Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 010156
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
956 PM AST SAT APR 30 2016

.UPDATE...IT REMAINED MOSTLY RAIN FREE ACROSS THE ISLANDS DURING
THE EVENING HOURS. THE FLASH FLOOD WATCH WAS LET TO EXPIRE AT 8 PM
AST FOR ALL LOCAL ISLANDS. HIGH CIRRUS CLOUDS WILL CONTINUE OVER
THE ISLANDS LEAVING VARIABLY CLOUDY SKIES. SOME SHOWERS CAN
DEVELOP OVER THE CARIBBEAN WATERS AND REACH THE COASTAL AREAS OF
THE ISLANDS THROUGH THE OVERNIGHT AND EARLY MORNING HOURS. LATEST
01/00Z TJSJ UPPER AIR SOUNDING CONTINUED TO INDICATE A DROP IN
PWAT FROM 1.94 INCHES EARLY THIS MORNING TO 1.75 INCHES
NOW...FORECAST SOUNDINGS INDICATE THAT PWAT SHOULD STAY SOMEWHAT
SIMILAR AND CONTINUE TO SLOWLY ERODE DURING THE NEXT FEW DAYS.
HOWEVER...WITH ANOTHER UPPER PERTURBATION MOVING OVER ON
SUNDAY...THE CHANCE FOR MORE RAIN AND THUNDERSTORMS STILL REMAIN
HIGH ACROSS THE FORECAST AREA. MINOR CHANGES MADE TO SHORT TERM
GRIDS.


&&


.AVIATION UPDATE...VFR OVERNIGHT ACROSS MUCH OF THE PR/USVI
TERMINALS. HOWEVER...BKN/OVC HIGH CIRRUS WILL CONTINUE ACROSS THE
AREA. -TSRA/SHRA CAN STILL AFFECT FROM TIME TO TIME THE LEEWARD
TERMINALS...INCREASING ACROSS THE USVI/SOUTHERN AND EASTERN PR
TERMINALS BY SUNDAY MORNING. LATEST TJSJ SOUNDING INDICATED SOUTH
WINDS BLO FL040 AT 10-20 KNOTS.


&&

.MARINE UPDATE...BUOYS ACROSS PR AND THE USVI ARE INDICATING SEAS
BETWEEN 2 TO 4 FEET AND SOUTH-SOUTHEAST WINDS AROUND 10 KNOTS.
SEAS SHOULD CONTINUE BELOW SMALL CRAFT ADVISORY CRITERIA FOR THE
NEXT SEVERAL DAYS.

&&

.CLIMATE...AS OF 5 PM AST...A RECORD RAINFALL OF 2.33 INCHES WAS
SET AT HENRY E. ROHLSEN AIR PORT IN ST. CROIX TODAY. THIS BROKE
THE PREVIOUS RECORD OF 1.20 INCHES SET BACK IN 2009.

&&

.PREV DISCUSSION... /ISSUED /

SYNOPSIS...AMPLIYING UPPER LEVEL TROUGH JUST WEST OF HISPANOLA IS
ENHANCING THE INSTABILITY AND MOISTURE TRANSPORT OVER PUERTO RICO
AND THE U.S. VIRGIN ISLANDS. ADDITIONAL MID TO UPPER SHORT-WAVE
TROUGHS WILL CONTINUE TO STREAM OVER THE LOCAL REGION THROUGH
NEXT WEEK. AMPLE AREA OF MOISTURE WILL REMAIN OVER THE NORTHEAST
CARIBBEAN REGION OVER THE NEXT SEVERAL DAYS. AS A RESULT...HIGHLY
UNSTABLE AND MOIST ATMOSPHERE REMAINS OVER THE FORECAST AREA...
FAVORING THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS EVERYDAY.
UNSETTLED PATTERN WILL LIKELY PREVAIL UNTIL AT LEAST EARLY NEXT
WEEK.

DISCUSSION...VERY UNSTABLE AND MOIST AIR MASS OVER THE FORECAST
AREA HAVE RESULTED IN THE DEVELOPMENT SHOWERS AND THUNDERSTORMS
WITH HEAVY RAINFALL ACROSS MOST OF THE FORECAST AREA. INTENSE
THUNDERSTORMS MOVED FROM WEST TO EAST SINCE EARLY THIS MORNING
AFFECTING THE WEST...SOUTH AND EAST PORTIONS OF PUERTO RICO
THROUGH LATE THIS MORNING. AT THIS TIME...MOST OF THUNDERSTORMS
HAVE MOVED OVER CULEBRA...VIEQUES AND THE U.S. VIRGIN ISLANDS.
TORRENTIAL RAINS...FREQUENT LIGHTNING AND GUSTY WINDS UP TO 35
KNOTS HAVE BEEN OBSERVED WITH THE HEAVIEST STORMS.

VERY MOIST SOUTHEASTERLY FLOW ACROSS THE EASTERN CARIBBEAN WILL
CONTINUE TO PROMOTE MOISTURE CONVERGENCE ACROSS PUERTO RICO AND
THE US VIRGIN ISLANDS EARLY NEXT WEEK. THIS COMBINES WITH INFLOW
OF MID LEVEL ENERGY AND FAVORABLE JET DYNAMICS WILL SUSTAIN
UNSETTLED CONDITIONS OVER THE NEXT SEVERAL DAYS. SOILS ARE
RELATIVELY SATURATED ACROSS MOST OF THE ISLANDS AND ADDITIONAL
HEAVY RAINFALL WILL INCREASE THE FLOODING THREAT ACROSS PR AND THE
USVI. FOR THIS REASON...A FLASH FLOOD WATCH REMAIN IN EFFECT UNTIL
AT LEAST 8 PM AST TONIGHT.

PATTERN WILL REMAIN HIGHLY FAVORABLE AND CONDUCIVE TO ORGANIZED
DEEP CONVECTION OVER THE NEXT SEVERAL DAYS. HIGH MOISTURE CONTENT
AND ADDITIONAL PERTURBATIONS AT MID-UPPER LEVELS WILL KEEP THE
CHANCES OF SHOWERS AND THUNDERSTORMS HIGH THROUGH THE FORECAST
PERIOD.

AVIATION...BRK IN CLD COVER OVR WRN PR TJBQ...TJMZ...TJPS.
HOWEVER...OVR ERN HALF OF PR AND EASTWARD TOWARDS THE NRN LEEWARDS
MULTIPLE CLD LYRS...SCT-BKN LYRS FL025...050...OVC BTW FL090-120.
ISOLD-SCT TSRA EN ROUTE BTW PR AND NRN LEEWARDS WITH LINE OF STRONG
SHRA/TSRA NOW CROSSING VIRGIN ISLANDS AND MOV W WITH MVFR/IFR CONDS
ATTM. MAX TOPS 450-500. MTN TOP OBSCR OVER ERN PR IN SHRA/LOW CIG
TIL 30/23Z. TEMPO MVFR/PSBL IFR CIG AND SHRA/TSRA EN ROUTE BTW
ISLANDS DURG PRD. PREVAILING VFR AT MOST LOCAL TERMINALS EXCEPT FOR
TEMPO IFR AT TISX...TIST WITH BRIEF MVFR IN SHRA/ISOLD TSRA
ELSEWHERE TIL 30/23Z.

MARINE...WINDS OF 5 TO 15 KNOTS AND SEAS OF 3 TO 5 FEET
RESPECTIVELY. MAIN HAZARD FOR MARINERS TODAY IS THE STRONG
THUNDERSTORMS OVER THE REGIONAL WATERS...ESPECIALLY NEAR
USVI...CULEBRA AND VIEQUES. SUDDEN WATERSPOUT WILL ALSO BE
POSSIBLE MAINLY BETWEEN EASTERN PUERTO RICO AND THE VIRGIN
ISLANDS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  88  75  87 /  20  50  40  30
STT  76  88  76  85 /  40  60  50  50

&&

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

$$

08/13



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