUIRE THE ISSUANCE OF AN ADVISORY FOR A PORTION OF THE WATERS. MONDAY THROUGH THURSDAY...A STATIONARY FRONT WILL BE SOUTH OF THE WATERS MONDAY WITH A DECENT NE WIND SURGE ONGOING EARLY IN THE DAY...POSSIBLY LEADING TO ADVISORY CONDITIONS IN CHARLESTON HARBOR FOR 20 KT WINDS AS WELL AS BEYOND 20 NM FOR 6 FT SEAS. SLOWLY IMPROVING CONDITIONS TUESDAY BEFORE WINDS/SEAS PICK UP A BIT WEDNESDAY/THURSDAY IN ASSOCIATION WITH A PASSING COLD FRONT. HOWEVER...ADVISORIES ARE NOT EXPECTED AT THIS TIME WITH THIS FEATURE. RIP CURRENTS...STRONG ONSHORE WINDS AND LINGERING ASTRONOMICAL INFLUENCES MAY LEAD TO AN ENHANCED RISK OF RIP CURRENTS MONDAY. && .TIDES/COASTAL FLOODING... A COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR THE ENTIRE LOWER SOUTH CAROLINA COAST...EXCLUDING TIDAL PORTIONS OF BERKELEY COUNTY... PER COORDINATION WITH WFO WILMINGTON. TIDAL DEPARTURES PEAKED AROUND 0.2-0.4 FT ABOVE PREDICTED WITH THIS MORNING/S HIGH TIDE CYCLE AND SHOULD SEE SIMILAR DEPARTURES WITH HIGH TIDE THIS EVENING. THIS PLACES TIDE LEVELS IN THE 7.2 TO 7.4 FT RANGE IN THE CHARLESTON HARBOR WHICH IS ABOVE THE LEVEL THAT TYPICALLY CAUSES SHALLOW COASTAL FLOODING PROBLEMS ALONG THE LOWER SOUTH CAROLINA COAST. LEVELS LOOK MARGINAL AT FORT PULASKI SO WILL HOLD OFF ON ISSUING AN ADVISORY FOR THE NORTH GEORGIA COAST...BUT THIS WILL BE REEVALUATED WITH THE AFTERNOON FORECAST PACKAGE. THE RISK FOR ELEVATED TIDES WILL PERSIST INTO MONDAY AND ADDITIONAL ADVISORIES MAY BE NEEDED. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...COASTAL FLOOD ADVISORY FROM 7 PM THIS EVENING TO MIDNIGHT EDT TONIGHT FOR SCZ048>051. MARINE...NONE. && $$ SYNOPSIS... NEAR TERM... SHORT TERM...RJB/JAQ LONG TERM...RJB AVIATION... MARINE... TIDES/COASTAL FLOODING...