Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 040201 AAA
AFDSJU

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
1001 PM AST SUN MAY 3 2015

.UPDATE...THE CURRENT FORECAST IS IN GOOD TRACK.

&&

.DISCUSSION...SOME SHOWERS DEVELOPED ACROSS THE INTERIOR AND
NORTHWESTERN SECTIONS OF PUERTO RICO DUE TO THE LOCAL EFFECTS AND
DIURNAL HEATING. SHOWER ACTIVITY DISSIPATED AFTER SUNSET...AND
SKIES BECAME MOSTLY CLEAR ACROSS CWA.

BRIEF PASSING PASSING SHOWERS WILL BE SEEN ON THE WINDWARD
SECTIONS OF PR AND THE USVI OVERNIGHT AND EARLY TOMORROW MORNING.
SOUTHERLY WINDS CONTINUES...MEANWHILE MODEL GUIDANCE ARE
SUGGESTING AN EASTERLY WIND FLOW AFTER TOMORROW MORNING. IN
ADDITION...THE INSTABILITY PARAMETERS ARE EXPECTED TO BE A BIT
MORE UNSTABLE WITH A SLIGHT INCREASE IN LOW LEVEL MOISTURE...THESE
COMBINED WITH DIURNAL HEATING AND LOCAL EFFECTS COULD LEAD TO THE
FORMATION OF MODERATE TO LOCALLY AFTERNOON CONVECTION ACROSS THE
INTERIOR AND WESTERN PUERTO RICO.

AFTER MONDAY NIGHT...WEATHER CONDITIONS ARE EXPECTED TO TURN DRIER
THAN NORMAL AND WILL CONTINUE AT LEAST UNTIL THE END OF THE WORK
WEEK. ALSO...A SAHARAN AIR MASS IS EXPECTED TO MOVE OVER THE
LOCAL AREA FROM TUESDAY TO THURSDAY. FIRE DANGER WILL INCREASE BY
MID WEEK IN RESPONSE TO THIS PATTERN.

&&

.AVIATION...MORNING SHOWERS POSSIBLE AT JSJ AND USVI TERMINALS.
BREEZY WITH WINDS BECOMING MORE EASTERLY THAN RECENT DAYS. DUST HAZE
WILL BEGIN AFFECTING LEEWARD ISLANDS DURING THE AFTERNOON AND SPREAD
WWD REACHING USVI AND PR TERMINALS BY THE END OF THE DAY REDUCING
VSBY TO 6SM.


&&

.MARINE...THE LOCAL PRESSURE GRADIENT IS EXPECTED TO TIGHTEN AS A
SURFACE HIGH PRESSURE EXIT THE MID ATLANTIC COAST BY EARLY MONDAY.
AS A RESULT...TRADE WIND WINDS AND SEAS WILL RISE WITH WINDS UP
TO 20 KT AND SEAS UP TO 7 FEET. THEREFORE...A SMALL CRAFT
ADVISORIES IS NOW IN EFFECT AFTER MONDAY NIGHT ON BOTH THE
ATLANTIC AND THE CARIBBEAN WATERS.

&&

.PREV DISCUSSION... /ISSUED 235 PM AST SUN MAY 3 2015/

SYNOPSIS...SURFACE HIGH PRESSURE WILL ENTER THE WESTERN ATLANTIC
OVERNIGHT AND BUILD NORTH OF THE AREA THRU THE WEEK...INCREASING
THE TRADE WINDS ACROSS THE FORECAST AREA. MID LEVEL RIDGE AND
SAHARAN AIR LAYER WILL KEEP DRY CONDITIONS FOR MUCH OF THE WORK WEEK.

DISCUSSION...ISOLATED PASSING SHOWERS WERE NOTED THIS MORNING
ACROSS NORTHEASTERN PR INCLUDING VIEQUES AND CULEBRA. HOWEVER...RAINFALL
ACCUMULATIONS WERE JUST A FEW HUNDREDTHS OF AN INCH. BY EARLY
AFTERNOON...THE DOPPLER RADAR DETECTED SMALL SHOWERS NEAR THE
INTERNATIONAL AIRPORT AND OVER THE NORTHWEST SECTIONS OF PR.
MODELS SUGGEST AN INCREASE IN SHOWER ACTIVITY BETWEEN LATE TONIGHT
AND EARLY MONDAY MORNING WITH PWAT VALUES INCREASING FROM 1.14 TO
1.40 INCHES BY 04/12Z. HOWEVER...KEPT ISOLATED SHOWERS IN THE FCST
BETWEEN EASTERN PR AND THE USVI THRU THE MORNING PERIOD AND OVER
THE INTERIOR AND WESTERN PR IN THE AFTERNOON.

A DRYING PATTERN IS EXPECTED QUICKLY FROM MONDAY NIGHT THRU AT
LEAST THURSDAY DUE TO AN AREA OF SAHARAN DUST AND LOW LEVEL WINDS
INCREASING IN RESPONSE TO A STRONG HIGH PRESSURE ESTABLISHING
OVER THE CENTRAL ATLANTIC. FIRE DANGER WILL INCREASE ON TUE-WED IN
RESPONSE TO THIS. MODEL GUIDANCE DOES NOT SUGGEST ANY SIGNIFICANT
INCREASE IN MOISTURE AT LEAST UNTIL THE SECOND WEEK OF MAY...AS
UPPER LEVEL TROUGH AMPLIFIES OVER THE WESTERN ATLANTIC INTO THE
CARIBBEAN. THEREFORE...DRY WEATHER AND ABOVE NORMAL TEMPERATURES
ARE EXPECTED TO CONTINUE UNTIL THEN. HOWEVER...THE LIMITED
AVAILABLE LOW LEVEL HUMIDITY COULD POP UP A FEW SHOWERS BRIEFLY
OVER NORTHWESTERN PR EACH AFTERNOON.

AVIATION...SCT SHRA EXPECTED NW PR TIL 03/22Z THEN FEW SHRA TIL
ARND 04/08Z. AFT 04/08Z SCT SHRA ERN QUARTER PR CLRG AFT 04/12Z.
MVFR CONDS BRIEF WITH SHRA OTHERWISE VFR EVERYWHERE. WINDS ALF ESE 5-
15 KT BLO FL090 BCMG S ARND 10 KT BTWN FL090 AND FL200. WINDS SSW 20-
30 KT UP TO FL400.

MARINE...NEAR SHORE BUOYS ACROSS PR AND THE USVI ARE INDICATING
SEAS OF 2 TO JUST BELOW 4 FEET AND SOUTHEAST WINDS AROUND 15
KNOTS. SEAS WILL INCREASE UP TO 7 FEET ACROSS THE OFFSHORE
ATLANTIC AND CARIBBEAN WATERS BY LATE MON-EARLY TUE DUE TO
DEVELOPING FRESH TO VIGOROUS TRADE WINDS OVER THE AREA. SMALL
CRAFT ADVISORIES WILL BE IN EFFECT BY THEN.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  77  91  78  91 /  10  10   0  10
STT  78  87  78  88 /  20  20  10  10

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
AM...SMALL CRAFT ADVISORY FROM 8 PM MONDAY TO 8 PM AST TUESDAY FOR
     ATLC WATERS OF PUERTO RICO AND USVI FROM 10NM TO 19.5N.

     SMALL CRAFT ADVISORY FROM 8 PM MONDAY TO 8 PM AST WEDNESDAY FOR
     CARIBBEAN WATERS OF PUERTO RICO FROM 10 NM TO 17N-MONA
     PASSAGE SOUTHWARD TO 17N.

&&

$$

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