Area Forecast Discussion
Issued by NWS San Juan, PR

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193
FXCA62 TJSJ 141507
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1107 AM AST SUN FEB 14 2016

.UPDATE...
A SURGE OF MOISTURE IS MOVING ACROSS THE ISLANDS PRODUCING MOSTLY
CLOUDY SKIES WITH PASSING SHOWERS MAINLY OVER THE LOCAL WATERS AND
THE EASTERN HALF OF PUERTO RICO...ST THOMAS AND ST CROIX.
INSTABILITY HAS INCREASED ACROSS THE REGION AS AN UPPER LEVEL
TROUGH CONTINUES TO AMPLIFIED OVER THE REGION. THEREFORE...EXPECT
TRADE WIND SHOWERS ACROSS EASTERN PUERTO RICO AND THE U.S.V.I.
DURING THE REST OF THE MORNING FOLLOWED BY AFTERNOON CONVECTION
ACROSS THE INTERIOR AND WESTERN SECTIONS OF PUERTO RICO. IN
ADDITION...THERE IS A SLIGHT RISK OF THUNDERSTORM DEVELOPMENT OVER
THE INTERIOR AND WESTERN SECTIONS OF PR...AS WAS INDICATED BY THE
GFS GALVEZ-DAVIDSON INDEX...GDI.

&&

.AVIATION...CLOUDS/SCT SHRA ARE MOVING ACROSS THE FLYING AREA AND
WILL CONTINUE THRU THE FORECAST PRD. THE LEEWARD AND USVI
TAF SHOULD CONTINUE TO EXPERIENCE PASSING -SHRA/SHRA FROM TIME TO
TIME. THEN...SHRA/TSRA COULD DEVELOPED OVER THE INTERIOR AND
WEST SECTIONS OF PUERTO RICO LATER IN THE AFTERNOON...RESULTING IN
VCTS TJMZ/TJBQ BETWEEN 17-21Z. SOME OF THIS TSRA COULD MOVE OVER
TJBQ OR TJMZ DURING THAT PERIOD TO PRODUCE BRIEF MVFR CONDITIONS.
SFC WINDS FORM THE E AT 10-15 KT WITH HIGHER GUSTS NEAR SHRA/TSRA.

&&

.MARINE...THE LOCAL BUOY NETWORK REPORTED SEAS AT LESS THAN 5 FT
AND WINDS AT LESS THAN 15 KT WITH HIGHER GUSTS. THE MARINE
CONDITIONS SHOULD DETERIORATE ACROSS THE OFFSHORE WATERS BY
EARLY MONDAY MORNING AS SEAS INCREASE AROUND 7 FT ACROSS THE
ATLANTIC AND THEN ACROSS THE CARIBBEAN OFFSHORE WATERS DURING THE
AFTERNOON. THEREFORE...SMALL CRAFT ADVISORIES WILL STARTED WILL
BE IN EFFECT FOR THOSE WATERS AFTER 2 AM AST ON MONDAY.

&&

.PREV DISCUSSION... /ISSUED /

SYNOPSIS...A MID TO UPPER LEVEL TROUGH WILL CONTINUE TO AMPLIFY
ACROSS THE WESTERN ATLANTIC...PASSING NORTH OF THE ISLANDS THROUGH
EARLY MONDAY. UPPER RIDGE BUILDS LATER DURING THE WEEK. SURFACE
HIGHS WILL PROMOTE AN EAST TO SOUTHEAST WIND FLOW ACROSS THE
EASTERN CARIBBEAN DURING THE NEXT SEVERAL DAYS. FRONTAL BOUNDARY
WILL REMAIN NORTH OF THE AREA...WITH ASSOCIATED INDUCED TROUGH
AFFECTING THE LOCAL ISLANDS THROUGH LATE MONDAY NIGHT.

DISCUSSION...SHOWERS INCREASED OVER THE WATERS WITH A FEW OF
THEM REACHING SECTIONS OF THE NORTHERN U.S. VIRGIN ISLANDS AND
EASTERN PR DURING THE OVERNIGHT HOURS. RAINFALL OVER LAND AREAS WAS
GENERALLY LESS THAN A TENTH OF AN INCH. MIMIC PWAT CONTINUES TO
INDICATE THAT ADDITIONAL MOISTURE IS MOVING TOWARD THE AREA FROM
THE LEEWARD ISLANDS. THEREFORE...SCATTERED SHOWERS ARE EXPECTED
THROUGH THE REST OF THE MORNING HOURS ACROSS THE ISLANDS. THEN IN
THE AFTERNOON...SCATTERED TO NUMEROUS SHOWERS SHOULD DEVELOP OVER
THE MOUNTAIN RANGES OF PR AND SPREAD A LITTLE MORE OVER WESTERN
PUERTO RICO. ISOLATED THUNDERSTORMS CANT BE RULED OUT DUE TO THE
PROXIMITY OF THE UPPER TROUGH.

AT LEAST UNTIL LATE MONDAY NIGHT...LOW LEVEL MOISTURE WILL
CONTINUE TO INCREASE AS THE INDUCED SFC TROUGH MOVES THROUGH THE
FORECAST AREA. BEST MOISTURE ADVECTION IS EXPECTED ON MONDAY. BEST
PWAT WILL POOL TONIGHT INTO EARLY MONDAY MORNING. THEREFORE...THE
FREQUENCY AND COVERAGE OF SHOWERS WILL INCREASE ACROSS THE USVI
AND THE EASTERN HALF OF PUERTO RICO DURING THAT PERIOD...AND WILL
THEN SPREAD ACROSS THE WESTERN HALF OF PUERTO RICO IN THE
AFTERNOON AS PWAT PEAKS OVER PR AROUND 15/18Z.

WINDS WILL INCREASE LATE MONDAY AS A STRONG HIGH PRESSURE MOVES
OVER THE WESTERN ATLANTIC AND INTO THE NORTH CENTRAL ATLANTIC. LOW
LEVEL MOISTURE WILL THEN ERODE WITH A SEASONABLE WEATHER PATTERN
EXPECTED TUESDAY THROUGH FRIDAY AS SUB-TROPICAL RIDGE BUILDS ALOFT.
FOR LATE FRIDAY AND THE UPCOMING WEEKEND...LATEST GUIDANCE
CONTINUES TO SUGGEST A SURFACE FRONT REACHING THE LOCAL ISLANDS
WITH A SHARP INCREASE IN LOW LEVEL MOISTURE.

AVIATION...CLOUDS AND SCT SHRA COULD AFFECT THE FLYING AREA
THRU THE FORECAST PERIOD. LEEWARD AND USVI TERMINAL COULD EXPERIENCE
-SHRA AT TIMES THRU 14Z. THEN...A FEW SHOWERS COULD DEVELOP OVER
WESTERN INTERIOR AND WEST SECTIONS OF PUERTO RICO AFTERNOON AND MAY
RESULT IN VCTS TJMZ/TJBQ BETWEEN 17-21Z. HOWEVER...NO SIG IMPACTS
ARE ANTICIPATED AT THIS TIME. LOW LEVEL WINDS WILL CONTINUE MAINLY
EAST AT 10-15 KTS.

MARINE...SMALL CRAFTS SHOULD CONTINUE TO EXERCISE CAUTION ACROSS
THE OFFSHORE ATLANTIC WATERS DUE TO SEAS UP TO 6 FEET. SEAS BELOW
5 FEET ARE EXPECTED ELSEWHERE. WINDS WILL CONTINUE FROM THE EAST
AT 10-15 KNOTS. ISOLATED THUNDERSTORMS ARE POSSIBLE OVER THE
COASTAL WATERS OF WESTERN PUERTO RICO THROUGH AT LEAST MONDAY
AFTERNOON AS SURFACE TROUGH MOVES ACROSS THE FORECAST AREA. WINDS
AND SEAS WILL INCREASE DURING THE FIRST HALF OF THE WEEK AS A
STRONG HIGH PRESSURE MOVES OVER THE WESTERN ATLANTIC.
THEREFORE...SMALL CRAFT ADVISORIES WILL BE REQUIRED LATER TODAY
FOR THE ATLANTIC WATERS AND ANEGADA PASSAGE.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  86  75  85  74 /  30  50  50  40
STT  84  74  84  75 /  50  60  60  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
AM...NONE.
&&

$$

27/23



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