Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 290917
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
517 AM AST THU JAN 29 2015

.SYNOPSIS...DEEP POLAR TROUGH WILL BECOME THE DOMINANT WX FEATURE
THROUGH SATURDAY. RIDGE OF HIGH PRESSURE SFC AND ALOFT BUILDS
SUNDAY THROUGH MUCH OF NEXT WEEK.

&&

.DISCUSSION...PARTLY CLOUDY SKIES PREVAILED OVERNIGHT ACROSS THE
LOCAL ISLANDS...WITH PASSING SHOWERS NOTED ACROSS THE EASTERN
THIRD OF PR...USVI AS WELL AS LOCAL WATERS. WINDS WERE LIGHT FROM
THE SOUTHEAST WITH COASTAL TEMPERATURES IN THE MID 70S.

DEEP POLAR TROUGH OVER THE WESTERN ATLANTIC WILL BECOME THE DOMINANT
WEATHER FEATURE THROUGH THE END OF THE WEEK. THIS WILL PROMOTE
MOISTURE TRANSPORT AND FAVORABLE UPPER LEVEL DYNAMICS INTO THE
REGION WITH SHOWERS AND T-STORMS EXPECTED THU-FRI. SOME OF THEM
MAY BECOME STRONG ENOUGH TO PRODUCE LOCALLY HEAVY RAINFALL...GUSTY
WINDS AND FREQUENT LIGHTING. URBAN AND SMALL STREAM FLOODING WILL
NOT BE RULED OUT. APPROACHING SHEARLINE AND ASSOCIATED SURFACE
TROUGH WILL FOCUS SHOWERS AND T-STORMS OVER SOUTHWEST PR TODAY.

TROUGH ALOFT AND NORTHEAST WINDS WILL BRING SHOWERS AND T-STORMS
NORTH OF THE CORDILLERA AS WELL AS OVER THE NORTHERN USVI
TONIGHT/FRIDAY MORNING. THEN SHOWERS/THUNDERSTORMS WILL BE FOCUSED
OVER AND SOUTH OF THE CORDILLERA FRIDAY AFTERNOON. TROUGH BEGINS
TO LIFT OUT SAT WITH RIDGE OF HIGH PRESSURE GRADUALLY STRENGTHENING.
THIS FEATURE AND ASSOCIATED SUBSIDENCE CAP COMBINED WITH NEAR TO
BELOW NORMAL PRECIPITABLE WATER WILL RESULT IN A GENERALLY FAIR
AND MAINLY STABLE WEATHER PATTERN MUCH OF NEXT WEEK. HOWEVER...
EARLY MORNING SHOWERS ACROSS WINDWARD AREAS AS WELL AS LIMITED
AFTERNOON CONVECTION OVER WEST PUERTO RICO CANT BE RULED OUT EACH
DAY. THE BEST CHANCE OF SHOWER ACTIVITY NEXT WEEK IS SUNDAY AND
MONDAY WITH A SHARP DECREASE TUESDAY AND INTO THE END OF THE WEEK.

&&

.AVIATION...MOSTLY VFR CONDITIONS WILL PREVAIL ACROSS THE FORECAST
AREA AT LEAST THROUGH 29/16Z WITH BRIEF SHRA ACROSS THE AREA CAUSING
VCSH AT THE LOCAL TERMINALS. SHRA/TSRA DEVELOPMENT EXPECTED TO
DEVELOP ACROSS CENTRAL-WESTERN-AND SW PR WILL CAUSE MTN OBSCURATIONS
AS WELL AS VCTS FOR TJPS AND TJMZ...ESPECIALLY BETWEEN 29/17Z AND
29/22Z...WHERE CIGS AROUND FL050 ARE POSSIBLE FOR PR/USVI AS WELL.
MVFR CONDS ARE POSSIBLE AT TJMZ DURING THAT TIME IN SHRA/TSRA. EASTERLY
WINDS WILL PREVAIL WITH SEA BREEZE VARIATIONS AT AROUND 10-15KT.

&&

.MARINE...NW SWELLS AFFECTING ATLC COASTAL WATERS WITH WAVE HEIGHTS
OF 5-7 FT...BUT SUBSIDING LATER TODAY. HOWEVER...SEVERAL PULSES OF
NNW SWELLS WILL CONTINUE THROUGH THE WEEKEND. WINDS STRENGTHEN SUN
INTO MON WITH SCA CONDITIONS MORE LIKELY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  86  75  83  73 /  50  50  50  30
STT  84  77  84  76 /  50  50  50  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 6 PM AST THIS EVENING FOR ATLC WATERS
     OF PUERTO RICO AND USVI FROM 10NM TO 19.5N.

&&

$$

25/23




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