Expires:No;;786719 FPUS52 KKEY 101935 ZFPKEY AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 330 PM EDT WED JUN 10 2009 .DISCUSSION... .CURRENTLY... LOCAL RADARS ARE DETECTING ONLY ISOLATED SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE WEST COAST SEABREEZE...WHILE THE EAST COAST SEA BREEZE IS BEING VERTICALLY CHALLENGED BY SIGNIFICANT DRY AIR. IN FACT...BEFORE THE EAST COAST SEA BREEZE PENETRATED INLAND WEST OF THE METROPOLITAN AREAS...DEWPOINTS DROPPED INTO THE MID 60S AT MIAMI AND TAMIAMI. SURFACE WISE...HIGH PRESSURE IS CENTERED OVER THE NORTH CENTRAL GULF OF MEXICO WITH A RIDGE REACHING INTO THE SOUTHEAST GULF AND INTO MOST OF OUR REGION. ALSO...A NORTH-SOUTH ORIENTED TROUGH OF LOW PRESSURE LIES JUST EAST OF THE FLORIDA PENINSULA AND THE UPPER KEYS. ACROSS THE MARINE DISTRICT...C-MAN STATION PLATFORMS INDICATE NORTHWEST TO NORTH WINDS OF 5 TO 10 KNOTS...EXCEPT WEST AT LESS THAN 5 KNOTS ON FLORIDA BAY AND SOUTHEAST OF THE UPPER KEYS. MEANWHILE...WATER VAPOR IMAGERY SHOWS AN EXTENSIVE AREA OF DRY AIR COVERING THE EASTERN HALF OF THE GULF OF MEXICO...MOST OF THE FLORIDA PENINSULA AND INTO THE NORTHWEST CARIBBEAN...WITH A TENACIOUS...ALBEIT WEAKENING TROUGH REACHING FROM THE BAHAMAS SOUTHWARD INTO EASTERN HALF OF THE ARCHIPELAGO OF CUBA. .SHORT TERM (TONIGHT THROUGH SATURDAY)... LITTLE CHANGE IN FORECAST REASONING...AS OUR REGION WILL LIE WITHIN THE EASTERN GRIP OF A DEEP LAYERED ANTICYCLONE OVER THE WESTERN HALF OF THE GULF OF MEXICO AND THE SUBSIDENCE PERIPHERY OF A TROUGH JUST TO OUR EAST FOR AT LEAST THE NEXT 36 HOURS. GIVEN THE LARGE SCALE SINKING MOTION AND A CHAOTIC WIND REGIME...BELOW NORMAL PWAT VALUES AND WARMING ALOFT WILL SIGNIFICANTLY CHALLENGE UPDRAFTS WITHIN DIURNAL CLOUD LINES. FURTHERMORE...DEEP CONVECTION COVERAGE ON THE SOUTH FLORIDA MAINLAND WILL BE LIMITED SINCE THE NORTH TO NORTHEAST STEERING FLOW WILL WEAK. SUBSEQUENTLY...ONLY ISOLATED POPS WILL BE MAINTAINED THROUGH THURSDAY NIGHT. THEREAFTER...THE MID AND UPPER LEVEL RIDGE MAY RETROGRADE ENOUGH TO ALLOW A SLIGHT INCREASE IN MOISTURE AND INSTABILITY PROVIDING ENOUGH UNCERTAINTY TO KEEP LOW CHANCE POPS ON FRIDAY THROUGH SATURDAY. OTHERWISE...AMPLE AND INTENSE INSOLATION WILL ALLOW HIGH TEMPERATURES TO RISE INTO THE UPPER 80S TO NEAR 90. MEANWHILE...LOW TEMPERATURES WILL BE TRICKY DUE TO LIGHT AND VARIABLE WINDS ALLOWING SOME ISLAND COMMUNITIES TO FALL INTO THE MID 70S. THEREFORE...WILL OPEN A LOW TEMPERATURE RANGE OF 75 TO 80. .LONG TERM (SATURDAY NIGHT THROUGH WEDNESDAY)... UNTIL GFS CAN CONTROL ITS SIGNIFICANT UPDRAFT PROBLEM...WILL LEAN TOWARD A MORE SEDATE ECMWF FOR THIS PERIOD. WITH THAT SAID...THE DEEP LAYERED ANTICYCLONE OVER THE WESTERN GULF AND SOUTHEAST UNITED STATES WILL MOVE LITTLE...WHILE THE WESTERN ATLANTIC RIDGE REMAINS TO OUR EAST. HENCE...OUR REGION WILL REMAIN IN A BROAD ANTICYCLONIC/NEUTRAL ENVIRONMENT ALOFT WITH AVERAGE PWAT VALUES OF AROUND 1.5 INCHES. GIVEN ENOUGH MOISTURE WITHIN A GENTLE TO LIGHT PREDOMINATE EASTERLY LOW LEVEL REGIME...WILL MAINTAIN LOW CHANCE POPS WITH TEMPERATURES CLIMBING INTO THE UPPER 80S TO NEAR 90...AND OVERNIGHT LOWS NEAR 80 OUTSIDE OF RAINFALL. && .MARINE... WITH OUR REGION LYING BETWEEN HIGH PRESSURE OVER THE GULF OF MEXICO AND LOWER PRESSURE TO THE EAST...A WEAK PRESSURE PATTERN RESULTING IN LIGHT TO GENTLE WINDS FOR AT LEAST THE NEXT COUPLE OF DAYS. THEREAFTER...A SUBTLE INCREASE IN WINDS WILL OCCUR WITH GENTLE TO PERHAPS MODERATE WINDS BY LATE SUNDAY OR EARLY NEXT WEEK. SUBSEQUENTLY...NO EXERCISE CAUTION STATEMENTS OR ADVISORIES WILL BE NECESSARY. && .AVIATION... VFR CONDITIONS WILL PREVAIL AT THE EYW AND MTH ISLAND TERMINALS TONIGHT. SURFACE WINDS WILL GENERALLY BE LIGHT AND VARIABLE. && .PRELIMINARY POINT TEMPS/POPS... KEY WEST 76 88 77 88 / 20 20 20 30 MARATHON 77 89 78 89 / 20 20 20 30 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ PUBLIC/MARINE/FIRE/CLIMATE/DIGITAL...APA AVIATION/NOWCASTS....................AL DATA ACQUISITION.....................DR/WH VISIT US ON THE WEB AT WWW.WEATHER.GOV/KEYWEST