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000 FXUS62 KMFL 240528 AFDMFL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 128 AM EDT WED SEP 24 2008 .AVIATION...NORTHEAST FLOW WILL CONTINUE THROUGH THE PERIOD AND BECOME 10 TO 15 KTS WITH HIGHER GUSTS ON WEDNESDAY. A FEW SHOWERS ARE EXPECTED TO PUSH INLAND FROM THE ATLANTIC THROUGH TODAY POSSIBLY CREATING BRIEF MVFR CONDITIONS AT THE EAST COAST SITES, HOWEVER MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD AT ALL SITES. /TINGLER && .PREV DISCUSSION... /ISSUED 1047 PM EDT TUE SEP 23 2008/ UPDATE...WEAK COLD FRONT CURRENTLY OVER THE NORTHERN SECTION OF THE LAKE WILL MOVE SLOWLY SOUTH OVERNIGHT PRODUCING SCATTERED SHOWERS AND POSSIBLY AN ISOLATED THUNDERSTORM OVER THE ATLANTIC AND EASTERN COASTAL AND METRO AREAS. WATER VAPOR SHOWS DECENT UPPER LEVEL DRYING MOVING SOUTH TO SUPPORT A DECREASING TREND THROUGH WEDNESDAY. MADE NO MAJOR CHGS TO FCSTS. PREV DISCUSSION... /ISSUED 728 PM EDT TUE SEP 23 2008/ AVIATION... SCATTERED SHOWERS WERE STILL OCCURRING OVER THE CWA EARLY THIS EVENING...ALONG WITH A FEW THUNDERSTORMS OVER THE SOUTHWEST AREAS OF THE CWA. THIS SHOULD CONTINUE THROUGH THE EVENING HOURS WHILE SLOWLY DISSIPATING ACROSS THE CWA. SO HAVE KEPT VCSH FOR ALL OF THE TAF SITES UNTIL AROUND 5Z...EXCEPT FOR APF TAF SITE WHERE VCTS WILL REMAIN UNTIL 3Z. AFTER 5Z. THE PRECIP SHOULD END FOR MOST SITES...AS THE DRAINAGE FLOW SHOULD SET UP. THE ONLY AREAS THAT COULD SEE SOME SHOWERS WILL STILL BE PBI AND FLL...DUE TO THE NORTHEAST WIND FLOW BETWEEN 5 TO 10 KNOTS. SO HAVE KEPT A VCSH FOR THE KFLL AND KPBI TAF SITES FOR THE LATE NIGHT HOURS TONIGHT. ON WEDNESDAY...THE NORTHEAST WINDS WILL CONTINUE OVER ALL OF THE CWA TAF SITES BETWEEN 10 TO 15 KNOTS WITH GUSTS UP TO 20 KNOTS. THE WX WILL ALSO BE DRY AT ALL OF THE TAF SITES. THE CEILING AND THE VIS FOR ALL OF THE TAF SITES TONIGHT INTO WEDNESDAY WILL REMAIN IN THE VFR CONDITIONS. AVIATION...54/BNB PREV DISCUSSION... /ISSUED 241 PM EDT TUE SEP 23 2008/ DISCUSSION... WATER VAPOR IMAGERY SHOWS A MOISTURE PLUME ACROSS SOUTH FLORIDA SLOWLY TRANSLATING TO THE SOUTH AS A TROUGH DEEPENS ALONG THE EASTERN CONUS COAST THIS AFTERNOON. LATEST RUC ANALYSIS SHOWS THE TROUGH IS IN THE PROCESS OF CLOSING OFF INTO A CLOSED/CUTOFF LOW JUST OFF THE CAROLINA COAST. A WEAK SURFACE LOW IS DEVELOPING OFFSHORE CAPE HATTERAS...WITH A STRONG SURFACE HIGH OVER WESTERN NEW YORK. THE STRONG GRADIENT BETWEEN THE TWO HAS GENERATED STRONG WINDS...AND MODERATE TO LARGE SWELLS AS FAR SOUTH AS OFF THE NE FLORIDA COAST ALREADY THIS AFTERNOON. LOCALLY...SCATTERED SHOWERS AND A FEW THUNDERSTORMS CONTINUE ACROSS THE CWA WITH MOVEMENT TO THE SOUTHWEST. MUCH OF THIS ACTIVITY WILL DIMINISH THIS EVENING WITH LOSS OF DAYTIME HEATING BUT SHOWERS COULD LINGER MUCH OF THE NIGHT ALONG THE EAST COAST METRO AREAS WITH INCREASING NE FLOW WHILE INTERIOR AND WEST COAST AREAS DRY OUT. BEYOND TONIGHT...THE UPPER TROUGH AXIS SWINGS THROUGH DISPLACING MOST DEEP-LAYER MOISTURE SOUTH OF THE FLORIDA PENINSULA ON NORTHERLY WINDS. MODELS HAVE BEEN VERY CONSISTENT IN SHOWING THIS ABUNDANCE OF DRY AIR MOVING SOUTH...AND WITH AN INCREASING SUBSIDENCE INVERSION AND MOSTLY WNW/NW FLOW CHANCES FOR RAIN WILL BE ALMOST NIL WEDNESDAY THROUGH FRIDAY ALTHOUGH WITH LINGERING NE FLOW SOME STRATOCU AND SHOWERS ARE POSSIBLE ACROSS EASTERN AREAS ON WEDNESDAY. THE CLOSED LOW WILL OPEN AND LIFT NORTHEAST TOWARDS SOUTHEASTERN CANADA BY THIS WEEKEND ALLOWING THE SUBTROPICAL RIDGE OVER THE ATLANTIC TO BUILD BACK ACROSS THE FLORIDA STRAITS. SOUTHERLY FLOW ON THE NORTH SIDE OF IT MAY ALLOW ABUNDANT DEEP-LAYER MOISTURE TO MOVE BACK NORTH ACROSS THE REGION...BUT ANY SHIFT OR DELAY IN THE RIDGE COULD CHANGE TIMING OF ANY MOISTURE/PRECIP INCREASE. THE DRIER AIRMASS MOVING IN WILL LEAD TO LOWER DEWPOINTS ESPECIALLY TOMORROW NIGHT THROUGH FRIDAY...WITH VALUES DROPPING INTO THE 60S MOST PLACES WITH GOOD MIXING FROM ABOVE EACH DAY...EXCEPT RIGHT ALONG THE IMMEDIATE EAST COAST AS ONSHORE FLOW KEEPS VALUES CLOSER TO 70. THE DRIEST AIR WILL BE ACROSS GLADES AND HENDRY COUNTIES WHERE 900MB DEWPOINTS ARE FORECAST TO BE QUIET LOW AND THIS MAY ALLOW SURFACE DEWPOINTS TO MIX OUT AS LOW AS 60F. TEMPERATURES WILL ALSO BE A FEW DEGREES COOLER THE NEXT FEW DAYS...MOST NOTICEABLY AT NIGHT. LOW TEMPS WILL RANGE FROM THE 60S ACROSS MUCH OF THE INTERIOR...COLDEST NORTHWEST...TO JUST ABOVE 70 ACROSS THE MIAMI AREA. SWELLS WILL INCREASE FROM THE NORTH TO NORTHEAST TONIGHT AND ARE ALREADY BEING REPORTED OFF THE NE FLORIDA COAST. SWELLS SHOULD PEAK AROUND 6FT ALONG THE PALM BEACH COUNTY COAST AND 3 TO 5FT ALONG THE MIAMI-DADE AND BROWARD COASTS LATE WEDNESDAY NIGHT AND THURSDAY WITH SOME HIGHER VALUES OFFSHORE. IF THESE SWELL HEIGHTS VERIFY...PERIODS OF AROUND 12S COULD LEAD TO 10FT BREAKERS ESPECIALLY ALONG THE PALM BEACH COAST DURING THAT TIME FRAME AND A HIGH SURF ADVISORY MAY BE NEEDED. MARINE... NORTHERLY WINDS WILL INCREASE TONIGHT AND WEDNESDAY TO NEAR OR JUST ABOVE EXERCISE CAUTION CRITERIA...AND THIS IS A LITTLE ABOVE GFS GUIDANCE BASED ON UPSTREAM OBS AND SURGES IN LOW-LEVEL WINDS JUST ABOVE THE SURFACE. SEAS WILL BUILD OVER 7FT IN RESPONSE TO THAT AND SMALL SWELL LATE TONIGHT...AND 8 TO 11FT LATE WEDNESDAY INTO THURSDAY AS SWELLS INCREASE TO AS MUCH AS 8FT OFFSHORE. FIRE WEATHER... LOWER DEWPOINTS EXPECTED LATE THIS WEEK WITH RH`S POSSIBLY NEARING 40 PERCENT ACROSS THE INTERIOR THURSDAY AND FRIDAY. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 86 73 86 69 / 20 20 10 10 FORT LAUDERDALE 86 75 87 73 / 20 20 10 10 MIAMI 86 76 86 74 / 20 20 10 10 NAPLES 88 72 87 69 / 10 10 10 10 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 AM EARLY THIS MORNING TO 8 AM EDT FRIDAY FOR AMZ650-AMZ651-AMZ670-AMZ671. GM...NONE. && $$