Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 020120
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
920 PM AST SAT AUG 1 2015

.DISCUSSION...00Z TJSJ SOUNDING SHOWED THE NEAR ABSENCE OF SAHARAN
AIR AS SHOWERS APPROACHING THE LOCAL ISLANDS FROM THE EAST AND
NORTHEAST. A LITTLE LESS ENHANCEMENT IN THOSE SHOWERS HAS BEEN
NOTED ON SATELLITE LAST SEVERAL HOURS. STILL...SCATTERED SHOWERS
TO PERSIST THROUGH THE NIGHT SINCE NO SAHARAN AIR IS INHIBITING
THEIR DEVELOPMENT BUT WILL INCREASE THEIR COVERAGE TO SCATTERED
FOR ALL BUT SW PR AND DOWNWIND OF THE ISLAND TOWARDS SOUTHWEST.
PRECIPITABLE WATER TO REMAIN AT OR BELOW NORMAL SO DO NOT SEE
SIGNFICANT RAINFALL COMING TONIGHT OR ON SUNDAY AS SOME OF THE
MOISTURE LINGERS FOR WESTERN PR. THE BEST MOISTURE...CURRENTLY
HANGING EAST OF THE TROPICAL WAVE AXIS WITH PRECIPITABLE WATER
APPROACHING 2 INCHES AND JUST ARRIVING INTO LEEWARD ISLANDS...WILL
ARRIVE USVI BY EARLY SUNDAY EVE. THE MOISTURE WILL EXIT TOWARDS
THE WEST OF PR BEFORE DAYTIME HEAT ON MONDAY CAN PRODUCE
WIDESPREAD SHOWERS.

&&

.AVIATION...VRY BRF MVFR XPCTD IN SOME SHRA TONITE BUT OVERALL VFR
CONT. SCT SHRA/TSRA CNTRL/WEST PR SUN AFT WI SOME OBSCD MTNS.
ISOLD SHRA ELSEWHERE. WIND BLW FL100 ENE- NE 15-25 KT TONITE BCMG
E BY MORNING THEN SE LATE AFT...INCR LATE SUN NITE AND MON TO
20-40 KT.

&&

.MARINE...NO CHANGES MADE AS MODERATE TRADES PERSIST.

&&

.PREV DISCUSSION... /ISSUED 256 PM AST SAT AUG 1 2015/

SYNOPSIS...BROAD UPPER LEVEL TROUGH WILL FORM AND HOLD THROUGH EARLY
MONDAY ACROSS THE CENTRAL-EASTERN CARIBBEAN. MEANWHILE...MID LEVEL
TROUGH WILL MOVE OVER THE ISLANDS ON SUNDAY AS TROPICAL WAVE
ENTERS THE EASTERN CARIBBEAN...BRINGING BETTER LOW LEVEL MOISTURE
BY EARLY MONDAY. HOWEVER...DRY AND STABLE AIR RETURNS LATE MONDAY/TUESDAY
AS MID LEVEL RIDGE ESTABLISHES THRU MIDWEEK. MID LEVEL
PERTURBATIONS AND WET TRADES WILL BRING SCATTERED SHOWERS FROM
MIDWEEK THROUGH THE END OF NEXT WEEK.

DISCUSSION...MOSTLY FAIR WEATHER CONDITIONS WITH LIMITED SHOWER
ACTIVITY PREVAILED TODAY ACROSS THE FORECAST AREA AND SIMILAR
CONDITIONS ARE EXPECTED TO CONTINUE THRU AT LEAST SUNDAY
NIGHT...WITH THE EXCEPTION OF LOCALIZED AFTERNOON CONVECTION OVER
WESTERN PR. THE COMBINATION OF MID/UPPER LEVEL TROUGH AND A
TROPICAL WAVE WILL BRING BETTER MOISTURE OVER THE ISLANDS BY LATE
SUNDAY/EARLY MONDAY. EARLY SCATTERED SHOWERS OVER THE USVI/EASTERN
PR AND ENHANCED AFTERNOON CONVECTION OVER WESTERN PR IS EXPECTED
ON MONDAY DUE THE SURGE IN MOISTURE AND FAVORABLE UPPER LEVEL
DYNAMICS. DRYING IS EXPECTED QUICKLY LATE MONDAY THRU MIDWEEK...AS
MID LEVEL RIDGE MOVES FROM THE CENTRAL TO WESTERN ATLANTIC...BUT
FROM MIDWEEK FORWARD...A SERIES OF MID LEVEL PERTURBATIONS AND
TRADE WIND SHOWERS WILL PASS FROM TIME TO TIME ACROSS THE FORECAST
AREA...INCREASING SOMEWHAT THE FREQUENCY OF EARLY MORNING
SHOWERS/AFTERNOON CONVECTION OVER WESTERN PR. HOWEVER...RAINFALL
ACCUMULATIONS SHOULD STAY BELOW TO NEAR NORMAL VALUES FOR MOST OF
THE WEEK.

AVIATION...SHRA W PR TIL 01/22Z. AS A RESULT...BRIEF MVFR CIGS IN
PASSING SHRA VCTY TJMZ.  FEW CU EN ROUTE BTW E PR AND USVI WITH
PASSING SHRA. SFC WND FM EAST AT 15-20 KT W/HIGHER GUST UP TO 25
KTS...BCMG FM E 5-10 KTS AFT 22Z.

MARINE...NEAR SHORE BUOYS ARE INDICATING SEAS OF 3-5 FEET ACROSS
THE USVI AND PR WATERS. OFFSHORE ATLANTIC BUOY RUNNING NEAR 5
FEET. EAST TO NORTHEAST WINDS ARE AROUND 15 KNOTS WITH GUSTS IN
THE LOW 20S. SIMILAR CONDITIONS ARE EXPECTED OVER THE NEXT FEW
DAYS...AN INCREASE IN WINDS IS EXPECTED OVER THE CARIBBEAN WATERS
ON MONDAY/TUESDAY AS TROPICAL WAVE MOVES ACROSS THE EASTERN
CARIBBEAN SEA.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  79  89  79  90 /  40  40  40  40
STT  78  89  80  89 /  40  40  50  50

&&

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

$$

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