Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 250304
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1104 PM AST SUN MAY 24 2015

.UPDATE...
TRANQUIL WEATHER CONDITIONS PREVAIL AFTER EVENING HOURS ACROSS
THE LOCAL ISLANDS. THE NATIONAL WEATHER SERVICE RADAR DOPPLER
DETECTED SCATTERED SHOWERS ACROSS THE LOCAL WATERS LATE IN THE
EVENING HOURS. ISOLATED SHOWERS MOVED INLAND ACROSS THE WINDWARD
SECTIONS...BUT SHOWERS WERE BRIEF AND WITHOUT SIGNIFICANT
RAINFALL ACCUMULATIONS. THE SAME WEATHER PATTERN IS EXPECTED FOR
MONDAY...WITH PASSING SHOWERS ACROSS THE WINDWARD SECTIONS OF PR
AND THE USVI FOLLOWED BY AFTERNOON CONVECTION ACROSS THE INTERIOR
AND WESTERN SECTIONS OF PR. NO CHANGES WERE MADE TO THE CURRENT
FORECAST PACKAGE.

&&

.AVIATION...
MOSTLY VFR CONDITIONS EXPECTED ON ALL TERMINALS THROUGH AT LEAST
25/16Z. BRIEF MVFR POSSIBLE AT JMZ WITH MTN TOP OBSCD FROM 17Z
THROUGH 21Z DUE TO POSSIBLE SHRA/TSRA OVER THE WESTERN INTERIOR.
WINDS BLO FL100 E-NE AT 10 TO 15 KT...GUSTING UP TO THE LOW 20S
AFTER 25/14Z.

&&

.MARINE...ACROSS THE LOCAL WATERS EXPECT WINDS AROUND 15 KNOTS
WHILE SEAS WILL BE 5 FEET OR LESS THROUGH AT LEAST MONDAY NIGHT.

&&

.PREV DISCUSSION... /ISSUED 304 PM AST SUN MAY 24 2015/

SYNOPSIS...AT MID AND UPPER LEVELS...THE AXIS OF THE SUB
TROPICAL JET IS JUST SOUTH WEST OF PUERTO RICO AS THE MAIN PORTION
OF THE JET PULLS AWAY TO THE EAST. A SHORT WAVE TROUGH WILL PASS
THROUGH THE AREA ON TUESDAY. A LOW WILL CUT OFF NORTHEAST OF THE
AREA AND DEEPEN UNTIL MONDAY NIGHT THEN CONTINUE MOVING TOWARD THE
AREA UNTIL WEDNESDAY EVENING. THE SUB TROPICAL JET WILL RE-CROSS
THE AREA FROM THE SOUTH ON FRIDAY MORNING. HIGH PRESSURE WILL
BUILD OVER THE AREA AND THE EASTERN CARIBBEAN NEXT WEEKEND. MID
LEVELS WILL REMAIN MOSTLY DRY UNTIL THURSDAY NIGHT.

AT LOWER LEVELS...HIGH PRESSURE DOMINATES THE SUB TROPICAL
ATLANTIC OCEAN WHILE EASTERLY TRADE WIND FLOW PERSISTS AT LOWER
LATITUDES. A WESTWARD MOVING TROUGH STRETCHING NORTHEAST FROM 60
WEST AT OUR LATITUDE WILL AMPLIFY AND MOVE TOWARD THE AREA BY
WEDNESDAY NIGHT. LOW PRESSURE AND SOUTHERLY FLOW GENERATED BY THE
LOW AT 700 MB FORMING NORTH OF THE AREA WILL BRING IN COPIOUS
MOISTURE FRIDAY THROUGH SUNDAY.

DISCUSSION...SHOWERS BEGAN LATE AND THUNDERSTORMS WERE NOTED
AFTER 2:30 PM AST OVER PUERTO RICO JUST NORTH OF YAUCO. SOME OF
THE SHOWERS WERE QUITE HEAVY AND MAY PRODUCE URBAN AND SMALL
STREAM FLOODING AFTER 3 PM AST. SHOWERS WILL DISSIPATE AND MOVE
WEST AFTER SUNSET. SOME SHOWERS WILL MOVE INTO THE SOUTHEAST
CORNER OF THE FORECAST AREA OVER THE CARIBBEAN SEA AND A FEW
SHOWERS ARE EXPECTED TO RETURN TO THE EASTERN SLOPES OF EL YUNQUE
TONIGHT. BETTER MOISTURE IS EXPECTED ON MONDAY BUT MOST OF THE
BEACHES WILL REMAIN DRY ON THE CARIBBEAN AND ATLANTIC SIDES.
MOISTURE IN THE LOWER LEVELS INCREASES SLOWLY UNTIL THURSDAY NIGHT
PROVIDING A SIMILAR PATTER OF SHOWERS FOR MOST OF THE WEEK. THEN
MOISTURE DECREASES AND RISES ABRUPTLY OVERNIGHT. THIS WILL MARK
THE BEGINNING OF THE WET PERIOD. MID LEVEL MOISTURE WILL MOVE IN
DURING THE DAY ON FRIDAY AND COLUMNAR MOISTURE WILL PEAK ON SUNDAY
MORNING AT AROUND 2.25 INCHES. CURRENTLY THE EXPECTATION IS THAT
SIGNIFICANT RAINS WILL BEGIN ON FRIDAY...AND PEAK ON
SATURDAY...BUT MAY STILL CONTINUE OVERNIGHT SATURDAY AND IN SOME
AREAS SUNDAY MORNING. SOME LOCAL FLOODING MAY BE POSSIBLE OVER THE
WEEKEND...MAINLY FRIDAY OR SATURDAY.

AVIATION...BRIEF MVFR POSSIBLE AT TJMZ TIL AT LEAST 21Z DUE TO
SHRA/TSRA OVER THE WESTERN INTERIOR. VFR ACROSS THE REST OF THE
TERMINALS. HOWEVER...BETWEEN 25/17-21Z MTN TOP OBSCD AND BRIEF MVFR
CONDS EXPECTED DUE TO SHRA/TSRA DEVELOPING ACROSS THE
INTERIOR/WESTERN PR...IMPACTING MAINLY TJMZ. WINDS BLO FL100 E-NE
AT 10 TO 15 KT...GUSTING UP TO THE LOW 20S AFTER 25/14Z.

MARINE...SEAS WILL REMAIN GENERALLY 5 FEET OR LESS AND TRADE
WINDS WILL CONTINUE TO BE MODERATE. SHOWERS AND THUNDERSTORM
ACTIVITY WILL INCREASE MUCH LATER THIS WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  77  89  77  87 /  20  20  30  30
STT  78  88  77  87 /  20  20  20  20

&&

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

$$

08/27



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