Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 261608
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1208 PM AST THU MAR 26 2015

.UPDATE...FORECAST ON TRACK...NO CHANGES WERE INTRODUCED TO SHORT
TERM GRIDS. STILL EXPECT SOME SHOWERS DEVELOPING ACROSS W PR IN
THE AFTERNOON HOURS.

A GENERALLY FAIR AND MAINLY STABLE WEATHER PATTERN WILL PREVAIL
OVER THE NEXT FEW DAYS AS RIDGE ALOFT HOLDS ACROSS THE AREA.
ALTHOUGH PASSING SHOWERS ACROSS WINDWARD AREAS STILL 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...BECOMING SOUTHEASTERLY AS A SURFACE HIGH ACROSS THE
WESTERN ATLANTIC MOVES EAST AND A SURFACE BOUNDARY APPROACHES FROM
THE WEST.

&&

.AVIATION...VFR CONDS EXPECTED AT ALL TAF SITES THRU THE PERIOD.
BRIEF MVFR CONDS WILL REMAIN POSSIBLE BETWEEN 26/16Z AND 26/22Z
IN AND AROUND JMZ. EASTERLY WINDS 10 TO 15 KNOTS THROUGH 26/22Z
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.

&&

.PREV DISCUSSION... /ISSUED 524 AM AST THU MAR 26 2015/

SYNOPSIS...
BROAD MID/UPPER LEVEL RIDGE WILL REMAIN THE DOMINANT FEATURE
ACROSS THE NORTHEASTERN CARIBBEAN THROUGH THE UPCOMING WEEKEND.
THIS WILL SUPPORT FAIRLY STRONG SUBSIDENCE CAP INVERSION ACROSS
THE FORECAST AREA. BY LATE SUNDAY AND INTO MONDAY HOWEVER...THE
UPPER RIDGE IS TO SLIGHTLY ERODE IN RESPONSE TO A DEEP/AMPLIFYING
LONG WAVE TROUGH MOVING ACROSS THE WESTERN ATLANTIC. MEANWHILE...
STRONG SURFACE HIGH SURFACE WILL CONTINUE TO SHIFT EASTWARD ACROSS
THE WESTERN AND CENTRAL ATLANTIC DURING THE NEXT FEW DAYS. THIS
WILL RESULT IN A TIGHTENING OF THE LOCAL PRESSURE GRADIENT...
RESULTING IN MODERATE EASTERLY TRADE WINDS THROUGH THE END OF THE
WEEK. WINDS ARE TO BECOME MORE SOUTHEASTERLY OVER THE UPCOMING
WEEKEND AS THE SURFACE HIGH MOVES FURTHER EAST...AND A FRONTAL
BOUNDARY AND ASSOCIATED LOW LEVEL CONVERGENCE ZONE WILL APPROACH
THE REGION FROM THE NORTHWEST.

DISCUSSION...
MOSTLY FAIR WEATHER SKIES EXPECTED ACROSS MUCH OF THE FORECAST
AREA TODAY UNDER MODERATE EASTERLY TRADE WINDS. OCCASIONAL PATCHES
OF TRADE WIND MOISTURE WILL HOWEVER CONTINUE MOVE ACROSS THE REGION.
THIS WILL BE SUFFICIENT TO COMBINE WITH DAYTIME HEATING AND LOCAL
TERRAIN EFFECTS FOR SOME AFTERNOON SHOWER DEVELOPMENT. AFTERNOON
CONVECTION SHOULD BE FOCUSED PRIMARILY OVER PARTS OF THE WESTERN
INTERIOR SECTIONS OF PUERTO RICO. NO SIGNIFICANT RAINFALL ACCUMULATIONS
ARE EXPECTED AS SHOWER DEVELOPMENT WILL BE SUPPRESSED BY THE FAIRLY
STRONG CAP INVERSION.

SIMILAR CONDITIONS EXPECTED ON FRIDAY EXCEPT FOR THE SLIGHT INCREASE
IN THE EASTERLY TRADE WINDS WHICH WILL SUPPORT MORE STREAMER LIKE
AFTERNOON CONVECTION ACROSS PARTS OF THE ISLANDS.

FOR THE UPCOMING WEEKEND...EXPECT A GENERALLY FAIR AND MAINLY
STABLE WEATHER PATTERN TO PREVAIL...AS THE RIDGE ALOFT SHOULD
HOLD IN PLACE AND LIMIT THE SHOWER DEVELOPMENT. HOWEVER...THE
MODERATE EAST TO SOUTHEAST TRADE WINDS WILL CONTINUE TO BRING
PERIODS OF EARLY MORNING SHOWERS TO SOME OF ISLANDS...FOLLOWED BY
ISOLATED TO SCATTERED AFTERNOON SHOWERS MAINLY ACROSS THE INTERIOR
AND WEST TO NORTHWEST SECTIONS OF PUERTO RICO.

BY LATE SUNDAY AND INTO EARLY PART OF NEXT WEEK THE APPROACH OF A
FRONTAL BOUNDARY AND CONVERGENCE ZONE/SHEAR LINE WILL ALLOW FOR AN
INCREASE IN LOW LEVEL MOISTURE. THIS WILL INCREASE THE CHANCES FOR
MORE SHOWER DEVELOPMENT ACROSS THE COASTAL WATERS AND PARTS OF THE
ISLANDS.

AVIATION...MOSTLY VFR CONDITIONS EXPECTED THROUGH THE NEXT 24
HOURS. ISOLATED -SHRA EXPECTED ACROSS THE LOCAL FLYING AREA BUT ARE
NOT EXPECTED TO HAVE A SIGNIFICANT IMPACT ON THE LOCAL FLYING AREA.
LIGHT EAST TO EAST NORTHEAST WINDS AT 5-10 KNOTS DURING THE EARLY
MORNING HOURS INCREASING TO AROUND 15 KNOTS AND GUSTY AFTER 26/14Z.
SCATTERED SHRA EXPECTED ACROSS WESTERN PR THIS AFTERNOON...INDUCING
VCSH AT TJMZ...WITH POSSIBLE CIGS AT FL040 AND TEMPO SHRA AT THE
TJMZ TERMINAL AFTER 26/18Z WITH LOCAL MOUNTAIN OBSCURATIONS.

MARINE....MARINE WILL CONTINUE RELATIVELY TRANQUIL MOST OF TODAY...
BUT THE MODERATE TRADE WINDS WILL AID IN SLIGHTLY INCREASING SEAS
TO NEAR 6 FEET IN EXPOSED WATERS OVERNIGHT THROUGH FRIDAY. FOR NOW
SMALL CRAFT ADVISORIES ARE NOT EXPECTED...BUT SMALL CRAFT OPERATORS
SHOULD EXERCISE CAUTION FROM THEN ON AND INTO THE UPCOMING WEEKEND
MAINLY DUE TO THE MODERATE TO LOCALLY FRESH TRADE WINDS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  88  75  89  76 /  20  30  30  30
STT  86  75  86  75 /  20  30  30  30

&&

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

$$

23/27





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