087
FXCA62 TJSJ 260703
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
303 AM AST SAT SEP 26 2026
KEY MESSAGES
ISSUED AT 153 AM AST SAT SEP 26 2026
- ELEVATED FLOODING RISK MAINLY DURING THE AFTERNOON HOURS ACROSS
THE WESTERN TO NORTHWESTERN SECTIONS OF PR DUE TO PREVIOUS RAINS
IN THOSE AREAS.
- A HEAT ADVISORY WILL BE IN EFFECT SINCE 9 AM THROUGH 4 PM AST
ACROSS PUERTO RICO AND THE U.S. VIRGIN ISLANDS DUE TO CLEAR
SKIES OVERNIGHT. HEAT WILL REMAIN A PERSISTENT RISK THROUGHOUT
THE WEEKEND, WITH THE POSSIBILITY OF ADDITIONAL HEAT-RELATED
PRODUCTS BEING ISSUED.
- A MODERATE RISK OF RIP CURRENTS IS EXPECTED TO CONTINUE ALONG
NORTHWESTERN TO EASTERN BEACHES OF PUERTO RICO AND NORTHERN
U.S. VIRGIN ISLANDS THROUGH AT LEAST SATURDAY NIGHT, THEN
POTENTIALLY INCREASING TO HIGH ON SUNDAY INTO EARLY NEXT WEEK.
SHORT TERM(TODAY THROUGH MONDAY)
ISSUED AT 153 AM AST SAT SEP 26 2026
OVERNIGHT, MOSTLY CLEAR SKIES WITH QUIET WEATHER PREVAILED
ACROSS PUERTO RICO AND THE U.S. VIRGIN ISLANDS. BRIEF PASSING
SHOWERS FILTERED PORTIONS OF EASTERN PUERTO RICO AND THE U.S.
VIRGIN ISLANDS WITH ACCUMULATIONS STAYING MINIMAL. TEMPERATURES
STAYED IN THE 70S ACROSS URBAN AND COASTAL AREAS, WHILE THE
MOUNTAINOUS AREAS OBSERVED TEMPERATURES FROM THE UPPER 60S TO
LOWER 70S. WINDS REMAINED LIGHT ACROSS THE ISLANDS.
THE LATEST MODEL GUIDANCE SUGGEST THE MID-LEVEL MOISTURE AND
PRECIPITABLE WATER VALUES FOR TODAY RANGING FROM BELOW NORMAL
VALUES (25TH PERCENTILE) TOWARD NEAR NORMAL LEVELS (50TH
PERCENTILE). THEREFORE, EXPECT LIMITED OVERALL CONVECTION, BUT
DAYTIME HEATING, LOCAL EFFECTS, AND INSTABILITY ASSOCIATED WITH
THE NEARBY UPPER-LEVEL TROUGH WILL SUPPORT AFTERNOON
THUNDERSTORMS, MAINLY ACROSS INTERIOR AND NORTHWESTERN PUERTO
RICO. EXCESSIVE RAINFALL WILL BE THE PRIMARY AFTERNOON HAZARD
ACROSS NORTHWESTERN PUERTO RICO, WHERE ALREADY SATURATED SOILS
WILL INCREASE THE POTENTIAL FOR URBAN AND SMALL- STREAM FLOODING,
RAPID RUNOFF, PONDING ON ROADS, AND ISOLATED LANDSLIDES OR
ROCKFALLS. EXCESSIVE HEAT WILL BE THE OTHER SIGNIFICANT HAZARD, AS
MOSTLY CLEAR SKIES THROUGH THE EARLY AFTERNOON WILL ALLOW STRONG
HEATING, WITH HEAT ADVISORY CONDITIONS EXPECTED ACROSS SUSCEPTIBLE
AREAS FROM 9 AM THROUGH AT LEAST 4 PM TODAY. THEREFORE, PEOPLE ARE
URGED TO STAY WELL HYDRATED AND TAKE BREAK TO ADEQUATELY COOL IF
OUTSIDE.
ON SUNDAY, MOISTURE SHOULD REMAIN NEAR NORMAL VALUES AS A
TROPICAL WAVE APPROACHES THE AREA WHILE THE TROUGH REMAINS
NEARBY. ALTHOUGH THE DEEPEST TROPICAL MOISTURE SHOULD STAY SOUTH,
STRONGER INSTABILITY AND LOCAL EFFECTS COULD MAKE SUNDAY THE MOST
ACTIVE DAY OF THE SHORT-TERM PERIOD, PARTICULARLY DURING THE
AFTERNOON HOURS. EXPECT, SOME PASSING SHOWERS ACROSS WINDWARD
AREAS, FOLLOWED BY THUNDERSTORMS OVER THE INTERIOR AND WESTERN TO
NORTHWESTERN PUERTO RICO, WHILE STREAMERS COULD ENHANCE RAINFALL
DOWNWIND OF EL YUNQUE AND THE SMALLER ISLANDS. HEAVY RAINFALL WILL
POSE AN ELEVATED FLOODING RISK, INCLUDING WATER ACCUMULATION ON
ROADS AND POORLY DRAINED AREAS, URBAN AND SMALL- STREAM FLOODING,
AND QUICK RISES ALONG SUSCEPTIBLE RIVERS. SATURATED TERRAINS WILL
ALSO REMAIN VULNERABLE TO LANDSLIDES. THUNDERSTORMS MAY PRODUCE
FREQUENT LIGHTNING AND GUSTY WINDS. BEFORE CONVECTION DEVELOPS,
SUFFICIENT SUNSHINE WILL SUPPORT ANOTHER DAY OF DANGEROUS HEAT
ACROSS THE ISLANDS.
BY MONDAY, THE WEATHER PATTERN SHOULD TRANSITION TOWARD A MORE
TYPICAL LATE-SEPTEMBER REGIME WITH NO ACTIVE TROPICAL SYSTEMS,
WITH PASSING MORNING SHOWERS OVER EASTERN AND WINDWARD AREAS AND
AFTERNOON CONVECTION FAVORING INTERIOR AND WESTERN PUERTO RICO.
THE RAINFALL HAZARD SHOULD BECOME MORE LOCALIZED. HEAT WILL
CONTINUE TO BE A CONCERN, ESPECIALLY WHERE PROLONGED MORNING AND
EARLY- AFTERNOON SUNSHINE OCCURS BEFORE SHOWERS DEVELOP, WITH
ELEVATED HEAT INDICES POSSIBLE ACROSS COASTAL AND URBAN AREAS. FOR
THAT REASON WE URGE PEOPLE TO MONITOR THE FORECAST IN ORDER TO
ENSURE THEIR SAFETY AND THE SAFETY OF THE ONCE THEY CARE.
LONG TERM(TUESDAY THROUGH SATURDAY)
ISSUED AT 153 AM AST SAT SEP 26 2026
DRIER CONDITIONS THAN THOSE USUALLY SEEN FOR THE SEASON ARE EXPECTED
THROUGHOUT THE LONG TERM PERIOD. WHILE MODEL GUIDANCE INDICATES SOME
VARIABILITY, WITH THE GFS SHOWING MORE FAVORABLE CONDITIONS ON
TUESDAY, THE MAJORITY OF THE HUMIDITY WILL BE CENTERED IN THE LOW
LEVELS OF THE TROPOSPHERE WHILE DRIER CONDITIONS WILL DOMINATE THE
LOW-TO-UPPER LEVELS (700-250HPA). AN UPPER-LEVEL LOW PRESSURE SYSTEM
WILL BE LOCATED TO THE NORTHEAST OF THE US VIRGIN ISLANDS AND PUERTO
RICO AT THE BEGINNING OF THE WEEK AND WILL SHIFT TO THE SOUTHEAST OF
THE REGION BY THE END OF THE WEEK EVENTUALLY MOVING AWAY FROM THE
CWA BY THE END OF THE FORECAST PERIOD. WHILE THESE CONDITIONS WILL
ACT TO LIMIT SHOWER AND THUNDERSTORM ACTIVITY, OTHER FACTORS MAY
FAVOR MORE ACTIVE PERIODS OVER THE ISLANDS. MID TROPOSPHERIC
TEMPERATURES REMAIN FAVORABLE FOR THE DEVELOPMENT OF DEEP CONVECTIVE
CELLS. LOCAL EFFECTS WILL ACT AS THE MAIN DRIVERS OF ACTIVITY
PARTICULARLY OVER THE US VIRGIN ISLANDS AND EASTERN PUERTO RICO IN
THE MORNINGS AND THE INTERIOR AND NORTHWESTERN PUERTO RICO IN THE
AFTERNOONS. INCREASING SURFACE WINDS MAY ALSO FAVOR THE DEVELOPMENT
OF STREAMERS FROM THE US VIRGIN ISLANDS, VIEQUES, CULEBRA AND EL
YUNQUE RAINFOREST. CONDITIONS ARE EXPECTED TO BECOME MORE ENHANCED
BY FRIDAY AFTERNOON WHEN A MORE HUMID VERTICAL PROFILE RETURNS
INCREASING THE POTENTIAL FOR THE DEVELOPMENT OF CONVECTION. CITIZENS
AND VISITORS ARE INVITED TO REMAIN WEATHER READY AND STAY UPDATED OF
THE EVOLVING WEATHER CONDITIONS.
THE LONG TERM PERIOD MIGHT ALSO BRING A RESPITE FROM THE ELEVATED
HEAT RISKS AND THE 925 MB TEMPERATURES SHOW A DECREASING TREND,
SUGGESTING MORE AMENABLE CONDITIONS MIGHT PREVAIL AS THE WEEK
PROGRESSES. NONETHELESS, INDIVIDUALS ARE RECOMMENDED TO STAY ALERT
AS THESE FORECASTED CONDITIONS MAY CHANGE.
AVIATION
(06Z TAFS)
ISSUED AT 153 AM AST SAT SEP 26 2026
EXPECT VFR CONDS ACROSS ALL TERMINALS DURING THE FORECAST PERIOD.
AFTN SHRA/TSRA DEVELOPMENT COULD RESULT IN VCTS AT TJBQ/TJPS BTW
26/17-23Z. BRIEF PERIODS OF MVFR PSBL ACROSS CENTRAL AND WESTERN
PR, PARTICULARLY AT TJBQ AFT 26/17Z. WINDS LGT/VRB TO CALM THRU
26/13Z, FROM E-SE 5-10 KT WITH HIGHER GUSTS AND SEA BREEZE
VARIATIONS THRU 26/23Z.
MARINE
ISSUED AT 153 AM AST SAT SEP 26 2026
LIGHT TO MODERATE EAST TO SOUTHEAST WINDS OF 10 TO 15 KNOTS OR LESS
AND SEAS GENERALLY BETWEEN 2 AND 4 FEET WILL PREVAIL TODAY. MARINE
CONDITIONS WILL GRADUALLY DETERIORATE FROM SUNDAY INTO EARLY NEXT
WEEK AS A NORTHERLY SWELL SPREADS ACROSS THE ATLANTIC WATERS AND
PASSAGES WHILE EASTERLY WINDS STRENGTHEN. SEAS WILL BUILD TO 5 TO 6
FEET ACROSS PORTIONS OF THE ATLANTIC WATERS AND LOCAL PASSAGES, WITH
OCCASIONAL SEAS UP TO 8 FEET POSSIBLE BY MONDAY NIGHT. SMALL CRAFT
ADVISORY CONDITIONS MAY BECOME POSSIBLE ACROSS PORTIONS OF THE
ATLANTIC WATERS AND LOCAL PASSAGES EARLY NEXT WEEK. SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS MAY ALSO RESULT IN LOCALLY HIGHER
WINDS AND SEAS, FREQUENT LIGHTNING, AND BRIEF REDUCTIONS IN
VISIBILITY.
BEACH FORECAST
ISSUED AT 153 AM AST SAT SEP 26 2026
A MODERATE RISK OF RIP CURRENTS WILL PREVAIL TODAY ALONG THE WEST-
NORTHWESTERN THROUGH NORTHEASTERN BEACHES OF PUERTO RICO, FROM
MAYAGüEZ TO HUMACAO ALONG THE ATLANTIC COASTLINE, AS WELL AS CULEBRA
AND THE NORTHERN U.S. VIRGIN ISLANDS. THE MODERATE RISK WILL SPREAD
TO ADDITIONAL BEACHES SUNDAY, WITH A HIGH RISK OF RIP CURRENTS
POSSIBLE BY MONDAY AS A NORTHERLY SWELL BUILDS, PARTICULARLY ALONG
THE MOST EXPOSED NORTHERN BEACHES. BREAKING WAVES WILL INCREASE TO
AROUND 5 TO 6 FEET DURING THIS PERIOD.
ADDITIONAL BEACH HAZARDS INCLUDE AFTERNOON HEAT AND ISOLATED
THUNDERSTORMS, ESPECIALLY ACROSS WESTERN PUERTO RICO, WHERE
LIGHTNING, BRIEF HEAVY RAINFALL, AND GUSTY WINDS MAY OCCUR.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HEAT ADVISORY FROM 9 AM THIS MORNING TO 4 PM AST THIS AFTERNOON
FOR PRZ001>013.
VI...HEAT ADVISORY FROM 9 AM THIS MORNING TO 4 PM AST THIS AFTERNOON
FOR VIZ001-002.
AM...NONE.
SHORT TERM/AVIATION...MMC
LONG TERM...RVM/MRR
MARINE/BEACH FORECAST...ICP
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