Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 030931
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
531 AM AST WED JUN 3 2015

.SYNOPSIS...MID TO UPPER LEVEL HIGH PRESSURE RIDGE WILL GRADUALLY
BUILD EASTWARD ACROSS THE REGION FROM THE CENTRAL CARIBBEAN THROUGH
FRIDAY AND INTO THE UPCOMING WEEKEND. SURFACE HIGH PRESSURE OVER
THE NORTH CENTRAL ATLANTIC AND AN INDUCED LOW LEVEL TROUGH MOVING
ACROSS THE NORTHEASTERN CARIBBEAN TODAY WILL MAINTAIN LIGHT TO
MODERATE TRADE WINDS ACROSS THE FORECAST AREA THROUGH AT LEAST
THURSDAY. A WEAK TROPICAL WAVE IS FORECAST TO MOVE ACROSS THE
EASTERN CARIBBEAN ON FRIDAY AND BRING ADDITIONAL TROPICAL MOISTURE
TO THE LOCAL AREA INTO THE UPCOMING WEEKEND. BY LATE SUNDAY AND
INTO EARLY NEXT WEEK DRIER CONDITIONS EXPECTED AS A SAHARAN AIR
LAYER AND EXTENSIVE AREA OF SUSPENDED SAHARAN DUST PARTICULATES
WILL SPREAD ACROSS THE EASTERN CARIBBEAN AND LOCAL REGION.

&&

.DISCUSSION...GOOD LOW LEVEL MOISTURE ACCOMPANYING THE LOW LEVEL
TROUGH MOVING ACROSS THE REGION TODAY WILL BE MORE THAN SUFFICIENT
TO COMBINE WITH DAYTIME HEATING AND LOCAL TERRAIN EFFECTS TO SUPPORT
ANOTHER ROUND OF LATE MORNING AND AFTERNOON CONVECTION ACROSS PORTIONS
OF THE ISLANDS TODAY. WITH THE PREVAILING EAST TO SOUTHEAST STEERING
FLOW...EXPECT AFTERNOON CONVECTION TO BE FOCUSED MAINLY ACROSS NORTH
CENTRAL AND NORTHWEST PORTIONS OF PUERTO RICO AS WELL AS PART OF
THE SAN JUAN METRO AREA EARLY IN THE AFTERNOON. PERIODS OF MODERATE
TO LOCALLY HEAVY RAINFALL WILL THEREFORE REMAIN LIKELY IN THESE AREAS...
AND THEREFORE MINOR FLOODING OF URBAN AREAS AND SMALL STREAMS WILL
AGAIN BE POSSIBLE. SHOWERS WILL ALSO CONTINUE TO AFFECT PORTIONS OF
THE U.S. VIRGIN ISLANDS THROUGHOUT THE DAY BUT WIDESPREAD RAINFALL
IS NOT EXPECTED AT THIS TIME.

BY THURSDAY...AS THE RIDGE BUILDS OVERHEAD...EXPECT A GRADUAL STRENGTHENING
OF THE CAP INVERSION OVER THE REGION. IN ADDITION SLIGHTLY DRIER AIR/SUBSIDENCE
JUST AHEAD OF THE APPROACHING TROPICAL SHOULD DECREASE CHANCES FOR CONVECTIVE
DEVELOPMENT ACROSS THE FORECAST AREA ON THURSDAY. HOWEVER...ON FRIDAY
AND INTO THE UPCOMING WEEKEND ANOTHER SURGE OF MOISTURE WILL ACCOMPANY
THE TROPICAL WAVE. THIS WILL ONCE AGAIN INCREASE THE CHANCES FOR
EARLY MORNING AND AFTERNOON CONVECTION ACROSS THE ISLANDS.

AS PREVIOUSLY MENTIONED...LATEST MODEL GUIDANCE SO FAR SUGGESTS
SOMEWHAT DRIER CONDITION BY LATE SUNDAY AND INTO THE EARLY PART OF
NEXT WEEK AS THE SAL AND ACCOMPANYING SAHARAN DUST WILL SPREAD
ACROSS THE REGION AND HELP TO SUPPRESS/LIMIT ANY SIGNIFICANT
CONVECTIVE DEVELOPMENT ACROSS THE REGION. WILL CONTINUE TO MONITOR
AND SEE HOW THIS UNFOLDS OVER THE NEXT COUPLE OF DAYS.

&&

.AVIATION...BRIEF PASSING SHOWERS WILL PROMOTE BRIEF PERIODS OF MVFR
CONDITIONS ACROSS TIST...TISX AND TJSJ DURING THE MORNING HOURS.
DURING THE AFTERNOON HRS...MVFR OR EVEN IFR CONDITIONS CAN BE
EXPECTED ACROSS TJBQ...TJMZ AND TJSJ DUE TO SHRA/TSRA...AND MOUNTAIN
OBSCURATIONS ACROSS THE CORDILLERA CENTRAL. EAST TO EAST-SOUTHEAST
SURFACE WINDS OF 10-15 KT WITH HIGHER GUSTS IN/NEAR SHRA/TSRA. SEA
BREEZE ACROSS THE COASTAL SECTIONS CAN BE EXPECTED AFT 03/12Z.

&&

.MARINE...WINDS AND SEAS WILL CONTINUE TO DIMINISH THROUGH AT LEAST
THURSDAY...THEN SLIGHTLY INCREASE ONCE AGAIN BY FRIDAY AND INTO THE
UPCOMING WEEKEND. HOWEVER...SMALL CRAFT ADVISORY CONDITIONS ARE NOT
ANTICIPATED AT THIS TIME...EXCEPT FOR NEAR ISOLATED THUNDERSTORM ACTIVITY
EXPECTED TO AFFECT PORTIONS OF THE LOCAL WATERS OVER THE NEXT FEW
DAYS. PLEASE REFER TO THE LATEST COASTAL WATERS FORECAST ISSUED BY
THE NATIONAL WEATHER SERVICE WFO SAN JUAN PR FOR ADDITIONAL
INFORMATION.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  88  78  91  78 /  60  30  30  20
STT  87  79  87  79 /  50  30  30  40

&&

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

$$

72/09



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