390
FXCA62 TJSJ 291745
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
145 PM AST WED OCT 29 2025
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 145 PM AST WED OCT 29 2025
* EXTREME HEAT RISKS ARE EXPECTED ON THURSDAY ACROSS PUERTO RICO AND
THE U.S. VIRGIN ISLANDS, WITH DANGEROUSLY HOT CONDITIONS FOR
SENSITIVE INDIVIDUALS. HEAT RISKS WILL TREND LOWER BUT REMAIN
LIMITED FROM FRIDAY INTO THE WEEKEND.
* MARINE AND SURF CONDITIONS WILL REMAIN GENERALLY FAVORABLE
THROUGH MIDWEEK BEFORE DETERIORATING OVER THE WEEKEND AS WINDS
STRENGTHEN AND LONG-PERIOD SWELLS GENERATED BY HURRICANE MELISSA
REACH THE LOCAL WATERS.
* A STABLE PATTERN WILL PREVAIL ACROSS THE REGION THROUGH THURSDAY,
FOLLOWED BY INCREASING FLOODING, LIGHTNING, AND WIND HAZARD
RISKS FROM FRIDAY INTO THE WEEKEND AS A TROPICAL WAVE AND AN
UPPER-LEVEL TROUGH APPROACH. THE U.S. VIRGIN ISLANDS WILL
EXPERIENCE A SIMILAR TREND, WITH ONLY A LOW CHANCE OF HIGH RIP
CURRENT RISK EARLY NEXT WEEK.
SHORT TERM
(TONIGHT THROUGH FRIDAY)
ISSUED AT 145 PM AST WED OCT 29 2025
MOSTLY CALM WEATHER PREVAILED ACROSS THE AREA TODAY. SATELLITE
IMAGES SHOWED MOSTLY CLEAR SKIES, WHILE RADAR DETECTED A FEW BRIEF
SHOWERS OVER THE U.S. VIRGIN ISLANDS AND EASTERN PUERTO RICO THIS
MORNING AND OVER SOUTHERN PUERTO RICO IN THE AFTERNOON, LEAVING
LITTLE TO NO MEASURABLE RAINFALL. NO NOTABLE CONVECTION DEVELOPED
OVER LAND THIS AFTERNOON. SOUTHEAST WINDS BETWEEN 10 AND 20 MPH,
WITH OCCASIONAL GUSTS NEAR 25 MPH, BROUGHT WARM AND HUMID AIR
ACROSS THE REGION, LEADING TO DANGEROUSLY HOT CONDITIONS FOR HEAT-
SENSITIVE INDIVIDUALS. AFTERNOON HIGHS REACHED THE LOWER 90S
ACROSS NORTHERN, WESTERN, AND SOUTHWESTERN PUERTO RICO AND THE
U.S. VIRGIN ISLANDS, WITH HEAT INDICES ABOVE 108°F IN SEVERAL
COASTAL AND URBAN AREAS.
AS HURRICANE MELISSA ACCELERATES NORTHEASTWARD ACROSS THE WESTERN
ATLANTIC, ITS INFLUENCE OVER THE LOCAL AREA WILL CONTINUE TO WANE.
HOWEVER, THE COMBINED EFFECTS OF THE DEPARTING CYCLONE AND A BROAD
SURFACE HIGH PRESSURE SYSTEM TO THE NORTHEAST WILL MAINTAIN
VEERING LOW-LEVEL WINDS OVER THE NEXT 12 TO 24 HOURS, BECOMING
SOUTHERLY BY THURSDAY EVENING. MEANWHILE, A STRENGTHENING MID TO
UPPER LEVEL RIDGE WILL CONTINUE TO STREAM ACROSS THE NORTHEASTERN
CARIBBEAN, PROMOTING DRYING AND INCREASED STABILITY ALOFT. THIS
PATTERN WILL REINFORCE THE TRADE WIND INVERSION, SUPPRESS DEEP
CONVECTION, AND SUPPORT A WARM AND STABLE AIR MASS. CONSEQUENTLY,
FAIR WEATHER WILL PREVAIL TONIGHT, WITH ONLY ISOLATED TO SCATTERED
BRIEF SHOWERS MAINLY OVER THE U.S. VIRGIN ISLANDS AND THE SOUTHERN AND
EASTERN PORTIONS OF PUERTO RICO. OVERALL, LAND-BASED HAZARDS WILL
REMAIN NONE TO LIMITED, WITH HIGH CONFIDENCE IN THIS FORECAST.
FROM THURSDAY INTO FRIDAY, THE MID TO UPPER LEVEL RIDGE WILL
REMAIN THE DOMINANT SYNOPTIC FEATURE BEFORE GRADUALLY SHIFTING
WESTWARD AS A TROPICAL WAVE AND AN UPPER LEVEL TROUGH APPROACH
FROM THE EAST LATE THURSDAY NIGHT INTO FRIDAY. ON THURSDAY, MID
LEVEL TEMPERATURES WILL REMAIN ABOVE TO WELL ABOVE NORMAL,
MAINTAINING STRONG ATMOSPHERIC STABILITY AND LIMITING CONVECTIVE
DEPTH DESPITE PRECIPITABLE WATER VALUES NEAR 1.5 TO 1.9 INCHES. AS
A RESULT, SHOWER AND THUNDERSTORM ACTIVITY WILL BE VERY LIMITED,
IF ANY, EVEN DURING PEAK DIURNAL HEATING, WITH ONLY A FEW BRIEF
SHOWERS POSSIBLE ACROSS THE INTERIOR AND NORTHERN PUERTO RICO.
BY LATE THURSDAY NIGHT AND INTO FRIDAY, AS THE TROPICAL WAVE AND
TROUGH ALOFT MOVE CLOSER, DEEP LAYER MOISTURE WILL INCREASE AND
MID LEVEL TEMPERATURES WILL GRADUALLY COOL, SUPPORTING A MORE
FAVORABLE ENVIRONMENT FOR SHOWER AND THUNDERSTORM DEVELOPMENT.
PRECIPITABLE WATER VALUES EXCEEDING 2.0 INCHES WILL FURTHER
SUPPORT MORE FREQUENT AND WIDESPREAD CONVECTION, FAVORING WINDWARD
AREAS EARLY FRIDAY MORNING AND FRIDAY NIGHT, AND SHIFTING TO THE
INTERIOR, NORTHERN, AND WESTERN SECTIONS BETWEEN THE LATE MORNING
AND EARLY EVENING HOURS. CONSEQUENTLY, FLOODING AND LIGHTNING
HAZARDS ARE EXPECTED TO INCREASE, WITH FLOODING RISKS RISING TO
ELEVATED LEVELS AND LIGHTNING TO LIMITED, WHILE WIND RISKS MAY
ALSO INCREASE LATE FRIDAY AS SURFACE FLOW BACKS TO THE EAST
SOUTHEAST AND STRENGTHENS. THROUGHOUT THE PERIOD, EXTREME HEAT
WILL LIKELY REMAIN THE PRIMARY HAZARD, AS WARM 925 MILLIBAR
TEMPERATURES AND WEAK TO MODERATE WINDS SUSTAIN DANGEROUSLY HIGH
HEAT INDICES. FORECAST CONFIDENCE FOR THURSDAY AND FRIDAY REMAINS
MODERATE, AS THE TIMING OF THE TRANSITION FROM THE RIDGE DOMINATED
PATTERN TO THE APPROACHING TROPICAL WAVE WILL LARGELY DETERMINE
RAINFALL COVERAGE AND INTENSITY.
LONG TERM
(SATURDAY THROUGH NEXT TUESDAY)
ISSUED AT 349 AM AST WED OCT 29 2025
A TROPICAL WAVE IS LIKELY TO MOVE ACROSS THE LESSER ANTILLES LATE
FRIDAY NIGHT INTO EARLY SATURDAY MORNING, WITH ITS LEADING EDGE
EXPECTED TO REACH THE US VIRGIN ISLANDS AND PUERTO RICO SOMETIME
BETWEEN SATURDAY MORNING AND AFTERNOON. CURRENT MODEL GUIDANCE
SUGGESTS AN INCREASING PROBABILITY OF WIDESPREAD SHOWER ACTIVITY,
WITH A MODERATE TO HIGH CHANCE (60-80%) OF THUNDERSTORMS
DEVELOPING IN THE AFTERNOON.
SHOWERS ARE EXPECTED TO GRADUALLY INCREASE THROUGH THE DAY, MOST
LIKELY BEGINNING OVER REGIONAL WATERS AND WINDWARD AREAS, THEN
SPREADING INLAND BY MID-MORNING INTO THE AFTERNOON. LOCAL EFFECTS,
DIURNAL HEATING, AND SEA-BREEZE CONVERGENCE COULD ENHANCE
RAINFALL INTENSITY, RAISING THE POTENTIAL (40-60%) FOR PERIODS OF
HEAVY RAIN, FREQUENT LIGHTNING, AND BRIEF GUSTY WINDS,
PARTICULARLY ACROSS PUERTO RICO. THE ACTIVITY SHOULD MOVE MORE
QUICKLY ACROSS THE US VIRGIN ISLANDS, LIMITING RAINFALL DURATION
THERE.
TROPICAL MOISTURE ASSOCIATED WITH THIS WAVE IS EXPECTED TO
DIMINISH GRADUALLY LATE SATURDAY NIGHT INTO EARLY SUNDAY MORNING.
AS IT DEPARTS, THE LOCAL AREA WILL LIKELY TRANSITION TO A MORE
SEASONAL PATTERN, CHARACTERIZED BY A MIX OF MOSTLY CLEAR SKIES AND
OCCASIONAL PASSING SHOWERS (30-40% CHANCE).
FROM SUNDAY ONWARD, ISOLATED TO SCATTERED AFTERNOON CONVECTION
REMAINS POSSIBLE EACH DAY, DRIVEN PRIMARILY BY LOCAL TOPOGRAPHY,
DIURNAL HEATING, AND SEA-BREEZE INTERACTIONS. THIS GENERAL PATTERN
WILL LIKELY DOMINATE THROUGH THE FIRST HALF OF NEXT WEEK, AS A
BUILDING HIGH-PRESSURE SYSTEM OVER THE REGION REDUCES ATMOSPHERIC
INSTABILITY AND LOWERS THE OVERALL PROBABILITY OF WIDESPREAD
THUNDERSTORM ACTIVITY.
AVIATION
(18Z TAFS)
ISSUED AT 145 PM AST WED OCT 29 2025
MAINLY VFR CONDS EXPECTED THRU PRD. QUIETER WX TODAY WITH LIMITED
CONVECTIVE DVLPMNT. BRIEF MVFR CONDS PSBL IN SHRA/TSRA, MAINLY AT
TJBQ AFT 28/16Z, WITH VCSH AT TJSJ AND USVI TERMINALS THRU PRD.
BRIEF REDNS IN VIS/CIGS PSBL WITH PASSING SHRA. SFC WINDS ESE–SE
10–15 KT WITH SEA-BREEZE INFLUENCE THRU AFTN/EVE, BCMG LGT/VRB AFT
28/23Z, THEN INCR TO 10–15 KT AFT 29/13Z.
MARINE
ISSUED AT 145 PM AST WED OCT 29 2025
MODERATE SOUTHEASTERLY WINDS WILL PREVAIL THROUGH FRIDAY,
GRADUALLY BACKING FROM THE EAST AND STRENGTHENING TO LOCALLY FRESH
OVER THE WEEKEND INTO EARLY NEXT WEEK. THIS PATTERN WILL BE
INITIALLY INFLUENCED BY THE DISTANT MAJOR HURRICANE MELISSA AND A
BROAD SURFACE HIGH PRESSURE SYSTEM LOCATED TO THE NORTHEAST, AND
LATER BY A PASSING TROPICAL WAVE. SEAS WILL IMPROVE TONIGHT AND
REMAIN MODERATE THROUGH THE END OF THE WORKWEEK. HOWEVER, MARINE
CONDITIONS WILL LIKELY DETERIORATE TO CAUTIONARY LEVELS OVER THE
WEEKEND AS NEW ROUNDS OF NORTHERLY SWELL PULSES GENERATED BY
MELISSA REACH THE REGIONAL WATERS AND AS WINDS STRENGTHEN AHEAD OF
THE APPROACHING WAVE. THIS SAME WAVE WILL ALSO INCREASE THE
POTENTIAL FOR SHOWERS AND THUNDERSTORMS, WHICH MAY LOCALLY
PRODUCE GUSTY WINDS AND CHOPPY SEAS. SMALL CRAFT OPERATORS SHOULD
CONTINUE TO EXERCISE CAUTION, PARTICULARLY LATE IN THE FORECAST
PERIOD.
BEACH FORECAST
ISSUED AT 145 PM AST WED OCT 29 2025
THE HIGH RISK OF RIP CURRENTS WAS CANCELLED EARLY THIS AFTERNOON
AS MARINE AND SURF CONDITIONS IMPROVED, WITH BREAKING WAVES NOW
BELOW HAZARDOUS LEVELS. A MODERATE RISK OF RIP CURRENTS HAS
REPLACED IT AND WILL PERSIST THROUGH THE WEEKEND AND INTO EARLY
NEXT WEEK, MAINLY ACROSS NORTH AND EAST FACING BEACHES OF PUERTO
RICO, INCLUDING VIEQUES AND CULEBRA, AND THE U.S. VIRGIN ISLANDS.
OVER THE WEEKEND, THE MODERATE RISK IS EXPECTED TO EXPAND TO MOST
LOCAL BEACHES AS WINDS STRENGTHEN AHEAD OF AN APPROACHING TROPICAL
WAVE, WITH A POSSIBLE RETURN TO HIGH RISK CONDITIONS FOR ST. CROIX
EARLY NEXT WEEK. INCREASED SHOWERS AND THUNDERSTORMS MAY LOCALLY
WORSEN SURF AND BEACH CONDITIONS, PRODUCING GUSTY WINDS, DANGEROUS
LIGHTNING, AND CHOPPY SURF THAT CAN QUICKLY MAKE SWIMMING UNSAFE,
PARTICULARLY FROM FRIDAY INTO THE WEEKEND. BEACHGOERS SHOULD
REMAIN CAUTIOUS AND FOLLOW GUIDANCE FROM LOCAL AUTHORITIES AND
LIFEGUARDS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HEAT ADVISORY UNTIL 4 PM AST THIS AFTERNOON FOR PRZ001>005-007-
008-010>013.
VI...HEAT ADVISORY UNTIL 4 PM AST THIS AFTERNOON FOR VIZ001-002.
AM...NONE.
SHORT TERM-AVIATION...ICP
PUBLIC-UA...MMC
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page