077
FXCA62 TJSJ 230739
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
339 AM AST SUN AUG 23 2026
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 335 AM AST SUN AUG 23 2026
* A HEAT THREAT IS EXPECTED FOR TODAY AS WELL WITH WARM
TEMPERATURES WITH HEAT INDICES IN THE 105 TO 111 DEGREES.
THEREFORE, A HEAT ADVISORY IS IN EFFECT FROM 10 AM TO 4 PM
AST.
* VARIABLE WEATHER CONDITIONS ARE EXPECTED TODAY AS A WEAK
TROPICAL WAVE MOVES ACROSS THE ISLANDS, BRINGING PERIODS OF
INCREASED SHOWER ACTIVITY.
* A WETTER AND MORE UNSTABLE PATTERN IS EXPECTED FROM TUESDAY
INTO WEDNESDAY, WITH AN INCREASED CHANCE OF SHOWERS AND
THUNDERSTORMS ACROSS THE ISLANDS DUE TO ANOTHER TROPICAL WAVE.
* A LOW TO MODERATE RISK OF RIP CURRENTS IS EXPECTED OVER THE
COMING DAYS AT LOCAL BEACHES.
SHORT TERM(TODAY THROUGH TUESDAY)
ISSUED AT 335 AM AST SUN AUG 23 2026
DURING THE OVERNIGHT AND EARLY MORNING HOURS, SOME CLOUDINESS WAS
OBSERVED ACROSS EASTERN SECTIONS OF PUERTO RICO, ALTHOUGH NO
SIGNIFICANT RAINFALL ACTIVITY WAS DETECTED ACROSS THE ISLANDS. IN
GENERAL, WEATHER CONDITIONS REMAINED FAIR, WITH ONLY PERIODS OF
PASSING CLOUDINESS AFFECTING PORTIONS OF THE REGION. SKIES
REMAINED MOSTLY CLEAR TO PARTLY CLOUDY ACROSS THE REST OF PUERTO
RICO AND THE U.S. VIRGIN ISLANDS. OVERNIGHT TEMPERATURES WERE IN
THE LOWER 80S ACROSS COASTAL AND URBAN AREAS. MEANWHILE,
TEMPERATURES DROPPED INTO THE LOWER TO MID-70S ACROSS THE
MOUNTAINOUS AND INTERIOR SECTIONS OF PUERTO RICO. WINDS WERE
GENERALLY FROM THE EAST AT AROUND 10 MPH, WITH SOME VARIATIONS
ASSOCIATED WITH THE LAND BREEZE ALONG COASTAL AREAS.
FOR TODAY, A SURFACE HIGH PRESSURE OVER THE WESTERN ATLANTIC, IN
COMBINATION WITH A LOW-PRESSURE SYSTEM OVER THE CENTRAL ATLANTIC,
WILL CONTINUE TO PROMOTE MODERATE EASTERLY WINDS ACROSS THE
REGION. UNDER THIS SURFACE PATTERN, THE MOISTURE FIELD ASSOCIATED
WITH A WEAK TROPICAL WAVE IS FORECAST TO MOVE ACROSS THE ISLANDS,
WITH PRECIPITABLE WATER VALUES INCREASING TO AROUND 1.7 TO 1.9
INCHES. THIS INCREASE IN MOISTURE WILL PROMOTE A MORE SHOWERY
PATTERN, INITIALLY ACROSS THE U.S. VIRGIN ISLANDS DURING THE
MORNING HOURS BEFORE SPREADING ACROSS PUERTO RICO AND THE REST OF
THE LOCAL ISLANDS. ALTHOUGH SURFACE CONDITIONS WILL REMAIN
FAVORABLE, A MID-LEVEL RIDGE WILL MAINTAIN SOME SUBSIDENCE,
POTENTIALLY LIMITING THE VERTICAL DEVELOPMENT. ADDITIONALLY, AN
/UPPER-LEVEL LOW OVER THE CARIBBEAN WILL PROMOTE DIFFLUENT FLOW,
SUPPORTING PERIODS OF HIGH-LEVEL CLOUDINESS AND PROVIDING SOME
UPPER-LEVEL VENTILATION. NEVERTHELESS, UNDER THE ACTUAL
CONDITIONS, THE FORECAST CALLS FOR LOCAL AFTERNOON CONVECTION AND
ISOLATED THUNDERSTORMS ALONG WESTERN SECTIONS DUE TO THE LOCAL
EFFECTS. IN TERMS OF HEAT THREAT, DESPITE THE EXPECTED INCREASE IN
CLOUDINESS AND SHOWER ACTIVITY, A HEAT THREAT COULD STILL DEVELOP
ACROSS SEVERAL AREAS, PARTICULARLY ACROSS NORTH-CENTRAL PUERTO
RICO AND PORTIONS OF THE SOUTHERN COASTAL PLAIN. CONDITIONS REMAIN
BORDERLINE BETWEEN LIMITED AND ELEVATED HEAT RISK; THEREFORE, A
HEAT ADVISORY IS IN EFFECT FROM 11 AM THROUGH 4 PM AST.
BY MONDAY, SLIGHTLY DRIER CONDITIONS ARE EXPECTED AS THE MOISTURE
ASSOCIATED WITH THE FIRST TROPICAL WAVE GRADUALLY MOVES AWAY FROM
THE REGION. NEVERTHELESS, ENOUGH LOW-LEVEL MOISTURE WILL REMAIN
AVAILABLE TO SUPPORT PASSING SHOWERS, MAINLY ACROSS WINDWARD AREAS
DURING THE MORNING HOURS. THIS BRIEF IMPROVEMENT WILL BE SHORT-
LIVED, AS ANOTHER SURGE OF TROPICAL MOISTURE ASSOCIATED WITH A
SECOND TROPICAL WAVE IS EXPECTED TO REACH THE ISLANDS LATE MONDAY
NIGHT INTO TUESDAY. AT THE SAME TIME, WINDS WILL GRADUALLY SHIFT
FROM THE EAST TO THE EAST-SOUTHEAST, FAVORING INCREASED MOISTURE
ADVECTION ACROSS THE REGION. CURRENT HIGH-RESOLUTION GUIDANCE
SUGGESTS AN INCREASE IN SHOWER ACTIVITY ACROSS EASTERN PUERTO RICO
AND THE U.S. VIRGIN ISLANDS BY EARLY TUESDAY MORNING. AS DEEPER
MOISTURE SPREADS ACROSS THE AREA, A MORE ACTIVE SHOWER AND
THUNDERSTORM PATTERN IS EXPECTED THROUGHOUT TUESDAY, PARTICULARLY
WHERE LOCAL AND DIURNAL EFFECTS ENHANCE CONVECTION.
LONG TERM(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 335 AM AST SUN AUG 23 2026
DURING THE LONG-TERM PERIOD, THE WEATHER PATTERN WILL BE MAINLY
DOMINATED BY HIGH PRESSURE ACROSS THE CENTRAL ATLANTIC AND THE
PASSAGE OF TROPICAL WAVES, PRIMARILY FROM THE EAST TO SOUTHEAST.
ALOFT, A MID-LEVEL RIDGE WILL DOMINATE FOR MOST OF THE PERIOD.
BY WEDNESDAY, REMNANT MOISTURE ASSOCIATED WITH A TROPICAL WAVE WILL
REMAIN ACROSS THE REGION. CURRENT GUIDANCE INDICATES THAT
PRECIPITABLE WATER VALUES WILL REMAIN NEAR SEASONAL LEVELS; HOWEVER,
MODERATE TO LOCALLY HIGH CONCENTRATIONS OF SAHARAN DUST WILL PERSIST
ACROSS THE REGION BEFORE DECREASING WEDNESDAY NIGHT INTO THURSDAY.
AS A RESULT, MAINLY FAIR WEATHER, HAZY SKIES, AND HOT TEMPERATURES
ARE EXPECTED ACROSS THE U.S. VIRGIN ISLANDS. ACROSS PUERTO RICO,
EXPECT PASSING MORNING SHOWERS OVER WINDWARD AREAS, WITH LIMITED
AFTERNOON CONVECTION ACROSS WESTERN MUNICIPALITIES.
BY THURSDAY, OVERALL DRIER AIR WILL DOMINATE, WITH PWAT VALUES
FALLING BELOW SEASONAL AVERAGES. HOWEVER, INTERMITTENT PATCHES OF
MOISTURE WILL CONTINUE TO MOVE ACROSS THE REGION. AN UPPER-LEVEL
TROUGH WILL LINGER, RESULTING IN COOLER 500-MB TEMPERATURES, WHILE
THE MID-LEVEL RIDGE WILL STILL PROVIDE SOME STABILITY. DESPITE THIS,
DIURNAL HEATING AND LOCAL EFFECTS WILL SUPPORT THE DEVELOPMENT OF
AFTERNOON CONVECTION, INCLUDING ISOLATED THUNDERSTORMS ACROSS
WESTERN PUERTO RICO, WHICH COULD RESULT IN A LIMITED FLOOD THREAT.
FROM FRIDAY INTO SATURDAY, CURRENT MODEL GUIDANCE SUGGESTS THE
ARRIVAL OF A TROPICAL WAVE, INCREASING TROPICAL MOISTURE UP TO 2.25
INCHES. UNCERTAINTY REMAINS IN THE FORECAST DURING THIS PERIOD, SO
RESIDENTS AND INTERESTS ACROSS THE REGION ARE ENCOURAGED TO CONTINUE
MONITORING THE LATEST FORECASTS AND THE EVOLUTION OF THE TROPICAL
WAVE. BY SUNDAY, PRECIPITABLE WATER VALUES ARE EXPECTED TO DECREASE
TO SEASONAL OR BELOW-NORMAL LEVELS, LIMITING RAINFALL CHANCES.
ONE PERSISTENT HAZARD THROUGHOUT THE PERIOD WILL BE EXCESSIVE HEAT,
WITH AN ELEVATED HEAT THREAT EXPECTED ON MOST DAYS. WEDNESDAY COULD
POSE A PARTICULARLY SIGNIFICANT HEAT THREAT DUE TO ABOVE-NORMAL 925-
MB TEMPERATURES, SOUTHEASTERLY WINDS, THE PRESENCE OF SAHARAN DUST,
AND SEASONAL MOISTURE LEVELS. RESIDENTS ARE ENCOURAGED TO STAY WELL
HYDRATED, WEAR LIGHTWEIGHT AND LOOSE-FITTING CLOTHING, TAKE FREQUENT
BREAKS FROM THE SUN, AND FOLLOW OTHER HEAT-SAFETY PRECAUTIONS.
AVIATION
(06Z TAFS)
ISSUED AT 335 AM AST SUN AUG 23 2026
VFR CONDS ARE EXPECTED TO PREVAIL ACROSS ALL TAF SITES. PASSING
SHRA ARE EXPECTED ACROSS THE USVI AND E PR TERMINALS DURING THE
MORNING HRS AS MOISTURE ASSOCIATED WITH A WEAK TROPICAL WAVE MOVES
ACROSS THE REGION. AFT 23/16Z, DIURNAL HEATING AND LOCAL EFFECTS
WILL PROMOTE SHRA/TSRA DEVELOPMENT, MAINLY AT/NEAR TJBQ AND TJSJ,
WITH BRIEF MVFR CONDS POSSIBLE DUE TO REDUCED VIS AND LOWER CIGS.
E WINDS AT 10-15 KT WILL PREVAIL, WITH LOCALLY HIGHER GUSTS ARE
POSSIBLE NEAR THE STRONGEST SHRA/TSRA.
MARINE
ISSUED AT 335 AM AST SUN AUG 23 2026
A WEAK TROPICAL WAVE WILL APPROACH THE REGION LATER TODAY AND INTO
TONIGHT, BRINGING INCREASED MOISTURE AND PASSING SHOWERS ACROSS THE
LOCAL WATERS. MODERATE EASTERLY TRADE WINDS WILL PREVAIL THROUGH THE
REST OF THE WEEKEND UNDER THE INFLUENCE OF SURFACE HIGH PRESSURE
OVER THE ATLANTIC. HOWEVER, WINDS MAY BRIEFLY WEAKEN AS THE PRESSURE
GRADIENT RELAXES. AFTERWARD, ANOTHER TROPICAL WAVE IS FORECAST TO
APPROACH THE EASTERN CARIBBEAN AROUND TUESDAY, BRINGING MORE
MOISTURE AND SHOWER ACTIVITY ALONG WITH GRADUALLY STRENGTHENING
EASTERLY WINDS.
BEACH FORECAST
ISSUED AT 335 AM AST SUN AUG 23 2026
BEACHGOERS CAN EXPECT A LOW RISK OF LIFE-THREATENING RIP CURRENTS
THROUGH AT LEAST TUESDAY AS WINDS REMAIN RELATIVELY LIGHT ACROSS THE
REGION. HOWEVER, LIFE-THREATENING RIP CURRENTS MAY STILL OCCUR,
ESPECIALLY NEAR GROINS, JETTIES, REEFS, AND PIERS. ALWAYS SWIM NEAR
A LIFEGUARD AND HEED THE ADVICE OF LOCAL BEACH PATROL AND FLAG
WARNING SYSTEMS.
THE RISK OF LIFE-THREATENING RIP CURRENTS IS EXPECTED TO INCREASE TO
MODERATE FROM WEDNESDAY ONWARD AS EASTERLY WINDS STRENGTHEN ACROSS
PUERTO RICO AND THE U.S. VIRGIN ISLANDS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HEAT ADVISORY FROM 10 AM THIS MORNING TO 4 PM AST THIS AFTERNOON
FOR PRZ001>003-005-007-008-010>013.
VI...HEAT ADVISORY FROM 10 AM THIS MORNING TO 4 PM AST THIS AFTERNOON
FOR VIZ001-002.
AM...NONE.
SHORT TERM, AVIATION & KEY MESSAGES...LIS
LONG TERM....YZR
MARINE & BEACH FORECAST...CAM
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