Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 271404
AFDMFL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
1004 AM EDT FRI MAR 27 2015

.UPDATE...
MIXED SIGNALS REGARDING STRONG THUNDERSTORM POTENTIAL THIS
AFTERNOON ACROSS THE SOUTHERN FLORIDA PENINSULA. LINE OF
SHOWERS/THUNDERSTORMS THIS MORNING ACROSS/OFFSHORE PALM BEACH
COUNTY ALONG OLD OUTFLOW BOUNDARY AND LOW LEVEL CONVERGENCE IS
GRADUALLY WANING AS LOW-LEVEL WINDS BECOMING S-SW ACROSS THE AREA
AND WASHING OUT THE BOUNDARY. MAIN MID-LEVEL SHORTWAVE TROUGH
ACROSS THE MISSISSIPPI VALLEY DOWN TO THE GULF COAST APPEARS TO BE
SHEARING OUT TO THE NE RATHER THAN DIVE DOWN INTO THE GULF/FLORIDA
PENINSULA. THIS IS ACTING TO LIMIT THE UPPER LEVEL DIVERGENCE AS
THE MAIN BAND OF MOISTURE WITH THE COLD FRONT APPROACHES THE AREA
LATE THIS AFTERNOON. A SIGN OF THIS IS THE PRESENT LACK OF DEEP
CONVECTION OVER THE EASTERN GULF OF MEXICO.

HOWEVER, AS WE APPROACH THE AFTERNOON HOURS LOW-LEVEL CONVERGENCE
WILL GRADUALLY INCREASE AHEAD OF THE FRONT, ESPECIALLY ACROSS THE
LAKE OKEECHOBEE AND PALM BEACH REGIONS. DESPITE CLOUD COVER THIS
MORNING, THERE SHOULD BE ENOUGH BREAKS IN THE CLOUDS TO ALLOW
TEMPERATURES TO WARM UP INTO THE 80S AND INCREASE THE ATMOSPHERIC
INSTABILITY. MODELS ARE RATHER CONSISTENT IN FOCUSING MOST OF THE
PRECIPITATION/THUNDERSTORM POTENTIAL THIS AFTERNOON ACROSS THE
LAKE OKEECHOBEE AND PALM BEACH AREAS, AND THIS LOOKS REASONABLE
BASED ON THESE INDICATORS. THIS IS ALSO THE AREA MOST LIKELY TO
SEE ANY STRONG/MARGINAL SEVERE STORMS TODAY, PROVIDED
THUNDERSTORMS DO INDEED DEVELOP.

ANOTHER AREA OF THUNDERSTORM CONCENTRATION MAY BE OVER THE GULF
WATERS OFF SOUTHWEST FLORIDA. PRESENT INDICATIONS ARE THAT MOST OF
THIS CONVECTION WILL STAY OFFSHORE AND NOT AFFECT THE GULF COAST,
WITH A NARROW BAND OF SHOWERS/FEW THUNDERSTORMS MOVING ONSHORE SW
FLORIDA THIS AFTERNOON.

THE WILD CARD IS WHETHER A SEA BREEZE WILL DEVELOP ALONG THE EAST
COAST. IF IT DOES DEVELOP AS THE HRRR SUGGESTS, THEN SOME STORMS
WILL LIKELY DEVELOP OVER MUCH OF THE EAST COAST METROS FROM PALM
BEACH TO MIAMI AREA BY MIDDAY/EARLY AFTERNOON. THIS SEA BREEZE
DEVELOPMENT APPEARS SOMEWHAT UNLIKELY DUE TO THE INCREASING SW
WINDS WHICH COULD PREVENT OR HOLD BACK THE SEA BREEZE FROM
SETTING UP. SOMETHING TO WATCH CLOSELY TODAY.

THE AREAS OF UPPER-LEVEL DIVERGENCE/LOW-LEVEL CONVERGENCE BEGIN
TO SPLIT LATE THIS AFTERNOON AND EARLY THIS EVENING, WITH THE
FAVORED COUPLETS OF UPPER LEVEL DIVERGENCE/LOW LEVEL CONVERGENCE
EAST AND WEST OF THE PENINSULA. THIS IMPLIES THAT COVERAGE OF
SHOWERS AND THUNDERSTORMS WILL DECREASE AS YOU GO SOUTH, POSSIBLY
LEAVING AREAS SUCH AS MIAMI-DADE COUNTY MOSTLY FREE OF
PRECIPITATION. FORECAST WILL STILL REFLECT POPS AREA-WIDE, WITH
TREND OF HIGHER TO LOWER POPS FROM NORTH TO SOUTH AS CURRENTLY
INDICATED. /MOLLEDA

&&

.PREV DISCUSSION... /ISSUED 742 AM EDT FRI MAR 27 2015/

AVIATION...
STRONG COLD FRONT TO CROSS THE REGION THROUGH THE PERIOD. STORMS
ONGOING NEAR KPBI AND ADDITIONAL DEVELOPMENT NEAR THE TERMINAL
COULD CREATE BRIEF MVFR CIGS WITH ANY TS. ACTIVITY SHOULD STAY
NORTH OF OTHER EAST COAST TERMINALS, AS OUTFLOW FROM CONVECTION
FURTHER WEST WHICH SPARKED THIS MORNINGS STORM, IS EXPECTED TO
STAY AWAY. HOWEVER, AS THE FRONT NEARS AND MIDLEVEL LAPSE RATES
INCREASE, STORMS WILL BECOME MORE PROBABLE FURTHER SOUTH, BUT
STILL JUST HANDLED WITH VCTS FOR NOW. SOME 30KT WIND GUSTS ARE
POSSIBLE WITH THE ACTUAL PASSAGE OF THE FRONT THIS EVENING.
STORMS COULD REDUCE CIG TO MVFR LATER THIS AFTERNOON AND EVENING.

PREV DISCUSSION... /ISSUED 406 AM EDT FRI MAR 27 2015/

.RESENT WITH SCA FOR THE ATLANTIC WATERS...

SHORT TERM (TODAY-SUNDAY)...
A HIGHLY AMPLIFIED FLOW ALOFT WILL CONTINUE TO EVOLVE OVER THE
U.S. WITH A LARGE TROUGH ACROSS THE EASTERN HALF. THE ASSOCIATED
COLD FRONT WITH THIS TROUGH IS CURRENTLY OVER THE FAR WESTERN
PORTION OF THE FLORIDA PANHANDLE AND AS THE TROUGH AXIS CONTINUES
TO DEEPEN, THE FRONT WILL PROCEED SOUTHEAST ACROSS THE PENINSULA
THIS AFTERNOON AND EVENING. A BAND OF SHOWERS ARE CURRENTLY WELL
AHEAD OF THE FRONT OVER CENTRAL FLORIDA WITH SCATTERED
THUNDERSTORMS ALSO OVER THE GULF WATERS. AS SIGNIFICANT HEIGHT
FALLS OCCUR WITH THE DEEPENING TROUGH, SUBSTANTIAL DESTABILIZATION
WILL BE UNDER WAY ESPECIALLY BY THIS AFTERNOON FOR SCATTERED
THUNDERSTORM DEVELOPMENT SPREADING EASTWARD ACROSS THE MAINLAND.
BOUNDARY LAYER FLOW WILL BE UNIDIRECTIONAL AHEAD OF THE FRONT
WHICH WILL LIMIT AND LOW LEVEL CIRCULATION BUT THERE COULD BE SOME
STRONGER STORMS GIVEN FAVORABLE DEEP LAYER SHEAR. THUS, THERE
COULD BE SOME ISOLATED STRONG STORMS WHICH COULD APPROACH
PRODUCING NEAR SEVERE WIND GUSTS THIS AFTERNOON WITH SOME OF THIS
ACTIVITY LINGERING INTO THE EARLY EVENING HOURS ESPECIALLY NEAR
THE SOUTHEAST COAST. THE TIMING APPEARS THAT THE GREATEST THREAT
FOR THUNDER WILL BE OVER THE LAKE OKEECHOBEE REGION BEGINNING
AROUND 16-17Z AND THE EAST COAST METRO REGION NEAR 20Z THROUGH
THE EARLY EVENING. AS THE TROUGH DEEPENS AND SHIFTS EAST, THE COLD
FRONT WILL CLEAR THE SOUTHEAST COAST LATE TONIGHT WITH SURFACE
HIGH PRESSURE BUILDING BEHIND THE FRONT. A MUCH DRIER AND COOLER
AIRMASS WITH THEN FILTER DOWN THE PENINSULA WITH COLD AIR
ADVECTION CONTINUING THROUGH SUNDAY. MINIMUM TEMPERATURES TONIGHT
INTO EARLY SATURDAY MORNING WILL BE IN THE 50S EXCEPT LOWER TO MID
60S ALONG THE EAST COAST WITH TEMPERATURES EARLY SUNDAY MORNING IN
THE UPPER 40S AND 50S WITH NEAR 60 ALONG THE SOUTHEAST COAST. THIS
WILL BE SUBSTANTIALLY COOLER FROM WHAT HAS BEEN EXPERIENCED OVER
THE PAST FEW WEEKS AND AROUND 10 DEGREES BELOW THE AVERAGES FOR
LATE MARCH.

LONG TERM (MONDAY-THURSDAY)...
A GRADUAL WARMING TREND WILL ENSUE NEXT WEEK AS THE UPPER FLOW
BECOMES ZONAL WITH THE TROUGH SHIFTING TO THE EAST AND THE SURFACE
FLOW WILL RETURN TO THE EAST AS THE RIDGE SHIFTS EAST INTO THE
ATLANTIC BY TUESDAY. TEMPERATURES WILL RETURN TO NEAR NORMAL BY
TUESDAY AND ABOVE NORMAL AGAIN BY LATE IN THE WEEK.

MARINE...
DETERIORATING MARINE CONDITIONS WILL TAKE PLACE TODAY THROUGH THE
WEEKEND AS THE SOUTHWEST WIND INCREASE TO NEAR 20 KNOTS OVER THE
ATLANTIC WATERS AND THEN SHIFTS TO THE NORTH BEHIND THE FRONT.
THE WIND WILL BEGIN TO DIMINISH LATE IN THE WEEKEND WITH SUBSIDING
SEAS ON SUNDAY INTO NEXT WEEK AS THE FLOW RETURNS TO THE EAST.

&&

.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH  88  61  73  54 /  70  30  10   0
FORT LAUDERDALE  87  63  74  59 /  50  30  10   0
MIAMI            88  64  77  60 /  50  30  10   0
NAPLES           83  63  74  54 /  70  30  10   0

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 8 PM EDT
     SATURDAY FOR AMZ650-651-670-671.

GM...NONE.
&&

$$

SHORT TERM...59/MOLLEDA
LONG TERM....59/MOLLEDA
AVIATION.....21/KM


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