033
FXCA62 TJSJ 181750
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
150 PM AST SUN OCT 18 2026
..NEW SHORT TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 150 PM AST SUN OCT 18 2026
* SLOW-MOVING THUNDERSTORMS MAY PRODUCE HEAVY RAINFALL LOCALLY
AND ISOLATED URBAN AND SMALL-STREAM FLOODING THIS AFTERNOON AND
MONDAY. INTERIOR AND NORTHERN PUERTO RICO ARE FAVORED TODAY,
WITH ACTIVITY SHIFTING TO INTERIOR AND WESTERN AREAS ON MONDAY.
* STRONGER STORMS MAY PRODUCE FREQUENT LIGHTNING AND GUSTY WINDS.
HEAT WILL PRIMARILY AFFECT HEAT-SENSITIVE INDIVIDUALS OUTDOORS
WITHOUT EFFECTIVE COOLING OR ADEQUATE HYDRATION, ESPECIALLY
DURING THE LATE MORNING AND EARLY AFTERNOON.
* MODERATE RIP CURRENT RISK IS EXPECTED TODAY ALONG EXPOSED
ATLANTIC-FACING BEACHES OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS. A MORE ENERGETIC NORTHWESTERLY SWELL ARRIVING MONDAY
EVENING WILL BRING BUILDING SEAS, HIGHER SURF, AND INCREASINGLY
HAZARDOUS RIP CURRENTS THROUGH MIDWEEK. THE SWELL WILL PEAK
TUESDAY AND SHIFT TO A NORTHERLY DIRECTION WEDNESDAY.
SHORT TERM(THIS EVENING THROUGH TUESDAY)
ISSUED AT 150 PM AST SUN OCT 18 2026
GENERALLY FAIR WEATHER PREVAILED EARLY THIS MORNING, WITH SHOWERS
MAINLY OVER THE LOCAL WATERS OCCASIONALLY MOVING INLAND ACROSS
THE U.S. VIRGIN ISLANDS AND WINDWARD PORTIONS OF PUERTO RICO. MOST
SHOWERS DISSIPATED BY MID-MORNING, LEAVING MOSTLY CLEAR SKIES
WITH PASSING CLOUDS. BY LATE MORNING, SHOWERS RETURNED TO PORTIONS
OF ST. THOMAS, ST. JOHN, ST. CROIX, VIEQUES, CULEBRA,
NORTHEASTERN PUERTO RICO DOWNWIND FROM LA SIERRA DE LUQUILLO, AND
THE SOUTHERN SLOPES OF THE CORDILLERA CENTRAL. USGS RIVER SENSORS
DETECTED A SURGE OF WATER ALONG RIO BLANCO, REACHING MINOR
FLOODING LEVELS. SHOWERS SPREAD ACROSS PUERTO RICO'S INTERIOR
MOUNTAINS IN THE EARLY AFTERNOON, WITH A FEW THUNDERSTORMS. WINDS
WERE GENERALLY LIGHT AND VARIABLE, WITH A BACKGROUND EAST-
SOUTHEAST FLOW AND LOCAL SEA BREEZES INFLUENCING COASTAL WIND
DIRECTIONS. HOT, HUMID CONDITIONS AGAIN POSED A RISK, ESPECIALLY
TO INDIVIDUALS SENSITIVE TO HEAT, PARTICULARLY THOSE OUTDOORS
WITHOUT EFFECTIVE COOLING OR ADEQUATE HYDRATION.
A MID- TO UPPER-LEVEL LOW NORTHEAST OF THE REGION WILL GRADUALLY
WEAKEN THE RIDGE'S INFLUENCE THROUGH MONDAY. THIS AFTERNOON,
AVAILABLE MOISTURE, DAYTIME HEATING, AND LOCAL CONVERGENCE WILL
SUPPORT SHOWERS AND THUNDERSTORMS, MAINLY ACROSS INTERIOR AND
NORTHERN PUERTO RICO. WEAK STEERING FLOW MAY ALLOW SLOW-MOVING
CELLS AND REPEATED DEVELOPMENT OVER THE SAME AREAS, RESULTING IN
LOCALLY HEAVY RAINFALL, PONDING ON ROADS AND IN POORLY DRAINED
AREAS, AND ISOLATED URBAN AND SMALL STREAM FLOODING. STRONGER
THUNDERSTORMS MAY PRODUCE FREQUENT LIGHTNING AND GUSTY WINDS.
ACTIVITY SHOULD DIMINISH OVERNIGHT, WITH OCCASIONAL SHOWERS
CONTINUING OVER THE LOCAL WATERS AND WINDWARD AREAS.
ON MONDAY, INCREASING MOISTURE DEPTH AND FURTHER WEAKENING OF THE
RIDGE WILL FAVOR DEEPER AND POTENTIALLY MORE PERSISTENT AFTERNOON
CONVECTION, PARTICULARLY ACROSS INTERIOR AND WESTERN PUERTO RICO.
ENSEMBLE GUIDANCE SUPPORTS LOCALLY ENHANCED RAINFALL, WHILE WEAK
STEERING FLOW WILL MAINTAIN THE POTENTIAL FOR LOCALIZED FLOODING
BENEATH PERSISTENT SHOWERS AND THUNDERSTORMS.
BY TUESDAY, SOUTHEASTERLY LOW-LEVEL WINDS AND INCREASINGLY
SOUTHERLY FLOW NEAR 700 MB MAY SHIFT AFTERNOON CONVECTION TOWARD
NORTHERN PUERTO RICO, ALTHOUGH COVERAGE AND INTENSITY MAY
DECREASE. MOISTURE IS EXPECTED TO DECREASE BRIEFLY TUESDAY NIGHT.
RISING LOW-LEVEL TEMPERATURES WILL ALSO SUPPORT A GRADUAL WARMING
TREND, PARTICULARLY ACROSS NORTHERN COASTAL AND URBAN AREAS. HEAT
IMPACTS THROUGH THE PERIOD SHOULD PRIMARILY AFFECT HEAT-SENSITIVE
INDIVIDUALS OUTDOORS WITHOUT EFFECTIVE COOLING OR ADEQUATE
HYDRATION, ESPECIALLY DURING THE LATE MORNING AND EARLY AFTERNOON.
CLOUDS AND SHOWERS MAY PROVIDE LOCALIZED, TEMPORARY RELIEF.
LONG TERM(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 235 AM AST SUN OCT 18 2026
RELATIVELY DRIER CONDITIONS ON WEDNESDAY WILL TRANSITION INTO A
WETTER AND MORE UNSETTLED PATTERN THURSDAY THROUGH SUNDAY. THE
INTERACTION BETWEEN A SURFACE HIGH OVER THE CENTRAL ATLANTIC AND A
DEEP-LAYER LOW OVER THE EASTERN CONUS WILL MAINTAIN A GENERALLY
SOUTHEAST TO SOUTHERLY WIND FLOW ACROSS THE REGION, WITH STEERING
WINDS STRENGTHENING LATE THURSDAY INTO SATURDAY. WEDNESDAY
APPEARS TO BE THE DRIEST DAY OF THE PERIOD, AS MODEL GUIDANCE
SUGGESTS BELOW-NORMAL LOW- TO MID-LEVEL MOISTURE, WITH
PRECIPITABLE WATER VALUES BELOW 1.6 INCHES. NEVERTHELESS, DAYTIME
HEATING AND LOCAL EFFECTS MAY STILL SUPPORT AFTERNOON SHOWERS
ACROSS PORTIONS OF PUERTO RICO.
A CONSIDERABLE INCREASE IN MOISTURE IS EXPECTED BY THURSDAY AS
DEEP TROPICAL MOISTURE SPREADS ACROSS THE NORTHEASTERN CARIBBEAN.
MODEL GUIDANCE SUGGESTS PRECIPITABLE WATER VALUES EXCEEDING 2.0
INCHES THROUGH MUCH OF THE REMAINDER OF THE PERIOD, OCCASIONALLY
APPROACHING 2.4 INCHES, WITH PERIODS OF ABOVE-NORMAL MOISTURE.
INCREASING MID-LEVEL HUMIDITY, COOLING TEMPERATURES ALOFT, AND
THE PROXIMITY OF A DEEP-LAYER TROUGH WILL SUPPORT A MORE FAVORABLE
ENVIRONMENT FOR DEEPER CONVECTION. ALTHOUGH A MID-LEVEL RIDGE MAY
GRADUALLY BUILD OVER THE EASTERN CARIBBEAN, ABUNDANT MOISTURE AND
LOCAL EFFECTS SHOULD CONTINUE TO FAVOR SHOWERS AND THUNDERSTORMS.
AN ADVECTIVE SHOWER PATTERN IS EXPECTED ACROSS WINDWARD SECTIONS
OF THE ISLANDS, PARTICULARLY DURING THE NIGHTTIME AND MORNING
HOURS, FOLLOWED BY AFTERNOON CONVECTION ACROSS THE INTERIOR AND
WESTERN PORTIONS OF PUERTO RICO. INCREASING STEERING WINDS LATE
THURSDAY THROUGH SATURDAY SHOULD ALLOW CONVECTION TO BECOME MORE
PROGRESSIVE, ALTHOUGH LOCALLY HEAVY RAINFALL MAY STILL RESULT IN
URBAN AND SMALL-STREAM FLOODING, ISOLATED FLASH FLOODING, AND
RISES IN RIVER LEVELS. BY SUNDAY, STEERING WINDS MAY WEAKEN AGAIN,
POTENTIALLY FAVORING SLOWER-MOVING THUNDERSTORMS AND GREATER
LOCALIZED RAINFALL ACCUMULATIONS.
UNDER THE PREVAILING SOUTHEAST TO SOUTHERLY FLOW, WARMER THAN
NORMAL TEMPERATURES ARE LIKELY, PARTICULARLY ACROSS NORTHERN
COASTAL AND URBAN AREAS OF PUERTO RICO. COMBINED WITH ABUNDANT
MOISTURE, HEAT INDICES MAY EXCEED 100 DEGREES FAHRENHEIT, MAINLY
DURING THE LATE MORNING AND EARLY AFTERNOON. HEAT IMPACTS MAY
RANGE FROM LIMITED TO ELEVATED, PARTICULARLY FOR INDIVIDUALS
SENSITIVE TO HEAT, AND HEAT PRODUCTS MAY BE ISSUED IF CONDITIONS
WARRANT.
AVIATION
(18Z TAFS)
ISSUED AT 150 PM AST SUN OCT 18 2026
TSRA/+TSRA ACROSS PR SITES MAY REDUCE CIGS/VIS AND LEAD TO
MVFR/IFR CONDS THIS AFTN. ALTHOUGH JSJ, JPS, AND JBQ HAVE TEMPOS
THROUGH AT LEAST 18/20-21Z, AMDS WILL BE ISSUED IF REQUIRED. AFT
18/22-23Z, VCSH COULD BE EXPCD ACROSS E TAF SITES, PARTICULARLY
ACROSS USVI SITES. MEANWHILE, ESE-SE WINDS WILL REMAIN LIGHT AND
VRB THROUGH 19/12-14Z, BTWN 8 - 10KT. AFTN CONV IS ALSO EXPCD AFT
19/16Z, WITH VCTS ONCE AGAIN ACROSS PR TERMINALS.
MARINE
ISSUED AT 150 PM AST SUN OCT 18 2026
A SURFACE LOW AND ITS ASSOCIATED FRONTAL BOUNDARY MOVING ACROSS
THE WESTERN ATLANTIC WILL MAINTAIN A WEAK LOCAL PRESSURE GRADIENT,
SUPPORTING GENTLE TO MODERATE EAST-SOUTHEAST WINDS THROUGH EARLY
NEXT WEEK. RESIDUAL NORTHERLY SWELL WILL CONTINUE TO SUBSIDE
TODAY. A MORE ENERGETIC NORTHWESTERLY SWELL WILL ARRIVE MONDAY
EVENING, PEAK TUESDAY, AND BECOME NORTHERLY BY WEDNESDAY. THIS
SWELL WILL PRODUCE BUILDING SEAS ACROSS THE ATLANTIC WATERS AND
EXPOSED PASSAGES, WITH ELEVATED SEAS PERSISTING THROUGH MIDWEEK.
THUNDERSTORMS MAY AFFECT COASTAL WATERS, PARTICULARLY IN THE
AFTERNOON AND EVENING THROUGH AT LEAST TUESDAY, PRODUCING LOCALLY
GUSTY WINDS, LIGHTNING, AND REDUCED VISIBILITY IN HEAVY RAIN.
BEACH FORECAST
ISSUED AT 150 PM AST SUN OCT 18 2026
A MODERATE RISK OF RIP CURRENTS WILL CONTINUE THIS AFTERNOON ALONG
THE ATLANTIC-FACING BEACHES OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS, PARTICULARLY THOSE EXPOSED TO NORTHERLY SWELL. CONDITIONS
WILL DETERIORATE MONDAY EVENING AS A MORE ENERGETIC NORTHWESTERLY
SWELL ARRIVES, BUILDING INTO TUESDAY, AND BECOMING NORTHERLY BY
WEDNESDAY. HIGHER SURF AND AN INCREASED RISK OF LIFE-THREATENING
RIP CURRENTS ARE EXPECTED ALONG EXPOSED BEACHES THROUGH MIDWEEK.
THUNDERSTORMS MAY AFFECT BEACHES IN THE AFTERNOON AND EVENING,
PARTICULARLY TODAY AND MONDAY, BRINGING LIGHTNING AND LOCALLY
GUSTY WINDS. BEACHGOERS SHOULD SEEK SHELTER IN A SUBSTANTIAL
BUILDING OR ENCLOSED VEHICLE WHEN THEY HEAR THUNDER.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
KEY MESSAGE/SHORT TERM/MARINE/BEACH FORECAST...CAM
LONG TERM/AVIATION....MNG
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