464
FXCA62 TJSJ 200545
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
145 AM AST TUE OCT 20 2026
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 145 AM AST TUE OCT 20 2026
* DANGEROUS SURF, HAZARDOUS SEAS, AND LIFE-THREATENING RIP
CURRENTS WILL AFFECT THE ATLANTIC WATERS, EXPOSED PASSAGES, AND
NORTH-FACING BEACHES OF PUERTO RICO, CULEBRA, AND THE NORTHERN
U.S. VIRGIN ISLANDS THROUGH WEDNESDAY, WITH CONDITIONS GRADUALLY
IMPROVING THEREAFTER.
* AFTERNOON THUNDERSTORMS MAY PRODUCE LIGHTNING, LOCALLY HEAVY
RAINFALL, AND URBAN OR SMALL-STREAM FLOODING ACROSS NORTHERN
PUERTO RICO TODAY. ACTIVITY SHOULD DECREASE WEDNESDAY BEFORE A
SURGE OF TROPICAL MOISTURE BRINGS MORE WIDESPREAD SHOWERS AND
RENEWED FLOODING CONCERNS THURSDAY INTO THE WEEKEND.
* WEDNESDAY WILL LIKELY BE THE WARMEST DAY OF THE PERIOD, WITH
HEAT PRIMARILY AFFECTING INDIVIDUALS EXTREMELY SENSITIVE TO
HEAT, ESPECIALLY THOSE OUTDOORS WITHOUT EFFECTIVE COOLING OR
ADEQUATE HYDRATION.
SHORT TERM(TODAY THROUGH THURSDAY)
ISSUED AT 145 AM AST TUE OCT 20 2026
A WEAK PRESSURE GRADIENT BETWEEN A FRONTAL BOUNDARY OVER THE
WESTERN ATLANTIC AND SUBTROPICAL HIGH PRESSURE TO THE EAST WILL
MAINTAIN WEAK SOUTHEAST TO SOUTHERLY FLOW THROUGH THE LOWER AND
MIDDLE LEVELS, WITH WINDS GENERALLY BETWEEN 5 AND 10 KNOTS,
OCCASIONALLY REACHING 15 KNOTS. SIMILAR TO YESTERDAY, SHOWERS OVER
THE SURROUNDING WATERS WILL MOVE INTO WINDWARD AREAS OF PUERTO
RICO AND THE U.S. VIRGIN ISLANDS OVERNIGHT INTO THE EARLY MORNING
HOURS, GRADUALLY DIMINISHING AS DAYTIME HEATING SHIFTS CONVECTIVE
DEVELOPMENT INLAND. DESPITE BELOW-NORMAL MOISTURE, SEA BREEZE
CONVERGENCE AND LOCAL TERRAIN EFFECTS WILL FAVOR SLOW-MOVING
AFTERNOON SHOWERS AND THUNDERSTORMS ACROSS THE NORTHERN HALF OF
PUERTO RICO, MAINLY FROM THE INTERIOR TOWARD NORTH-CENTRAL SECTIONS
AND THE SAN JUAN METRO AREA.
WEDNESDAY WILL BRING LESS ACTIVE WEATHER, WITH PRECIPITABLE WATER
VALUES DECREASING TO AROUND 1.4 TO 1.5 INCHES. GREATER SUNSHINE
AND WEAK SOUTHERLY FLOW WILL LIKELY MAKE IT THE WARMEST DAY OF THE
PERIOD, WITH REDUCED AFTERNOON CONVECTION. HOWEVER, GLOBAL MODELS
AGREE ON A SURGE OF TROPICAL MOISTURE BEGINNING WEDNESDAY EVENING,
SUSTAINED BY SOUTHERLY FLOW THROUGH THURSDAY AND INTO THE WEEKEND.
INCREASING UPPER-LEVEL MOISTURE WILL FAVOR EXPANDING CLOUD COVER
THURSDAY MORNING, POTENTIALLY LIMITING DAYTIME HEATING AND
FAVORING MORE WIDESPREAD PASSING SHOWERS. BY THURSDAY AFTERNOON,
DEEP TROPICAL MOISTURE SHOULD COVER THE FORECAST AREA, WITH
PRECIPITABLE WATER VALUES INCREASING TO AROUND 2.2 TO 2.3 INCHES.
THIS WILL BEGIN A WETTER PATTERN THROUGH SATURDAY, FOLLOWED BY
GRADUAL DRYING BEGINNING SUNDAY EVENING.
REGARDING HAZARDS, AFTERNOON THUNDERSTORMS TODAY COULD PRODUCE
FREQUENT LIGHTNING, PONDING OF WATER ON ROADS AND POORLY DRAINED
AREAS, AND LOCALIZED URBAN AND SMALL-STREAM FLOODING, PARTICULARLY
ACROSS NORTHERN PUERTO RICO. THESE IMPACTS SHOULD BECOME LESS
LIKELY WEDNESDAY AS SHOWER AND THUNDERSTORM COVERAGE DECREASES.
MEANWHILE, WARMER TEMPERATURES AND GREATER SUNSHINE WILL PRIMARILY
AFFECT INDIVIDUALS EXTREMELY SENSITIVE TO HEAT, ESPECIALLY THOSE
OUTDOORS WITHOUT EFFECTIVE COOLING OR ADEQUATE HYDRATION. BY
THURSDAY, INCREASING TROPICAL MOISTURE WILL FAVOR MORE WIDESPREAD
SHOWERS AND LOCALLY HEAVY RAINFALL, POTENTIALLY RESULTING IN
FLOODING OF URBAN AREAS, ROADS, SMALL STREAMS, AND POORLY DRAINED
LOCATIONS, WITH A LOW CHANCE OF ISOLATED FLASH FLOODING. EXTENSIVE
CLOUD COVER COULD LIMIT THUNDERSTORM DEVELOPMENT, WHILE BREAKS IN
THE CLOUDS AND LOCAL CONVERGENCE MAY FAVOR HEAVIER CONVECTION AND
LIGHTNING. THE AREAS MOST SUSCEPTIBLE TO FLOODING WILL DEPEND ON
WHERE PERSISTENT OR REPEATED RAINFALL DEVELOPS, WITH THEIR
LOCATION POTENTIALLY SHIFTING AS FORECAST GUIDANCE EVOLVES.
LONG TERM(FRIDAY THROUGH TUESDAY)
ISSUED AT 145 AM AST TUE OCT 20 2026
NO MAJOR CHANGES WERE INTRODUCED TO THE LONG-TERM FORECAST. WET
AND UNSETTLED WEATHER CONDITIONS ARE EXPECTED ACROSS PUERTO RICO
AND THE U.S. VIRGIN ISLANDS THROUGH MUCH OF THE WEEKEND, WITH THE
GREATEST POTENTIAL FOR WIDESPREAD SHOWERS AND THUNDERSTORMS
FRIDAY INTO SATURDAY, FOLLOWED BY GRADUALLY IMPROVING CONDITIONS
BEGINNING SUNDAY.
A SOUTHEAST TO SOUTHERLY STEERING FLOW WILL PERSIST ACROSS THE
REGION DUE TO THE INTERACTION BETWEEN A DEEP-LAYER LOW MOVING
ACROSS THE EASTERN UNITED STATES AND SURFACE HIGH PRESSURE OVER
THE CENTRAL ATLANTIC. THIS PATTERN WILL ALLOW DEEP TROPICAL
MOISTURE TO SPREAD ACROSS THE REGION, WITH PRECIPITABLE WATER
VALUES AROUND OR EXCEEDING 2 INCHES. LATEST MODEL GUIDANCE ALSO
INDICATES ANOMALOUSLY HIGH MID-LEVEL RELATIVE HUMIDITY, FAVORING
ENHANCED SHOWER AND THUNDERSTORM DEVELOPMENT AND LOCALLY HEAVY
RAINFALL. DESPITE A BUILDING MID-LEVEL RIDGE OVER THE EASTERN
CARIBBEAN, DAYTIME HEATING, SEA BREEZE CONVERGENCE, AND LOCAL
TOPOGRAPHIC EFFECTS WILL SUPPORT PASSING SHOWERS ACROSS WINDWARD
AREAS DURING THE OVERNIGHT AND MORNING HOURS, FOLLOWED BY
SCATTERED TO NUMEROUS AFTERNOON THUNDERSTORMS ACROSS INTERIOR,
NORTHERN, AND WESTERN PUERTO RICO. UNSETTLED CONDITIONS WILL
LIKELY CONTINUE INTO SATURDAY, ALTHOUGH INCREASING STEERING WINDS
SHOULD FAVOR MORE PROGRESSIVE SHOWERS AND THUNDERSTORMS. BY
SUNDAY, A GRADUAL REDUCTION IN ATMOSPHERIC MOISTURE IS EXPECTED,
LEADING TO DECREASING SHOWER COVERAGE. HOWEVER, WEAKENING STEERING
WINDS LATE IN THE WEEKEND COULD ALLOW THUNDERSTORMS TO MOVE MORE
SLOWLY, INCREASING THE POTENTIAL FOR LOCALIZED RAINFALL
ACCUMULATIONS. THE MAIN HAZARDS FRIDAY THROUGH THE WEEKEND WILL
INCLUDE LIGHTNING, URBAN AND SMALL-STREAM FLOODING, AND ISOLATED
FLASH FLOODING, PARTICULARLY WHERE REPEATED OR PERSISTENT HEAVY
SHOWERS OCCUR. MEANWHILE, PERSISTENT SOUTHEAST TO SOUTHERLY WINDS
WILL MAINTAIN HOT AND HUMID CONDITIONS, WITH THE GREATEST HEAT
IMPACTS EXPECTED ACROSS NORTHERN COASTAL AND URBAN AREAS,
PARTICULARLY FOR INDIVIDUALS SPENDING EXTENDED PERIODS OUTDOORS
WITHOUT ADEQUATE COOLING OR HYDRATION.
A MORE NOTICEABLE IMPROVEMENT IN WEATHER CONDITIONS IS FORECAST
FOR MONDAY INTO TUESDAY AS DRIER AIR SPREADS THROUGH THE
ATMOSPHERIC COLUMN AND INCREASING SUBSIDENCE ASSOCIATED WITH THE
MID-LEVEL RIDGE LIMITS CONVECTIVE DEVELOPMENT. THIS SHOULD FAVOR A
DRIER AND MORE STABLE WEATHER PATTERN ACROSS THE REGION EARLY NEXT
WEEK.
AVIATION
(06Z TAFS)
ISSUED AT 145 AM AST TUE OCT 20 2026
PASSING SHRA MAY PRODUCE BRIEF MVFR CIGS/VSBYS ACROSS USVI
TERMINALS AND TJSJ THROUGH 20/13-14Z. AFTN SHRA/TSRA MAY BRING
MVFR/IFR CONDS TO TJSJ AFTER 20/15-16Z AND TJBQ AFTER 20/16-17Z,
MAINLY DUE TO REDUCED VSBYS IN HEAVIER SHRA/TSRA AND LOCALLY LOW
CIGS. VCTS ALSO POSSIBLE NEAR TJPS AND USVI TERMINALS, WITH
ACTIVITY DIMINISHING AFTER 20/22Z. SFC WINDS LIGHT/VRB OVERNIGHT,
BECOMING ESE-SE AT 5-10 KT AFTER 20/13Z, WITH SEA BREEZE
VARIATIONS AND LOCALLY GUSTY WINDS NEAR TSRA.
MARINE
ISSUED AT 145 AM AST TUE OCT 20 2026
A WEAK PRESSURE GRADIENT BETWEEN A FRONTAL BOUNDARY OVER THE
WESTERN ATLANTIC AND HIGH PRESSURE TO THE EAST WILL MAINTAIN
GENTLE TO MODERATE EAST TO SOUTHEAST WINDS THROUGH MIDWEEK.
DESPITE THE RELATIVELY LIGHT WINDS, A SIGNIFICANT LONG-PERIOD
NORTH-NORTHWESTERLY SWELL IS EXPECTED TO PEAK TODAY BEFORE
BECOMING MORE NORTHERLY WEDNESDAY. SEAS NEAR 6 FEET ACROSS THE
ATLANTIC WATERS AND EXPOSED PASSAGES WILL WARRANT CAUTION FOR
SMALL CRAFT OPERATORS, WITH CONDITIONS GRADUALLY IMPROVING AS THE
SWELL SUBSIDES. MEANWHILE, INCREASING TROPICAL MOISTURE THURSDAY
INTO THE WEEKEND MAY FAVOR MORE WIDESPREAD SHOWERS AND
THUNDERSTORMS, POTENTIALLY BRINGING LIGHTNING, LOCALLY GUSTY
WINDS, AND REDUCED VISIBILITY OVER THE WATERS.
BEACH FORECAST
ISSUED AT 145 AM AST TUE OCT 20 2026
A SIGNIFICANT LONG-PERIOD NORTH-NORTHWESTERLY SWELL IS EXPECTED TO
PEAK TODAY, WITH BREAKING WAVES OF 8 TO 12 FEET POSSIBLE ALONG
EXPOSED NORTHERN AND NORTHWESTERN BEACHES OF PUERTO RICO, FROM
RINCON TO FAJARDO. A HIGH SURF ADVISORY REMAINS IN EFFECT THROUGH
6 PM AST THIS EVENING, WITH DANGEROUS SWIMMING CONDITIONS AND
POSSIBLE LOCALIZED BEACH AND DUNE EROSION. HIGH TIDE AROUND 3 TO 4
PM AST, REACHING APPROXIMATELY 1.5 FEET ALONG NORTHERN PUERTO
RICO, VIEQUES, AND CULEBRA, MAY ENHANCE WAVE RUNUP AND LOCALIZED
BEACH EROSION ALONG EXPOSED SHORELINES. LARGE WAVES MAY ALSO WASH
OVER EXPOSED ROCKS AND JETTIES.
A HIGH RIP CURRENT RISK WILL CONTINUE THROUGH WEDNESDAY AFTERNOON
ALONG THESE BEACHES AND THE NORTH-FACING BEACHES OF CULEBRA. THE
RISK IS ALSO EXPECTED TO INCREASE TO HIGH ALONG THE NORTH-FACING
BEACHES OF ST. THOMAS, ST. JOHN, AND ADJACENT ISLANDS BEGINNING
THIS EVENING THROUGH WEDNESDAY AFTERNOON. ALTHOUGH SURF HEIGHTS
SHOULD GRADUALLY DECREASE WEDNESDAY AS THE SWELL BECOMES MORE
NORTHERLY AND SUBSIDES, LIFE-THREATENING RIP CURRENTS WILL REMAIN
A CONCERN.
BEACHGOERS SHOULD REMAIN OUT OF THE WATER AT AFFECTED BEACHES AND
AWAY FROM EXPOSED ROCKS AND JETTIES. IMPROVING SURF CONDITIONS
LATER IN THE WEEK MAY BE ACCOMPANIED BY INCREASING SHOWERS AND
THUNDERSTORMS, POTENTIALLY BRINGING LIGHTNING AND GUSTY WINDS TO
COASTAL AREAS. SEEK SHELTER IN A SUBSTANTIAL BUILDING OR ENCLOSED
VEHICLE WHEN THUNDER IS HEARD. FOR ADDITIONAL INFORMATION, REFER
TO THE LATEST COASTAL HAZARD MESSAGE (CFWSJU).
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH WEDNESDAY AFTERNOON FOR PRZ001-002-
005-008-010-012.
HIGH SURF ADVISORY UNTIL 6 PM AST THIS EVENING FOR PRZ001-002-
005-008-010.
VI...HIGH RIP CURRENT RISK FROM THIS EVENING THROUGH WEDNESDAY
AFTERNOON FOR VIZ001.
AM...NONE.
EVE...MRR/MMC
MID...ICP
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page