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000 FXUS62 KMFL 221838 AFDMFL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 238 PM EDT MON SEP 22 2008 .DISCUSSION... WATER VAPOR IMAGERY SHOWS MID/UPPER LEVEL TROUGH AXIS ACROSS THE SPINE OF THE APPALACHIANS INTO THE NORTHERN GULF OF MEXICO. A DEEP MOISTURE PLUME LIES AHEAD OF IT ROUGHLY ALONG OR JUST OFF THE EAST COAST OF THE CONUS...STRETCHING SW INTO THE NE GULF. LOCALLY...SCATTERED SHOWERS WERE HAVING A TOUGH TIME GETTING GOING ACROSS THE INTERIOR AND WEST COAST THIS AFTERNOON BUT A GRADUAL INCREASE WITH SOME THUNDER IS EXPECTED THROUGH EARLY THIS EVENING. MODEL GUIDANCE AGREES THAT THE UPPER TROUGH AXIS WILL DRIFT SE TONIGHT AND EARLY TUESDAY FORMING A CLOSED/CUTOFF LOW SOMEWHERE IN THE VICINITY OF THE CAROLINA COAST...WITH WEAK SFC LOW DEVELOPMENT ALONG THE WEAK/DIFFUSE BAROCLINIC BOUNDARY JUST OFFSHORE. THE TROUGH AXIS WILL SWING THROUGH DURING THE DAY ON TUESDAY AS A LARGE RESERVOIR OF DRY AIR OVER NORTH GA/AL SURGES SOUTH DOWN THE FL PENINSULA. MEANWHILE...NNE/NE FLOW WILL GRADUALLY INCREASE THROUGH TUESDAY EVENING WITH A SLIGHT INCREASE IN THE PRESSURE GRADIENT ACROSS THE REGION. AS THE TROUGH/MOISTURE AXIS SAG THROUGH...EXPECT MORE WIDESPREAD SHOWER AND THUNDERSTORM CHANCES TOMORROW. THINGS SHOULD GET GOING FAIRLY EARLY ACROSS THE NORTHERN THIRD OF THE CWA AND THEN SAG SOUTH AS THE DAY PROGRESSES DUE TO INCREASING NORTHERLY COMPONENT OF THE LOW/MID LEVEL FLOW OVER A DEEP LAYER. NE LOW LEVEL WINDS HOWEVER COMBINED WITH INSTABILITY WILL FAVOR REGENERATION OF SHOWERS FURTHER NORTH EVEN INTO THE AFTERNOON AS THE TROUGH AXIS DOES NOT CLEAR UNTIL EVENING. FOR THE TUESDAY NIGHT THROUGH FRIDAY PERIOD...MOST MODEL GUIDANCE AGREES THE CLOSED UPPER LOW AND ANY WEAK SURFACE LOW DEVELOPMENT BENEATH IT OFF THE CAROLINA COAST WILL RETROGRADE WEST BACK INLAND ACROSS THE SOUTHEAST STATES AND STALL LATE IN THE WEEK. AS THIS HAPPENS...IT WOULD LIKELY PULL ANY TROPICAL ENTITY CURRENTLY NEAR THE NORTH COAST OF HISPANIOLA NORTHWARD INTO THE WESTERN ATLANTIC WELL EAST OF THE FL PENINSULA. THE STALLED UPPER LOW WILL CONTINUE A WNW MID-LEVEL FLOW OF DRY AIR AND SUBSIDENCE INTO SOUTH FL...WITH SEVERAL DAYS OF ISOLATED SHOWERS POSSIBLE AT BEST DUE TO INCREASING MID-LEVEL SUBSIDENCE INVERSION AND PWATS DROPPING BELOW 1.3 INCHES. DEWPOINTS MAY ALSO DROP INTO THE 60S ACROSS THE NW INTERIOR FOR A TIME AS WELL ALONG WITH LIGHT AND VARIABLE SURFACE WINDS. HOWEVER THIS TIME PERIOD IS OPEN TO A LOT OF CHANGES BECAUSE THE INTERACTION BETWEEN THE CUTOFF LOW...ASSOCIATED WEAK SURFACE LOW...AND ANY POSSIBLE TROPICAL ENTITY GETTING INTERTWINED WITH IT IS LIKELY TO BE A COMPLEX PROCESS WHICH THE MODELS MAY NOT HAVE A GOOD HANDLE ON. BEYOND FRIDAY...MODELS SUGGEST THAT THE DEEP LAYERED MOISTURE PLUME THAT GETS SUPPRESSED TO OUR SOUTH BY THE UPPER LOW WILL SLOWLY MIGRATE BACK NORTH ACROSS THE CWA...WITH INCREASING POPS IF THIS VERIFIES. && .MARINE... DIFFICULT MARINE FORECAST THIS PERIOD. GFS AND THUS WAVEWATCH CONTINUES TO SUGGEST IDEAL FETCH FOR MODERATE LONG-PERIOD SWELLS TO IMPACT MUCH OF THE ATLANTIC WATERS BEGINNING WEDNESDAY AND PEAKING THURSDAY. ECMWF/CANADIAN/UKMET MODELS SUGGEST UPPER SYSTEM AND ASSOCIATED WEAK SURFACE REFLECTION WILL DEVELOP CLOSER TO THE COAST AND MOVE INLAND FASTER...LEADING TO LITTLE OR NO SWELL DUE TO UNFAVORABLE FETCH. WILL TAKE AN IN-BETWEEN APPROACH AT THIS POINT WITH 4-6 FT SWELLS ACROSS THE NORTHERN ATLANTIC LEG...BUT AFTER WEDNESDAY NIGHT ACTUAL WIND WAVES MAY BE NEGLIGIBLE DUE TO LIGHT OFFSHORE FLOW LESS THAN 10 KTS INTO FRIDAY. MARINERS SHOULD CHECK THE LATEST THE NEXT FEW DAYS AS THIS IS A HIGHLY UNCERTAIN SITUATION. && .FIRE WEATHER... NO CONCERNS THIS PERIOD EVEN AS DEWPOINTS FALL A FEW DEGREES MID TO LATE WEEK. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 77 86 73 86 / 30 60 30 30 FORT LAUDERDALE 79 87 74 86 / 30 60 40 30 MIAMI 78 89 74 86 / 30 60 40 30 NAPLES 74 88 71 87 / 30 60 20 20 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. GM...NONE. && $$ PUBLIC/MARINE/FIRE WX: STRASSBERG AVIATION: GREGORIA