155
FXCA62 TJSJ 311741
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
141 PM AST FRI OCT 31 2025
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 128 PM AST FRI OCT 31 2025
* HEAVY SHOWERS AND THUNDERSTORMS DUE TO THE PASSAGE OF A
TROPICAL WAVE WILL PERSIST THROUGH THE EVENING HOURS. THIS WILL
RESULT IN A LIMITED TO ELEVATED FLOODING RISK MOSTLY ACROSS
PORTIONS OF WESTERN/NORTHWESTERN PUERTO RICO. FREQUENT LIGHTNING
AND GUSTY WIND CONDITIONS CAN BE EXPECTED WITH THE STRONGEST
THUNDERSTORMS.
* THE TROPICAL WAVE WILL LINGER THROUGH SATURDAY,BRINGING PERIODS
OF MODERATE TO HEAVY RAIN WITH ISOLATED THUNDERSTORMS.
* 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.
SHORT TERM (THIS EVENING THROUGH SUNDAY)
ISSUED AT 128 PM AST FRI OCT 31 2025
OVERALL, TODAY BEGAN WITH TRANQUIL WEATHER CONDITIONS ACROSS THE
REGION, WITH SOME POCKETS OF SHOWERS OVER THE SURROUNDING WATERS.
THIS WAS FOLLOWED BY AN ACTIVE AFTERNOON AS SHOWERS AND
THUNDERSTORMS DEVELOPED ACROSS THE INTERIOR AND WESTERN PORTIONS OF
PUERTO RICO. EARLIER, ISOLATED SHOWERS AFFECTED THE U.S. VIRGIN
ISLANDS AND EASTERN PUERTO RICO, RESULTING IN MINIMAL ACCUMULATIONS.
THE CALM WEATHER AND CLEAR SKIES IN THE MORNING ALLOWED TEMPERATURES
TO REACH THE UPPER 80S TO LOW 90S, WITH HEAT INDICES INCREASING INTO
THE 100S DURING THE AFTERNOON HOURS.
TONIGHT INTO SATURDAY, A SLIGHTLY UNSETTLED PATTERN WITH FREQUENT
SHOWERS WILL PERSIST AS ABUNDANT TROPICAL MOISTURE ASSOCIATED WITH A
TROPICAL WAVE MOVES MAINLY SOUTH OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS. PRECIPITABLE WATER (PW) VALUES ARE INCREASING FROM AROUND
1.80 INCHES TO NEAR 2.00 INCHES TONIGHT, SUPPORTING HIGHER MOISTURE
CONTENT ACROSS THE REGION. ON SATURDAY, PW VALUES BETWEEN 2.0 AND
2.50 INCHES, COMBINED WITH 500-MB TEMPERATURES NEAR -7°C, WILL
PROMOTE AN UNSTABLE ATMOSPHERE. THESE CONDITIONS WILL FAVOR THE
VERTICAL DEVELOPMENT OF SHOWERS AND THUNDERSTORMS, LEADING TO
ANOTHER ACTIVE AFTERNOON ACROSS THE INTERIOR AND WESTERN
MUNICIPALITIES OF PUERTO RICO, AS WELL AS DOWNWIND OF THE LOCAL
ISLANDS AND EL YUNQUE. ACTIVITY WILL FAVOR WINDWARD AND EASTERN
AREAS OVERNIGHT INTO EARLY SATURDAY MORNING. AS A RESULT, THERE WILL
BE AN ELEVATED RISK OF FLOODING AND A LIMITED RISK OF LIGHTNING
THROUGH LATE SATURDAY.
A SIGNIFICANT CHANGE IN WEATHER CONDITIONS IS EXPECTED ON SUNDAY AS
A MUCH DRIER AIR MASS FILTERS INTO THE REGION FROM THE EAST.
PRECIPITABLE WATER VALUES ARE FORECAST TO DROP TO NEAR OR BELOW THE
25TH PERCENTILE FOR THIS TIME OF YEAR, LEADING TO A NOTICEABLE
DECREASE IN SHOWER ACTIVITY. MOSTLY FAIR WEATHER IS ANTICIPATED,
WITH ONLY BRIEF, LIGHT SHOWERS POSSIBLE IN WINDWARD AREAS.
LONG TERM (MONDAY THROUGH NEXT THURSDAY)
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
(18Z TAFS)
ISSUED AT 128 PM AST FRI OCT 31 2025
MOST TAF SITE SHLD EXPERIENCE MAINLY VFR CONDS. HOWEVER, MVFR
CONDS POSSIBLE WITH THE AFTERNOON CONVECTIVE DVLPMNT. VCTS AND
SHRA POSSIBLE ACROSS TJBQ AND TJPS EXPECTED THROUGH 31/22Z. AFTER
31/23Z SHOWERS ARE POSSIBLE ACROSS THE TISX, TIST, TJSJ, AND TJBQ
ALONG WITH VCTS POSSIBLE AS A TROPICAL WAVE MOVES SOUTH OF THE
AREA. SFC WNDS E-SE 5 TO 10KT OCCASIONAL HIGHER GUST.
MARINE
ISSUED AT 128 PM AST FRI OCT 31 2025
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 128 PM 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...NONE.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...MMC
LONG TERM...MIDNIGHT CREW
MARINE/BEACH FORECAST...CVB
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