752
FXCA62 TJSJ 300810
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
410 AM AST THU OCT 30 2025
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 400 AM AST THU OCT 30 2025
* THE US VIRGIN ISLANDS AND PUERTO RICO CAN EXPECT AN ELEVATED
RISK OF EXCESSIVE HEAT ACROSS THE COASTAL AND URBAN AREAS TODAY
AND POSSIBLY TOMORROW. THUS, A HEAT ADVISORY IS IN EFFECT FROM
10 AM AST TO 5 PM AST TODAY.
* THE NORTH-FACING BEACHES IN PR AND THE US VIRGIN ISLANDS HAVE A
MODERATE RISK OF RIP CURRENTS TODAY.
* A TROPICAL WAVE WILL PROVIDE THE BEST OPPORTUNITY TO SEE
THUNDERSTORMS BRINGING PERIODS OF MODERATE TO HEAVY RAIN
ACROSS THE REGION FROM LATE FRIDAY AFTERNOON INTO SATURDAY.
SHORT TERM (TODAY THROUGH SATURDAY)
ISSUED AT 400 AM AST THU OCT 30 2025
OVERNIGHT, QUIET AND CALM CONDITIONS PREVAILED ACROSS PUERTO RICO
AND THE US VIRGIN ISLANDS UNDER MOSTLY CLEAR SKIES. DOPPLER RADAR
AND SATELLITE OBSERVATIONS SHOWED ISOLATED SHOWERS MOVING INTO
PORTIONS OF SOUTHERN AND SOUTHEASTERN PUERTO RICO, RESULTING IN
MINIMAL RAINFALL ACCUMULATIONS. LOW TEMPERATURES RANGED FROM THE
UPPER 70S TO THE LOW 80S IN COASTAL AND URBAN AREAS, INTO THE
UPPER 60S AND LOW 70S ALONG THE CENTRAL MOUNTAIN RANGE. WINDS WERE
GENERALLY LIGHT AND VARIABLE, REMAINING BELOW 10 MPH.
TODAY, AS HURRICANE MELISSA CONTINUES TO TRACK NORTHEASTWARD
TOWARD BERMUDA, ITS INFLUENCE OVER THE LOCAL AREA WILL STEADILY
DIMINISH. HOWEVER, THE COMBINED EFFECT OF MELISSA AND A STRONG
HIGH-PRESSURE SYSTEM IN THE CENTRAL ATLANTIC WILL MAINTAIN A
SOUTH-SOUTHEASTERLY WIND FLOW ACROSS THE ISLANDS THROUGH EARLY
FRIDAY. WINDS ARE THEN EXPECTED TO SHIFT FROM THE EAST-SOUTHEAST
FROM FRIDAY ONWARD AS MELISSA MOVES WELL NORTH AND THE HIGH
PRESSURE STRENGTHENS. MAINLY FAIR WEATHER IS FORECAST ACROSS
PUERTO RICO AND THE US VIRGIN ISLANDS THROUGH AT LEAST FRIDAY,
DRIVEN BY A STRONG MID-TO-UPPER-LEVEL RIDGE OVER THE ATLANTIC THAT
WILL PROMOTE DRIER, STABLE CONDITIONS ALOFT. THE LATEST
PRECIPITABLE WATER ANALYSIS (PWAT) SUGGESTS NEAR-NORMAL TO
SLIGHTLY BELOW-NORMAL VALUES (NEAR 1.75 INCHES) THROUGH FRIDAY.
CONSEQUENTLY, SHOWER ACTIVITY WILL BE VERY LIMITED, WITH ONLY A
FEW BRIEF SHOWERS POSSIBLE ACROSS THE INTERIOR AND NORTHERN PUERTO
RICO.
A TROPICAL WAVE IS EXPECTED TO MOVE ACROSS THE LESSER ANTILLES
LATE FRIDAY NIGHT INTO EARLY SATURDAY MORNING, AND REACH THE LOCAL
AREA BY SATURDAY. CURRENT MODEL GUIDANCE SUGGESTS AN INCREASED
POTENTIAL FOR WIDESPREAD SHOWERS AND THUNDERSTORMS DEVELOPING IN
THE AFTERNOON. SHOWERS WILL GRADUALLY INCREASE THROUGHOUT THE DAY,
STARTING OVER REGIONAL WATERS AND THE US VIRGIN ISLANDS, THEN
SPREADING INLAND BY MID-MORNING INTO THE AFTERNOON. LOCAL EFFECTS,
INCLUDING DIURNAL HEATING AND SEA-BREEZE CONVERGENCE, COULD
ENHANCE RAINFALL INTENSITY, LEADING TO PERIODS OF HEAVY RAIN,
FREQUENT LIGHTNING, AND BRIEF GUSTY WINDS, PARTICULARLY ACROSS
PUERTO RICO.
ELEVATED HEAT CONDITIONS ARE EXPECTED THROUGH FRIDAY, DRIVEN BY
ABOVE-NORMAL TEMPERATURES AT THE 925 MB LEVEL, BEFORE DROPPING TO
NEAR-NORMAL OR BELOW-NORMAL TEMPERATURES ON SATURDAY (BASED ON THE
LATEST GUIDANCE). MAXIMUM TEMPERATURES IN COASTAL AND URBAN AREAS
ARE FORECAST TO RANGE FROM THE UPPER 80S TO THE LOW 90S, WHILE
MOUNTAIN AREAS WILL SEE HIGHS IN THE UPPER 70S TO THE LOW 80S.
HEAT INDICES ARE EXPECTED TO BE ELEVATED, AND HEAT ADVISORIES MAY
BECOME NECESSARY FOR COASTAL AND URBAN ZONES EACH DAY. RESIDENTS
AND VISITORS SHOULD PLAN TO STAY WELL-HYDRATED AND PROTECT
THEMSELVES FROM PROLONGED SUN EXPOSURE.
AVIATION...99
LONG TERM (SUNDAY THROUGH THURSDAY)
ISSUED AT 400 AM AST THU OCT 30 2025
A MID- TO UPPER-LEVEL RIDGE OF HIGH PRESSURE IS LIKELY TO REMAIN
IN PLACE THROUGH MUCH OF THE LONG-TERM FORECAST, BUT BY MONDAY OR
TUESDAY, A WEAK UPPER-LEVEL LOW-PRESSURE SYSTEM WILL MOVE ACROSS
THE CARIBBEAN SEA, WEAKENING ATMOSPHERIC STABILITY. CONFIDENCE IN
THIS OUTCOME REMAINS MEDIUM (30% - 50%). DESPITE THIS UPPER-LEVEL
FEATURE, A STRONG RIDGE NEAR THE 700 MB LEVEL IS EXPECTED TO
PERSIST ACROSS THE NORTHEAST CARIBBEAN, MAINTAINING GENERALLY
STABLE CONDITIONS ALOFT.
AT THE SURFACE, HIGH PRESSURE BUILDING OVER THE WESTERN ATLANTIC
AND EXPANDING INTO THE CENTRAL ATLANTIC WILL LIKELY STRENGTHEN THE
LOCAL PRESSURE GRADIENT, RESULTING IN BREEZY EAST TO EAST-
SOUTHEAST WINDS ACROSS THE ISLANDS. THIS PATTERN SHOULD TRANSPORT
PATCHES OF LOW-LEVEL MOISTURE, LEADING TO A VARIABLE MIX OF MOSTLY
CLEAR SKIES AND OCCASIONAL PASSING SHOWERS. THERE IS A MODERATE
CHANCE (30-50%) THAT THIS SCENARIO WILL OCCUR ACROSS THE ISLANDS
EACH DAY.
WHILE ISOLATED AFTERNOON CONVECTION CANNOT BE RULED OUT (20%-30%
CHANCE), MAINLY DUE TO LOCAL TOPOGRAPHY, SEA-BREEZE INTERACTIONS,
AND DIURNAL HEATING, ONLY A SLIGHT CHANCE (LESS THAN 30%) EXISTS
FOR THUNDERSTORM DEVELOPMENT GIVEN THE PERSISTENT TRADE-WIND
INVERSION AND DRY AIR ALOFT. THE MOST FAVORABLE WINDOW FOR
AFTERNOON SHOWERS OR AN ISOLATED THUNDERSTORM APPEARS TO BE MONDAY
INTO TUESDAY (WITH A 30-50% CHANCE), ALTHOUGH OVERALL CONFIDENCE
IN SIGNIFICANT CONVECTIVE ACTIVITY REMAINS LOW.
(06Z TAFS)
ISSUED AT 400 AM AST THU OCT 30 2025
MAINLY VFR CONDS EXPECTED ACROSS AL TERMINALS DURING THE NEXT 24
HRS. CALM WEATHER CONDS ARE EXPECTED THROUGH MOST OF THE DAY WITH
OCCASIONAL TRADE-WIND SHRA NEAR THE ISLANDS. AFTERNOON SHRA/TSRA
ACROSS CENTRAL PR, WILL RESULT IN VCSH AT TJPS/TJBQ WITH BRIEF
VIS/CIGS REDUCTIONS THRU 30/23Z. LGT/VRB WINDS THRU 30/13-14Z, THEN
BECOMING FROM THE SE AT 08-12 KT WITH SEA BREEZE VARIATIONS AND
HIGHER GUSTS.
MARINE
ISSUED AT 400 AM AST THU OCT 30 2025
THE REGION WILL CONTINUE UNDER A SOUTHEASTERLY WIND FLOW TODAY, AS
MELISSA MOVES INTO THE WESTERN ATLANTIC. THEN, A FRONTAL BOUNDARY
WILL APPROACH THE REGION FROM THE WEST, INTERACTING WITH A SURFACE
HIGH PRESSURE ANCHORED ACROSS THE CENTRAL ATLANTIC AROUND FRIDAY,
PROMOTING THE RETURN OF A MODERATE TO LOCALLY FRESH EASTERLY WIND
FLOW. A TROPICAL WAVE WILL MOVE NEAR THE NORTHEAST CARIBBEAN AND THE
LOCAL WATERS AROUND SATURDAY, INCREASING THE POTENTIAL FOR SHOWERS
AND THUNDERSTORMS.
BEACH FORECAST
ISSUED AT 400 AM AST THU OCT 30 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 THROUGH THE WEEKEND AND 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 5 PM AST THIS AFTERNOON
FOR PRZ001>005-007-008-010>013.
VI...HEAT ADVISORY FROM 10 AM THIS MORNING TO 5 PM AST THIS AFTERNOON
FOR VIZ001-002.
AM...NONE.
MIDNIGHT CREW...CAM/GRS
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