Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 041458
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1058 AM AST WED MAY 4 2016

.SYNOPSIS...UPPER RIDGE WILL CONTINUE TO BUILD OVER THE NORTHEAST
CARIBBEAN REGION THROUGH THURSDAY. HOWEVER...MOISTURE CONTENT
REMAINS ABOVE NORMAL AS SOUTHEASTERLY FLOW CONTINUES TO PUSH DEEP
MOISTURE FROM THE EASTERN CARIBBEAN. ALTHOUGH...UPPER DYNAMICS ARE
NEUTRAL OR LESS FAVORABLE FOR DEEP CONVECTION...HIGH MOISTURE
CONTENT WILL HELP TO INCREASE THE CONVECTIVE INSTABILITY ACROSS
THE AREA TODAY. STILL EXPECTING THE HEAVIEST SHOWERS AND THUNDERSTORMS
CONCENTRATING ALONG THE CORDILLERA CENTRAL...NORTH CENTRAL AND
NORTHWEST PUERTO RICO LATE THIS MORNING AND IN THE AFTERNOON.SOME
SHOWERS MAY ALSO AFFECT PORTIONS OF SOUTH CENTRAL PR AT TIMES.
MINOR CHANGES WERE INTRODUCED TO THE FORECAST PACKAGE...MAINLY TO
INCREASE THE POPS OVER THE INTERIOR AND NW PR THIS AFTERNOON.

&&

.AVIATION...MVFR CONDS PSBL AT TJMZ AND TJBQ IN PASSING TSRA THRU
22Z. SOME VCSH/VCTS MAY AFFECT BRIEFLY TJSJ THIS AFTERNOON. ESE
WINDS OF 10-15 KT EXPECTED BELOW FL100.

&&

.MARINE...WINDS OF 5 TO 15 KNOTS AND SEAS OF 3 TO 5 FEET WILL
PREVAIL OVER THE NEXT SEVERAL DAYS. NO SMALL CRAFT ADVISORIES ARE
ANTICIPATED OVER THE NEXT 5-7 DAYS.

&&

.PREV DISCUSSION... /ISSUED /

SYNOPSIS...AN UPPER LEVEL RIDGE WILL BUILD ACROSS THE REGION
BETWEEN TODAY AND THURSDAY...AS THE MID TO UPPER LEVEL TROUGH
MOVES EASTWARD. BY THE UPCOMING WEEKEND...A POLAR TROUGH IS
EXPECTED TO REACH THE AREA. AT THE SURFACE...A DISTURBANCE WILL
MOVES ACROSS THE REGION TODAY. A SURFACE HIGH PRESSURE OVER THE
CENTRAL ATLANTIC WILL MAINTAIN A GENERALLY MOIST SOUTHEASTERLY
FLOW ACROSS THE LOCAL ISLANDS THROUGH THE WEEKEND.

DISCUSSION...PARTLY TO MOSTLY CLOUDY SKIES WERE OBSERVED ACROSS
THE ISLANDS. THE DOPPLER RADAR DETECTED A BAND OF SHOWERS ACROSS
THE ATLANTIC OFFSHORE AND CARIBBEAN WATERS OVERNIGHT. SOME SHOWERS
MOVED ACROSS THE SOUTHERN AND EASTERN SECTIONS OF PUERTO RICO.
ALSO...THUNDERSTORM ACTIVITY WAS DETECTED ACROSS THE CARIBBEAN
WATERS.

UNDER WEAKENING TROUGH...THE SOUTHERLY FLOW AND THE AVAILABLE LOW
LEVEL MOISTURE...CONTINUE TO EXPECT SHOWER ACTIVITY ACROSS THE
LOCAL WATERS...AND THE WINDWARD SECTIONS OF PUERTO RICO THIS
MORNING. ALSO...THE U.S. VIRGIN ISLANDS CAN EXPECT ONE OR TWO
SHOWERS DURING THE MORNING HOURS. FOR THE AFTERNOON HOURS...THE
AVAILABLE MOISTURE IS FORECAST TO COMBINE WITH THE DIURNAL AND
LOCAL EFFECTS TO AID IN THE DEVELOPMENT OF SHOWERS AND ISOLATED
THUNDERSTORMS. MINOR URBAN AND SMALL STREAM FLOODING WILL ONCE
AGAIN BE POSSIBLE TODAY WITH THE HEAVIEST AND MOST PERSISTENT
SHOWERS.

AS THE UPPER LEVEL RIDGE BUILDS OVER THE REGION TODAY INTO
FRIDAY...SHOWER ACTIVITY IS EXPECTED TO DIMINISH SOMEHOW DURING
THAT PERIOD. HOWEVER...IT IS NOT STRONG ENOUGH TO SUPPRESS THE
SHOWER AND THUNDER ACTIVITY OVER AND NORTH OF THE CORDILLERA EACH
AFTERNOON. AN UPPER LEVEL TROUGH IS FORECAST TO RETURN TO THE
FORECAST AREA BY LATE FRIDAY INTO THE WEEKEND. BASED ON THE LATEST
MODEL GUIDANCE...MOIST AND UNSTABLE CONDITIONS ARE EXPECTED TO
RETURN DURING THE UPCOMING MOTHERS DAY WEEKEND.

AVIATION...VFR CONDITIONS WILL PREVAIL ACROSS ALL TAF SITES THROUGH
AT LEAST 04/16Z. PERIODS OF MVFR CONDITIONS WITH MOUNTAIN
OBSCURATIONS ARE EXPECTED OVER TJMZ AND TJBQ FROM 04/16-04/22Z. VCSH
ARE EXPECTED OVER TJSJ. LOW LEVEL WINDS WILL BE MAINLY SOUTHEAST AT
10 TO 15 KTS.

MARINE...TRANQUIL MARINE CONDITIONS EXPECTED DURING THE NEXT FEW
DAYS...WITH SEAS UP TO 5 FEET AND WINDS AROUND 15 KNOTS. SEAS AND
WINDS LOCALLY HIGHER IN THUNDERSTORMS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  76  90  77  91 /  20  40  20  40
STT  78  87  78  86 /  20  30  30  30

&&

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

$$

11/09



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