Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 270247
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1047 PM AST THU MAR 26 2015

.UPDATE...A FEW SHOWERS AFFECTED PORTIONS OF WESTERN PR IN THE
AFTERNOON WITH RADAR ESTIMATES MAINLY AROUND HUNDREDTHS OF AN INCH
OF RAIN ACCUMULATING AND ONE ISOLATED AREA OVER MARICAO ESTIMATING
JUST OVER HALF AN INCH OF RAIN. AFTER THE SHOWERS DISSIPATED LATE
IN THE AFTERNOON...PARTLY CLOUDY SKIES REMAINED WITH LITTLE TO NO
SHOWER ACTIVITY DETECTED. NOW LATE IN THE EVENING A FEW LIGHT
PASSING SHOWERS ARE EXPECTED TO MOVE ACROSS THE LOCAL AREA AND
REMAIN THROUGH LATE TONIGHT. THE ACCUMULATIONS ARE NOT EXPECTED TO
BE SIGNIFICANT AND THESE SHOWERS SHOULD BE VERY BRIEF OVER ANY ONE
AREA. NO CHANGES WERE MADE TO THE INHERITED FORECAST. ISOLATED TO SCATTERED
SHOWERS IN THE MORNING ACROSS EASTERN PR...USVI...AND THE LOCAL
WATERS...THEN SCATTERED SHOWERS IN THE AFTERNOON ACROSS THE WESTERN
INTERIOR AND WESTERN SECTIONS OF PR. SIMILAR PATTERN EXPECTED ON
SATURDAY...MAYBE A BIT MORE SHOWERS ACROSS NW PR DUE TO THE WIND
FLOW AND THEN ON SUNDAY THE SHOWER COVERAGE MAY INCREASE AS
ADDITIONAL MOISTURE WILL MOVE IN.

&&

.AVIATION...VFR CONDS EXPECTED AT ALL TAF SITES THRU THE FORECAST
PERIOD. HOWEVER...BRIEF MVFR CONDS WILL REMAIN POSSIBLE AT TNCM AND
TKPK FROM 27/02Z TO 27/06Z AND AT TJMZ AND VCNTY FROM 27/17Z THROUGH
26/22Z. MTN OBSCURATIONS IN LUQUILLO RANGE 27/10Z-27/17Z AND
CORDILLERA CENTRAL AFT 27/16Z. EASTERLY WINDS 10 TO 15 KNOTS...
BECOMING LIGHT AND VARIABLE OVERNIGHT AT SURFACE...BUT REMAINING 15
TO 20 KNOTS UP TO FL080...SWITCHING TO WNW ABV FL150 AND INCRG TO 45
KT BY FL400.

&&

.MARINE...WINDS UP TO 20 KNOTS AND SEAS UP TO 6 FEET EXPECTED
TONIGHT INTO THE WEEKEND. LOCAL NEAR-SHORE BUOYS ARE AROUND 3 FEET
WITH THE OFF-SHORE BUOY 41043 NOW OVER 5 FEET. WE EXPECT SEAS TO
SLOWLY INCREASE UP TO 6 FEET ACROSS THE LOCAL OFFSHORE WATERS WITH
WINDS ALSO INCREASING SLIGHTLY.

&&

.PREV DISCUSSION... /ISSUED 401 PM AST THU MAR 26 2015/

SYNOPSIS...
BROAD MID/UPPER LEVEL RIDGE WILL REMAIN THE DOMINANT FEATURE
ACROSS THE NORTHEASTERN CARIBBEAN THROUGH THE UPCOMING WEEKEND.
A GENERALLY FAIR AND MAINLY STABLE WEATHER PATTERN WILL CONTINUE
DURING THIS PERIOD ACROSS THE FORECAST AREA...DUE TO STRONG
SUBSIDENCE ALOFT. BY LATE SUNDAY AND INTO MONDAY WEATHER
CONDITIONS ARE EXPECTED TO DETERIORATE AS THE UPPER RIDGE ERODE
IN RESPONSE TO A DEEP/AMPLIFYING LONG WAVE TROUGH MOVING ACROSS
THE WESTERN ATLANTIC. AT THE SURFACE...STRONG SURFACE HIGH
PRESSURE WILL CONTINUE TO BE THE DOMINANT WEATHER FEATURE DURING
THE NEXT FEW DAYS.

DISCUSSION...
A GENERALLY FAIR AND MAINLY STABLE WEATHER PATTERN WILL CONTINUE
TO PREVAIL FRIDAY AND THE UPCOMING WEEKEND AS RIDGE PATTERN ALOFT
HOLDS ACROSS THE FORECAST AREA. ALTHOUGH PASSING SHOWERS ACROSS
WINDWARD AREAS ARE EXPECTED FROM TIME TO TIME...WITH LIMITED
AFTERNOON CONVECTION OVER AND WEST OF THE CORDILLERA EACH DAY.

EASTERLY WINDS WILL REMAIN IN PLACE UNTIL SATURDAY...AS A STRONG
SURFACE HIGH PRESSURE DRIFT MOVES EAST INTO THE CENTRAL ATLANTIC.
THIS WILL RESULT IN A TIGHTENING OF THE LOCAL PRESSURE GRADIENT...
CREATING A MODERATE EASTERLY TRADE WINDS THROUGH THE END OF THE
WORK WEEK. OVER THE WEEKEND...WINDS ARE EXPECTED TO BECOME MORE
SOUTHEASTERLY...AS THE SURFACE HIGH MOVES FURTHER EAST...AND A
FRONTAL BOUNDARY AND ASSOCIATED LOW LEVEL CONVERGENCE ZONE WILL
APPROACH THE REGION FROM THE NORTHWEST.

BY LATE SUNDAY AND INTO MONDAY...THE UPPER LEVEL RIDGE IS
EXPECTED TO ERODES...INCREASING THE POTENTIAL FOR SHOWERS WITH
POSSIBLE ISOLATED THUNDERSTORMS GENERALLY ACROSS THE ATLANTIC
OFFSHORE WATERS.

AVIATION...VFR CONDS EXPECTED AT ALL TAF SITES THRU THE FORECAST
PERIOD. HOWEVER...BRIEF MVFR CONDS WILL REMAIN POSSIBLE THROUGH
26/22Z IN AND AROUND JMZ. EASTERLY WINDS 10 TO 15 KNOTS...BECOMING
LIGHT AND VARIABLE OVERNIGHT.

MARINE....WINDS AROUND 20 KNOTS WITH SEAS UP TO 6 FEET. 6 FEET
MAINLY ACROSS THE OFFSHORE ATLANTIC WATERS...ELSEWHERE NEAR 5
FEET. OVERNIGHT...MODERATE TRADE WINDS WILL AID IN SLIGHTLY
INCREASING SEAS TO NEAR 6 FEET IN EXPOSED WATERS. AT THIS
MOMENT...SMALL CRAFT ADVISORIES ARE NOT EXPECTED...BUT SMALL
CRAFT OPERATORS SHOULD EXERCISE CAUTION INTO THE UPCOMING WEEKEND
MAINLY DUE TO THE MODERATE TO LOCALLY FRESH TRADE WINDS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  89  75  90 /  30  30  30  30
STT  75  86  74  86 /  30  30  30  20

&&

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

$$

12/25




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