460
FXCA62 TJSJ 210540
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
140 AM AST WED OCT 21 2026
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 140 AM AST WED OCT 21 2026
* A RELATIVELY QUIET AND WARM DAY WILL GIVE WAY TO WETTER
CONDITIONS AS A SURGE OF TROPICAL MOISTURE SWEEPS ACROSS THE
REGION THURSDAY THROUGH THE WEEKEND. MORE FREQUENT SHOWERS AND
THUNDERSTORMS, INCLUDING NIGHTTIME ACTIVITY, MAY PRODUCE
LIGHTNING, GUSTY WINDS, AND LOCALLY HEAVY RAINFALL CAPABLE OF
CAUSING FLOODING.
* A HIGH RISK OF RIP CURRENTS CONTINUES THROUGH THIS AFTERNOON AS
NORTHERLY SWELL SUBSIDES. CONDITIONS BRIEFLY IMPROVE THURSDAY
BEFORE ANOTHER SWELL BRINGS RENEWED RIP CURRENT HAZARDS AND
POTENTIALLY HAZARDOUS SEAS FOR SMALL CRAFT FRIDAY INTO THE
WEEKEND.
* WARM TEMPERATURES TODAY MAY AFFECT INDIVIDUALS SENSITIVE OR
VULNERABLE TO HEAT. ANOTHER PERIOD OF WARMER WEATHER IS POSSIBLE
SUNDAY INTO MONDAY.
SHORT TERM(TODAY THROUGH FRIDAY)
ISSUED AT 140 AM AST WED OCT 21 2026
SLOW-MOVING TO NEARLY STATIONARY STRONG THUNDERSTORMS DEVELOPED
OVER THE ATLANTIC WATERS NORTH OF PUERTO RICO OVERNIGHT, PRODUCING
FREQUENT LIGHTNING AND HEAVY DOWNPOURS, WITH POSSIBLE WATERSPOUTS
AND LOCALLY HAZARDOUS SEAS. THIS ACTIVITY SHOULD GRADUALLY
DIMINISH AFTER SUNRISE, WITH DAYTIME HEATING SHIFTING SHOWER AND
THUNDERSTORM DEVELOPMENT TOWARD THE INTERIOR AND NORTHERN TO
NORTHWESTERN PORTIONS OF PUERTO RICO DURING THE AFTERNOON. LIGHT
SOUTHEASTERLY STEERING WINDS WILL FAVOR SLOW-MOVING CONVECTION,
PARTICULARLY WHERE SEA-BREEZE CONVERGENCE AND LOCAL TERRAIN
EFFECTS ENHANCE DEVELOPMENT. HOWEVER, RELATIVELY DRY AIR AND
BELOW-NORMAL MOISTURE SHOULD LIMIT OVERALL COVERAGE. GREATER
SUNSHINE WILL FAVOR WARMER TEMPERATURES, PARTICULARLY ACROSS
COASTAL AND URBAN AREAS. TONIGHT, DEEPER TROPICAL MOISTURE WILL
BEGIN SPREADING NORTHWARD ACROSS THE CARIBBEAN WATERS, SUPPORTING
AN INCREASE IN OVERNIGHT SHOWERS AND THUNDERSTORMS.
A WETTER AND MORE ACTIVE PATTERN IS EXPECTED THURSDAY AND FRIDAY
AS TROPICAL MOISTURE SPREADS ACROSS THE REGION. MODEL GUIDANCE
INDICATES PRECIPITABLE WATER VALUES INCREASING TO AROUND 2.2 TO
2.3 INCHES, WELL ABOVE NORMAL, WITH SOME ADDITIONAL SUPPORT FROM
AN UPPER-LEVEL TROUGH. ALTHOUGH INCREASING CLOUDINESS MAY LIMIT
DAYTIME HEATING, PASSING SHOWERS AND LOCALLY DRIVEN CONVECTION
SHOULD FAVOR SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS, WITH
ACTIVITY PEAKING DURING THE AFTERNOON AS DAYTIME HEATING, SEA-
BREEZE CONVERGENCE, AND TERRAIN EFFECTS ENHANCE DEVELOPMENT. SOME
OF THIS ACTIVITY MAY PERSIST INTO THE EVENING, WHILE ADDITIONAL
SHOWERS AND THUNDERSTORMS MAY DEVELOP OVERNIGHT, PARTICULARLY OVER
THE SURROUNDING WATERS AND NEAR COASTAL AREAS WHERE LAND-BREEZE
CONVERGENCE OCCURS. WINDS WILL GRADUALLY SHIFT TOWARD A MORE
EASTERLY TO SOUTHEASTERLY DIRECTION THURSDAY AND FRIDAY, REMAINING
GENERALLY GENTLE TO MODERATE, WITH LOCALLY FRESH WINDS POSSIBLE
ACROSS THE CARIBBEAN WATERS AND SOUTHERN COASTAL AREAS BEGINNING
THURSDAY AFTERNOON.
THE MAIN HAZARDS THURSDAY AND FRIDAY WILL INCLUDE FREQUENT
LIGHTNING, GUSTY THUNDERSTORM WINDS, AND LOCALLY HEAVY RAINFALL.
PONDING OF WATER ON ROADS AND IN POORLY DRAINED AREAS WILL BE
POSSIBLE ACROSS PUERTO RICO AND THE U.S. VIRGIN ISLANDS, WHILE
SLOW-MOVING OR REPEATED THUNDERSTORMS COULD LEAD TO URBAN AND
SMALL-STREAM FLOODING AND ISOLATED FLASH FLOODING. AS RAINFALL
ACCUMULATES OVER SEVERAL DAYS, THE RISK OF LANDSLIDES WILL
GRADUALLY INCREASE, PARTICULARLY IN STEEP TERRAIN. THESE HAZARDS
MAY EXTEND INTO THE EVENING AND OVERNIGHT HOURS. ALTHOUGH
CONFIDENCE REMAINS HIGH IN A WETTER PATTERN, UNCERTAINTY PERSISTS
REGARDING WHERE THE HEAVIEST RAINFALL WILL OCCUR.
LONG TERM(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 140 AM AST WED OCT 21 2026
WET AND UNSETTLED WEATHER CONDITIONS ARE EXPECTED ACROSS PUERTO
RICO AND THE U.S. VIRGIN ISLANDS ON SATURDAY, FOLLOWED BY GRADUAL
IMPROVEMENT SUNDAY AND A TRANSITION TOWARD A DRIER AND MORE
STABLE WEATHER PATTERN EARLY NEXT WEEK.
A SOUTHEAST TO SOUTHERLY FLOW, MAINTAINED BY A DEEP-LAYER LOW
EXITING THE EASTERN COAST OF THE UNITED STATES AND SURFACE HIGH
PRESSURE ACROSS THE CENTRAL ATLANTIC, WILL CONTINUE TO TRANSPORT
TROPICAL MOISTURE INTO THE REGION. LATEST GFS GUIDANCE INDICATES
PRECIPITABLE WATER VALUES ABOVE 2 INCHES AND ELEVATED MID-LEVEL
RELATIVE HUMIDITY THROUGH SATURDAY, SUPPORTING SCATTERED TO
NUMEROUS SHOWERS AND THUNDERSTORMS. DAYTIME HEATING, SEA-BREEZE
CONVERGENCE, AND LOCAL TERRAIN EFFECTS WILL FAVOR THE GREATEST
CONVECTIVE ACTIVITY ACROSS INTERIOR, NORTHERN, AND WESTERN PUERTO
RICO. INCREASING STEERING WINDS SHOULD PROMOTE MORE PROGRESSIVE
SHOWERS AND THUNDERSTORMS, ALTHOUGH PERIODS OF HEAVY RAINFALL
REMAIN POSSIBLE. SOME ACTIVITY MAY PERSIST INTO THE EVENING, WITH
ADDITIONAL SHOWERS AND THUNDERSTORMS DEVELOPING OVERNIGHT OVER THE
SURROUNDING WATERS AND COASTAL AREAS. THE MAIN HAZARDS SATURDAY
WILL INCLUDE FREQUENT LIGHTNING, LOCALLY HEAVY RAINFALL, AND GUSTY
THUNDERSTORM WINDS. HEAVY DOWNPOURS COULD LEAD TO PONDING OF
WATER ON ROADWAYS, REDUCED VISIBILITY, URBAN AND SMALL-STREAM
FLOODING, AND ISOLATED FLASH FLOODING, PARTICULARLY WHERE REPEATED
SHOWERS OCCUR. AS RAINFALL ACCUMULATES OVER SEVERAL DAYS, THE
CONCERN FOR LANDSLIDES WILL ALSO INCREASE, ESPECIALLY IN AREAS OF
STEEP TERRAIN.
BY SUNDAY, A GRADUAL DECREASE IN MOISTURE SHOULD RESULT IN REDUCED
SHOWER COVERAGE. HOWEVER, LINGERING MOISTURE AND LOCAL EFFECTS
WILL CONTINUE TO SUPPORT AFTERNOON THUNDERSTORMS, PARTICULARLY
ACROSS INTERIOR AND WESTERN PUERTO RICO. WEAKENING STEERING WINDS
MAY ALLOW SOME THUNDERSTORMS TO MOVE SLOWLY, INCREASING THE
POTENTIAL FOR LOCALIZED RAINFALL ACCUMULATIONS AND ISOLATED
FLOODING DESPITE THE OVERALL IMPROVING TREND.
A MORE NOTICEABLE IMPROVEMENT IS EXPECTED MONDAY THROUGH WEDNESDAY
AS DRIER AIR SPREADS THROUGH THE ATMOSPHERIC COLUMN AND SUBSIDENCE
ASSOCIATED WITH A STRENGTHENING MID-LEVEL RIDGE SUPPRESSES
WIDESPREAD CONVECTIVE DEVELOPMENT. MODEL GUIDANCE CONTINUES TO
SUPPORT THIS TRANSITION, WITH BELOW-NORMAL PRECIPITABLE WATER
VALUES AND SUBSTANTIALLY LOWER MID-LEVEL RELATIVE HUMIDITY.
ALTHOUGH PASSING SHOWERS AND ISOLATED AFTERNOON CONVECTION WILL
REMAIN POSSIBLE, THE POTENTIAL FOR WIDESPREAD HEAVY RAINFALL AND
FLOODING SHOULD DECREASE CONSIDERABLY.
AVIATION
(06Z TAFS)
ISSUED AT 140 AM AST WED OCT 21 2026
STRONG, SLOW-MOVING TSRA OVER THE ATL WATERS N OF PR SHOULD
GRADUALLY DIMINISH AFT SUNRISE, WITH VCSH/VCTS PSBL NEAR TJSJ/TJPS
AND USVI TERMINALS. VFR CONDS EXPECTED TO PREVAIL OVERNIGHT. AFTN
SHRA/TSRA MAY PRODUCE BRIEF MVFR/IFR CIGS/VSBYS AT TJSJ/TJBQ,
MAINLY DUE TO +RA AND LOW CIGS. ACTIVITY SHOULD DIMINISH AFT
21/23Z. SFC WINDS LIGHT/VRB OVERNIGHT, BCMG SE AT 5-10 KT AFT
21/13Z, WITH SEA-BREEZE VARIATIONS AND LOCALLY GUSTY WINDS NEAR
TSRA.
MARINE
ISSUED AT 140 AM AST WED OCT 21 2026
LIGHT TO GENTLE SOUTHEASTERLY WINDS WILL GRADUALLY BECOME MORE
EASTERLY AND INCREASE TO MODERATE TO LOCALLY FRESH SPEEDS TOWARD
THE END OF THE WEEK AND INTO THE WEEKEND, PARTICULARLY ACROSS THE
CARIBBEAN WATERS. A LONG-PERIOD NORTHERLY SWELL CONTINUES TO
SUBSIDE, ALLOWING SEAS TO GRADUALLY IMPROVE. HOWEVER, ANOTHER
SWELL ARRIVING FRIDAY WILL LIKELY BRING HAZARDOUS SEAS FOR SMALL
CRAFT THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. INCREASING
TROPICAL MOISTURE WILL ALSO FAVOR MORE FREQUENT SHOWERS AND
THUNDERSTORMS, INCLUDING NIGHTTIME ACTIVITY, WITH LIGHTNING, GUSTY
WINDS, AND REDUCED VISIBILITY.
BEACH FORECAST
ISSUED AT 140 AM AST WED OCT 21 2026
A HIGH RISK OF RIP CURRENTS REMAINS IN EFFECT THROUGH THIS
AFTERNOON ALONG NORTH-FACING BEACHES OF PUERTO RICO, CULEBRA, ST.
THOMAS, AND ST. JOHN. CONDITIONS SHOULD BRIEFLY IMPROVE AS THE
CURRENT NORTHERLY SWELL SUBSIDES. HOWEVER, ANOTHER SWELL ARRIVING
FRIDAY WILL LIKELY BRING A RENEWED HIGH RISK OF RIP CURRENTS AND
POSSIBLE HIGH SURF IMPACTS ALONG EXPOSED NORTHERN BEACHES THROUGH
THE WEEKEND AND INTO EARLY NEXT WEEK. BEACHGOERS SHOULD AVOID
SWIMMING AT AFFECTED BEACHES AND STAY AWAY FROM EXPOSED ROCKS AND
JETTIES. SHOWERS AND THUNDERSTORMS MAY ALSO BRING LIGHTNING AND
GUSTY WINDS TO COASTAL AREAS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH THIS AFTERNOON FOR PRZ001-002-005-
008-010-012.
VI...HIGH RIP CURRENT RISK THROUGH THIS AFTERNOON FOR VIZ001.
AM...NONE.
EVE...MRR/MMC
MID...ICP
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