Area Forecast Discussion
Issued by NWS San Juan, PR

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492
FXCA62 TJSJ 140124 AAA
AFDSJU

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
924 PM AST SAT FEB 13 2016

.UPDATE...SHOWERS FORMED OVER WESTERN PUERTO RICO DURING THE LATE
AFTERNOON AND EVENING HOURS AND DESPITE THE EAST SOUTHEASTERLY
FLOW SOME SHOWERS OVER SOUTHWEST PUERTO RICO MOVED OFFSHORE TO THE
SOUTH AND CONTINUED TO GROW. SHOWERS WERE ALSO SEEN OVER AND
AROUND MONA ISLAND AND ALSO IN THE ANEGADA PASSAGE AND DOWN STREAM
FROM SAINT CROIX. SHOWERS OVER NORTHWEST PUERTO RICO LEFT UP TO
2.5 INCHES IN PARTS OF THE CAMUY AND LARES MUNICIPALITIES. THE
MOISTURE IN THE 14/00Z SOUNDING HAS INCREASED SLIGHTLY IN THE LAST
24 HOURS WITH TOPS OF THE MOISTURE JUST UNDER 10 KFT.

&&

.DISCUSSION...SHOWERS OVER LAND ARE EXPECTED TO CONTINUE TO MOVE
WESTWARD AND WEAKEN AND SHOULD LEAVE PUERTO RICO RAIN-FREE BY
MIDNIGHT. SHOWERS OVER THE WATER WILL INCREASE SLOWLY OVERNIGHT.
FORECAST OVERNIGHT CALLED FOR SHOWERS TO INCREASE OVER EASTERN
PUERTO RICO AND THE NORTHERN U.S. VIRGIN ISLANDS DURING THE
MORNING HOURS AND MIMIC PRODUCTS DO CONFIRM THAT SOME MOISTURE IS
MOVING TOWARD THE AREA FOR AN EARLY MORNING ARRIVAL. SHOWERS
IN THE AFTERNOON SHOULD SPREAD A LITTLE MORE OVER WESTERN PUERTO
RICO AND SEEM MORE LIKELY THAN THEY WERE TODAY...THEREFORE HAVE
UPDATED THE GRIDS FOR THIS AND MADE SLIGHT ADJUSTMENTS IN THE MIN
AND MAX TEMPERATURES FOR THE NEXT 24 HOURS.

&&

.AVIATION...MAINLY VFR CONDITIONS WILL PREVAIL ACROSS ALL TAF SITES
THROUGH 15/00Z. SOME CLOUDINESS AND ISOLD SHRA COULD AFFECT THE ERN
TERMINALS OVERNIGHT AND WIL MENTION VCSH ON TIST...TISX AND
TNCM/TKPK BUT NO SIGNIFICANT IMPACTS EXPECTED. A FEW SHOWERS COULD
DEVELOP OVER WESTERN INTERIOR AND WEST SECTIONS OF PUERTO RICO
SUNDAY AFTERNOON AND MAY RESULT IN VCSH TJMZ/TJBQ BETWEEN 17-21Z.
LOW LEVEL WINDS WILL CONTINUE MAINLY EAST AT 10-15 KTS.

&&

.MARINE...WINDS AND SEAS WILL REACH A MINIMUM OVERNIGHT...BUT WILL
BEGIN TO INCREASE AGAIN ON SUNDAY. SMALL CRAFT ADVISORIES MAY BE
NEEDED SUNDAY NIGHT...BUT ARE EXPECTED TO BE IN EFFECT BY MONDAY
OVER OUTER WATERS AND PASSAGES FOR SEAS UP TO 7 FEET AS WINDS
INCREASE AND SOME SWELL FROM THE NORTH NORTHWEST ENTERS THE AREA.
ALSO CURRENT INDICATIONS ARE THAT THE RISK OF RIP CURRENTS WILL
RETURN TO HIGH ON MONDAY MORNING.

&&

.PREV DISCUSSION... /ISSUED 311 PM AST SAT FEB 13 2016/

SYNOPSIS...A MID TO UPPER LEVEL TROUGH WILL CONTINUE TO AMPLIFY
ACROSS THE WESTERN ATLANTIC...MOVING NORTH OF THE LOCAL ISLANDS.
MIGRATORY SURFACE HIGHS WILL PROMOTE AN EAST TO SOUTHEAST WIND
FLOW ACROSS THE EASTERN CARIBBEAN DURING THE NEXT SEVERAL DAYS.
SURFACE FRONT WILL STALL NORTH OF THE AREA...WITH ITS ASSOCIATED
INDUCED TROUGH AFFECTING THE LOCAL ISLANDS SUNDAY AND MONDAY.

DISCUSSION...MOSTLY SUNNY SKIES PREVAILED EARLY IN THE MORNING...
BECOMING PARTLY TO MOSTLY CLOUDY IN THE AFTERNOON. SHOWER ACTIVITY
INCREASED ACROSS THE AREA AS A PATCH OF CLOUDINESS AND MOISTURE
MOVED ACROSS THE EASTERN CARIBBEAN. SO FAR...RAINFALL ACCUMULATIONS
ASSOCIATED WITH THIS FEATURE WERE MINIMAL SO FAR.

LOW LEVEL MOISTURE WILL CONTINUE TO POOL ACROSS THE LOCAL ISLANDS
AS THE AFOREMENTIONED INDUCED TROUGH REACHES THE AREA SUNDAY AND
MONDAY. THIS...IN COMBINATION WITH THE PROXIMITY OF THE UPPER
TROUGH WILL RESULT IN A BETTER CHANCE FOR PERIODS OF SHOWERS
SUNDAY AFTERNOON THROUGH AT LEAST EARLY TUESDAY. BEST MOISTURE
ADVECTION IS EXPECTED ON MONDAY...AND THEREFORE THE BEST AREAL
COVERAGE OF SHOWERS AS WELL. ATTM DECIDED TO KEEP THE THUNDERSTORMS
ISOLATED AND DURING THE AFTERNOON HOURS SUNDAY AND MONDAY...DUE
TO THE LACK OF UPPER VENTILATION. HAVING SAID THAT...EXPECT
PASSING SHOWERS ACROSS THE USVI AND THE EAST COASTAL AREAS OF PR
TONIGHT... WITH SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING
ACROSS NORTHWEST PR TOMORROW AFTERNOON. SUNDAY NIGHT AND INTO
MONDAY...THE FREQUENCY OF SHOWER ACTIVITY WILL INCREASE ACROSS
THE USVI AND THE EASTERN HALF OF PUERTO RICO AND WILL THEN SPREAD
ACROSS THE WESTERN HALF OF PUERTO RICO IN THE AFTERNOON.

WINDS WILL INCREASE TUESDAY AS A STRONG HIGH PRESSURE MOVES OVER
THE WESTERN ATLANTIC AND INTO THE NORTH CENTRAL ATLANTIC. IN
ADDITION...RIDGE ALOFT WILL BUILD BACK FROM THE SOUTH...AND HOLD
THROUGH THE END OF THE WORK WEEK. AS A RESULT...LOW LEVEL MOISTURE
WILL THEN ERODE WITH A SEASONABLE WEATHER PATTERN EXPECTED TUESDAY
THROUGH FRIDAY. 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...VFR CONDITIONS WILL PREVAIL ACROSS ALL TAF SITES THROUGH
THE FORECAST PERIOD. SOME CLOUDINESS AND SHRA ARE EXPECTED OVER
WESTERN INTERIOR AND WEST SECTIONS OF PUERTO RICO THIS AFTERNOON.
THIS MAY RESULT IN VCSH AND BRIEF MVFR CIGS AT TJMZ BETWEEN 17-
21Z. LOW LEVEL WINDS WILL CONTINUE MAINLY EAST AT 10-15 KTS.

MARINE...SMALL CRAFT OPERATORS SHOULD EXERCISE CAUTION ACROSS
THE OFFSHORE ATLANTIC DUE TO SEAS 4-6 FEET. ELSEWHERE...SEAS UP
TO 5 FEET ARE EXPECTED UNDER EAST SOUTHEAST WINDS AT LESS THAN
18 KNOTS. WINDS AND SEAS WILL INCREASE EARLY NEXT WEEK AS A
STRONG HIGH PRESSURE MOVES OVER THE WESTERN ATLANTIC.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  73  86  73  85 /  30  30  50  50
STT  74  86  73  84 /  50  50  50  50

&&

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

$$

08/12



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