138
FXCA62 TJSJ 221813
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
213 PM AST TUE SEP 22 2026
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 210 PM AST TUE SEP 22 2026
* THE HEAT THREAT DUE TO WARM CONDITIONS WILL PERSIST ACROSS PUERTO
RICO AND THE U.S. VIRGIN ISLANDS DURING THE UPCOMING DAYS, WITH A
LIMITED TO ELEVATED HEAT INDICES EXPECTED, PARTICULARLY ACROSS
COASTAL AND URBAN AREAS.
* BY LATE WEDNESDAY INTO THURSDAY, A TROPICAL WAVE AND INCREASING
INSTABILITY WILL INCREASE THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS AS MOISTURE SPREADS ACROSS THE REGION.
* A MODERATE RISK OF RIP CURRENTS WILL CONTINUE ALONG PORTIONS OF
THE LOCAL BEACHES, WITH THE POTENTIAL FOR HAZARDOUS COASTAL
CONDITIONS TO INCREASE DURING THE UPCOMING WEEKEND.
* ACROSS THE U.S. VIRGIN ISLANDS, AN INCREASE IN PASSING SHOWERS IS
EXPECTED FROM LATE WEDNESDAY INTO THURSDAY MORNING AS THE TROPICAL
WAVE MOVES ACROSS THE REGION.
SHORT TERM(THIS EVENING THROUGH THURSDAY)
ISSUED AT 210 PM AST TUE SEP 22 2026
A GENERALLY FAIR WEATHER PATTERN WAS OBSERVED ACROSS THE ISLANDS
DURING THE MORNING HOURS, WITH SOME ISOLATED SHOWERS AFFECTING
NORTHEASTERN COASTAL SECTIONS. AS THE DAY PROGRESSED, TEMPERATURES
WARMED QUICKLY, ESPECIALLY ACROSS COASTAL AREAS, WHERE MAXIMUM
TEMPERATURES INCREASED INTO THE UPPER 80S TO LOWER 90S, WHILE
TEMPERATURES REMAINED IN THE MID 80S ACROSS THE MOUNTAINOUS
SECTIONS. HEAT INDICES ACROSS COASTAL AREAS RANGED FROM THE UPPER
90S TO LOWER 100S, WITH THE HIGHEST VALUES OBSERVED ACROSS NORTH-
CENTRAL PUERTO RICO. AS OF 12 PM, SATELLITE IMAGERY SHOWED
INCREASING CLOUDINESS DEVELOPING OVER THE EL YUNQUE AREA AND THE
MOUNTAINS OF WESTERN PUERTO RICO, CONSISTENT WITH THE ONSET OF LOCAL
AND DIURNAL CONVECTION. SHOWER AND THUNDERSTORM ACTIVITY DEVELOPED
ACROSS THE SAN JUAN METRO AREA WITH THE HIGHEST ACCUMULATIONS ACROSS
CAROLINA WITH ALMOST TWO INCHES ACCORDING TO THE RAINFALL RADAR
ESTIMATES. SHOWERS ALSO DEVELOP ACROSS THE INTERIOR SECTIONS WITH
STRONGEST SHOWERS ALONG OROCOVIS ALL THE WAY TROUGH LARES. THIS
CONVECTION WILL CONTINUE FOR THE REST OF THE AFTERNOON AT
SUNSET.
FOR WEDNESDAY, A TYPICAL WEATHER PATTERN WILL CONTINUE UNDER THE
INFLUENCE OF A BROAD SURFACE HIGH PRESSURE OVER THE CENTRAL
ATLANTIC, RESULTING IN EAST-SOUTHEAST WINDS ACROSS THE REGION. UNDER
THIS WIND FLOW, PASSING SHOWERS WILL CONTINUE TO MOVE ACROSS
WINDWARD SECTIONS OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS,
PARTICULARLY DURING THE MORNING HOURS, WITH MINIMAL RAINFALL
ACCUMULATIONS EXPECTED. AS THE DAY PROGRESSES, AFTERNOON CONVECTION
WILL MAINLY DEVELOP ACROSS INTERIOR AND WESTERN PUERTO RICO. WITH
PRECIPITABLE WATER VALUES REMAINING NEAR CLIMATOLOGICAL NORMALS,
AROUND 1.9 TO 2.0 INCHES, SUFFICIENT MOISTURE WILL BE AVAILABLE TO
SUPPORT AFTERNOON CONVECTION. AT THE UPPER LEVELS, AN ELONGATED
TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) WILL REMAIN POSITIONED
NORTH OF THE REGION, PROVIDING ADDITIONAL UPPER-LEVEL SUPPORT AND
CONTRIBUTING TO PERIODS OF INSTABILITY. THEREFORE, SHOWERS AND
ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING THE AFTERNOON,
PARTICULARLY ACROSS WESTERN AND INTERIOR PUERTO RICO.
FROM LATE WEDNESDAY INTO THURSDAY, A WEAK TROPICAL WAVE IS FORECAST
TO MOVE ACROSS THE REGION, INCREASING THE FREQUENCY OF SHOWERS AND
THUNDERSTORMS. ALTHOUGH THE WAVE IS EXPECTED TO REMAIN WEAK, AN
INCREASE IN MOISTURE COMBINED WITH INSTABILITY ALOFT WILL FAVOR MORE
ACTIVE WEATHER ACROSS THE ISLANDS AND SURROUNDING WATERS. SHOWER
ACTIVITY SHOULD GRADUALLY INCREASE LATE WEDNESDAY, WITH THE MOST
ACTIVE PERIOD EXPECTED WEDNESDAY NIGHT INTO THURSDAY AS THE WAVE
CROSSES THE REGION. PERIODS OF LOCALLY HEAVY RAINFALL AND ISOLATED
THUNDERSTORMS WILL BE POSSIBLE, WITH LOCALIZED URBAN AND SMALL
STREAM FLOODING POSSIBLE IN AREAS RECEIVING PERSISTENT RAINFALL.
OVERALL, THE COVERAGE AND INTENSITY OF CONVECTION WILL REMAIN
DEPENDENT ON THE AVAILABLE MOISTURE, LOCAL EFFECTS, AND DAYTIME
HEATING.
LONG TERM(FRIDAY THROUGH NEXT MONDAY)
ISSUED AT 210 PM AST TUE SEP 22 2026
THE MAIN SYNOPTIC FEATURES DURING THE LONG TERM PERIOD ARE A COUPLE
OF MULTI LEVEL LOW PRESSURE SYSTEMS ACROSS THE EASTERN ATLANTIC
OCEAN THAT WILL PROMOTE AN EAST-TO-SOUTHEAST WIND FLOW ACROSS THE
CWA. WINDS ARE EXPECTED TO BRING CALM-TO-BREEZY CONDITIONS
THROUGHOUT THE REGION POTENTIALLY FAVORING THE OCASIONAL DEVELOPMENT
OF STREAMERS FROM THE US VIRGIN ISLANDS, VIEQUES, CULEBRA AND EL
YUNQUE RAINFOREST. LOW-TO-MODERATE CONCENTRATIONS OF SAHARAN DUST
WILL FILTER BY FRIDAY ONWARDS BRINGING PWAT VALUES DOWN TO 1.2
INCHES DURING THE WEEKEND. SENSITIVE GROUPS SHOULD REMAIN ALERT AS
AIR QUALITY MAY DETERIORATE. PWAT VALUES WILL RETURN TO SEASONAL
LEVELS BY MONDAY. THE POTENTIAL FOR RAIN EACH DAY IS EXPECTED TO BE
FOCUSED ON THE NORTHWESTERN SIDE OF PUERTO RICO AND WILL BE DRIVEN
BY LOCAL EFFECTS SUCH AS SEA-BREEZE CONVERGENCE, OROGRAPHIC EFFECTS
AND DIURNAL HEATING.BESIDES THE FLOODING RISK, VISITORS AND CITIZENS
SHOULD EXPERIENCE PERIODS OF EXCESSIVE HEAT THREATS. WITH HUMIDITY
VALUES RANGING AROUND SEASONAL LEVELS AND 925MB TEMPERATURES BEING 2
STANDARD DEVIATIONS ABOVE THE NORMAL VALUES, THE EXTREME HEAT RISK
REMAINS ELEVATED THROUGH SUNDAY ACROSS COASTAL, URBAN, AND
EXPOSED AREAS, WITH CONDITIONS EXPECTED TO VARY WITH CLOUD
COVERAGE. THIS LEVEL OF HEAT AFFECTS ANYONE WITHOUT EFFECTIVE
COOLING AND/OR ADEQUATE HYDRATION. WITH IMPACTS LIKELY IN SOME
HEALTH SYSTEMS, HEAT SENSITIVE INDUSTRIES AND INFRASTRUCTURE. IT
IS RECOMMENDED THAT INDIVIDUALS LIMIT OUTDOOR ACTIVITIES AND
REMAIN HYDRATED. IT IS RECOMMENDED THAT INDIVIDUALS FOLLOW THE
INSTRUCTIONS OF HEALTH OFFICIALS AND MONITOR THE EVOLVING WEATHER
CONDITIONS.
AVIATION
(18Z TAFS)
ISSUED AT 210 PM AST TUE SEP 22 2026
VFR WILL PERSIST WITH SOME MVFR CONDITIONS DUE TO THE AFTERNOON
CONVECTION ALONG THE ISLANDS. THEREFORE, LOWER CEILING AND A
REDUCTION IN VIS IS FORECAST ACROSS TJSJ, TJPS AND TJBQ UNTIL
22/21Z. WINDS WILL CONTINUE FROM THE E-SE WITH SEA BREEZE
VARIATION DIMINISHING AT 22/06Z, AND INCREASING AGAIN BY 23/15Z.
VCSH ARE EXPECTED ACROSS THE WINDWARD TAF SITES. A TROPICAL WAVE
WAVE FORECAST FOR TOMORROW WILL INCREASE THE SHOWERS LOWERING VIS
AND CEILINGS FROM 23/17Z ALONG TIST & TISX.
MARINE
ISSUED AT 210 PM AST TUE SEP 22 2026
A MID- TO UPPER-LEVEL TROUGH WILL PROMOTE AN UNSTABLE WEATHER
PATTERN DURING THE NEXT FEW DAYS, PARTICULARLY DURING THE
AFTERNOON AND EVENING HOURS. A TROPICAL WAVE ARRIVING LATE
WEDNESDAY NIGHT INTO THURSDAY WILL PROLONG UNSETTLED CONDITIONS.
MODERATE EAST TO EAST-SOUTHEAST WINDS WILL MAINTAIN CHOPPY SEAS,
WHILE A LOW-ENERGY NORTHEASTERLY SWELL SPREADS ACROSS THE LOCAL
WATERS LATE WEDNESDAY NIGHT THROUGH THE END OF THE WORKWEEK.
BEACH FORECAST
ISSUED AT 210 PM AST TUE SEP 22 2026
A LOW RISK OF RIP CURRENTS IS EXPECTED ACROSS MOST BEACHES OF
PUERTO RICO AND THE U.S. VIRGIN ISLANDS THROUGH AT LEAST
WEDNESDAY AFTERNOON. HOWEVER, LIFE-THREATENING RIP CURRENTS REMAIN
POSSIBLE NEAR GROINS, JETTIES, REEFS, AND PIERS. ALWAYS SWIM NEAR
A LIFEGUARD AND FOLLOW BEACH-PATROL GUIDANCE AND POSTED FLAG
WARNINGS.
A SMALL NORTHEASTERLY SWELL WILL LIKELY INCREASE THE RIP-CURRENT
RISK TO MODERATE ALONG NORTH- AND EAST-FACING BEACHES LATE
WEDNESDAY NIGHT THROUGH THE END OF THE WORKWEEK, POSSIBLY
CONTINUING INTO THE WEEKEND.
BEACHGOERS SHOULD ALSO REMAIN WEATHER-READY, AS THUNDERSTORMS MAY
DEVELOP EACH AFTERNOON. IF THUNDER IS HEARD, LEAVE THE BEACH AND
SEEK SAFE SHELTER IMMEDIATELY.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM, KEY MESSAGES, AVIATION...LIS
LONG TERM....RVM
MARINE & BEACH FORECAST...CAM
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