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