Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 310150
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
950 PM AST WED JUL 30 2014

.UPDATE...ISOLATED SHOWERS WILL CONTINUE TO MOVE ACROSS THE LOCAL
WATERS...WITH A SLIGHT INCREASE AFTER MIDNIGHT. SOME SHOWERS WILL
MOVE OVER LAND AND MAINLY AFFECT THE EASTERN PORTIONS OF PUERTO
RICO AND THE USVI.


&&

.AVIATION...VFR CONDS WILL PREVAIL AT ALL TAF SITES THROUGH THE FCST
PRD. HOWEVER OVERNIGHT AND EARLY MORNING ISOLD-SCT SHRA/-SHRA MAY
BRING BRIEF MVFR CIGS ACROSS THE COASTAL WATERS BTW ERN PR AND THE
NRN LEEWARDS FM 31/04Z-31/12Z WITH VCSH NR TJSJ...TJNR...TISX AND
TIST. ON THURSDAY...PASSING SHRA FM 31/17-31/22Z W/BRIEF MVFR CIGS
PSBL DUE ISOLD-SCT SHRA/ISOLD TSRA MAINLY ACROSS THE CTRL INTERIOR
AND NORTHWESTERN SECTIONS OF PR AFFECTING TJBQ AND TJMZ...VCSH PSBL
AT TJSJ. GENERAL WND BLO FL150 FM SE AT 5-15 KTS DURG PRD. NO OTHER
SIG OPERATIONAL WX IMPACT ATTM.


&&

.MARINE...SEAS UP TO 4 FEET AND WINDS UP TO 17 KNOTS ARE EXPECTED
TO CONTINUE ACROSS THE COASTAL WATERS THROUGH FRIDAY. CONDITIONS
WILL QUICKLY DETERIORATE ON SATURDAY AS A STRONG TROPICAL WAVE
MOVES ACROSS THE LOCAL WATERS BETWEEN LATE SATURDAY THROUGH
SUNDAY. MARINERS ARE URGED TO MONITOR THE DEVELOPMENT OF THIS
TROPICAL SYSTEM AS REACH THE LOCAL WATERS.


&&

.PREV DISCUSSION... /ISSUED 300 PM AST WED JUL 30 2014/

SYNOPSIS...UPPER LEVEL TROUGH NORTH OF THE AREA WILL LINGER NEXT
SEVERAL DAYS CLOSE TO THE LOCAL AREA. A SURFACE TROUGH WILL MOVE
ACROSS THE REGION THURSDAY INTO FRIDAY. A VERY STRONG TROPICAL
WAVE...LOCATED THIS AFTERNOON NEAR 1300 MILES SOUTHEAST OF PUERTO
RICO IS FORECAST TO MOVE WEST NORTHWEST AND WILL APPROACH THE
LOCAL AREA SATURDAY NIGHT INTO SUNDAY.

DISCUSSION...SHOWERS AND THUNDERSTORMS DEVELOPED THIS AFTERNOON
OVER THE WESTERN INTERIOR SECTION OF PUERTO RICO. RAINFALL
ACCUMULATION OF BETWEEN 1 TO 2 INCHES WERE OBSERVED WITH THIS
ACTIVITY. THIS ACTIVITY WAS PRIMARILY ASSOCIATED WITH THE
COMBINATION OF AN UPPER LEVEL TROUGH AND DAYTIME HEATING.

FOR TOMORROW...A SURFACE TROUGH WILL MOVE ACROSS THE LOCAL
REGION...BRINGING WITH IT AN INCREASE IN SHOWERS AND POSSIBLE
THUNDERSTORMS OVER THE LOCAL REGION. AS THIS SURFACE TROUGH
INTERACTS WITH THE UPPER LEVEL TROUGH TO OUR NORTH...SOME
LOCALIZED URBAN FLOODING CAN BE EXPECTED TOMORROW AFTERNOON.

A STRONG TROPICAL WAVE...LOCATED NEAR 1300 MILES SOUTHEAST OF
PUERTO RICO THIS AFTERNOON...IS FORECAST TO MOVE WEST NORTHWEST
AND WILL APPROACH THE LOCAL AREA SATURDAY NIGHT INTO SUNDAY. THIS
TROPICAL WAVE STILL HAVE THE POTENTIAL TO BECOME A TROPICAL
DEPRESSION DURING THE NEXT COUPLE OF DAYS. THE EXPECTED IMPACTS
OVER THE WEEKEND FOR THE LOCAL ISLANDS ARE STILL UNCERTAIN.
HOWEVER AT THIS TIME...MODEL GUIDANCE SEEM TO AGREE A BIT MORE
WITH ONE ANOTHER AND HAS THIS SYSTEM PASSING VERY CLOSE TO THE
NORTHERN USVI. THIS SCENARIO WOULD GIVE NORTHEASTERN PR AND THE
NORTHERN USVI SOME MUCH NEEDED RAIN. HOWEVER...CONFIDENCE IS LOW
IN THIS FORECAST AS WE ARE STILL UNSURE OF WHEN WILL CYCLOGENESIS
WILL OCCUR AND HOW IT WILL EVOLVE OVER THE NEXT SEVERAL DAYS. STAY TUNED.

AVIATION...VFR CONDS WILL PREVAIL AT ALL TAF SITES THROUGH THE FCST
PERIOD WITH VCSH...EXCPT FOR BRIEF MVFR CIGS PSBL DUE ISOLD-SCT
SHRA/TSRA ACROSS THE CENTRAL INTERIOR AND NORTHWESTERN SECTIONS OF
PR...ENDING ARND 30/21Z. E-SE WINDS 10-15 KTS WITH ISOLD HIGHER
GUSTS NR STORMS.

MARINE...SEAS UP TO 5 FEET AND WINDS UP TO 17 KNOTS ARE EXPECTED
TO CONTINUE ACROSS THE COASTAL WATERS THROUGH THURSDAY.

&&

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

&&

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

$$

09/10




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