Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 311523
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1123 AM AST FRI OCT 31 2014

.UPDATE...THE DOPPLER WEATHER RADAR DETECTED ISOLATED TO SCATTERED
SHOWERS AND A FEW THUNDERSTORMS ACROSS THE WATERS SURROUNDING THE
U.S. VIRGIN ISLANDS...VIEQUES...CULEBRA AND EASTERN SECTIONS OF
PUERTO RICO THIS MORNING. AN UPPER LEVEL TROUGH OVER THE REGION
AND A WEAK LOW PRESSURE NORTH OF PUERTO RICO WILL CONTINUE TO
ENHANCE THE SHOWERS AND THUNDERSTORMS ACTIVITY ACROSS PUERTO RICO
AND THE U.S. VIRGIN ISLANDS TODAY. THE INSTABILITY ASSOCIATED WITH
THE LOW PRESSURE CENTER IS EXPECTED TO COMBINE WITH DAYTIME
HEATING...SEA BREEZE CONVERGENCE AND OROGRAPHIC EFFECTS TO INDUCE
THE DEVELOPMENT OF SCATTERED TO NUMEROUS SHOWERS AND ISOLATED
THUNDERSTORMS ALONG THE CORDILLERA CENTRAL EARLY IN THE
AFTERNOON...MOVING OVER THE NORTHERN HALF OF PUERTO RICO INCLUDING
THE METROPOLITAN AREA BY MID AFTERNOON. A SLIGHT IMPROVE IN
WEATHER CONDITIONS ARE EXPECTED FOR THE WEEKEND.

&&

.AVIATION...SHRA/TSRA WILL DEVELOP EARLY THIS AFTERNOON NORTH OF
CORDILLERA CENTRAL...AFFECTING TJSJ...TJMZ AND TJBQ WITH PERIODS
OF MVFR OR EVEN IFR CONDITIONS UNTIL 31/22Z. CIGS AROUND
FL020-040 AND REDUCTION IN VISIBILITY TO AROUND 3 MILES AS THE
ACTIVITY AFFECTS THESE TERMINALS...OTHERWISE VCSH/VCTS ARE LIKELY
ACROSS THE REST OF THE LOCAL FLYING AREA.

&&

.MARINE...SOUTH OR SSE WINDS 10 KT OR LESS THROUGH SAT. TRADES
RETURN SAT NIGHT AND STRENGTHEN UP TO 20 KT. SEAS MAINLY 2-3 FT
THROUGH SUN THEN BUILD 5-7 FT BY MON NIGHT IN NNW SWELLS AND ENE
WIND WAVES. THIS LIKELY TO RESULT IN ROUGH SURF CONDITIONS WITH
HIGH RISK OF RIP CURRENTS ON ATLC AND NW PR BEACHES.

&&

.PREV DISCUSSION... /ISSUED 412 AM AST FRI OCT 31 2014/

SYNOPSIS...UPPER LEVEL RIDGE WILL BUILD THROUGH THE WEEKEND. DEEP
CUTOFF LOW EXPECTED TO EVOLVE OVR THE WINDWARD PASSAGE/CNTRL
CARIBBEAN MID NEXT WEEK AND BRING COOLER AND UNSETTLED WEATHER.

DISCUSSION...DEEP CONVECTION OVER THE USVI AND ADJANCENT WATERS
IS BEING ENHANCED BY AN UPPER LEVEL TROUGH CURRENTLY MOVING
THROUGH THE AREA WITH CLEARING ONGOING OVER WRN PR. TROF AXIS WILL
PULL AWAY FROM THE AREA TODAY WITH HEIGHTS ALOFT RISING RAPIDLY
LEADING TO IMPROVING WX CONDITIONS. SOME AFTERNOON CONVECTION
STILL POSSIBLE OVR NRN PR THIS AFTERNOON BUT AREAL COVERAGE AND
INTENSITY WILL BE SIGNIFICANTLY LESS THAN YESTERDAY AFTERNOON AND
EVENING. HEIGHTS ALOFT CONTINUE TO RISE THROUGH THE WEEKEND WITH
FURTHER DRYING EXPECTED.

ON MONDAY...HEIGHTS ALOFT WILL FALL SHARPLY AS AN UPPER LEVEL
TROUGH CUTS OFF OVR THE SW ATLC. 31/00Z ECMWF MORE AGGRESSIVE THAN
GFS SHOWING AN ANOMALOUS DEEP CUTOFF OVR THE CNTRL CARIBBEAN.
COMBINATION OF HEIGHT FALLS AND STRENGTHENING TRADE WINDS WILL
LEAD TO RAPID MOISTURE ADVECTION MON NIGHT THROUGH TUE EVENING
WITH SHOWERS INCREASING IN AREAL COVERAGE OVR ERN PR DURING THE
NIGHT/EARLY MORNING AND WRN PR DURING THE AFTERNOON. SUBSTANTIAL
MID-HIGH LEVEL CLOUD DECK ASSOCIATED WITH AN UPPER LEVEL JET
STREAK WITH COOLER TEMPS/LOWER HEIGHTS IS FCST BY GLOBAL MODELS
NEXT WEEK SHOULD BRING A SIG RELIEF TO THE HOT WEATHER OF THIS WEEKEND.
UPPER LEVEL LOW BEGINS TO FILL ON WED WITH WX CONDITIONS IMPROVING
SOMEWHAT ALTHOUGH CONSIDERABLE MID-HIGH LEVEL CLOUDS ARE LIKELY TO
PERSIST FOR SVRL MORE DAYS.

AVIATION...SHRA/TSRA AROUND THE USVI WILL CAUSE TEMPO MVFR CONDS
WITH AT TISX AND TIST TIL 31/12Z...WITH CIGS AROUND FL020-040 AND
REDUCTION IN VISIBILITY TO AROUND 3 MILES AS THE ACTIVITY AFFECTS
THE TERMINALS...OTHERWISE VCSH/VCTS IS LIKELY. VCTS IS ALSO POSSIBLE
FOR TNCM. THE REST OF THE TERMINALS SHOULD REMAIN VFR THROUGH THE
FORECAST PERIOD. AFTERNOON CONVECTION EXPECTED ACROSS NW-PR WHICH
MAY BRIEFLY AFFECT TJBQ BETWEEN 31/18Z AND 31/22Z.

MARINE...SOUTH OR SSE WINDS 10 KT OR LESS THROUGH SAT. TRADES
RETURN SAT NIGHT AND STRENGTHEN UP TO 20 KT. SEAS MAINLY 2-3 FT
THROUGH SUN THEN BUILD 5-7 FT BY MON NIGHT IN NNW SWELLS AND ENE
WIND WAVES. THIS LIKELY TO RESULT IN ROUGH SURF CONDITIONS WITH
HIGH RISK OF RIP CURRENTS ON ATLC AND NW PR BEACHES.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  89  80  88  81 /  40   0  10  10
STT  89  82  89  82 /  20  10  10  10

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...NONE.
&&

$$

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