Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 011601
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1201 PM AST SUN FEB 1 2015

.UPDATE...ISOLATED TO SCATTERED SHOWERS WERE OBSERVED DURING THE
EARLY MORNING ACROSS THE LOCAL AREA AND THE SURROUNDING COASTAL
WATERS. THIS ACTIVITY DISSIPATED BY MORNING AND AT THIS TIME
THERE IS NOT SIGNIFICANT PRECIPITATION OVER LAND AREAS. THE USVI
REMAINED FAIRLY DRY WITH ONLY A FEW SPRINKLES. LATEST SATELLITE
PICTURES AND RADAR OBSERVATIONS INDICATED A RELATIVELY DRIER AIR
MOVING ACROSS THE LOCAL ISLANDS TODAY. HOWEVER THERE MAY STILL BE
ENOUGH MOISTURE TO INDUCE THE DEVELOPMENT OF ISOLATED TO SCATTERED
SHOWERS THIS AFTERNOON...ESPECIALLY ACROSS THE SOUTHWESTERN
QUADRANT OF PUERTO RICO. WIND SPEED WILL INCREASE THIS AFTERNOON
IN RESPONSE TO A STRONG SURFACE HIGH PRESSURE TO THE NORTH
OF THE LOCAL ISLANDS. AN UPPER LEVEL RIDGE IS EXPECTED TO BUILD
OVER THE AREA FOR THE NEXT SEVERAL DAYS. THIS FEATURE WILL LIMIT
THE SHOWERS AND THUNDERSTORMS DEVELOPMENT OVER THE REGION FOR THE
SEVERAL DAYS.

&&

.AVIATION...MOSTLY VFR CONDITIONS ARE EXPECTED ACROSS THE LOCAL
FLYING AREA THIS AFTERNOON AND TONIGHT...WITH VCSH POSSIBLE IN
AND AROUND JBQ/JSJ/IST. AFTER 01/18Z... SHRA DEVELOPMENT EXPECTED
ACROSS SOUTHWEST PR...THIS MAY CAUSE MVFR CONDITIONS AT JMZ/JPS
THRU 01/22Z. NE WINDS OF 10-20 KT WITH SOME SEA BREEZE VARIATIONS.

&&

.MARINE...NOT CHANGES FROM PREVIOUS REASONING.

&&

.PREV DISCUSSION... /ISSUED 602 AM AST SUN FEB 1 2015/

SYNOPSIS...SURFACE HIGH PRESSURE WILL BUILD ACROSS THE WESTERN
ATLANTIC...MOVING TO THE EAST AND PASSING TO THE NORTH OF THE
LOCAL AREA EARLY THIS WEEK WHILE A SURFACE LOW MOVES ALONG THE
EAST COAST OF THE US. PRESSURE GRADIENT WILL TIGHTEN LATER TODAY
INTO MONDAY WHILE THE SURFACE HIGH PASSES TO OUR NORTH. UPPER
RIDGE IS DEVELOPING JUST WEST OF THE LOCAL AREA AND WILL MOVE OVER
THE LOCAL AREA EARLY THIS WEEK...REMAINING IN PLACE FOR THE FIRST
HALF OF THE WEEK.

DISCUSSION...ISOLATED TO LOCALLY SCATTERED SHOWERS WERE OBSERVED
DURING THE OVERNIGHT HOURS ACROSS THE LOCAL AREA...MAINLY
AFFECTING THE LOCAL WATERS AS WELL AS THE NORTH AND EASTERN
SECTION OF PR. THE USVI REMAINED FAIRLY DRY WITH ONLY A FEW
SPRINKLES. FOR THE MORNING HOURS THE REMAINING SHOWERS ARE EXPECTED
TO GRADUALLY DISSIPATE. SATELLITE DERIVED PRECIPITABLE WATER
IMAGERY INDICATES THAT THERE IS DRIER AIR TO THE NORTH OF THE
LOCAL AREA. MODEL GUIDANCE INDICATES THAT THE DRIER AIR SHOULD
START MOVING INTO THE LOCAL ISLANDS TODAY AND TONIGHT. HOWEVER
THERE MAY STILL BE ENOUGH MOISTURE TO CAUSE ISOLATED TO LOCALLY
SCATTERED SHOWERS IN THE AFTERNOON...ESPECIALLY ACROSS THE
SOUTHWESTERN QUADRANT OF PR SINCE THAT IS THE AREA HIGH HIGHEST
LOW LEVEL CONVERGENCE. HAVING SAID THAT...SLIGHTLY STRONGER WINDS ARE
ALSO EXPECTED LATER TODAY INTO TOMORROW AS THE PRESSURE GRADIENT
TIGHTENS OVER THE AREA...WHICH MEANS THAT THE SEA BREEZE
CONVERGENCE TODAY ACROSS SW-PR WILL LIKELY BE MINIMAL.
THEREFORE...NO MORE THAN SCATTERED SHOWERS ARE EXPECTED.

THE BUILDING UPPER RIDGE WHICH IS EXPECTED TO DOMINATE THE AREA
FOR MUCH OF THIS WEEK WILL LIMIT THE CHANCES OF THUNDERSTORM
DEVELOPMENT FOR THIS WEEK AND THE RELATIVELY DRIER AIR MOVING IN
WILL ALSO LIMIT THE PROBABILITIES OF SIGNIFICANT SHOWERS TO
DEVELOP. SO ISOLATED TO LOCALLY SCATTERED SHOWERS ARE POSSIBLE BUT
THE ACCUMULATIONS WILL PROBABLY NOT BE THAT MUCH DUE TO THE LACK
OF MOISTURE THAT IS EXPECTED. THE LATEST GFS MODEL HAS THE
PRECIPITABLE WATER VALUES FOR MONDAY ONWARDS AT 1.35 INCHES OR
LESS...SO NOT MUCH MORE THAN A FEW PASSING SHOWERS IN THE
OVERNIGHT HOURS AND THEN SOME SHOWER DEVELOPMENT IN THE AFTERNOONS
ARE EXPECTED. THE AFTERNOON SHOWERS WILL PROBABLY BE IN AREAS OF
HIGHEST SEA BREEZE CONVERGENCE. THIS PATTERN IS EXPECTED FOR MUCH
OF THIS WEEK.

AVIATION...MOSTLY VFR CONDITIONS EXPECTED AT ALL TAF SITES THRU
01/17Z...WITH VCSH POSSIBLE IN AND AROUND JBQ/JSJ/IST. AFT 01/17Z...
SHRA DEVELOPMENT EXPECTED ACROSS SW PR...THIS MAY CAUSE MVFR
CONDITIONS AT JMZ/JPS THRU 01/22Z. NE WINDS OF 10-20 KT WITH SOME
SEA BREEZE VARIATIONS.

MARINE...NORTHERLY SWELLS WILL INVADE AND GRADUALLY SPREAD
ACROSS THE ATLANTIC WATERS AND LOCAL PASSAGES TODAY AND INTO EARLY NEXT WEEK.
THIS ALONG WITH THE INCREASING TRADE WINDS WILL LEAD TO CHOPPY
AND HAZARDOUS SEAS ACROSS THE OFFSHORE ATLANTIC WATERS BY THIS
AFTERNOON. THE SMALL CRAFT ADVISORY FOR THE OFFSHORE ATLANTIC
WATERS AND THE MONA PASSAGE WILL ALSO COVER THE OFFSHORE CARIBBEAN
WATERS AS WELL AS NEAR-SHORE WATERS STARTING MIDNIGHT TONIGHT. FOR
MONDAY AND TUESDAY...THE INCREASING NORTHERLY SWELL ACTION AND
ROUGH SEAS WILL INCREASE THE RISK OF DANGEROUS RIP CURRENTS AS
WELL AS DETERIORATING SURF ZONE CONDITIONS. PLEASE REFER TO THE
LATEST COASTAL WATERS FORECAST AND MARINE WEATHER STATEMENT ISSUED
BY THE NATIONAL WEATHER SERVICE WFO SAN JUAN PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  83  73  85  74 /  20  40  40  20
STT  84  73  83  75 /  20  40  40  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...
VI...
COASTAL WATERS...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM AST TUESDAY
     FOR ANEGADA PASSAGE SOUTHWARD TO 17N-CARIBBEAN WATERS OF
     PUERTO RICO FROM 10 NM TO 17N-COASTAL WATERS OF NORTHERN
     PUERTO RICO OUT 10 NM-COASTAL WATERS OF NORTHERN USVI AND
     CULEBRA OUT 10 NM-COASTAL WATERS OF NORTHWESTERN PUERTO
     RICO OUT 10 NM-COASTAL WATERS OF SOUTHERN USVI VIEQUES AND
     EASTERN PUERTO RICO OUT 10 NM.

     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM AST TUESDAY
     FOR MONA PASSAGE SOUTHWARD TO 17N.

     SMALL CRAFT ADVISORY UNTIL 6 PM AST TUESDAY FOR ATLC WATERS OF
     PUERTO RICO AND USVI FROM 10NM TO 19.5N.

&&

$$

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