FXUS62 KMLB 200847 AFDMLB AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MELBOURNE FL 440 AM EDT SAT SEP 20 2008 .DISCUSSION... ...NE SWELLS AND INCREASING THREAT FOR RIP CURRENTS EXPECTED AT THE BEACHES THIS WEEKEND... ...ONSHORE FLOW WILL PERSIST THROUGH NEXT WEEK... TODAY/TONIGHT...MID/UPPER LEVEL TROUGHING REMAINS JUST EAST OF THE PENINSULA EARLY THIS MORNING WHILE SHORTWAVE RIDGING TRIES TO NUDGE INTO THE WESTERN PENINSULA. WATER VAPOR IMAGERY CONTINUES TO SHOW VERY DRY AIR ALOFT OVER THE REGION AND THIS IS BACKED UP BY LAST NIGHT'S 22Z KXMR SOUNDING WITH A PWAT OF 1.37". RADAR SHOWS ISOLD ATLC SHOWERS MOVING TOWARD THE EAST COAST WITH SLIGHTLY BETTER COVERAGE NORTHWARD WHERE CONVERGENCE IS GREATEST AND A STRONGER GRADIENT IS LOCATED. THE LOW-LEVEL FLOW REMAINS BACKED OUT OF THE NORTHEAST AS AN INVERTED TROUGH REMAINS WELL OFFSHORE. EXPECT OUR LOW-LEVEL FLOW TO REMAIN OUT OF THE NORTHEAST WITH SURFACE WINDS 10-15 MPH TODAY AS THE INVERTED TROUGH REMAINS LOCATED OFF OF THE EAST COAST OVER THE NEXT 24 HOURS. HIGH PRESSURE WILL IN TURN REMAIN SITUATED ALONG THE EASTERN SEABOARD. EXPECT A GRADUAL DEEPENING OF LOW-LEVEL MOISTURE FROM THE SOUTH NORTHWARD LATE TODAY INTO THE OVERNIGHT PERIOD. WITH DRY CONDITIONS STILL AROUND FOR ONE MORE DAY WILL CARRY ONLY LOW END CHC POPS (30%) ACROSS ECFL DURING THE DAY AND THIS MAY BE A LITTLE HIGH. CONTINUED ONSHORE FLOW WILL KEEP HIGHS MODERATED IN THE MIDDLE/UPPER 80S AND LOWS IN THE LOWER 70S INLAND AND MIDDLE 70S CLOSER TO THE COAST. SUN-TUE...MID/UPR SHORT WAVE TROUGH OVER THE CTRL CONUS WILL MOVE TO THE ERN SEABOARD..THEN BEGIN TO DROP SEWD OVER THE WRN ATLC AS IT GETS TRAPPED SOUTH OF A HIGH AMPLITUDE SHORT WAVE RIDGE (ALMOST A CUTOFF HIGH). CONFLUENT FLOW OVER THE NERN CONUS WILL RESULT IN A STRENGTHENING SFC HIGH BUILDING SEWD DOWN THE ATLC SEABOARD. AS IT DOES...INCREASING MID/UPR LEVEL FORCED ASCENT OFFSHORE THE SERN SEABOARD WILL REINVIGORATE THE REMNANT TROUGH CURRENTLY OUT THERE. SO WHILE PGRAD WILL SLOWLY WEAKEN SUN INTO MON...IT WILL TIGHTEN BEGINNING TUE AS FRONTOGENESIS OCCURS...ALONG WITH AN INCREASE IN MEAN MOISTURE. HAVE KEPT 50% POPS FOR THE ENTIRE SHORT RANGE... WITH 20-30 POPS AT NIGHT GIVEN SUFFICIENT ONSHORE COMPONENT TO SFC -H85 FLOW. WOULD NOT BE AT ALL SURPRISED TO SEE POPS HAVING TO BE INCREASED TO LKLY/NMRS TUE IF GUIDANCE CONTINUES TO INCRS MOISTURE WITH FALLING HGHTS AS BASE OF H50 TROUGH MOVES OVHD. WED-SAT...THERE REMAINS SOME DIFFS IN THE MED RANGE GUIDANCE W/R/T HOW THE MID/UPR LEVEL TRAPPED ALONG THE SERN SEABOARD EVOLVES. BOTH THE ECM AND GFS DEPICT A SOMEWHAT ODD LOOKING PATTERN OF A LARGE ELONGATED (E-W) H50 TROUGH WITH ITS AXIS DRIFTING SWWD FROM THE CAROLINAS BTWN ABOUT 65-80W...INTO NORTH FL BTWN 70-85W. GIVEN THE POSITION OF THE FORCED ASCENT FROM THE TROUGH OVER THE TOP OF THE STALLED FRONT...EXPECT SFC CYCLOGENESIS TO OCCUR NE OF THE BAHAMAS WITH SOME PSBLTY OF A HYBRID TYPE LOW GIVEN THE LOW LATITUDE AND STILL WARM OCEAN TEMPS. EXPECT ONSHORE PGRAD TO REMAIN FAIRLY TIGHT THROUGHOUT THE REMAINDER OF THE WEAK ON THE BACK SIDE OF THE LOW ...PERHAPS WEAKENING SOME LATE FRI OR SAT AS THE LOW BEGINS TO PULL NEWD WELL AWAY FROM FL. ECM HAS BACKED OFF ON EXTENT OF DRYING WORKING INTO FL BEHIND THE LOW...AND AGREES ON KEEPING FAIRLY DEEP MOISTURE IN A CONTINUED ONSHORE FLOW REGIME. HAVE KEPT MID-HIGH END SCT POPS GOING THRU THE XTD RANGE. FOR BOTH THE SHORT AND XTD RANGE...HAVE TRENDED TS DOWN TO ISOLD COVRG AS THE MAJORITY OF PRECIP ACTIVITY WILL BE OF THE SHRA VARIETY DUE TO LESS UNSTABLE LAPSE RATES CAUSED BY WEAKER INSOLATION OF MID-LATE SEPTEMBER. && AVIATION...BRIEF MVFR CONDITIONS NEAR THE COAST THIS MORNING INVOF ISOLD SHRA'S. ISOLD-WDLY SCT SHRA/ISOLD TSRA THIS AFTN. && .MARINE...TODAY/TONIGHT...INVERTED TROUGH WELL OFFSHORE WILL KEEP NORTHEAST FLOW OVER THE COASTAL WATERS FOR THE NEXT 24 HOURS. SPEEDS MAINLY 10-15 KTS. A PERSISTENT LONG PERIOD NORTHEAST SWELL WILL KEEP SEAS ELEVATED WITH 3-5 FT SEAS NEARSHORE AND 4-6 FT SEAS OFFSHORE. SMALL CRAFT WILL NEED TO EXERCISE CAUTION FOR SEAS OFFSHORE. BOTH WIND CHOP AND SWELL WILL CONTINUE TO SLOWLY ABATE THROUGH EARLY NEXT WEEK AS LOCAL ONSHORE PGRAD GRADUALLY RELAXES. HOWEVER...SHOULD SEE INCREASING WINDS/BUILDING SEAS BEGINNING WED AS STRONG HIGH PRES REBUILDS SWD FROM THE ERN SEABOARD INTO FL. THE SWELL WILL PERSIST ENOUGH TO KEEP AN ELEVATED RIP CURRENT RISK THROUGH THIS WEEKEND. && .HYDROLOGY...SLOW FALL TO CONTINUE OVER THE MIDDLE ST JOHNS RIVER BASIN THRU EARLY NEXT WEEK...ALTHOUGH ALL FORECAST POINTS WILL CONTINUE ABOVE FLOOD STAGE. ASSUMING NO WIDESPREAD RAINFALL... BOTH ASTOR AND DELAND WILL DROP TO WITHIN A FEW TENTHS OF FLOOD STAGE BY LATE NEXT WEEK. FOR THE LATEST INFO ON ST JOHNS RIVER LEVEL SEE THE RIVER FLOOD STATEMENT /MIAFLSMLB/. && .PRELIMINARY POINT TEMPS/POPS... DAB 84 71 85 72 / 30 20 50 30 MCO 88 72 88 73 / 30 20 50 20 MLB 86 73 86 72 / 30 20 50 30 VRB 86 71 86 72 / 30 20 50 30 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. && $$ SHORT TERM/AVIATION...SEDLOCK LONG TERM....CRISTALDI