179
FXCA62 TJSJ 130747
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
347 AM AST SAT SEP 13 2025
KEY MESSAGES
* ANOTHER ACTIVE AFTERNOON IS EXPECTED, WITH SHOWERS AND
THUNDERSTORMS DEVELOPING ALONG THE CORDILLERA CENTRAL AND
SPREADING TOWARD THE WEST AND NORTH HALF OF PUERTO RICO. THERE
IS AN ELEVATED RISK OF URBAN AND SMALL STREAM FLOODING, RAPID
RIVER RISES, WATER SURGES, LANDSLIDES, AND LIGHTNING STRIKES
WITH THIS ACTIVITY.
* PASSING SHOWERS AND THUNDERSTORMS ARE ALSO EXPECTED ACROSS THE
VICINITY OF THE VIRGIN ISLANDS. EVEN THOUGH FLOODING IS NOT
EXPECTED, WATER SURGES ALONG GUTS AND ISOLATED LIGHTNING STRIKES
CAN BE EXPECTED.
* HOT TEMPERATURES ARE EXPECTED EACH DAY, WITH A LEVEL OF HEAT
THAT WILL AFFECT THOSE SENSIBLE TO HEAT, ESPECIALLY WITHOUT
EFFECTIVE COOLING OR ADEQUATE HYDRATION. THESE CONDITIONS WILL
BE OBSERVED IN PUERTO RICO AND IN THE VIRGIN ISLANDS.
* A TROPICAL WAVE WILL APPROACH ON SUNDAY AND ANOTHER ON TUESDAY
AND WEDNESDAY. THIS WILL INCREASE THE FREQUENCY OF SHOWERS AND
THUNDERSTORMS ACROSS PUERTO RICO AND THE VIRGIN ISLANDS.
SHORT TERM...TODAY THROUGH MONDAY
MAINLY FAIR WEATHER CONDITIONS WERE OBSERVED OVERNIGHT ACROSS THE
ISLANDS. DOPPLER RADAR OBSERVATIONS INDICATED SOME SHOWERS REACHING
PORTIONS OF THE U.S. VIRGIN ISLANDS AND EASTERN PUERTO RICO, LEAVING
ESTIMATED RAINFALL ACCUMULATIONS OF LESS THAN 0.50 INCHES,
PARTICULARLY OVER THE NORTHEASTERN MUNICIPALITIES OF PUERTO RICO.
LOWS WERE IN THE UPPER 70S TO LOW 80S ALONG THE COASTAL AND URBAN
AREAS, AND FROM THE UPPER 60S TO LOW 70S IN THE MOUNTAINS.
TODAY, ANOTHER ACTIVE DAY IS EXPECTED. FOR THE U.S. VIRGIN ISLANDS,
PASSING SHOWERS WILL CONTINUE TO MOVE THROUGH OCCASIONALLY DURING
THE MORNING. FOR PUERTO RICO, AFTERNOON THUNDERSTORMS ARE EXPECTED
TO DEVELOP ALONG THE CENTRAL MOUNTAIN RANGE, SPREADING TOWARD THE
NORTHWEST AND WESTERN PORTIONS OF THE ISLANDS. ADDITIONALLY,
STREAMER ACTIVITY DEVELOPING FROM "EL YUNQUE" WILL AFFECT, ONCE
AGAIN, THE SAN JUAN METRO AREA AND ADJACENT MUNICIPALITIES. THIS
ACTIVITY MAY RESULT IN URBAN AND SMALL STREAM FLOODING, QUICK RIVER
RISES, WATER SURGES, AND LANDSLIDES. IN ADDITION, FREQUENT LIGHTNING
AND GUSTY WINDS ARE EXPECTED WITH THE STRONGEST THUNDERSTORMS.
BY EARLY SUNDAY, A TROPICAL WAVE WILL BEGIN TO APPROACH THE REGION
FROM THE EAST. THE LATEST PRECIPITABLE WATER GUIDANCE SHOWS ABOVE-
NORMAL VALUES REACHING 2.25 INCHES THROUGH MONDAY. WITH THE
ANTICIPATED WAVE, THE U.S. VIRGIN ISLANDS, PORTIONS OF EASTERN
PUERTO RICO, VIEQUES, AND CULEBRA WILL SEE AN INCREASE IN SHOWERS
AND ISOLATED THUNDERSTORMS DURING THE MORNING. THEN, AS THE DAY
PROGRESSES, AFTERNOON THUNDERSTORMS WILL DEVELOP ONCE AGAIN ACROSS
CENTRAL AND WESTERN PUERTO RICO DUE TO THE AVAILABLE MOISTURE FROM
THE TROPICAL WAVE, OROGRAPHIC LIFTING, AND DAYTIME HEATING. FOR
THESE REASONS, THE FLOODING RISK REMAINS ELEVATED. BY MONDAY, AFTER
THE WAVE EXITS, A DRIER AIRMASS WILL QUICKLY MOVE INTO THE AREA,
PROMOTING FAIR WEATHER FOR MOST. HOWEVER, A PATCH OF MOISTURE WILL
FOLLOW, ENHANCING THE RAINFALL AND THUNDERSTORM POTENTIAL ACROSS THE
REGION. RESIDENTS AND VISITORS ARE URGED TO CONTINUE MONITORING THE
WEATHER CONDITIONS AS THE WEEKEND PROGRESSES AND PLAN ACCORDINGLY IF
YOU LIVE IN A FLOOD-PRONE AREA.
THE 925 MB TEMPERATURE IS EXPECTED TO REMAIN NORMAL TO ABOVE-NORMAL
AT THE BEGINNING OF THE WEEK. A HEAT ADVISORY IS IN EFFECT FOR ALL
COASTAL AND URBAN AREAS OF PUERTO RICO, VIEQUES, CULEBRA, AND THE
U.S. VIRGIN ISLANDS FROM 10 AM TO 3 PM AST. A HEAT ADVISORY MEANS
THAT PEOPLE SENSITIVE TO HEAT WILL BE AFFECTED, ESPECIALLY THOSE
WITHOUT EFFECTIVE COOLING OR ADEQUATE HYDRATION. TAKE EXTRA
PRECAUTIONS WHEN OUTSIDE.
LONG TERM...TUESDAY THROUGH SATURDAY
UNSETTLED WEATHER CONDITIONS ARE EXPECTED DURING THE WORKWEEK AS A
COUPLE OF TROPICAL WAVES MOVES INTO THE REGION. THE FIRST WAVE
MOVES IN TUESDAY AND WEDNESDAY, BRINGING AN INCREASE IN SHOWERS
ACROSS THE VIRGIN ISLANDS, AND THEN THIS CLUSTER OF MOISTURE WILL
REACH PUERTO RICO. AS A RESULT, THE FREQUENCY OF SHOWERS AND
THUNDERSTORMS WILL INCREASE. AREAS THAT RECEIVE HEAVY RAIN WILL
EXPERIENCE FLOODING, AND RAPID RIVER RISES. LIGHTNING STRIKES WILL
REMAIN A CONCERN FOR THOSE IN THE EXTERIOR AT THE TIMES OF
THUNDERSTORMS. INSTABILITY WILL INCREASE FURTHER ON THURSDAY AS AN
UPPER LEVEL LOW MOVES JUST NORTH OF THE ISLANDS. BY THE END OF THE
PERIOD, YET ANOTHER TROPICAL WAVE MOVES CLOSE TO THE ISLANDS,
BRINGING INTERMITTENT PERIODS OF SHOWERS INTO THE REGION.
AREAS THAT DO NOT EXPERIENCE RAIN OR CLOUDINESS, HOWEVER, WILL
CONTINUE TO OBSERVE ELEVATED HEAT INDICES, MUCH ABOVE NORMAL
VALUES. AS IT HAS BEEN CONSISTENTLY HOT FOR THE PAST COUPLE OF
WEEK, THOSE WITHOUT EFFECTIVE COOLING OR ADEQUATE HYDRATION WILL
COULD BE AFFECTED.
AVIATION
(06Z TAFS)
MAINLY VFR CONDITIONS EXPECTED TO PREVAIL ACROSS ALL TAF SITES
DURING THE FCST PERIOD. SHRA ACTIVITY WILL PROMOTE VCSH ACROSS
TIST/TISX/TJSJ DURING THE MORNING HOURS. LATER IN THE AFTERNOON,
STRONG CONVECTIVE ACTIVITY OVER THE CENTRAL MOUNTAIN RANGE AND
WESTERN PR WILL RESULT IN SHRA/TSRA AFT 13/17Z ACROSS
TJBQ/TJPS/TJSJ. THIS ACTIVITY WILL LEAD TO BRIEF MVFR/IFR CONDS,
REDUCED VIS AND LOW CIGS THRU 13/22Z. WINDS WILL BE LIGHTER, OUT OF
THE ESE AT 08-12 KTS.
MARINE
A SURFACE HIGH PRESSURE ACROSS THE CENTRAL ATLANTIC AND A FRONT OVER
THE WESTERN ATLANTIC WILL PROMOTE LIGHT TO MODERATE EAST TO SOUTHEAST
WINDS THROUGH THE WEEKEND. AFTERNOON SHOWERS AND THUNDERSTORMS ARE LIKELY
EACH DAY, PARTICULARLY OVER THE WESTERN WATERS OF PUERTO RICO AND
OVER THE MONA PASSAGE. ADDITIONALLY, A TROPICAL WAVE WILL APPROACH
FOR SUNDAY AND EARLY NEXT WEEK, WITH EVEN MORE SHOWERS AND
THUNDERSTORMS ACROSS THE LOCAL WATERS.
BEACH FORECAST
THE RISK OF RIP CURRENTS IS LOW THROUGH SUNDAY. THE RISK WILL
BECOME MODERATE AFTER SUNDAY, FOR MOST OF EASTERN AND NORTHERN
PUERTO RICO AND FOR SAINT CROIX.
EVEN WITH A LOW RISK, LIFE- THREATENING RIP CURRENTS CAN STILL
OCCUR NEAR GROINS, JETTIES, REEFS, AND PIERS, SO BEACHGOERS ARE
ADVISED TO EXERCISE CAUTION AT ALL TIMES.
ADDITIONALLY, THUNDERSTORMS ARE LIKELY IN THE AFTERNOON, WITH
COULD INCREASE THE RISK OF LIGHTNING IMPACTS TO BEACH-GOERS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HEAT ADVISORY FROM 10 AM THIS MORNING TO 3 PM AST THIS AFTERNOON
FOR PRZ001>005-007-008-010>013.
VI...HEAT ADVISORY FROM 10 AM THIS MORNING TO 3 PM AST THIS AFTERNOON
FOR VIZ001-002.
AM...NONE.
SHORT TERM...GRS
LONG TERM....ERG
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