313
FXCA62 TJSJ 302031
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
431 PM AST MON DEC 30 2024
SYNOPSIS
A SEASONAL ADVECTIVE PATTERN WITH PLEASANT TEMPERATURES IS
FORECAST EACH DAY AS A SURFACE HIGH MOVES FROM THE WESTERN TO
CENTRAL ATLANTIC. ADVECTIVE SHOWERS STEERED BY NORTHEASTERLY WINDS
WILL MOVE OVER WINDWARD SECTORS AT TIMES. THERE IS A SLIGHT TO
MODERATE CHANCE THAT INSTABILITY AND RAIN ACTIVITY WILL INCREASE
BY NEXT WEEKEND DUE TO ANOTHER COLD FRONT AND A POLAR TROUGH THAT
COULD MOVE NEAR THE NORTHEAST CARIBBEAN. PULSES OF NORTHEASTERLY
SWELLS PRODUCING DANGEROUS BREAKING WAVES WILL CREATE LIFE-
THREATENING RIP CURRENTS ALONG THE NORTH AND EAST-FACING BEACHES
OF THE USVI AND PUERTO RICO THROUGHOUT MIDWEEK AND THEN LATER BY
THE END OF THE WORKWEEK AND INTO THE WEEKEND.
SHORT TERM...TONIGHT THROUGH WEDNESDAY
DURING THE EARLY MORNING HOURS, LIGHT AND BRIEF PASSING SHOWERS
STEERED BY NORTHEASTERLY WINDS MOVED ACROSS SECTORS OF THE EASTERN
REGION, LEAVING MINIMAL (RADAR ESTIMATED) ACCUMULATIONS OVER NORTH-
CENTRAL AND EASTERN PR, AS WELL AS OVER VIEQUES, CULEBRA AND ST.
THOMAS. PATCHY FOG OVER THE INTERIOR WAS ALSO OBSERVED DURING THE
EARLY MORNING, AND DURING THE DAY, GENERALLY PLEASANT WEATHER AND
COOL TEMPERATURES PREVAILED. BY 3:40 PM, HIGHS RANGED IN THE LOW 80S
ALONG MOST LOWER ELEVATIONS OF THE ISLANDS (LOCALIZED AREAS IN
SOUTHERN PR REACHED THE MID 80S) AND IN THE UPPER 60S TO LOW 70S
ACROSS HIGHER ELEVATIONS OF PUERTO RICO.
HIGH PRESSURE DOMINATES THE REGION, MAINTAINING MOSTLY CALM AND
STABLE CONDITIONS. SHALLOW MOISTURE AND NORTH-NORTHEASTERLY FLOW IS
CREATING LOW TO MID LEVEL CLOUD COVER ACROSS THE REGION, AS WELL AS
A FEW SHOWERS OVER WINDWARD LOCATIONS IN PUERTO RICO. 850-700 MB
MOISTURE WILL ALLOW SHOWERS TO PUSH FURTHER INLAND AND AS FAR SOUTH
AS ST. CROIX. THIS SEASONABLE PATTERN IS EXPECTED TO PREVAIL THROUGH
MIDWEEK, BRINGING A CHANCE OF SHOWERS EVERY AFTERNOON IN
SOUTHEASTERN PUERTO RICO. SHOWERS ARE LIKELY TOMORROW MORNING IN
EASTERN PORTIONS OF PUERTO RICO, VIEQUES, CULEBRA, AND THE U.S.
VIRGIN ISLANDS. MORNING SHOWERS SHOULD TAPER OFF BY MID AFTERNOON,
LEAVING SUNSHINE AND CLOUDS IN THEIR WAKE. TEMPERATURES WILL REMAIN
NEAR-NORMAL, ALTHOUGH DRIER MID-LEVELS WILL KEEP THE AIR FEELING
FRESH. HIGH TEMPERATURES IN THE 80S WILL PREVAIL THROUGH THE SHORT
TERM AND 70S IN THE MOUNTAINS, AND LOW TEMPERATURES IN THE 50S TO
70S.
LONG TERM...THURSDAY THROUGH MONDAY
/FROM PREV DISCUSSION
ISSUED AT 450 AM AST MON DEC 30 2024/
A SUBTROPICAL SURFACE HIGH PRESSURE WILL CONTINUE TO PROMOTE
TRADE WINDS, PUSHING A COOLER AIR MASS AND THUS COOLING LOCAL
TEMPERATURES. MEANWHILE, POCKETS OF MOISTURE EMBEDDED IN THE
TRADES WILL OCCASIONALLY BRING QUICK PASSING SHOWERS.
A FRONTAL BOUNDARY WILL MOVE OUT OF THE EASTERN U.S. AROUND
WEDNESDAY, GRADUALLY MOVING EASTWARD BEHIND THE SURFACE HIGH
PRESSURE SYSTEM. BY NEXT WEEKEND, IT WILL APPROACH THE NORTHEAST
CARIBBEAN, BRINGING ADDITIONAL MOISTURE TO THE AREA. THERE IS A
SLIGHT CHANCE OF A PRE-FRONTAL TROUGH DEVELOPING NEAR THE LOCAL
ISLANDS. ALONG WITH THE FRONT, A MID TO UPPER-LEVEL TROUGH WILL
PASS NEAR THE ISLANDS, INCREASING LOCAL INSTABILITY. GIVEN THIS
WEATHER PATTERN, WE CAN ANTICIPATE AN INCREASE IN SHOWER ACTIVITY,
ALONG WITH A SLIGHT TO MODERATE CHANCE OF ISOLATED TO SCATTERED
THUNDERSTORMS FROM SATURDAY AFTERNOON INTO SUNDAY, IF THIS PATTERN
PERSISTS.
THE GLOBAL MODELS DIFFER SLIGHTLY ON WHETHER THE FRONT WILL CROSS
THE ISLANDS BY NEXT WEEK, PROMOTING AN EXTENSION IN THE TYPICAL
WINTER COOLER TEMPERATURES. THEREFORE, WE WILL EXAMINE THIS
POSSIBILITY MORE CLOSELY AS TIME PASSES.
AVIATION
(18Z TAFS)
MOSTLY VFR CONDITIONS FOR ALL TERMINALS WITH SOME LOW TO MID LEVEL
CLOUD COVERAGE THROUGH THE EARLY AFTERNOON. LIGHT TO MODERATE NE
WINDS WILL PREVAIL FOR THE FORECAST PERIOD WITH PATCHES OF SHALLOW
MOISTURE PROMOTING -SHRA AND VCSH THIS AFTERNOON THROUGH 22Z.
BRIEFLY HEAVIER SHOWERS MAY REDUCE VISIBILITY TO MVFR FOR BRIEF
PERIODS OVERNIGHT. WINDS ARE EXPECTED TO BECOME LIGHT OVERNIGHT
EXCEPT DURING PERIODS OF SHOWERS.
MARINE
MODERATE NORTHEAST WINDS IN PLACE FOR EARLY THIS WEEK UNDER A
SURFACE HIGH PRESSURE IN THE WESTERN ATLANTIC AND SURFACE LOW OVER
THE CENTRAL ATLANTIC. SEAS UP TO AND EXCEEDING 7 FEET WILL
CONTINUE WITH THE NORTHERLY SWELL THROUGH AT LEAST TONIGHT.
ANOTHER FRONT FROM THE EASTERN US WILL MOVE INTO THE WESTERN
ATLANTIC BY MIDWEEK, APPROACHING THE NORTHEAST CARIBBEAN BY THE
WEEKEND. ANOTHER LONG- PERIOD NORTHERLY SWELL WILL PROMOTE
HAZARDOUS SEAS BY THE END OF THIS WEEK THROUGH THE WEEKEND. A
SMALL CRAFT ADVISORY IS IN EFFECT THROUGH 6 AM AST TUESDAY FOR THE
OFFSHORE AND NEARSHORE ATLANTIC WATERS, THE NEARSHORE WATERS
NORTHWEST OF PUERTO RICO, THE MONA PASSAGE, AND THE ANEGADA
PASSAGE. PLEASE REFER TO THE LATEST COASTAL WATERS FORECAST
(CWFSJU & CWFSPN) AND THE LATEST MARINE WEATHER MESSAGE (MWWSJU)
FOR MORE DETAILS.
BEACH FORECAST
PULSES OF NORTHEASTERLY SWELLS ARE MOVING ACROSS THE ATLANTIC
OFFSHORE WATERS AND CARIBBEAN PASSAGES, PRODUCING DANGEROUS
BREAKING WAVES ALONG THE NORTH AND EAST-FACING BEACHES IN PR AND
THE US VIRGIN ISLANDS. THERE IS A HIGH SURF ADVISORY IN EFFECT
THROUGH 6 AM AST TOMORROW FOR THE NORTH FACING BEACHES OF PUERTO
RICO, FROM AGUADILLA TO FAJARDO, AND CULEBRA. THERE IS A HIGH RISK
OF RIP CURRENTS IN EFFECT FOR THE NORTH FACING BEACHES OF PUERTO
RICO, FROM AGUADILLA TO FAJARDO, AND CULEBRA, THROUGH AT LEAST 6
AM AST WEDNESDAY. THERE IS A HIGH RISK OF RIP CURRENTS IN EFFECT
FOR THE BEACHES OF RINCON, AGUADA, AND THE USVI THROUGH AT LEAST 6
AM AST TOMORROW. A LOW RISK OF RIP CURRENTS IS EXPECTED ACROSS
THE SOUTHERN PROTECTED BEACHES OF PUERTO RICO. ANOTHER LONG-
PERIOD NORTHERLY SWELL WILL AGAIN DETERIORATE COASTAL CONDITIONS
BY THE END OF THIS WEEK THROUGH THE WEEKEND. FOR ADDITIONAL
INFORMATION, PLEASE REFER TO THE COASTAL HAZARD MESSAGE (CFWSJU)
AND SURF ZONE FORECAST (SRFSJU).
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH LATE TUESDAY NIGHT FOR PRZ001-002-
005-008-012.
HIGH SURF ADVISORY UNTIL 6 AM AST TUESDAY FOR PRZ001-002-005-008-
012.
HIGH RIP CURRENT RISK THROUGH LATE TONIGHT FOR PRZ010.
VI...HIGH RIP CURRENT RISK THROUGH LATE TONIGHT FOR VIZ001-002.
AM...SMALL CRAFT ADVISORY UNTIL 6 AM AST TUESDAY FOR AMZ711-712-716-
723-741-742.
SHORT TERM...WFO BRO
LONG TERM....CAM
AVIATION...WFO BRO
MARINE...CVB
BEACH FORECAST...MRR
PUBLIC DESK...MRR
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