Issued by NWS
000 FXUS62 KKEY 211423 AFDKEY AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 930 AM EST SAT NOV 21 2009 .DISCUSSION...IN THE MIDDLE AND UPPER LEVELS...700-200 MB...LATEST WATER VAPOR AVAILABLE SATELLITE IMAGERY OVERLAID WITH STREAMLINE ANALYSIS AS OF 9 AM CONTINUE TO DEPICT A SPLIT FLOW PATTERN ACROSS THE CONUS. A NEAR 100 KNOT JET AT 250 MB TRAVERSES THE SOUTHERN PORTION OF NORTH AMERICA AS IT MOVES ACROSS BAJA...NORTHERN MEXICO...THEN NORTHEASTWARD TO THE CAROLINAS. A DISORGANIZED UPPER LOW OVER OKLAHOMA DIVES THE NORTHERN STREAM FROM THE SOUTHERN STREAM OF THE OF THE JET. THE FLORIDA KEYS ARE BENEATH A WIDE BAND OF THE SOUTHERN JETSTREAM...WITH CIRRUS MOVING OVERHEAD IN THE LOWER TO MIDDLE LEVELS...SURFACE TO 700 MB...LATEST IR SATELLITE IMAGERY OVERLAID WITH AVAILABLE SURFACE AND MARINE OBSERVATIONS DETAIL A 1008 MB LOW OVER THE NORTHWESTERN GULF OF MEXICO. A WARM FRONT IS ANALYZED EASTWARD TOWARD THE FLORIDA PENINSULA...WHILE A COLD FRONT SWINGS SOUTH FROM THE SYSTEM TO CENTRAL MEXICO. AS A RESULT...THE 12Z SOUNDING THIS MORNING ILLUSTRATES A GENTLE BUT MOISTENING EAST TO SOUTHEAST FLOW FROM THE SURFACE TO ABOUT 10000 FEET...WITH PWAT(PRECIPITABLE WATER) THAT HAS RISEN IN 24 HOURS FROM 1.46 INCHES OR ALMOST 1.5 INCHES FROM ONLY 1.08 INCHES YESTERDAY MORNING. ENOUGH ISENTROPIC LIFT IS AVAILABLE ALONG THE 300K SURFACE...WITH ISOLATED SHOWERS DELIVERING BRIEF PERIODS OF LIGHT RAIN FALLING FROM CLOUD BASES BETWEEN 4000 AND 5000 FEET. .CURRENTLY...AS OF 900 AM...SKIES ARE PARTLY CLOUDY OVER THE ISLANDS AND ADJOINING WATERS. KEY WEST RADAR SCANS SHOW A DWINDLING AREA OF LIGHT SHOWERS CONFINED TO THE WATERS WITHIN 30 NM OFFSHORE OF THE FLORIDA REEF BETWEEN SOMBRERO KEY LIGHT AND EAST SAMBO LIGHT. TEMPERATURES ARE PRESENTLY IN THE MID TO UPPER 70S WITH DEWPOINTS IN THE LOWER 70S. C-MAN STATIONS ALONG THE REEF ARE REGISTERING NORTHEAST TO SOUTHEAST WINDS AROUND 10 KNOTS...EXCEPT 10 TO 15 KNOTS OUT AT PULASKI SHOAL LIGHT. .SHORT TERM (REST OF TODAY)...IN THE MIDDLE AND UPPER LEVELS...(700-200 MB)...ALL LARGE SCALE MODELS SLIDE THE LOW PRESSURE AREA OVER THE SOUTHERN PLAINS EASTWARD AND FILL A FEW DECAMETERS THROUGH 00Z. JUST A FEW CIRRUS CLOUDS WILL BE TRANSPORTED OVER THE KEYS THRU THE DAY. IN THE LOWER TO MID LEVELS...SURFACE TO 700 MB...THE WEAK SURFACE LOW OVER THE NORTHWEST GULF WILL CONTINUE TO MOVE NORTHEASTWARD TO JUST OFF THE LOUISIANA COAST BY DAYS END. DRYER AIR IN THE MIDDLE LEVELS WILL GRADUALLY FILTER ACROSS THE KEYS FROM THE EAST LATER THIS MORNING...PUTTING AN END TO ANY CHANCE FOR MEASURABLE RAIN TODAY. TEMPERATURES AND HUMIDITY LEVELS WILL CONTINUE TO BE SLIGHTLY ABOVE NORMAL...REACHING INTO THE LOWER 80S. WILL JUST DO A LAST MINUTE UPDATE THIS MORNING TO TAKE OUT TRANSITIONAL WORDING AND REMOVE SHOWER THREAT OVER THE ISLANDS. && .MARINE...LIGHT TO GENTLE WINDS WILL INCREASE TO GENTLE TO MODERATE THIS AFTERNOON AND TONIGHT && .AVIATION...THROUGH 22/12Z...PREVAILING VFR CONDITIONS ARE EXPECTED AT EYW AND MTH. A FEW LIGHT SHOWERS IN THE VICINITY OF EYW THIS MORNING SHOULD DISSIPATE BY 15Z. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ PUBLIC/MARINE/GRIDS............FUTTERMAN AVIATION/NOWCASTS..............KASPER DATA ACQUISITION/UPPER AIR.....ROSS VISIT US ON THE WEB AT WWW.WEATHER.GOV/KEYWEST
