204
FXCA62 TJSJ 270655
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
255 AM AST THU AUG 27 2026
...NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER...
KEY MESSAGES
UPDATED AT 255 AM AST THU AUG 27 2026
* DANGEROUS HEAT TODAY: HEAT INDICES WILL REACH DANGEROUS LEVELS,
PARTICULARLY ACROSS URBAN AND COASTAL AREAS. A HEAT ADVISORY IS
IN EFFECT FROM 10 AM THROUGH 5 PM TODAY.
* SHOWERS AND THUNDERSTORMS TODAY: INCREASING MOISTURE WILL
SUPPORT PASSING SHOWERS THIS MORNING ACROSS THE WINDWARD
SECTIONS, FOLLOWED BY AFTERNOON SHOWERS AND ISOLATED
THUNDERSTORMS ACROSS INTERIOR AND WESTERN PUERTO RICO. A LIMITED
TO ELEVATED FLOODING RISK IS EXPECTED.
* DRIER FRIDAY: A STRENGTHENING MID-LEVEL RIDGE AND DRIER AIR
WILL LIMIT RAINFALL TONIGHT THROUGH MUCH OF FRIDAY, ALTHOUGH
AFTERNOON SHOWERS MAY DEVELOP ACROSS WESTERN PUERTO RICO.
* UNSETTLED PATTERN RETURNS: A WEAK TROPICAL WAVE WILL BRING
SHOWERS AND ISOLATED THUNDERSTORMS LATE FRIDAY NIGHT INTO EARLY
SATURDAY. ADDITIONAL MOISTURE ASSOCIATED WITH AL96 MAY SUPPORT A
WETTER PATTERN SUNDAY INTO EARLY NEXT WEEK, BUT UNCERTAINTY
REMAINS REGARDING ITS EVOLUTION.
* INCREASING RIP CURRENT RISK: A MODERATE RISK OF LIFE-
THREATENING RIP CURRENTS IS EXPECTED ACROSS MOST EXPOSED BEACHES
OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS AS WIND-DRIVEN SEAS
INCREASE, COMBINED WITH A SMALL NORTHEASTERLY SWELL.
SHORT TERM(TODAY THROUGH SATURDAY)
ISSUED AT 255 AM AST THU AUG 27 2026
A TRADE-WIND PERTURBATION BROUGHT INCREASED SHOWER ACTIVITY
ACROSS THE LOCAL WATERS OVERNIGHT, WHILE LOW-LEVEL CONVERGENCE
SUPPORTED SHOWERS ACROSS THE U.S. VIRGIN ISLANDS AND EASTERN
PUERTO RICO. HOWEVER, MOST OF THE ACTIVITY REMAINED OVER THE
WATERS. ALTHOUGH TEMPERATURES ARE SOMEWHAT COOLER THAN LAST NIGHT,
WARMER-THAN-NORMAL CONDITIONS PERSIST, WITH READINGS GENERALLY IN
THE UPPER 70S TO LOW 80S ACROSS COASTAL AREAS AND LOCALLY
REACHING THE MID-80S. COOLER TEMPERATURES PREVAIL ACROSS HIGHER
ELEVATIONS AND SHELTERED VALLEYS. WINDS REMAIN MAINLY FROM THE
EAST TO EAST-NORTHEAST AT 10 MPH OR LESS, WITH SOMEWHAT STRONGER
WINDS ALONG EXPOSED COASTAL AREAS.
THE TRADE-WIND PERTURBATION WILL CONTINUE TO INCREASE TROPICAL
MOISTURE ACROSS THE REGION TODAY, RESULTING IN MORE FREQUENT
PASSING SHOWERS ACROSS WINDWARD AREAS DURING THE MORNING.
MEANWHILE, SEA SURFACE TEMPERATURES SURROUNDING THE ISLANDS REMAIN
AROUND 1 TO 2 DEGREES CELSIUS ABOVE NORMAL. GIVEN THE STRONG
INFLUENCE OF THE SURROUNDING WATERS ON ISLAND TEMPERATURES, ABOVE-
NORMAL AIR TEMPERATURES WILL PERSIST. THE COMBINATION OF WARMER
TEMPERATURES AND INCREASING MOISTURE WILL ONCE AGAIN PRODUCE
DANGEROUS HEAT INDICES, PARTICULARLY ACROSS URBAN AND COASTAL
AREAS. A HEAT ADVISORY IS IN EFFECT FROM 10 AM THROUGH 5 PM TODAY.
BY THIS AFTERNOON, DAYTIME HEATING AND LOCAL EFFECTS WILL PROMOTE
SHOWER DEVELOPMENT ACROSS THE INTERIOR AND WESTERN PORTIONS OF
PUERTO RICO, WITH ISOLATED THUNDERSTORMS POSSIBLE. THE STRONGEST
AND MOST PERSISTENT ACTIVITY MAY CAUSE PONDING ON ROADS AND
LOCALIZED URBAN AND SMALL-STREAM FLOODING, SUPPORTING A LIMITED TO
ELEVATED FLOODING RISK.
MOST OF THE ASSOCIATED MOISTURE WILL MOVE WEST OF THE REGION BY
THIS EVENING. IN ITS WAKE, A DRIER AIR MASS AND A STRENGTHENING
MID-LEVEL RIDGE WILL PROMOTE SUBSIDENCE ALOFT AND REINFORCE THE
TRADE-WIND INVERSION, LIMITING SHOWER DEVELOPMENT TONIGHT THROUGH
MUCH OF FRIDAY. A MODEST INCREASE IN LOW-LEVEL MOISTURE ON FRIDAY
MAY SUPPORT A FEW PASSING SHOWERS, FOLLOWED BY LOCALLY INDUCED
AFTERNOON CONVECTION ACROSS WESTERN PUERTO RICO. NEVERTHELESS,
SIGNIFICANT RAINFALL IS NOT ANTICIPATED.
LATE FRIDAY NIGHT INTO EARLY SATURDAY, A WEAK TROPICAL WAVE WILL
CROSS THE REGION, BRINGING ANOTHER INCREASE IN MOISTURE AND A
BETTER OPPORTUNITY FOR PASSING SHOWERS AND ISOLATED THUNDERSTORMS.
THE WAVE'S PROGRESSIVE NATURE SHOULD FAVOR FAST-MOVING ACTIVITY,
LIMITING THE OVERALL FLOODING THREAT. HOWEVER, LOW-LEVEL
CONVERGENCE AND OROGRAPHIC ENHANCEMENT COULD SUPPORT LOCALLY
HEAVIER DOWNPOURS ACROSS EASTERN PUERTO RICO, WHERE A LIMITED
FLOODING RISK IS EXPECTED. A FEW BRIEF DOWNPOURS ARE ALSO POSSIBLE
ACROSS THE U.S. VIRGIN ISLANDS. THE WAVE AND ITS ASSOCIATED
MOISTURE WILL QUICKLY MOVE WESTWARD, WITH ANOTHER DRIER AIR MASS
ARRIVING BY MID-MORNING SATURDAY AND LIMITING SHOWER ACTIVITY
THROUGH THE AFTERNOON. DESPITE THE DRYING TREND, ABOVE-NORMAL
TEMPERATURES ARE EXPECTED TO PERSIST, AND ADDITIONAL HEAT PRODUCTS
MAY BE REQUIRED WHERE DANGEROUS HEAT INDICES DEVELOP.
LONG TERM(SUNDAY THROUGH THURSDAY)
ISSUED AT 255 AM AST THU AUG 27 2026
FORECAST UNCERTAINTY REMAINS HIGHER THAN USUAL HEADING INTO EARLY
NEXT WEEK, PRIMARILY ASSOCIATED WITH THE EVOLUTION OF AL96,
CURRENTLY OVER THE CENTRAL TROPICAL ATLANTIC. ACCORDING TO THE
LATEST TROPICAL WEATHER OUTLOOK FROM THE NATIONAL HURRICANE
CENTER, THE DISTURBANCE HAS BECOME SOMEWHAT BETTER ORGANIZED AND
HAS A HIGH CHANCE OF TROPICAL CYCLONE FORMATION DURING THE NEXT 2
TO 7 DAYS. HOWEVER, ENVIRONMENTAL CONDITIONS ARE EXPECTED TO
BECOME LESS CONDUCIVE FOR DEVELOPMENT THIS WEEKEND. REGARDLESS OF
DEVELOPMENT, THE EVOLUTION OF AL96 AND ITS ASSOCIATED MOISTURE
FIELD WILL CONTINUE TO BE MONITORED FOR POTENTIAL IMPACTS ACROSS
PUERTO RICO AND THE U.S. VIRGIN ISLANDS.
THE CURRENT FORECAST GENERALLY FOLLOWS THE TIMING DEPICTED BY THE
GFS AND ECMWF, BOTH OF WHICH INDICATE INCREASING MOISTURE AND
PRECIPITABLE WATER VALUES FROM LATE SUNDAY THROUGH AT LEAST
TUESDAY. ALTHOUGH THEIR TIMING IS RELATIVELY SIMILAR, THE GFS
REMAINS MORE AGGRESSIVE WITH MOISTURE AND RAINFALL THAN THE ECMWF.
PART OF THIS DIFFERENCE APPEARS RELATED TO THE EVOLUTION OF THE
MID-LEVEL RIDGE. THE ECMWF MAINTAINS STRONGER RIDGING CLOSER TO
THE NORTHEASTERN CARIBBEAN SUNDAY INTO MONDAY, WHICH WOULD FAVOR
GREATER SUBSIDENCE AND POTENTIALLY DISRUPT THE DISTURBANCE AND ITS
MOISTURE FIELD. IN CONTRAST, THE GFS SHIFTS THE RIDGE FARTHER
WEST AHEAD OF AL96, ALLOWING DEEPER MOISTURE TO APPROACH THE
REGION.
GIVEN THESE TRENDS, THE FORECAST FAVORS A WETTER PATTERN SUNDAY
INTO MONDAY, WITH INCREASING SHOWER AND THUNDERSTORM ACTIVITY AND
A MORE WIDESPREAD LIMITED FLOODING RISK. STEERING FLOW SHOULD
FAVOR PASSING SHOWERS ACROSS WINDWARD AREAS, FOLLOWED BY AFTERNOON
CONVECTION MAINLY ACROSS THE INTERIOR AND WESTERN TO NORTHWESTERN
PORTIONS OF PUERTO RICO. LOCALLY HEAVIER RAINFALL WILL ULTIMATELY
DEPEND ON THE TRACK AND STRUCTURE OF AL96 AND THE DISTRIBUTION OF
ITS ASSOCIATED MOISTURE.
MOISTURE SHOULD GRADUALLY DECREASE BY LATE TUESDAY AS GUIDANCE
INDICATES LOW TO MODERATE CONCENTRATIONS OF SAHARAN DUST REACHING
THE REGION. NEVERTHELESS, PRECIPITABLE WATER VALUES ARE FORECAST
TO REMAIN NEAR THE UPPER END OF CLIMATOLOGICAL VALUES OR ABOVE
NORMAL THROUGH MUCH OF THE REMAINDER OF THE PERIOD. LINGERING
MOISTURE ASSOCIATED WITH AL96, FOLLOWED BY ANOTHER TROPICAL WAVE
PASSING MAINLY SOUTH OF THE ISLANDS WEDNESDAY NIGHT INTO THURSDAY,
SHOULD MAINTAIN PERIODS OF PASSING SHOWERS ACROSS WINDWARD AREAS
AND AFTERNOON CONVECTION OVER PUERTO RICO UNDER PERSISTENT EAST-
SOUTHEAST FLOW.
MEANWHILE, SEASONAL TO ABOVE-SEASONAL 925-MB TEMPERATURES ARE
EXPECTED TO PERSIST, MAINTAINING THE POTENTIAL FOR ELEVATED TO
SIGNIFICANT HEAT IMPACTS, PARTICULARLY DURING PERIODS OF REDUCED
CLOUD COVER AND RAINFALL. GIVEN THE UNCERTAINTY SURROUNDING AL96,
CONTINUE TO MONITOR THE LATEST TROPICAL WEATHER OUTLOOK FROM THE
NATIONAL HURRICANE CENTER AND SUBSEQUENT FORECASTS FROM NWS SAN
JUAN FOR CHANGES IN ITS EVOLUTION AND POTENTIAL IMPACTS.
AVIATION
(06Z TAFS)
ISSUED AT 255 AM AST THU AUG 27 2026
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. SHRA WILL
INCREASE ACROSS THE USVI AND EASTERN PR TERMINALS THIS MORNING AS
A TRADE-WIND PERTURBATION MOVES THROUGH. AFTERNOON SHRA/ISOLATED
TSRA ARE EXPECTED MAINLY OVER INTERIOR AND WESTERN PR, POTENTIALLY
CAUSING BRIEF MVFR CONDITIONS AND MOUNTAIN OBSCURATIONS,
PARTICULARLY NEAR TJBQ. WINDS WILL REMAIN FROM THE E AT 10-15 KT,
WITH HIGHER GUSTS AND SEA-BREEZE VARIATIONS AFTER 14Z.
MARINE
ISSUED AT 255 AM AST THU AUG 27 2026
SURFACE HIGH PRESSURE ACROSS THE CENTRAL ATLANTIC WILL PROMOTE A
MODERATE EAST-TO-EAST-SOUTHEAST WIND FLOW THROUGH THE WEEKEND. A
WEAK LONG-PERIOD NORTHEASTERLY SWELL IS EXPECTED TO ARRIVE AND
SPREAD ACROSS THE REGIONAL WATERS THIS MORNING. BY FRIDAY NIGHT INTO
SATURDAY MORNING, AN INCREASE IN SHOWERS AND ISOLATED THUNDERSTORMS
IS ANTICIPATED ACROSS THE REGIONAL WATERS AS WEAK TROPICAL WAVE
APPROACHES THE AREA. WINDS MAY BRIEFLY BECOME MODERATE TO LOCALLY
FRESH AS THE TROPICAL WAVE MOVES ACROSS THE AREA, WITH SEAS BETWEEN
3 AND 5 FEET, OCCASIONALLY 6 FEET; SMALL CRAFT MUST EXERCISE CAUTION.
BEACH FORECAST
ISSUED AT 255 AM AST THU AUG 27 2026
A MODERATE RISK OF RIP CURRENTS WILL CONTINUE ALONG THE NORTHERN AND
EASTERN EXPOSED BEACHES OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS
DURING THE NEXT SEVERAL DAYS. BEACHGOERS MUST EXERCISE CAUTION, AS
LIFE-THREATENING RIP CURRENTS ARE POSSIBLE ALONG THE SURF ZONE. A
WEAK LONG-PERIOD NORTHEASTERLY SWELL IS EXPECTED TO ARRIVE AND
SPREAD ACROSS THE REGIONAL WATERS THIS MORNING, HOWEVER, SEAS WILL
REMAIN AT 3 TO 5 FEET IN THE NEARSHORE WATERS. BEACHGOERS ARE
URGED TO REMAIN WEATHER ALERT AS SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED TO DEVELOP EACH AFTERNOON ACROSS
WESTERN AND NORTHWESTERN COASTAL AREAS OF PUERTO RICO.
FIRE WEATHER
ISSUED AT 255 AM AST THU AUG 27 2026
PLENTY OF DRY FUELS REMAIN ACROSS THE REGION. HOWEVER, A TRADE-
WIND PERTURBATION WILL BRING A SLIGHT INCREASE IN MOISTURE TODAY,
MAINTAINING RELATIVE HUMIDITY VALUES ABOVE CRITICAL THRESHOLDS.
EASTERLY WINDS WILL GENERALLY REMAIN MODERATE, ALTHOUGH LOCALLY
HIGHER GUSTS ARE POSSIBLE. THEREFORE, DESPITE THE DRY FUELS,
CRITICAL FIRE-WEATHER CONDITIONS ARE NOT EXPECTED TODAY. AFTERNOON
SHOWERS MAY ALSO PROVIDE LOCALIZED WETTING RAINFALL, MAINLY ACROSS
INTERIOR AND WESTERN PUERTO RICO.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HEAT ADVISORY FROM 10 AM THIS MORNING TO 5 PM AST THIS AFTERNOON
FOR PRZ001>003-005-007-008-010>013.
VI...HEAT ADVISORY FROM 10 AM THIS MORNING TO 5 PM AST THIS AFTERNOON
FOR VIZ001-002.
AM...NONE.
KEY MESSAGES/SHORT TERM/AVIATION/FIRE WEATHER...CAM
LONG TERM....MRR
MARINE/BEACH FORECAST...GRS
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