345
FXCA62 TJSJ 240554
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
154 AM AST THU SEP 24 2026
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 117 AM AST THU SEP 24 2026
- SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED TO INCREASE TODAY
ACROSS PUERTO RICO AND U.S. VIRGIN ISLANDS DUE TO THE
COMBINATION OF MOISTURE FROM A TROPICAL WAVE AND AN INDUCED
SURFACE THROUGH. THIS COULD ENHANCE THE RISK OF SMALL AND URBAN
FLOODING, ISOLATED FLASH FLOODING AND LANDSLIDES ON AREAS
WHERE TERRAIN IS ALREADY SATURATED FROM RAINFALL OVER THE PAST
DAYS.
- HEAT-RELATED RISKS WILL CONTINUE EACH DAY AND INTO THE
WEEKEND. HEAT-SENSITIVE INDIVIDUALS SHOULD AVOID OUTDOOR
ACTIVITIES AND STAY HYDRATED.
- A DRIER AIR MASS WILL APPROACH OUR LOCAL AREA BY FRIDAY
EXTENDING INTO SATURDAY, SLIGHTLY LIMITING SHOWERS AND
THUNDERSTORM DEVELOPMENT OVER THE ISLANDS.
- A MODERATE RIP CURRENT RISK WILL BE IN EFFECT TODAY, EXTENDING
THROUGH THE WEEKEND.
SHORT TERM(TODAY THROUGH SATURDAY)
ISSUED AT 117 AM AST THU SEP 24 2026
AN INCREASE IN SHOWER AND THUNDERSTORM ACTIVITY HAVE BEEN
OBSERVED OVERNIGHT AS A SURFACE DISTURBANCE APPROACHES THE CWA,
WITH SOME OF THESE ACTIVITY REACHING EASTERN AND NORTHERN COASTAL
AREAS. TEMPERATURES HAVE FALLEN OVERNIGHT BETWEEN THE HIGH 70S TO
LOW 80S OVER COASTAL AREAS, WHILE INTERIOR OBSERVATIONS HAVE
REPORTED TEMPERATURES BETWEEN MID 60S AND LOW 70S.
THIS MORNING, BRIEF SHOWERS AND ISOLATED THUNDERSTORMS ARE POSSIBLE
ACROSS EASTERN PUERTO RICO, VIEQUES, CULEBRA AND THE U.S. VIRGIN
ISLANDS. ENHANCED INSTABILITY IS LIKELY LATER THIS AFTERNOON ACROSS
THE REGION, AS A SURFACE THROUGH INDUCED BY A LINGERING TROPICAL
UPPER-LEVEL THROUGH (TUTT) AND MOISTURE ASSOCIATED TO A TROPICAL
WAVE REACHES THE ISLANDS. THIS SCENARIO, COMBINED WITH DAYTIME
HEATING, LOCAL EFFECTS AND A ESE FLOW, WILL FAVOR THE DEVELOPMENT
OF STRONGER SHOWERS AND THUNDERSTORMS OVER EASTERN, NORTHERN AND
NORTHWESTERN PORTIONS OF PUERTO RICO, WHILE ISOLATED ACTIVITY IS
POSSIBLE ELSEWHERE. BY FRIDAY, UPPER-LEVEL DIVERGENCE FROM THE
TUTT WILL CONTINUE TO SUPPORT SLIGHTLY FAVORABLE CONDITIONS FOR
SHOWERS AND THUNDERSTORMS DEVELOPMENT. ALTHOUGH, A DRIER AIRMASS
APPROACHING THE ISLANDS COULD LIMIT DEEP CONVECTION, AS A RESULT
AFTERNOON CONVECTION COULD BE MORE LOCALIZED, MAINLY OVER NORTH TO
NORTHWESTERN PORTIONS OF PUERTO RICO. MOVING INTO THE WEEKEND,
THE DRIER AIR MASS WILL SETTLE OVER THE CWA, DRAGGING IN LOW
CONCENTRATIONS OF SAHARAN DUST. THUS, EXPECT A PATTERN SIMILAR TO
FRIDAY.
OVERALL, THE PRIMARY WEATHER HAZARDS WILL INCLUDE LOCALIZED HEAVY
RAINFALL, AND ISOLATED THUNDERSTORMS, WHICH COULD BE ACCOMPANIED BY
FREQUENT LIGHTNING AND STRONG WIND GUSTS, PARTICULARLY TODAY. A
LIMITED TO ELEVATED EXCESSIVE RAINFALL RISK IS EXPECTED TODAY AS
CONDITIONS BECOME MORE FAVORABLE FOR STRONGER CONVECTION, AND
LIMITED ON FRIDAY AND SATURDAY AS A RESULT OF A DRIER AIR MASS
OVER THE ISLANDS. CONSEQUENTLY, SHOWER ACTIVITY TODAY MAY LEAD TO
WATER PONDING ON ROADWAYS, URBAN AND SMALL STREAM FLOODING, AND
EVEN ISOLATED FLASH FLOODS WITH PERIODS OF HEAVY RAINFALL,
ALONGSIDE A CONTINUED RISK OF LANDSLIDES WHERE TERRAIN IS ALREADY
SATURATED FROM RECENT RAINFALL.
AN ELEVATED EXCESSIVE HEAT RISK IS LIKELY ON SATURDAY AS DRIER AIR
WILL LIMIT CLOUD COVER OVER THE ISLANDS, WHILE IT REMAINS LIMITED ON
TODAY AND FRIDAY.
LONG TERM(SUNDAY THROUGH THURSDAY)
ISSUED AT 117 AM AST THU SEP 24 2026
THE WEATHER CONDITIONS OVER THE LONG TERM PERIOD WILL CONTINUE TO BE
INFLUENCED BY SEVERAL SYNOPTIC FEATURES. OVER THE EASTERN ATLANTIC
OCEAN A LOW LEVEL HIGH PRESSURE SYSTEM WILL PROMOTE AN ENE WIND
FLOW. THE CONDITIONS ARE EXPECTED TO BECOME BREEZY TO LOCALLY WINDY
ACROSS THE US VIRGIN ISLANDS AND PUERTO RICO FROM MONDAY INTO MID-
WEEK. ADDITIONALLY, A LINGERING UPPER-LEVEL LOW PRESSURE SYSTEM
LOCATED TO THE EAST OF THE CWA WILL CONTINUE TO DRIVE UPPER-LEVEL
CONVERGENCE THROUGH MID-TO-LATE NEXT WEEK. THIS WILL ACT TO LIMIT
THE POTENTIAL FOR THE DEVELOPMENT OF DEEP CONVECTION OVER THE
REGION. ON THE OTHER HAND, WHILE A TROPICAL WAVE IS EXPECTED TO
REACH THE FORECAST REGION BETWEEN MONDAY AND TUESDAY THE MOISTURE
FIELD ASSOCIATED WITH THE SYSTEM WILL REMAIN TO THE NORTH AND SOUTH
OF THE US VIRGIN ISLANDS AND PUERTO RICO WITH LOWER THAN AVERAGE
PRECIPITABLE WATER (PWAT) VALUES INTRUDING THE REGION. NONETHELESS,
ON MONDAY THE ATMOSPHERIC COLUMN IS EXPECTED TO BE MOISTER THAN MOST
OF THE DAYS IN THE LONG TERM PERIOD. COUPLED WITH LOCAL EFFECTS, THE
DAY IS EXPECTED TO BE FAVORABLE FOR THE DEVELOPMENT OF ISOLATED
SHOWER AND THUNDERSTORM ACTIVITY.
GIVEN THAT THE SYNOPTIC FEATURES ARE CURRENTLY ACTING TO LIMIT
WEATHER ACTIVITY, THE DAY-TO-DAY IS EXPECTED TO BE DRIVEN PRIMARILY
BY LOCAL EFFECTS WITH SEASONAL CONDITIONS DOMINATING THE OBSERVED
WEATHER PATTERN THROUGH LATE NEXT WEEK. WITH RAINFALL ACTIVITY
EXPECTED OVER THE US VIRGIN ISLANDS AND EASTERN PUERTO RICO IN THE
MORNING AND OVER THE INTERIOR AND NORTHWESTERN PUERTO RICO DURING
THE AFTERNOON. WEATHER CONDITIONS WILL BECOME MORE FAVORABLE BY
THURSDAY, WITH A MORE HUMID VERTICAL PROFILE RETURNING. MID-
TROPOSPHERIC TEMPERATURES ARE ALSO FORECASTED TO BE BELOW -6 DEGREES
CELSIUS, INCREASING THE POTENTIAL FOR THE DEVELOPMENT OF DEEP
CONVECTIVE CELLS. RISKS ASSOCIATED TO EXTREME HEAT CONTINUE TO BE
ONE OF THE MAIN CONCERNS THROUGHOUT THE REST OF THE FORECAST PERIOD
WITH 925 MB TEMPERATURES EXPECTED TO BE 2 STANDARD DEVIATIONS ABOVE
NORMAL RANGES FOR THE SEASON INTO EARLY NEXT WEEK. AS INDIVIDUALS
PREPARE FOR THE WEEKEND IT IS RECOMMENDED TO ADJUST OUTSIDE
ACTIVITIES AND EVENTS ACCORDINGLY AND TO REMAIN HYDRATED. CITIZENS
ANDS VISITORS ARE INVITED TO STAY ALERT OF THE EVOLVING WEATHER
CONDITIONS AS WE MOVE INTO THE WEEKEND.
AVIATION
(06Z TAFS)
ISSUED AT 117 AM AST THU SEP 24 2026
MAINLY VFR CONDS ARE EXPECTED ACROSS ALL TERMINALS DURING THE
FORECAST PERIOD. HOWEVER, AFTN SHRA/TSRA DEVELOPMENT COULD RESULT
IN BRIEF PERIODS OF MVFR/IFR WITH MTN OBSCURATIONS ACROSS CENTRAL
AND WESTERN PR, AFFECTING TJBQ/TJPS/TJSJ AFT 24/17Z. VCSH LINGERS
TJSJ/TIST/TISX OVERNIGHT INTO FRIDAY. WINDS LGT/VRB TO CALM THRU
24/14Z, BECOMING E-ESE 10-15 KT WITH HIGHER GUSTS AND SEA BREEZE
VARIATIONS THRU 24/23Z, THEN LGT/VRB OVERNIGHT.
MARINE
ISSUED AT 117 AM AST THU SEP 24 2026
LIGHT TO MODERATE EAST TO SOUTHEAST WINDS WILL PREVAIL ACROSS THE
REGIONAL WATERS, WITH SEAS GENERALLY BETWEEN 2 AND 4 FEET. A WEAK
LONG-PERIOD NORTHEASTERLY SWELL WILL CONTINUE TO SPREAD ACROSS THE
LOCAL ATLANTIC WATERS AND PASSAGES, GRADUALLY INCREASING SEAS
THROUGH THE WEEKEND. MEANWHILE, AN UPPER-LEVEL TROUGH INTERACTING
WITH A WEAK TROPICAL WAVE WILL SUPPORT INCREASED SHOWER AND
THUNDERSTORM ACTIVITY TODAY, WITH THUNDERSTORMS CAPABLE OF PRODUCING
LOCALLY STRONG WIND GUSTS, FREQUENT LIGHTNING, AND BRIEF REDUCTIONS
IN VISIBILITY.
BEACH FORECAST
ISSUED AT 117 AM AST THU SEP 24 2026
A MODERATE RISK OF RIP CURRENTS WILL CONTINUE ALONG THE NORTH- AND
EAST-FACING BEACHES OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS
THROUGH THE WEEKEND. NORTHERLY TO NORTHEASTERLY SWELLS WILL
GRADUALLY INCREASE THE RISK, WITH HIGH RIP CURRENT CONDITIONS LIKELY
AT SOME NORTHERN EXPOSED BEACHES LATE THIS WEEKEND INTO EARLY NEXT
WEEK.
BEACHGOERS SHOULD ALSO BE ALERT FOR HOT CONDITIONS AND PERIODS OF
SHOWERS AND THUNDERSTORMS. THUNDERSTORMS MAY PRODUCE FREQUENT
LIGHTNING, GUSTY WINDS, AND RAPIDLY CHANGING BEACH CONDITIONS. IF
THUNDER IS HEARD, LEAVE THE WATER AND SEEK SHELTER IMMEDIATELY.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
KEY MESSAGES/SHORT TERM...JCP
LONG TERM....MRR
AVIATION...GRS
MARINE/BEACH FORECAST...ICP
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page