066
FXCA62 TJSJ 170134
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
934 PM AST WED JAN 16 2019
UPDATE
MODERATE TO HEAVY RAINFALL FELL ACROSS PORTIONS OF ARECIBO THIS
EVENING, WHICH CAUSED A FLASH FLOOD ADVISORY TO BE ISSUED FOR THE
AREA. THE SEA BREEZE DEVELOPED LATE THIS AFTERNOON AND ENHANCED
SHOWERS ACTIVITY ACROSS EASTERN, INTERIOR AND NORTHERN AREAS OF
PUERTO RICO. ADDITIONALLY LOW-LEVEL MOISTURE ALSO AIDED IN SHOWER
DEVELOPMENT.
MOISTURE IS FORECAST TO INCREASE TOMORROW AND FINALLY REACH A
PEAK LATE FRIDAY. THEREFORE, EXPECT SHOWERS ACTIVITY TO INCREASE
TOMORROW THROUGH FRIDAY AS A RESULT OF INCREASING MOISTURE.
HOWEVER, SHOWERS WILL BE SHORT-LIVED DUE TO DRIER AIR THAT WILL
BE IN THE MID AND UPPER LEVELS OF THE ATMOSPHERE. THE DRIER WILL
LIMIT VERTICAL DEVELOPMENT OF SHOWERS OVER THE AREA, THUS SHOWERS
ARE EXPECTED TO BE SHORT-LIVED.
AVIATION
VRF CONDS ARE FORECAST TO CONTINUE ACROSS MOST TERMINAL SITES
THROUGH 17/12Z, BUT +SHRA COULD CAUSE SOME TERMINAL SITES TO FALL
BRIEFLY TO MVRF CONDS. MOISTURE OVER THE AREA IS CAUSING +RA OVER
PORTIONS OF EASTERN AND CENTRAL PUERTO RICO. SHRA ARE POSSIBLE
ACROSS THE LOCAL TERMINALS DURING THE OVERNIGHT AND EARLY MORNING
HOURS, ESPECIALLY FOR TERMINALS TJSJM TIST, AND TISX. SFC WINDS
WILL BE OUT OF THE EAST AT 5 TO 10 KTS, WIND BRIEFLY TURN TO THE
SOUTHEAST AT 014 TO 016 KFT, THEN WIND TURN TO THE WEST TO
NORTHWEST AT 024 TO 046 KFT WITH WINDS RANGING FROM 30 TO 60 KTS.
MARINE
SEAS WILL REMAIN BETWEEN 3 TO 5 FEET ACROSS MOST OF THE LOCAL
WATERS THROUGH FRIDAY. A NORTHERLY SWELL WILL CONTINUE TO MOVE
INTO THE AREA THROUGH FRIDAY, THUS INCREASING RISK OF RIP
CURRENTS TO HIGH FROM THE COASTLINE OF ARECIBO TO CAROLINA ON
THURSDAY MORNING.
PREV DISCUSSION
/ISSUED 423 PM AST WED JAN 16 2019/
SYNOPSIS...
TRADE WINDS BROUGHT A SURGE OF MOISTURE ACROSS THE ISLANDS TODAY.
THE SOUTH-SOUTHEAST STEERING WIND FLOW SUPPORTED THE DEVELOPMENT
OF SHOWERS ALONG AND TO THE NORTH OF THE CORDILLERA CENTRAL THIS
AFTERNOON. MOISTURE ADVECTION WILL CONTINUE ACROSS THE AREA AND
PREVAIL THROUGH THE WEEKEND. LACK OF UPPER LEVEL SUPPORT WILL
SUPPRESS ANY VERTICAL DEVELOPMENT LIMITING RAINFALL ACCUMULATIONS
THROUGH THE FORECAST PERIOD.
SHORT TERM...TONIGHT THROUGH FRIDAY...
A SURGE OF MOISTURE AND SOUTH-SOUTHEAST STEERING WIND FLOW AID IN
THE DEVELOPMENT OF SCATTERED SHOWERS ALONG AND TO THE NORTH OF
THE CORDILLERA CENTRAL THIS AFTERNOON. THIS ACTIVITY WILL CONTINUE
THROUGH THIS EVENING. RAINFALL ACCUMULATIONS WILL BE MINIMAL DUE
TO THE LACK OF UPPER LEVEL SUPPORT. RAINFALL ACTIVITY WILL SLOWLY
DIMINISH ACROSS THE NORTH AND WESTERN SECTIONS OF PUERTO RICO LATE
TONIGHT, WHILE THE WINDWARD SECTIONS OF U.S. VIRGIN ISLANDS AND
PUERTO RICO WILL CONTINUE TO OBSERVE BRIEF PASSING SHOWERS AT
TIMES. THE SOUTHERN SLOPES OF PUERTO RICO COULD EXPECT MOSTLY
CLEAR SKIES WITH NO SHOWER ACTIVITY.
SATELLITE IMAGERY DETECTED ANOTHER SURGE OF MOISTURE WHICH MODEL
GUIDANCE SUGGEST ITS ARRIVAL ACROSS THE U.S. VIRGIN ISLANDS AND
EASTERN PUERTO RICO AFTER MIDNIGHT INTO FRIDAY MORNING. SHOWERS
WILL AFFECT THESE AREAS, WHILE THE REST OF PUERTO RICO WILL HAVE
MOSTLY CLEAR SKIES. BY FRIDAY AFTERNOON, A SURFACE PERTURBATION
WILL INTERACT WITH THIS MOISTURE INDUCING AFTERNOON SHOWERS ACROSS
AND TO THE WEST OF THE CORDILLERA CENTRAL. SOME SHOWERS SHOULD NOT
BE RULED OUT OVER THE SAN JUAN METRO AREA. AN ADVECTIVE PATTERN
WILL CONTINUE ON FRIDAY AS ADDITIONAL CLOUDS AND SHOWERS WILL
CONTINUE TO MOVE ACROSS THE ISLANDS.
LONG TERM...SATURDAY THROUGH WEDNESDAY...PREVIOUS DISCUSSION.
ENOUGH LOW-LEVEL MOISTURE WILL REMAIN PRESENT ON SATURDAY TO
RESULT IN BRIEF PASSING SHOWERS ACROSS PORTIONS OF EASTERN PUERTO
RICO AND THE USVI DURING THE MORNING HOURS. THIS WILL BE FOLLOWED
BY THE DEVELOPMENT OF LOCALLY AND DIURNALLY INDUCED SHOWERS
ACROSS INTERIOR AND WESTERN PORTIONS OF PUERTO RICO DURING THE
MID TO LATE AFTERNOON HOURS.
AS THE AFORMENTIONED MID TO UPPER-LEVEL RIDGE AMPLIFIES OVERHEAD
LATE IN THE WEEKEND THROUGH THE FIRST PART OF NEXT WEEK, THE LOW-
LEVEL MOISTURE IS EXPECTED TO GRADUALLY ERODE. THIS WILL RESULT IN
MAINLY FAIR WEATHER CONDITIONS WITH VERY LIMITED SHOWER ACTIVITY
EXPECTED ACROSS THE REGION. BY THE MIDDLE OF NEXT WEEK, MODEL
GUIDANCE IS SUGGESTING AN INCREASE IN THE WINDS FROM THE NORTHEAST
AS A STRONG SURFACE HIGH PRESSURE MOVES OFF THE NORTHEAST COAST
OF THE UNITED STATES INTO THE WESTERN ATLANTIC, TIGHTENING THE
PRESSURE GRADIENT SOMEWHAT.
AVIATION...VFR CONDITIONS EXPECTED ACROSS THE LOCAL TERMINALS
THROUGH THE FORECAST PERIOD. HOWEVER, SHRA MAY RESULT IN BRIEF MVFR
CONDITIONS AT TJMZ THROUGH 17/00Z. AFTERNOON CONVECTION WILL ALSO
BRING VCSH TO TJBQ, TJPS AND TJSJ THROUGH 16/22Z. AS PATCHES OF
MOISTURE MOVE ACROSS THE REGION, VCSH ARE EXPECTED AT TIST, TISX,
TNCM AND TKPK, PARTICULARLY BETWEEN 16/22Z AND 17/14Z. SURFACE WINDS
WILL CONTINUE FROM THE EAST SOUTHEAST AT AROUND 10-15KT WITH SEA
BREEZE VARIATIONS THROUGH 16/22Z, BECOMING LIGHT AND VARIABLE
OVERNIGHT.
MARINE...
TRANQUIL MARINE CONDITIONS ARE EXPECTED TO CONTINUE ACROSS THE
REGIONAL WATERS THROUGH THE FORECAST PERIOD. WINDS AROUND 15 KNOTS
WILL VEER FROM THE EAST-SOUTHEAST THROUGH AT LEAST FRIDAY, WHEN
THE TYPICAL EASTERLY TRADE ARE FORECAST TO RETURN. SEAS WILL RANGE
BELOW 5 FEET. A NORTHERLY SWELL IS MOVING ACROSS THE ATLANTIC
WATERS AND WILL CONTINUE THROUGH AT LEAST SATURDAY.
THERE IS A MODERATE RIP CURRENT RISK FOR A FEW BEACHES ALONG THE
NORTH COAST OF PUERTO RICO. ELSEWHERE, A LOW RIP CURRENT RISK IS
IN EFFECT. A HIGH RISK OF RIP CURRENTS IS FORECAST FOR SOME NORTH
FACING BEACHES OF PUERTO RICO TOMORROW.
PRELIMINARY POINT TEMPS/POPS
SJU 71 84 72 84 / 40 30 10 20
STT 72 84 71 84 / 40 40 30 30
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK FROM 6 AM AST THURSDAY THROUGH LATE
THURSDAY NIGHT FOR NORTH CENTRAL-SAN JUAN AND VICINITY.
VI...NONE.
AM...NONE.
SHORT TERM...99
LONG TERM....99
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