Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 050156 AAA
AFDSJU

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
956 PM AST FRI SEP 4 2015

.UPDATE...THE 05/00Z SOUNDING CAME IN QUITE A BIT WETTER THAN
YESTERDAY AT THIS TIME AND REFLECTS THE BETTER COLUMNAR MOISTURE
THAT HAS MOVED IN FROM THE EAST AS SEEN IN THE MIMIC PRODUCT. THIS
IS ALREADY BEING MANIFESTED AS WIDELY SCATTERED SHOWERS OVER THE
CARIBBEAN SOUTHWEST OF SAINT THOMAS TO 17 NORTH. THE WATER VAPOR
IMAGE ALSO SHOWS A WIDE SWATH OF MOISTURE MOVING ALONG THE
SOUTHEAST SIDE OF THE UPPER LEVEL LOW NOW CENTERED JUST NORTH OF
THE MONA CHANNEL.

&&

.DISCUSSION...THE LATEST GFS SHOWS BETTER MOISTURE ON SATURDAY BUT
STABILITY WILL BE GREATER AS THE 500 MB TEMPERATURES WARM. HIGH
PRESSURE WILL EDGE OUT THE MOISTURE AND CONSIDERABLE DRYING IS
EXPECTED TO APPEAR FROM SOUTHEAST TO NORTHWEST SUNDAY DURING THE
DAY. THIS SHOULD BRING SHOWERS TO AN EARLIER END SUNDAY NIGHT.

&&

.AVIATION...VFR CONDS EXPECTED OVERNIGHT ACROSS THE LOCAL TERMINALS
WITH VCSH EXPECTED AS A TROPICAL WAVE MOVES IN. SHRA/TSRA
DEVELOPMENT EXPECTED ACROSS SEVERAL SECTORS IN PR WHICH WILL LIKELY
CAUSE VCTS FOR TJBQ/TJMZ/TJSJ/TJPS...AS WELL AS POSSIBLY AFFECT THE
ACTUAL STATION...CAUSING MVFR CONDS AT DIFFERENT POINTS BETWEEN
05/16Z AND 05/24Z. WINDS WILL BE MAINLY LIGHT AND VARIABLE
OVERNIGHT...BECOMING E-SE AT AROUND 10KT WITH SEA BREEZE VARIATIONS
AFTER 05/13Z.

&&

.MARINE...WINDS AND SEAS REMAIN TRANQUIL BUT WILL PICK UP A LITTLE
AFTER THE WAVE PASSAGE.

&&

.PREV DISCUSSION... /ISSUED 328 PM AST FRI SEP 4 2015/

SYNOPSIS...
AN UPPER LEVEL TROUGH WILL LINGER OVER THE AREA DURING THE
WEEKEND. IT IS EXPECTED TO WEAKEN AS IT MOVES WESTWARD OVER THE
WESTERN CARIBBEAN. A MID LEVEL RIDGE IS EXPECTED TO BUILD OVER THE
REGION...AS IT MOVES FROM THE CENTRAL ATLANTIC INTO EASTERN
CARIBBEAN DURING THE UPCOMING DAYS. A WEAK TROPICAL WAVE IS
EXPECTED TO REACH THE LOCAL AREA BY LATE TONIGHT INTO EARLY
SATURDAY MORNING. ANOTHER TROPICAL WAVE IS EXPECTED TO REACH THE
ISLANDS SUNDAY INTO MONDAY.

DISCUSSION...
MOSTLY SUNNY SKIES PREVAILED ACROSS THE LOCAL AREA DURING THE
MORNING HOURS. CLOUDINESS AND SHOWERS INCREASED OVER THE LOCAL
AREA DURING THE AFTERNOON HOURS. SHOWER ACTIVITY DEVELOPED OVER ST
CROIX AND ST JOHN AROUND NOON HOURS. ALSO...AFTERNOON SHOWERS
DEVELOPED OVER CAROLINA...CANOVANAS...COAMO...VILLALBA...OROCOVIS
AND TRUJILLO ALTO BY EARLY AFTERNOON. THE AFTERNOON CONVECTION
MOVED OVER THE INTERIOR AND WESTERN SECTIONS OF PUERTO RICO BY
EARLY AFTERNOON HOURS. ENHANCE CONVECTION REMAINS POSSIBLE DUE TO
THE PROXIMITY OF AN UPPER LEVEL TROUGH...THE AVAILABLE MOISTURE
AND LOCAL EFFECTS. SHOWER AND THUNDERSTORM ACTIVITY WILL CONTINUE
AT LEAST UNTIL EVENING HOURS.

TRANQUIL WEATHER CONDITIONS PRECEDING A WEAK TROPICAL WAVE WHICH
IS EXPECTED TO REACH THE LOCAL AREA BY LATE TONIGHT INTO EARLY
SATURDAY MORNING. THE TROPICAL WAVE AND THE UPPER LEVEL TROUGH
WILL ENHANCE THE INSTABILITY AND THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS MAINLY OVER THE SOUTH AND EASTERN SECTIONS OF PUERTO
RICO AND THE US VIRGIN ISLANDS.

ANOTHER TROPICAL WAVE IS EXPECTED TO REACH THE LOCAL AREA BY
SUNDAY INTO MONDAY...TO INCREASE THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS.

AVIATION...
VCTS EXPECTED AT ALL PR AND USVI TERMINALS THROUGH 04/22Z. AFT
04/22Z VCSH AT LEEWARD AND USVI TERMINALS AS WELL AS TJSJ AS A
WEAK TROPICAL WAVE MOVES ACROSS THE EASTERN CARIBBEAN. EASTERLY
WINDS AT AROUND 10 KNOTS WITH SEA BREEZE VARIATIONS BUT BECOMING
LIGHT AND VARIABLE OVERNIGHT.

MARINE...LIGHT TO GENTLE WINDS OF LESS THAN 15 KNOTS TONIGHT WITH
SEAS OF 4 FEET OR LESS. EXPECT THESE CONDITIONS TO CONTINUE
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. THERE ARE NO MARINE
PRECAUTIONARY STATEMENTS OR ADVISORIES IN EFFECT AT THIS TIME.
HOWEVER...A TROPICAL WAVE IS EXPECTED TO REACH THE LOCAL WATERS BY
LATE TONIGHT INTO EARLY SATURDAY MORNING INCREASING THE POTENTIAL
FOR SHOWER AND THUNDERSTORM ACTIVITY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  79  90  78  90 /  30  60  30  40
STT  79  89  79  89 /  40  50  30  30

&&

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

$$

25/99


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