Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 020936
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
536 AM AST MON MAR 2 2015

.SYNOPSIS...MID TO UPPER LEVEL HIGH PRESSURE RIDGE IS TO ERODE
SOMEWHAT TODAY AND TUESDAY AS A SHORT WAVE TROUGH MOVES EASTWARD
ACROSS THE ATLANTIC AND JUST NORTH OF THE FORECAST AREA. RIDGE ALOFT
IS TO REESTABLISH ITSELF AND BUILD ACROSS THE REGION ONCE AGAIN BY
WEDNESDAY.THIS IN TURN WILL REINFORCE THE TRADE WIND CAP INVERSION...
AND THEREFORE MAINTAIN MODERATE TO FAIRLY STRONG EASTERLY TRADE WINDS.
SURFACE HIGH PRESSURE ACROSS THE SOUTHWEST AND CENTRAL ATLANTIC WILL
ALSO WEAKEN SLIGHTLY AND SHIFT FARTHER EAST TODAY THROUGH TUESDAY...AS
A STRONG AREA OF LOW PRESSURE AND ASSOCIATED COLD FRONT EXITS THE NORTHEASTERN
UNITED STATES...AND MOVES ACROSS THE WEST AND CENTRAL ATLANTIC. SURFACE
HIGH PRESSURE WILL ONCE AGAIN BE REINFORCED ACROSS THE WEST AND SOUTHWESTERN
ATLANTIC BY WEDNESDAY AND DURING THE REMAINDER OF THE WORK WEEK...AND
CONSEQUENTLY INDUCE AN MAINTAIN MODERATE TO STRONG NORTHEAST TO EAST
TRADE WIND FLOW.

&&

.DISCUSSION...WEAK PERTURBATION IN THE PREVAILING EASTERLIES
CONTINUED TO BRING PATCHES OF LOW TO MID LEVEL MOISTURE ACROSS
THE REGION DURING THE OVERNIGHT AND EARLY MORNING HOURS. THE DOMINANT
EAST NORTHEAST WINDS STEERED THE CLOUDINESS AND ACCOMPANYING LIGHT
TO MODERATE SHOWERS ACROSS THE COASTAL WATERS AND PORTIONS OF THE
NORTH AND EAST COASTAL SECTIONS OF THE ISLANDS. A FEW SHOWERS WERE
LOCALLY HEAVY AT TIMES BUT WERE OF SHORT DURATION AND FAST MOVING
LEAVING NO SIGNIFICANT RAINFALL ACCUMULATIONS. FOR THE REST OF THE
DAY...THE COMBINATION OF AVAILABLE MOISTURE BEING ADVECTED ACROSS
THE REGION...ALONG WITH THE ERODING RIDGE ALOFT AND WEAK SHORT WAVE
MOVING THROUGH THE REGION...SHOULD BE ENOUGH TO ALLOW FOR AFTERNOON
CONVECTION ACROSS THE ISLANDS. IN ADDITION...DUE TO THE MARGINAL INSTABILITY
ALOFT...THESE IS A SLIGHT CHANCE OF AN ISOLATED THUNDERSTORM MAINLY
OVER PARTS OF THE WEST AND SOUTHWEST SECTIONS OF PUERTO RICO...UNDER
THE PREVAILING LOW TO MID LEVEL STEERING FLOW. AT THIS TIME...ONLY
ISOLATED AREAS OF HEAVY RAINFALL WILL BE POSSIBLE IN THESE AREAS
AS THE MAJORITY OF THE AFTERNOON CONVECTION SHOULD BE FAST MOVING.

FOR THE REST OF THE WEEK...MUCH OF THE SAME WEATHER PATTERN IS
EXPECTED ACROSS THE REGION...WITH THE PREVAILING EAST TO NORTHEAST
WIND FLOW DOMINATING THE LOCAL WEATHER PATTERN...AND HIGH PRESSURE
BUILDING ALOFT ONCE AGAIN TO MAINTAIN AN OVERALL SUBSIDENT PATTERN
WHICH SHOULD SUPPRESS OR LIMIT ANY SIGNIFICANT CONVECTIVE DEVELOPMENT.
SO FOR NOW...EXPECT INTERVALS OF SHALLOW PASSING CLOUDS AND SHOWERS
DURING THE EVENING AND EARLY MORNINGS...FOLLOWED BY ISOLATED TO SCATTERED
AFTERNOON CONVECTION MOSTLY ACROSS PARTS OF THE INTERIOR AND WEST SECTIONS
OF PUERTO RICO. FOR THE U.S. VIRGIN ISLANDS...FEW PASSING SHOWERS WILL
REMAIN POSSIBLE EACH DAY...BUT MOSTLY FAIR WEATHER SKIES SHOULD PREVAIL.

&&

.AVIATION...BRIEF PERIODS OF MVFR CONDITIONS EXPECTED THIS MORNING
ACROSS TJSJ...TISX...TIST...TNCM AND TKPK IN QUICK PASSING SHOWERS.
WINDS WILL BE MAINLY FROM THE EAST TO E-NE AT AROUND 10 KTS EARLY
THIS MORNING INCREASING TO AROUND 15 KTS AND GUSTY WITH SEA BREEZE
VARIATIONS AFTER 02/13Z. A SLIGHT CHANCE OF TSRA ACROSS THE VICINITY
OF TJMZ AFTER 02/16Z.

&&

.MARINE...SMALL CRAFT ADVISORIES WILL REMAIN IN EFFECT FOR MOST OF
THE REGIONAL WATERS...EXCEPT FOR THE NEAR SHORE WATERS OF WEST AND
SOUTHERN PUERTO RICO...WHERE SMALL CRAFT OPERATORS SHOULD EXERCISE
CAUTION. ALTHOUGH THE WINDS WILL SLIGHTLY DIMINISH TODAY ACROSS THE
COASTAL WATERS...STILL EXPECT THE MODERATE TO LOCALLY STRONG EAST
NORTHEAST TRADE WINDS TO GENERATE ROUGH AND HAZARDOUS WIND DRIVEN
SEA CONDITIONS. PLEASE REFER TO THE LATEST COASTAL WATERS FORECAST
AND MARINE WEATHER MESSAGE ISSUED BY THE NATIONAL WEATHER SERVICE
WFO SAN JUAN PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  87  74  84  75 /  30  20  20  20
STT  86  73  85  74 /  30  20  20  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...

VI...NONE.
COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 6 AM AST FRIDAY FOR ANEGADA PASSAGE
     SOUTHWARD TO 17N-ATLC WATERS OF PUERTO RICO AND USVI FROM
     10NM TO 19.5N-CARIBBEAN WATERS OF PUERTO RICO FROM 10 NM TO
     17N-COASTAL WATERS OF NORTHERN PUERTO RICO OUT 10 NM-
     COASTAL WATERS OF NORTHERN USVI AND CULEBRA OUT 10 NM-
     COASTAL WATERS OF SOUTHERN USVI VIEQUES AND EASTERN PUERTO
     RICO OUT 10 NM-MONA PASSAGE SOUTHWARD TO 17N.

&&

$$

72/09





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