Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 270906
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
506 AM AST FRI MAR 27 2015

.SYNOPSIS...
BROAD MID TO UPPER LEVEL RIDGE WILL PERSIST ACROSS THE NORTHEASTERN
CARIBBEAN TODAY AND THROUGH THE EARLY PARTS OF THE UPCOMING WEEKEND.
THIS WILL ALLOW FOR FAIRLY STRONG SUBSIDENCE CAP WITH OVERALL DRY
CONDITIONS ALOFT.  HOWEVER...BY LATE SUNDAY AND INTO MONDAY WEATHER
CONDITIONS THE UPPER RIDGE IS TO GRADUALLY ERODE IN RESPONSE TO A
DEEP/AMPLIFYING LONG WAVE TROUGH MOVING ACROSS THE WESTERN ATLANTIC.
STRONG SURFACE HIGH PRESSURE NORTH OF THE REGION WILL CONTINUE TO SHIFT
FARTHER EAST INTO THE CENTRAL ATLANTIC ATLANTIC TODAY. THIS WILL ALLOW
THE MODERATE EASTERLY TRADE WINDS TO BECOME MORE SOUTHEASTERLY ACROSS
THE NORTHEASTERN CARIBBEAN DURING THE NEXT SEVERAL DAYS. MEANWHILE
A DISSIPATING FRONTAL BOUNDARY WILL MOVE ACROSS THE WESTERN ATLANTIC
AND APPROACH THE REGION FROM THE NORTHWEST LATE SUNDAY INTO MONDAY.

&&

.DISCUSSION...
LATEST SATELLITE IMAGERY AND THE NATIONAL WEATHER SERVICE DOPPLER
WEATHER RADAR SHOWED PATCHES OF SHALLOW LOW LEVEL MOISTURE AND A
FEW VERY LIGHT SHOWERS MOVING ACROSS THE COASTAL WATERS IN THE
PREVAILING EASTERLIES. HOWEVER LITTLE OR NO PRECIPITATION WAS
OBSERVED OR DETECTED OVER THE LAND AREAS SO FAR THIS MORNING.

BY THE MID-MORNING HOURS A FEW LIGHT PASSING SHOWERS MAY BRUSH
THE EAST COASTAL SECTIONS OF SOME OF THE ISLANDS. DURING THE REST
OF THE DAY...MOSTLY FAIR WEATHER SKIES WILL PREVAIL ACROSS MOST OF
THE ISLANDS. LOW LEVEL MOISTURE ADVECTION ALONG WITH DAYTIME HEATING
AND LOCAL EFFECTS MAY STILL LEAD TO INCREASED CLOUDINESS AND ISOLATED
TO SCATTERED AFTERNOON SHOWERS MAINLY ACROSS PARTS OF THE INTERIOR
AND WEST SECTIONS OF PUERTO RICO. THIS ACTIVITY WILL BE OF SHORT
DURATION AND QUICK PASSING DUE TO THE INCREASING TRADES AND STRONG
SUBSIDENCE ALOFT.

OVER THE WEEKEND...MORE OF THE SAME WEATHER PATTERN ON SATURDAY
AND INTO EARLY SUNDAY WITH MOSTLY FAIR WEATHER SKIES PREVAILING
AND LESSER CHANCE FOR SHOWER ACTIVITY DURING THE AFTERNOON AND
EARLY MORNING HOURS. BY LATE SUNDAY INTO THE EARLY PART OF NEXT WEEK...
LATEST GFS MODEL GUIDANCE MODEL CONTINUED TO SUGGEST THE DISSIPATING
FRONTAL BOUNDARY/SHEAR LINE TO STALL JUST NORTH OF THE REGION. STILL
EXPECT THERE WILL BE SUFFICIENT LOW LEVEL MOISTURE TRANSPORT AND
CONVERGENCE ACROSS THE FORECAST AREA TO INCREASE THE CHANCES FOR SHOWER
DEVELOPMENT ACROSS THE COASTAL WATERS AND PARTS OF THE ISLANDS. IN
ADDITION...THE GRADUAL EROSION OF THE UPPER LEVEL RIDGE BY LATE SUNDAY
AND MONDAY...WILL ALSO SLIGHTLY INCREASE THE POTENTIAL FOR ONE OR TWO
ISOLATED THUNDERSTORMS IN RESPONSE TO WEAKENING CAP INVERSION. FOR
NOW WILL CONTINUE TO MONITOR THE MOISTURE ADVECTION AND NOT INCLUDE
THUNDERSTORMS IN THE FORECAST JUST YET.

&&

.AVIATION...MOSTLY VFR CONDITIONS EXPECTED THROUGH THE NEXT 24 HOURS
ACROSS THE LOCAL FLYING AREA. ISOLATED -SHRA EXPECTED ACROSS THE
LOCAL FLYING AREA BUT ARE NOT EXPECTED TO HAVE A SIGNIFICANT IMPACT
ACROSS THE LOCAL TAF SITES. LIGHT EAST TO EAST NORTHEAST WINDS AT
5-10 KNOTS DURING THE EARLY MORNING HOURS INCREASING TO AROUND 15
KNOTS AND GUSTY AFTER 27/14Z. 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 27/18Z WITH LOCAL
MOUNTAIN OBSCURATIONS.

&&

.MARINE...LATEST DATA FROM THE BUOY 41043 SUGGEST SEAS NOW AROUND
7 FEET AROUND 9 SECONDS AS THE EASTERLY TRADE INCREASE ACROSS THE
REGION. MEANWHILE... THE LOCAL NEAR-SHORE BUOY 41053 SUGGEST SEAS
BETWEEN 3-4 FEET. EXPECT WINDS TO CONTINUE TO INCREASE UP TO 20
KNOTS AND SEAS OF 6 FEET OR LESS ACROSS MOST OF THE REGIONAL WATERS
TODAY AND INTO THE UPCOMING WEEKEND. SMALL CRAFT OPERATORS SHOULD
THEREFORE EXERCISE CAUTION.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  89  75  89  75 /  30  30  30  10
STT  86  75  86  75 /  30  30  20  30

&&

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

$$

72/09





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