Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 020936
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
536 AM AST MON MAY 2 2016

.SYNOPSIS...AT UPPER LEVELS...A WEAK SHORT WAVE MOVED THROUGH THE
AREA OVERNIGHT AND ANOTHER IS EXPECTED TODAY AS WINDS RETURN TO
WEST SOUTHWEST UNTIL TUESDAY AFTERNOON. A BROAD RIDGE THEN PASSES
OVER ON WEDNESDAY NIGHT. THIS RIDGE MOVES INTO THE TROPICAL
ATLANTIC OVER THE WEEKEND. A STRONG LOW IS CURRENTLY PROGGED TO
MOVE INTO THE WESTERN ATLANTIC NEAR NEW JERSEY FRIDAY NIGHT MOVING
EAST AND ITS FRINGES SHOULD BEGIN AFFECTING THE LOCAL AREA
SATURDAY NIGHT OR SUNDAY.

AT MID LEVELS..WEAK TROUGHINESS EXTENDS INTO THE AREA FROM THE
NORTH THROUGH MID WEEK WHILE HIGH PRESSURE OCCUPIES MOST OF THE
CARIBBEAN. HIGH PRESSURE CONTINUES OVER THE CARIBBEAN THROUGH THE
WEEKEND AS THE LOW MOVES INTO THE WESTERN ATLANTIC NORTH OF THE
AREA SUNDAY AND MONDAY.

AT LOWER LEVELS...HIGH PRESSURE NORTH OF THE AREA AND IN THE
NORTHEAST ATLANTIC WILL CONSOLIDATE DURING THE MIDDLE OF THE WEEK
AND BUILD THROUGH FRIDAY OVER THE CENTRAL ATLANTIC. THIS WILL
MAINTAIN SOUTHEAST FLOW OVER THE LOCAL AREA WITH ABUNDANT MOISTURE
THROUGH AT LEAST MONDAY OF NEXT WEEK.

&&

.DISCUSSION...SHOWERS STAYED CLEAR OF THE FORECAST AREA FOR MUCH
OF THE NIGHT. BUT DURING THE PRE-DAWN HOURS...SHOWERS FROM THE
BAND OF MOISTURE TO OUR SOUTHEAST BEGAN MOVING INTO THE FORECAST
AREA EAST OF SAINT CROIX AND SOUTH OF VIEQUES AND SAINT CROIX. AT
5 AM AST SHOWERS WERE MOVING BETWEEN SAINT JOHN AND SAINT CROIX.
MODELS AGREE THAT SHOWERS WILL APPROACH THE AREA FROM THE
SOUTHEAST AGAIN TODAY...BUT THE GFS WAS MUCH TOO WET OVERNIGHT
PUTTING 60 TO 100 PERCENT POPS IN THE 02/06Z FORECAST IN VARIOUS
PLACES...MAINLY OVER WATER. SKIES ARE MOSTLY CLEAR OVER PUERTO
RICO AND THE U.S. VIRGIN ISLANDS AND THE EARLY PART OF THE MORNING
IS EXPECTED TO BE MOSTLY SUNNY WITH A RAPID WARM-UP. THEN CLOUDS
WILL FORM WITH SHOWERS OVER THE INTERIOR OF PUERTO RICO.
THUNDERSTORMS COULD BEGIN A EARLY AS 11 AM AST... BUT MOST WILL
WAIT TILL AFTERNOON.

TODAY IS A LITTLE DIFFERENT THAN YESTERDAY. THE BAND OF MOISTURE
IS A LITTLE FARTHER EAST AND WIND FLOW ALSO APPEARS TO BE A LITTLE
MORE EASTERLY. HOWEVER IN THE LOWEST 10 KFT THE GFS SHOWS THE
WIND VEERING FROM THE NORTHEAST AT 02/00Z TO EAST SOUTHEAST AT
02/18Z AND THIS SHOULD ALLOW SHOWERS AND THUNDERSTORMS TO VISIT
THE NORTHERN COASTAL PLAINS OF PUERTO RICO AS WELL AS THE
NORTHWEST CORNER OF THE ISLAND WITH THE POSSIBILITY OF A STREAMER
CROSSING SOUTHERN CAROLINA AND THE SAN JUAN BAY WITH HEAVY RAIN
DURING THE AFTERNOON. A SIMILAR PATTERN IS EXPECTED FOR TUESDAY
AND WEDNESDAY. THEN THURSDAY WINDS TURN MORE SOUTHERLY AND HEAVY
RAIN SHOWERS WILL FAVOR MORE OF THE NORTH COAST OF PUERTO RICO.
URBAN AND SMALL STREAM FLOODING SHOULD BE EXPECTED THIS WEEK
ACROSS A NUMBER OF AREAS MAINLY NORTH OF THE CORDILLERA CENTRAL.
MOS TENDS TO WARM UP CONSIDERABLY BEGINNING TOMORROW AND
STEEPENING THROUGH FRIDAY...BUT CLOUDS COULD KEEP IT FROM REACHING
THE LAST FEW DEGREES. NEVERTHELESS EXPECT SOME LOWER 90S BY FRIDAY
AS MENTIONED YESTERDAY.

MID LEVELS CONTINUE TO HAVE MODEST MOISTURE UNTIL DRIER AIR MOVES
IN SOMETIME NEXT WEEK. ALTHOUGH MODELS BRING IN A BULLS EYE OVER
STRONG DIVERGENCE IN THE THE UPPER LEVELS ON MOTHERS DAY THAT
WOULD APPEAR TO FAVOR STRONGER CONVECTION...IT IS STILL TOO FAR
OUT TO PLACE ANY CONFIDENCE IN HEAVY RAIN FOR THE WEEKEND.
NEVERTHELESS THE SITUATION BEARS MONITORING.

&&

.AVIATION...PASSING SHRA AND VCTS CAN BE EXPECTED MAINLY ACROSS
TIST/TISX/TJPS/TNCM/TKPK DURING THE MORNING HOURS. MOUNTAIN
OBSCURATIONS ACROSS THE INTERIOR AND WESTERN PR WITH TSRA/SHRA
AFT 02/16Z. AS A RESULT...EXPECT BKN CEILING AT FL025-FL060 AT
TJBQ/TJMZ/TJPS AND POSSIBLY AT TJSJ. THE SURFACE WINDS WILL
CONTINUE FROM THE SOUTH TO EAST-SOUTHEAST AT 10 TO 15 KNOTS WITH
SEA BREEZE VARIATIONS AFT 02/13Z.

&&

.MARINE...SEAS WILL PEAK AT AROUND 4.5 FEET ON TUESDAY NIGHT...BUT
IT IS MOSTLY EASTERLY WIND WAVES WITH LITTLE NORTHERLY SWELL. SEAS
THEN SUBSIDE UNTIL THURSDAY. NO SMALL CRAFT ADVISORIES ARE
EXPECTED THROUGH THE WEEKEND IN ANY LOCAL WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  85  75  87  75 /  60  30  30  20
STT  85  75  86  77 /  50  30  20  20

&&

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

$$

27/12



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