Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 310959
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
559 AM AST SAT JAN 31 2015

.SYNOPSIS...MID TO UPPER LEVEL TROUGH ENTERING THE WESTERN
ATLANTIC WILL MOVE OVER THE OPEN ATLANTIC WATERS THROUGH THE
WEEKEND. AVAILABLE MOISTURE WILL REMAIN CONSTANT FOR THE NEXT FEW
DAYS. SURFACE HIGH PRESSURE BUILDS TO THE NORTH OF THE LOCAL AREA
EARLY NEXT WEEK...TIGHTENING THE LOCAL PRESSURE GRADIENT.


&&

.DISCUSSION...ISOLATED TO LOCALLY SCATTERED PASSING SHOWERS WERE
OBSERVED OVER THE LOCAL WATERS THROUGH THE OVERNIGHT HOURS. OF
THOSE SHOWERS ONLY A FEW OF THEM BRIEFLY AFFECTED ANY LAND AREAS
AND THE ACCUMULATIONS WERE MINIMAL IF ANY. UPPER LEVEL TROUGH AND
ASSOCIATED INDUCED WEAK SURFACE TROUGH COMBINED WITH THE
LINGERING MOISTURE WILL HELP WITH THE DEVELOPMENT OF SHOWERS AND
POSSIBLE THUNDERSTORMS ACROSS THE INTERIOR INTO THE WEST AND SOUTHWESTERN
PORTIONS OF PR THIS AFTERNOON. ISOLATED TO SCATTERED SHOWERS ARE
EXPECTED ELSEWHERE. FOR THE NEXT FEW DAYS...ISOLATED TO SCATTERED
PASSING SHOWERS ARE EXPECTED ACROSS THE LOCAL WATERS AS WELL AS
ACROSS THE USVI AND THE NORTHERN AND EASTERN SECTIONS OF PR IN THE
OVERNIGHT HOURS...WHILE DURING THE AFTERNOON YOU CAN EXPECT
SHOWERS DEVELOPING MAINLY IN AREAS WHERE SEA BREEZE CONVERGENCE
OCCURS...WITH A SLIGHT CHANCE OF SHOWERS ELSEWHERE.

AS A SURFACE HIGH PRESSURE BUILDS AND MOVES TO THE NORTH OF THE
LOCAL AREA...THE LOCAL PRESSURE GRADIENT WILL TIGHTEN...WHICH WILL
INCREASE THE WIND SPEEDS. THIS MAY CAUSE THE SHOWERS THAT DO
DEVELOP TO MOVE SLIGHTLY FASTER THAT THOSE EXPECTED TODAY. MID TO
UPPER LEVEL RIDGE WILL MOVE INTO THE LOCAL AREA EARLY NEXT
WEEK...WHICH SHOULD LIMIT THE VERTICAL DEVELOPMENT OF AFTERNOON
CONVECTION AND THEREFORE LIMITING THE CHANCES OF THUNDERSTORM
DEVELOPMENT EARLY NEXT WEEK.


&&

.AVIATION...MOSTLY VFR CONDITIONS EXPECTED AT ALL TAF SITES THRU
31/17Z...WITH VCSH POSSIBLE IN AND AROUND JBQ/JSJ/IST. AFT 31/17Z...
SHRA/TSRA DEVELOPMENT EXPECTED ACROSS SW PR...THIS MAY CAUSE MVFR
CONDITIONS AND MOUNTAIN OBSCURATIONS AT JMZ/JPS THRU 31/22Z. ENE
WINDS 5 TO 10 KNOTS WITH SOME SEA BREEZE VARIATIONS.


&&

.MARINE...SMALL CRAFT SHOULD EXERCISE CAUTION AS SEAS ARE EXPECTED
TO BE UP TO 6 FEET ACROSS THE ATLANTIC WATERS. ELSEWHERE THE SEAS
WILL BE GENERALLY 3 TO 5 FEET. HOWEVER A PULSE OF A NORTHWESTERLY
SWELL IS EXPECTED TO START INVADING THE LOCAL WATERS LATE TONIGHT.
THIS SWELL WILL AFFECT THE LOCAL WATERS FROM THE NORTHWEST THEN
GRADUALLY BECOMING NORTHEASTERLY SWELL BY TUESDAY. SEAS WILL
BECOME HAZARDOUS STARTING LATE TONIGHT AND THEREFORE A SMALL CRAFT
ADVISORY WILL GO INTO EFFECT STARTING MIDNIGHT TONIGHT ACROSS THE
OFFSHORE ATLANTIC WATERS FOR SEAS OF 7 FEET ON SUNDAY AND UP TO 8
FEET ON MONDAY. THE WATERS IN THE NEARSHORE AND LOCAL PASSAGES
WILL BECOME HAZARDOUS STARTING LATE SUNDAY NIGHT...STAY TUNED FOR
POSSIBLE ISSUANCE OF A SMALL CRAFT ADVISORY ACROSS THE NEARSHORE
WATERS AND LOCAL PASSAGES STARTING LATE SUNDAY NIGHT OR MONDAY.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  84  74  81  73 /  50  50  50  40
STT  84  73  83  75 /  50  50  50  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM AST WEDNESDAY
     FOR ATLC WATERS OF PUERTO RICO AND USVI FROM 10NM TO 19.5N.

&&

$$

23/25




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