853
FXCA62 TJSJ 310807
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
407 AM AST FRI OCT 31 2025
..NEW SHORT TERM, LONG TERM, AVIATION
KEY MESSAGES
ISSUED AT 335 AM AST FRI OCT 31 2025
* TODAY, THERE IS AN ELEVATED RISK OF EXCESSIVE HEAT ACROSS THE
COASTAL AND URBAN AREAS OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS TODAY. THEREFORE, A HEAT ADVISORY IS IN EFFECT FROM 10
AM AST THIS MORNING TO 4 PM AST THIS AFTERNOON.
* A LIMITED TO ELEVATED FLOODING RISK IS EXPECTED TODAY ACROSS
PORTIONS OF NORTHWESTERN PUERTO RICO, DUE TO AFTERNOON SHOWERS
ACROSS THE AREA.
* FOR THE U.S. VIRGIN ISLANDS, EXPECT PERIODS OF PASSING SHOWERS
PARTICULARLY DURING THE MORNING HOURS THIS WEEKEND.
* A MODERATE RIP CURRENT RISK WILL CONTINUE THROUGH EARLY NEXT
WEEK ACROSS THE NORTH-FACING BEACHES IN PUERTO RICO AND THE U.S.
VIRGIN ISLANDS.
* A TROPICAL WAVE WILL APPROACH THE REGION LATER TONIGHT INTO
SATURDAY,BRINGING PERIODS OF MODERATE TO HEAVY RAIN WITH
ISOLATED THUNDERSTORMS.
SHORT TERM (TODAY THROUGH SUNDAY)
ISSUED AT 335 AM AST FRI OCT 31 2025
SINCE MIDNIGHT, RADAR ESTIMATED ACCUMULATIONS SHOW AT LEAST MINIMAL
ACCUMULATIONS OVER THE USVI, VIEQUES, CULEBRA AND OVER EASTERN TO
SOUTHEASTERN TO SOUTH-CENTRAL PUERTO RICO. LOWS HAVE BEEN IN THE
UPPER 70S TO THE LOW 80S ACROSS COASTAL AREAS OF THE ISLANDS AND
FROM THE UPPER 60S TO MID 70S AT HIGHER ELEVATIONS OF PUERTO RICO.
CURRENT SATELLITE DERIVED PRECIPITABLE WATER (PWAT) IMAGERY
INDICATES AN AIRMASS WITH VALUES ABOVE 2 INCHES MOVING OVER OUR AREA
IN RELATION TO AN APPROACHING TROPICAL WAVE. AN UPPER LOW IS ALSO
OVER THE CARIBBEAN SEA, AND WILL CONTINUE TO MOVE WESTWARD TODAY. AN
UPPER LEVEL RIDGE WILL THEN ESTABLISH ITSELF AND DOMINATE THROUGHOUT
THE REST OF THE PERIOD. STEERING FLOW IN GENERAL WILL CONTINUE FROM
THE ESE FOR MOST OF THE PERIOD. EVEN AS HURRICANE MELISSA CONTINUES
TO TRACK NORTHWARD TOWARD THE NORTH ATLANTIC AND ITS INFLUENCE OVER
OUR LOCAL AREA DIMINISHES, A STRONG HIGH PRESSURE SYSTEM OVER THE
CENTRAL ATLANTIC WILL MAINTAIN THE EAST-SOUTHEASTERLY STEERING FLOW.
AS THE TROPICAL WAVE APPROACHES AND MOVES MAINLY AT AND SOUTH OF
PR/USVI, PARTICULARLY BETWEEN TONIGHT AND TOMORROW, A MORE FAVORABLE
ENVIRONMENT FOR SHOWER AND T-STORM ACTIVITY WILL BE OBSERVED DURING
THE AFTERNOON HOURS. DIURNAL HEATING AND SEA BREEZE CONVERGENCE WILL
ALSO AID IN THE FORMATION OF AFTERNOON CONVECTION. SHOWERS AND
ISOLATED T-STORMS ARE EXPECTED TO FAVOR WINDWARD SECTORS OF THE
ISLANDS DURING THE OVERNIGHT AND MORNING HOURS (PARTICULARLY TONIGHT
TO TOMORROW). AFTERNOON SHOWERS AND T-STORMS WILL ALSO DEVELOP AT
INTERIOR TO WESTERN PUERTO RICO, AS WELL AS DOWNWIND OF THE LOCAL
ISLANDS AND EL YUNQUE, ELEVATING THE FLOODING AND LIGHTNING RISKS.
WINDS ARE FORECAST TO BE MORE BREEZY, PARTICULARLY LATE TONIGHT
THROUGH THE REST OF THE SHORT TERM PERIOD. BY SUNDAY, DRIER AIR WILL
START TO FILTER IN, LIMITING AVAILABLE MOISTURE, ALONG WITH POSSIBLY
MORE EASTERLY FLOW AS THE HIGH PRESSURE MOVES NORTHWARD.
ABOVE-NORMAL TEMPERATURES AT 925 MB ARE ALSO EXPECTED TODAY, DURING
PERIODS WITH PROLONGED SUNSHINE, BEFORE DROPPING TO NEAR-NORMAL OR
BELOW-NORMAL TEMPERATURES DURING THE REST OF THE PERIOD. FOR THIS
REASON, A HEAT ADVISORY HAS BEEN ISSUED FOR URBAN AND COASTAL
AREAS OF PUERTO RICO, AS WELL AS THE EASTERN INTERIOR OF PUERTO
RICO, VIEQUES, CULEBRA, AND THE U.S. VIRGIN ISLANDS. HIGHS ARE
FORECAST TO RANGE FROM THE UPPER 80S TO THE LOW/MID 90S OVER URBAN
AND COASTAL AREAS, AND FROM THE UPPER 70S TO THE LOW 80S AT
HIGHER ELEVATIONS OF PR.
LONG TERM (MONDAY THROUGH FRIDAY)
ISSUED AT 335 AM AST FRI OCT 31 2025
THE FIRST HALF OF THE LONG-TERM PERIOD WILL BE INFLUENCED BY AN
UPPER-LEVEL LOW-PRESSURE SYSTEM MOVING SOUTH OF THE AREA, OVER THE
CARIBBEAN WATERS. THIS WILL LEAD TO A WEAKENING OF ATMOSPHERIC
STABILITY ACROSS THE REGION. IN COMBINATION WITH SUFFICIENT LOW-
LEVEL MOISTURE, THIS PATTERN WILL HELP PROMOTE SHOWERS ACROSS THE
AREA FROM MONDAY THROUGH AT LEAST TUESDAY.
DESPITE THE UPPER-LEVEL LOW, A STRONG MID-LEVEL RIDGE IS EXPECTED TO
PERSIST THROUGH THE ENTIRE PERIOD, PROMOTING STABLE AND RELATIVELY
DRIER CONDITIONS ALOFT. AT THE SURFACE, A STRONG HIGH-PRESSURE
SYSTEM OVER THE CENTRAL ATLANTIC IS FORECAST TO TIGHTEN THE PRESSURE
GRADIENT, RESULTING IN BREEZY EASTERLY WINDS THROUGH LATE TUESDAY.
WINDS WILL THEN SHIFT FROM THE SOUTHEAST FROM WEDNESDAY ONWARD.
UNDER THIS PATTERN, PATCHES OF LOW-LEVEL MOISTURE WILL CONTINUE TO
FILTER INTO PUERTO RICO AND THE U.S. VIRGIN ISLANDS. THIS WILL BRING
A LOW TO MEDIUM CHANCE (20 TO 40%) OF OCCASIONAL PASSING SHOWERS
OVER THE WINDWARD PORTIONS OF THE U.S. VIRGIN ISLANDS AND EASTERN
PUERTO RICO DURING THE MORNING HOURS. LATER IN THE AFTERNOON, SHOWER
ACTIVITY IS LIKELY OVER PORTIONS OF WESTERN AND NORTHWESTERN PUERTO
RICO DUE TO LOCAL OROGRAPHIC EFFECTS, SEA-BREEZE INTERACTIONS, AND
DIURNAL HEATING. A FEW ISOLATED THUNDERSTORMS ARE POSSIBLE AND
CANNOT BE RULED OUT.
LIMITED TO ELEVATED HEAT CONDITIONS ARE EXPECTED NEXT WEEK, DRIVEN
BY NORMAL TO ABOVE-NORMAL TEMPERATURES AT THE 925 MB LEVEL. MAXIMUM
TEMPERATURES ALONG THE COASTAL AND URBAN AREAS ARE FORECAST TO RANGE
FROM THE MID TO UPPER 80S, AND IN THE MOUNTAIN AREAS, HIGHS ARE
EXPECTED TO BE IN THE UPPER 70S TO LOW 80S.
AVIATION
(06Z TAFS)
ISSUED AT 335 AM AST FRI OCT 31 2025
MAINLY VFR CONDS EXPECTED. SHRA/ISO-TSRA WILL CONTINUE TO AFFECT
EASTERN AND SOUTHERN TERMINALS DURING THE MORNING HOURS. AFTERNOON
SHRA/TSRA ACROSS CENTRAL PR, WILL RESULT IN SHRA/TSRA AT OR IN THE
VCTY OF MAINLY TJSJ/TJPS/TJBQ WITH BRIEF MVFR CONDITIONS POSSIBLE.
ESE WINDS UP TO 15 KTS AFTER 31/13Z WITH SEA BREEZE VARIATIONS AND
HIGHER GUSTS. SHRA/ISO-TSRA OVER EASTERN AND SOUTHERN TERMINALS
DURING THE OVERNIGHT HOURS OF TONIGHT TO TOMORROW.
MARINE
ISSUED AT 335 AM AST FRI OCT 31 2025
GENTLE TO MODERATE SOUTHEAST WINDS WILL CONTINUE ACROSS THE REGION
TODAY AS HURRICANE MELISSA CONTINUES TO MOVE ACROSS THE WESTERN
ATLANTIC. A SURFACE HIGH PRESSURE OVER THE CENTRAL ATLANTIC AND A
TROPICAL WAVE MOVING ACROSS THE EASTERN CARIBBEAN WILL PROMOTE
MODERATE TO LOCALLY FRESH TRADE WINDS THIS WEEKEND. ADDITIONALLY,
THUNDERSTORM ACTIVITY IS EXPECTED ACROSS THE LOCAL WATERS AND
PASSAGES AS THE TROPICAL WAVE MOVES ACROSS THE REGION.
BEACH FORECAST
ISSUED AT 335 AM AST FRI OCT 31 2025
BEACHGOERS CAN EXPECT A MODERATE RISK OF RIP CURRENTS ALONG THE
NORTH AND EAST-FACING BEACHES IN PR AND THE USVI. THE MODERATE
RISK WILL PERSIST THIS WEEKEND INTO EARLY NEXT WEEK. OVER THE
WEEKEND, THE MODERATE RISK WILL EXPAND TO MOST LOCAL BEACHES AS
WINDS STRENGTHEN AHEAD OF AN APPROACHING TROPICAL WAVE.
ADDITIONALLY, THE POTENTIAL FOR THUNDERSTORMS WILL INCREASE ON
SATURDAY DUE TO THE ARRIVAL OF A TROPICAL WAVE. BEACHGOERS SHOULD
REMAIN CAUTIOUS AND FOLLOW GUIDANCE FROM LOCAL AUTHORITIES AND
LIFEGUARDS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HEAT ADVISORY FROM 10 AM THIS MORNING TO 4 PM AST THIS AFTERNOON
FOR PRZ001>005-007-008-010>013.
VI...HEAT ADVISORY FROM 10 AM THIS MORNING TO 4 PM AST THIS AFTERNOON
FOR VIZ001-002.
AM...NONE.
MIDNIGHT CREW...MRR/GRS
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