881
FXUS62 KMFL 220113
AFDMFL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
913 PM EDT SUN MAR 21 2010
UPDATE
SIGNIFICANTLY REDUCED POPS AREA WIDE AS LAND STABILITY
IS A MAJOR INHIBITOR TO CONVECTION BEING MAINTAINED...AS EVIDENCED
BY RADAR/LIGHTNING DATA WHICH SHOWS A SOLID LINE OF CONVECTION
OFF EAST CENTRAL FL EXTENDING SW TO JUST OFF THE PALM BEACH
COAST...THEN ANOTHER BAND OF CONVECTION OVER FL BAY WITH JUST A
FEW SHOWERS OVER THE MAINLAND. THE MIAMI SOUNDING SHOWS TWO
INVERSIONS REMAINING...ONE AT NEAR 8K FT...AND THE OTHER MORE
SIGNIFICANT ONE AT NEAR 17K FT. K-INDEX IS -13...PWAT ONLY 1.44
INCHES. CAPE THOUGH IS AROUND 1300 J/KG. STILL...GIVEN
TRENDS...TOOK POPS DOWN FROM CATEGORICAL...AND LOWERED TO 50% EAST
COAST TO 30% GULF COAST. MOST OF THE ACTIVITY WILL BE
SHOWERS...BUT A FEW STORMS WILL REMAIN POSSIBLE TONIGHT.
HOWEVER...WILL TONE DOWN HAZARDOUS WEATHER OUTLOOK. /GREGORIA
PREV DISCUSSION
/ISSUED 737 PM EDT SUN MAR 21 2010/
AVIATION...MOSTLY CLOUDY SKIES WILL PREVAIL AS A FRONTAL BOUNDARY
MOVES ACROSS SOUTH FLORIDA TONIGHT. MOST OF THE ACTIVITY IS
EXPECTED TO REMAIN NEAR KPBI...BUT KEPT VCSH/VCTS AT ALL TERMINALS
OVERNIGHT DUE TO UNCERTAINTY. WILL AMEND IF NECESSARY. KEPT SW FLOW
AT ALL TERMINALS SLOWING DOWN OVERNIGHT AND PICKING UP SPEED BY
22/11Z.
PREV DISCUSSION... /ISSUED 617 PM EDT SUN MAR 21 2010/
UPDATE...
THE LINE OF SHOWERS AND THUNDERSTORMS THAT HAS BEEN APPROACHING
THE NORTHERN AND WESTERN AREAS OF SOUTH FLORIDA THIS AFTERNOON IS
STARTING TO STALL FROM ABOUT THE WEST PALM BEACH SOUTHWEST TO
NAPLES AREA EARLY THIS EVENING. THE LATEST MODELS ARE STILL
SHOWING THE LINE SHOULD STALL OVER THE NORTHERN AREAS THIS EVENING
AS THE STEERING FLOW BECOMES SOUTHWEST...BEFORE MOVING SLOWLY
SOUTH THROUGH REST OF THE CWA LATE TONIGHT INTO MONDAY MORNING
WITH THE PASSAGE OF THE COLD FRONT. SO WILL CONTINUE WITH CATEGORICAL
POPS TONIGHT OVER THE CWA...WITH THE HIGHEST POPS OVER THE
NORTHERN AREAS THIS EVENING SHIFTING TO THE SOUTHERN AREAS AFTER
MIDNIGHT.
THERE COULD STILL BE A FEW STRONG STORMS TONIGHT OVER THE
CWA...DUE TO THE SAME REASON MENTION BELOW IN PARAGRAPH 6.
SO NO CHANGES ARE PLAN AT THIS TIME...EXCEPT TO REMOVE THE
AFTERNOON AND EVENING WORDING.
UPDATE...54/BNB
PREV DISCUSSION... /ISSUED 330 PM EDT SUN MAR 21 2010/
RAIN LIKELY TONIGHT WITH A FEW STRONG STORMS POSSIBLE...
DISCUSSION...
A LOW PRESSURE SYSTEM WAS LOCATED OVER THE MISSISSIPPI VALLEY WITH A
TRAILING SOUTHWARD COLD FRONT SOUTHWARD INTO THE EASTERN GULF OF
MEXICO EARLY THIS AFTERNOON. A PRE FRONTAL TROUGH OF LOW PRESSURE
WAS LOCATED FROM ABOUT ORLANDO SOUTHWEST THROUGH FORT MYERS INTO
THE SOUTHEAST GULF OF MEXICO WHERE SHOWERS AND THUNDERSTORMS WERE
OCCURRING.
THE PRE-FRONTAL TROUGH WILL CONTINUE TO MOVE EAST BUT BECOME
STATIONARY OVER THE NORTHERN AREAS OF THE CWA THIS EVENING...AS
THE STEERING FLOW BECOME PAROLEE TO THE TROUGH. SO THE SHOWERS AND
THUNDERSTORMS SHOULD PUSH INTO THE NORTHERN AREAS...BEFORE
BECOMING STATIONARY FROM ABOUT WEST PALM BEACH SOUTHWEST TO NAPLES
AREA THIS EVENING.
SOME SHOWERS HAVE ALSO DEVELOP OVER THE WESTERN ARES OF THE CWA
THIS AFTERNOON...DUE TO THE HEATING AND UNSTABLE AIR AHEAD OF
THE PRE-FRONTAL TROUGH. SHOWERS AND EVEN A THUNDERSTORM OR TWO
SHOULD DEVELOP OVER THE CWA THROUGH THE AFTERNOON HOURS AHEAD OF
THE TROUGH OF LOW PRESSURE.
SO HAVE UP THE POPS TO LIKELY OVER THE NORTHERN INTERIOR
AREAS...WITH CHANCE CAT OVER REST OF THE CWA FOR THIS AFTERNOON
INTO THIS EVENING. THERE IS ALSO A THUNDER THREAT NOW OVER THE
CWA...WITH THE HIGHEST TREAT OVER THE NORTHERN PORTIONS OF THE CWA.
THE LOW PRESSURE MENTION ABOVE WILL ALSO MOVE SLOWLY EAST INTO THE
SOUTHEAST UNITED STATES TONIGHT PUSHING THE COLD FRONT SLOWLY EAST
AND THROUGH SOUTH FLORIDA MAINLY AFTER MIDNIGHT. THIS WILL HELP TO
PUSH THE LINE OF SHOWERS AND THUNDERSTORMS OVER THE NORTHERN AREAS
SLOWLY SOUTHWARD AFTER MIDNIGHT...AND SHOULD BE OVER THE SOUTHEAST
METRO AREAS BY SUNRISE MONDAY OR JUST OFFSHORE. THEREFORE...HAVE
UP THE POPS TO CATEGORICAL OVER THE CWA FOR TONIGHT...WITH THE
NORTHERN AREAS SEE THE HIGHEST POPS THIS EVENING BEFORE SHIFTING
INTO THE SOUTHERN AREAS AFTER MIDNIGHT.
A SHORT WAVE OVER THE YUCATAN PENINSULA THIS AFTERNOON WILL ALSO
MOVE NORTHEAST AND THROUGH SOUTH FLORIDA TONIGHT ALONG THE FRONT.
THERE WILL ALSO BE MID TO UPPER LEVEL JET OF 100 TO 120 KNOTS
MOVING THROUGH CENTRAL FLORIDA WHICH WILL PUT SOUTH FLORIDA IN THE
RIGHT REAR QUADRANT OF THE JET...AND THE MID LEVELS OF THE
ATMOSPHERE WILL ALSO BE COOLING DOWN INTO THE -10 TO -13 DEGREES
RANGE LATE TONIGHT. THIS USUALLY MEANS THAT THERE COULD BE SOME
STRONG TO SEVERE STORMS IN THIS TYPE OF ENVIRONMENT.
HOWEVER...THERE IS NO LOW LEVEL JET AND THE TIMING OF THE LINE OF
SHOWERS AND THUNDERSTORMS IS AT NIGHT WHICH IS USUALLY WEAKER DUE
TO THE LACK OF HEATING. SPC ALSO ONLY HAVE US IN A SEE TEXT FOR
TONIGHT. SO AT THIS TIME WILL MENTION A FEW STRONG STORMS OVER
SOUTH FLORIDA TONIGHT IN THE HWO PRODUCT WITH THE PRIMARY IMPACTS
BEING GUSTY WINDS AND SMALL HAIL...AND CONTINUE TO MONITOR THE
LATEST MODEL RUNS FOR TONIGHT.
THE LOW WILL CONTINUE TO MOVE SLOWLY EAST ON MONDAY INTO THE
WESTERN ATLANTIC WATERS PUSHING THE COLD FRONT EAST INTO THE
WESTERN ATLANTIC WATERS AND AWAY FROM SOUTH FLORIDA. THIS WILL
ALLOW FOR THE SHOWERS AND THUNDERSTORMS TO SLOWLY DISSIPATE MONDAY
MORNING INTO EARLY MONDAY AFTERNOON OVER THE CWA. SO WILL CONTINUE
WITH A CHANCE OF POPS OVER THE NORTHERN AREAS TO LIKELY POPS OVER
THE SOUTHERN AREAS MONDAY MORNING...BEFORE TAPERING DOWN TO
SLIGHT CHANCE NORTH TO CHANCE SOUTH FOR EARLY MONDAY AFTERNOON.
HIGH PRESSURE WILL THEN BUILD INTO FLORIDA PENINSULA MONDAY NIGHT
INTO WEDNESDAY. THIS WILL ALLOW FOR DRY CONDITIONS ALONG WITH
COOLER AIR TO WORK INTO THE CWA FROM THE NORTH.
EXTENDED FORECAST...
THE HIGH WILL THEN MOVE EAST INTO THE ATLANTIC WATERS LATE THIS
WEEK INTO NEXT WEEKEND ALLOWING FOR ANOTHER WEAK COLD FRONT TO
MOVE THROUGH THE AREA. SO WILL CONTINUE THE CHANCE OF SHOWERS
OVER THE CWA FRIDAY AND SLIGHT CHANCE OF SHOWERS EARLY NEXT
WEEKEND...BEFORE GOING DRY FOR THE SECOND HALF OF NEXT WEEKEND.
MARINE...
THE WINDS EARLY THIS AFTERNOON HAVE BEEN COMING FROM THE SOUTH TO
SOUTHEAST AROUND 20 KNOTS WITH GUSTS UP TO AROUND 30 KNOTS. THE
SOUTHERLY WINDS WILL BECOME SOUTHWEST THIS EVENING BEFORE GOING
WESTERLY LATE TONIGHT INTO MONDAY. THE SPEEDS WILL ALSO DECREASE
FROM 15 TO 20 KNOTS THIS EVENING TO 10 TO 15 KNOTS BY LATE TONIGHT
INTO MONDAY. SO THE ATLANTIC SEAS WILL SLOWLY FALL FROM 4 TO 6
FEET THIS AFTERNOON TO LESS THAN 6 FEET BY LATE TONIGHT INTO MONDAY.
FOR THE GULF SIDE...A NORTHWEST SWELL OF 1 TO 2 FEET WILL WORK
INTO THESE WATERS OVERNIGHT INTO MONDAY. THIS WILL ALLOW FOR THE
SEAS TO BUILD FROM LESS THAN 6 FEET THIS AFTERNOON TO 5 TO 7 FEET
MONDAY MORNING IN THE GULF WATERS AND 3 TO 5 FEET NEAR-SHORE. THE
NORTHEAST SWELL WILL CONTINUE TO INCREASE TO 2 TO 3 FEET ON MONDAY
ALLOWING FOR THE SEAS TO BUILD TO 7 TO 9 FEET OFFSHORE AND 4 TO 6
FEE NEAR-SHORE.
SO WILL CONTINUE THE SCA FOR ALL WATERS UNTIL THIS EVENING BEFORE
CHANGING THE SCA TO A SCEC. THE ONLY EXCEPTION IS TO KEEP THE SCA FOR
THE OFFSHORE GULF WATERS DUE TO THE SEAS BUILDING OVERNIGHT INTO
MONDAY.
THERE IS ALSO A HIGH RISK OF RIP CURRENTS THIS AFTERNOON ALONG THE
EAST COAST BEACHES OF SOUTH FLORIDA. SO WILL HEADLINE THIS IN THE
AFTERNOON ZONES.
FIRE WEATHER...
THE RELATIVE HUMIDITIES WILL REMAIN ABOVE THE CRITICAL VALUE OF 35
PERCENT ON MONDAY DUE TO THE COOLER TEMPERATURES. HOWEVER...ON
TUESDAY THE RELATIVE HUMIDITIES COULD FALL APPROACH THE 35 PERCENT
OVER THE NORTHWEST INTERIOR AREAS...DUE TO LOWER DEW POINTS AND
HIGHER TEMPERATURES. SO WILL CONTINUE TO MONITOR THE RELATIVE
HUMIDITIES FOR TUESDAY IN THE LATEST MODEL RUNS TO SEE IF A FIRE
WEATHER WATCH WILL BE NEEDED FOR THE NORTHWEST INTERIOR AREAS ON
MONDAY FOR TUESDAY.
PRELIMINARY POINT TEMPS/POPS
WEST PALM BEACH 62 73 56 76 / 50 50 10 -
FORT LAUDERDALE 65 74 58 77 / 50 50 10 -
MIAMI 64 75 59 78 / 50 50 10 -
NAPLES 60 69 57 76 / 30 30 10 -
MFL WATCHES/WARNINGS/ADVISORIES
FL...NONE.
AM...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 8 AM EDT TUESDAY FOR GULF WATERS FROM
CHOKOLOSKEE TO BONITA BEACH, FL EXTENDING FROM 20 TO 60 NM.
LONG TERM...57/DG
SHORT TERM/AVIATION...17/ERA
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