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574 FXUS62 KMFL 210547 AFDMFL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 147 AM EDT TUE MAY 21 2013 .AVIATION... THE BULK OF THE HEAVY RAINFALL HAS SHIFTED OFF THE COAST OVER THE ADJACENT ATLANTIC WATERS EARLY THIS MORNING. THE LATEST SHORT- TERM GUIDANCE INDICATES THIS REMAINING OFF THE COAST THROUGH THE NIGHT...THEN SHIFTING BACK ASHORE THROUGH THE DAY. AT THIS TIME...CONFIDENCE REMAINS TOO LOW TO KNOW EXACTLY WHERE THE HEAVIEST RAINFALL WILL BECOME CONCENTRATED THROUGH THE DAY. THEREFORE...WE WILL CONTINUE WITH VCSH WORDING THROUGH THE NIGHT, THEN VCTS THROUGH THE DAY AS INSTABILITY INCREASES AND MODIFY THE TAFS AS CONDITIONS EVOLVE. && .PREV DISCUSSION... /ISSUED 734 PM EDT MON MAY 20 2013/ AVIATION... THE WINDS SHOULD REMAIN EASTERLY TONIGHT AT ALL OF THE TAF SITES BUT WIND SPEEDS AROUND 5 KNOTS OR LESS. THIS WILL ALLOW FOR THE ISOLATED SHOWERS OVER THE ATLANTIC WATERS TO MOVE WEST INTO THE EAST COAST METRO AREAS BEFORE DISSIPATING. SO WILL KEEP VCSH IN FOR ALL OF THE EAST COAST TAF SITES FOR TONIGHT. FOR KAPF TAF SITE...THE THREAT OF SHOWERS SHOULD COME TO AN END AFTER 03Z TONIGHT. THE SHOWER THREAT WILL CONTINUE FOR ALL OF THE TAF SITES TUESDAY MORNING ALONG WITH EASTERLY WINDS OF 5 TO 10 KNOTS. AS THE HEATING OF THE DAY GETS GOING OVER SOUTH FLORIDA AND THE SEA BREEZES DEVELOPS AND PUSHES INLAND...THUNDERSTORMS WILL DEVELOP OVER SOUTH FLORIDA. SO AFTER 17Z ON TUESDAY ALL OF THE TAF SITES IN SOUTH FLORIDA WILL HAVE VCTS. THE WINDS WILL ALSO REMAIN EASTERLY AT 10 TO 15 KNOTS TUESDAY AFTERNOON AT MOST OF THE SOUTH FLORIDA TAF SITES...EXCEPT FOR KAPF TAF SITE WHERE THEY WINDS WILL BECOME WESTERLY AROUND 10 KNOTS AFTER 17Z. THE CEILING AND VIS WILL ALSO REMAIN IN THE VFR CONDITIONS TONIGHT INTO TUESDAY...DUE TO THE UNKNOWN TIMING OF THE SHOWERS FOR TONIGHT AND THE SHOWERS AND THUNDERSTORMS FOR TUESDAY. THE ONLY EXCEPTION IS AT KFLL TAF SITE WHERE THEY COULD FALL INTO THE MVFR CONDITIONS BETWEEN 00Z AND 02Z...DUE TO KFLL SEE CURRENTLY BKN015 FROM A SHOWER NEAR BY. AVIATION...54/BNB PREV DISCUSSION... /ISSUED 237 PM EDT MON MAY 20 2013/ SHORT TERM (TONIGHT THROUGH WEDNESDAY NIGHT)... A SOUTHERN STREAM MID LEVEL TROUGH THAT MOVED ACROSS THE SOUTHERN STATES THE PAST FEW DAYS IS NOW GETTING CUT OFF OVER THE FLORIDA PENINSULA AS A STRONGER NORTHERN STREAM TROUGH CUTS OFF OVER THE NORTHERN PLAINS STATES. THE LOW OVER FLORIDA WILL MOVE VERY LITTLE THROUGH THIS PERIOD WHICH HAS CAUSED THE ATMOSPHERE TO BECOME VERY UNSTABLE AS 500 MB TEMPERATURES HAVE COOLED FROM -6.7 CELSIUS FROM LAST EVENING TO -7.5 THIS MORNING. AT THE SURFACE, A RIDGE OF HIGH PRESSURE WILL ALSO REMAIN NEARLY STATIONARY FROM THE SOUTHEAST STATES STRETCHING INTO THE ATLANTIC. ATMOSPHERIC MOISTURE HAS ALSO BEEN ON THE INCREASE WITH PWAT GOING UP TO 1.66 INCHES THIS MORNING WHICH IS CLOSE TO AVERAGE FOR THE TRANSITIONAL PERIOD GOING INTO THE LAST HALF OF MAY. EVEN THOUGH OVERALL MOISTURE IS NOT TERRIBLY IMPRESSIVE, THE MAIN ISSUE IS THE COLD TEMPERATURES ALOFT ALONG WITH VERY SLOW STORM MOTION AS LOW LEVEL FLOW IS FROM THE SOUTHEAST AND FLOW ABOVE 10K IS FROM THE WEST. THUS, WITH THE PATTERN CHANGING VERY LITTLE THE NEXT 48 HOURS THERE WILL BE A CONTINUED CHANCE OF THUNDERSTORMS MAINLY DURING THE LATE MORNING INTO THE EARLY EVENING HOURS. LONG TERM (THURSDAY THROUGH MONDAY)... IN THE EXTENDED PERIOD, THE NORTHERN STREAM TROUGH WILL DEEPEN AND SLOWLY DRIFT TO THE SOUTHEAST WHILE THE LOW OVER THE PENINSULA GETS PHASED IN WITH THIS DEEPENING TROUGH AND LIFTS TO THE NORTHEAST ON THURSDAY AND FRIDAY. THE DEEPENING TROUGH WILL ALSO FORCE A COLD FRONT TO MOVE INTO NORTH FLORIDA ON FRIDAY AND THEN MOVE SLOWLY SOUTH DOWN THE PENINSULA OVER THE WEEKEND WITH A SLOW DRYING TREND. THERE WILL BE HOWEVER ENOUGH RESIDUAL MOISTURE AND INSTABILITY ACROSS SOUTH FLORIDA FOR LOW CHANCES FOR AFTERNOON/EVENING THUNDERSTORMS EACH DAY. AVIATION... QUITE AN ACTIVE AFTERNOON AND EVENING AHEAD OF US FOR THE EASTERN TERMINALS. SHOWERS AND THUNDERSTORMS WILL CONTINUE DEVELOPING WHILE MOVING IN ALL DIRECTIONS. ALTHOUGH MOST OF THE ACTIVITY IS REMAINING WEST OF THE TERMINALS...A FEW COULD GET CLOSE ENOUGH...THEREFORE AMENDMENTS ARE EXPECTED. SOUTHEASTERLY FLOW WILL PREVAIL FOR THESE TERMINALS...WITH STRONG GUSTS EXPECTED AS STORMS APPROACH. SHOWERS WILL CONTINUE LINGERING THROUGH THE NIGHT...SO VCSH WAS KEPT AT ALL EASTERN TERMINALS. FOR KAPF...SEA BREEZE ALREADY DEVELOPED AND PUSHED INLAND...AND PREVAILING UNTIL 18-01Z. AFTER THAT...EASTERLY FLOW WILL PREVAIL WITH NO OTHER CONCERNS. MARINE... AN EAST TO SOUTHEAST WIND OF 15 KNOTS OR LESS WILL CONTINUE THROUGH THE END OF THE WEEK WITH SEAS GENERALLY LESS THAN 4 FEET. FIRE WEATHER... NO PROBLEMS OR CONCERNS WITH AMPLE TROPICAL MOISTURE REMAINING THROUGH THE MIDDLE OF THE WEEK. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 84 74 84 74 / 60 40 50 30 FORT LAUDERDALE 85 75 85 75 / 50 40 40 20 MIAMI 86 74 86 74 / 50 30 40 20 NAPLES 86 70 85 72 / 40 20 30 20 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. GM...NONE. && $$ DISCUSSION/MARINE/FIRE...10/CD AVIATION/RADAR...85/AG
