995
FXCA62 TJSJ 241753
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
153 PM AST FRI JUL 24 2026
...NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER...
KEY MESSAGES
UPDATED AT 143 PM AST FRI JUL 24 2026
* ISOLATED SHOWERS AND THUNDERSTORMS WILL RESULT IN PONDING OF WATER
ACROSS ROADWAYS AND POORLY DRAINED AREAS ACROSS WESTERN PUERTO
RICO THIS AFTERNOON.
* MODERATE TO HIGH CONCENTRATIONS OF SAHARAN DUST WILL CONTINUE TO
SPREAD ACROSS THE ISLANDS FOR THE REST OF TODAY THROUGH SATURDAY.
SENSITIVE GROUPS MUST FOLLOW MEDICAL RECOMMENDATIONS.
* A MORE VIGOROUS TROPICAL WAVE IS FORECAST FROM LATE SUNDAY INTO
MONDAY, INCREASING THE POTENTIAL FOR SHOWER ACTIVITY AND FLOODING
POTENTIAL.
* THE MODERATE RISK OF RIP CURRENTS CONTINUES ACROSS LOCALLY
EXPOSED BEACHES THIS WEEKEND AND EARLY NEXT WEEK.
SHORT TERM(THIS EVENING THROUGH SUNDAY)
ISSUED AT 143 PM AST FRI JUL 24 2026
DRIER CONDITIONS PREVAILED ACROSS THE AREA DURING THE MORNING
HOURS, AS SHOWN BY THE 24/12Z TJSJ SOUNDING WITH A PWAT OF 1.29
INCHES AND SURFACE WINDS OUT OF THE EAST, LEADING TO MOSTLY SUNNY
SKIES ACROSS THE LOCAL ISLANDS. BY AROUND 11 AM TO NOON, SOME
CLOUDINESS DEVELOPED IN A STREAMER PATTERN AFFECTING EASTERN
SECTIONS OF PUERTO RICO. AN INCREASE IN MOISTURE WAS OBSERVED BY
THE GOES-DERIVED SATELLITE PRECIPITABLE WATER, WITH VALUES RISING
FROM 1.3 TO 1.5 INCHES AND GRADUALLY INCREASING THE POTENTIAL FOR
SHOWER DEVELOPMENT ACROSS THE LOCAL WATERS AND LAND AREAS. MAXIMUM
TEMPERATURES PEAKED IN THE UPPER 80S ACROSS COASTAL AREAS AND IN
THE MID-80S ALONG MOUNTAIN AREAS. SURFACE WINDS REMAINED FROM THE
EAST AT 15 MPH OR LESS, WITH GUSTY CONDITIONS, ESPECIALLY NEAR
THE COASTAL AREAS.
FOR THE REST OF THE AFTERNOON AND INTO TONIGHT, AS A WEAK TROPICAL WAVE
MOVES ACROSS THE AREA, THE MOISTURE FIELD WILL CROSS THE LOCAL
ISLANDS AND INCREASE OVERALL LOW-LEVEL MOISTURE. THESE CONDITIONS,
IN COMBINATION WITH SUSPENDED SAHARAN DUST PARTICLES TRAPPING
HEAT, WILL ENHANCE WARM CONDITIONS ACROSS THE REGION, RESULTING IN
WARMER NIGHT TEMPERATURES AND SOME PASSING SHOWERS. THE LATEST
GUIDANCE FROM THE HIGH-RESOLUTION MODELS SUGGESTS PASSING SHOWER
ACTIVITY FROM 2 AM THROUGH THE DAY ON SATURDAY. FOR SATURDAY,
SURFACE WINDS WILL PERSIST FROM THE EAST AS THE SURFACE HIGH
PRESSURE REMAINS THE DOMINANT FEATURE, HOLDING MODERATE EASTERLY
WINDS. A DECREASE IN SAHARAN DUST PARTICLES IS EXPECTED AS THE
MAJOR CONCENTRATION MOVES FURTHER WESTWARD INTO THE WESTERN
ATLANTIC, LEAVING THE ISLANDS ONLY WITH SOME MINIMAL TO TRACE
CONCENTRATIONS FOR THE REST OF THE DAY. AT MID LEVELS, COLDER
TEMPERATURES AT 500 MB WILL REMAIN PRESENT AS AN UPPER LOW STAYS
NORTH OF THE AREA, MAINTAINING ENOUGH INSTABILITY FOR LOCALIZED
AFTERNOON SHOWERS.
SUNDAY IS A TRANSITION DAY INTO A MORE ACTIVE AND WET WEATHER
PATTERN ACROSS THE REGION. AT THE SURFACE, A SIGNIFICANT INCREASE
IN MOISTURE IS FORECAST DUE TO THE APPROACH OF A MORE VIGOROUS
TROPICAL WAVE. CONCURRENTLY, THE SURFACE HIGH PRESSURE WILL BUILD
FURTHER, RESULTING IN WINDS SHIFTING MORE FROM THE EAST-SOUTHEAST
AND A SLIGHT DECREASE IN WIND SPEEDS ACROSS THE LOCAL AREA. ALOFT,
THE CUT-OFF LOW WILL DIG INTO THE WESTERN CARIBBEAN, POSITIONING
THE FAVORABLE, DIVERGENT SIDE OF THE UPPER SYSTEM DIRECTLY OVER
THE REGION. THIS DYNAMIC SETUP WILL SIGNIFICANTLY ENHANCE
ATMOSPHERIC INSTABILITY AND MOISTURE CONVERGENCE, INCREASING THE
OVERALL POTENTIAL FOR WIDESPREAD SHOWERS AND THUNDERSTORM
DEVELOPMENT, LEADING TO A LIMITED-TO-ELEVATED FLOOD THREAT,
PARTICULARLY FOR WESTERN PUERTO RICO.
LONG TERM(MONDAY THROUGH NEXT THURSDAY)
ISSUED AT 143 PM AST FRI JUL 24 2026
CURRENT MODEL GUIDANCE SUGGESTS A WETTER PATTERN AT THE BEGINNING OF
NEXT WORK WEEK. THE COMBINATION OF A TROPICAL WAVE AND AN UPPER-
LEVEL LOW WILL BRING INCREASED CHANCES OF RAIN. AS THE TROPICAL WAVE
MOVES ACROSS THE REGION, PWAT VALUES ARE EXPECTED TO INCREASE TO
ABOVE-NORMAL LEVELS THROUGH AT LEAST TUESDAY, EXCEEDING 2 INCHES,
WHICH IS AROUND THE 75TH PERCENTILE FOR THIS TIME OF YEAR. ALOFT, AN
UPPER-LEVEL LOW POSITIONED OVER THE ISLANDS THROUGH MONDAY WILL
MAINTAIN LOWER 250-MB HEIGHTS AND COOLER 500-MB TEMPERATURES (AROUND
-8 TO -9°C), WITH BOTH REMAINING NEAR TO BELOW SEASONAL NORMALS.
THIS PATTERN WILL INCREASE THE POTENTIAL FOR THUNDERSTORM
DEVELOPMENT. MOISTURE WILL ALSO INCREASE IN THE MID AND UPPER
LEVELS, CREATING A MORE UNSTABLE ENVIRONMENT ACROSS THE ISLANDS. AS
A RESULT, MONDAY IS EXPECTED TO BE THE DAY WITH BETTER DYNAMICS FOR
THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS. ADDITIONALLY, WINDS
ARE FORECAST TO REMAIN VERY LIGHT THAT DAY, RESULTING IN SLOW-MOVING
SHOWERS AND THUNDERSTORMS CAPABLE OF PRODUCING HIGHER RAINFALL
ACCUMULATIONS. AS A RESULT, THE FLOOD THREAT WILL REMAIN ELEVATED ON
MONDAY ACROSS THE INTERIOR AND WESTERN PORTIONS OF PUERTO RICO, WITH
THE POTENTIAL FOR FLOODING IN URBAN AREAS, ALONG ROADS, IN SMALL
STREAMS, AND IN WASHES. A MORE LIMITED FLOOD THREAT IS EXPECTED
ACROSS EASTERN PUERTO RICO AND THE USVI.
BY TUESDAY AND WEDNESDAY, THE UPPER-LEVEL LOW WILL SHIFT SLIGHTLY
WEST OF THE AREA, ALLOWING SOME STABILITY ALOFT, AS REFLECTED BY
RISING HEIGHTS AND TEMPERATURES. AT THE SAME TIME, ATLANTIC HIGH
PRESSURE WILL GRADUALLY STRENGTHEN, CAUSING EASTERLY TO
SOUTHEASTERLY WINDS TO INCREASE AND BECOME BREEZY TO LOCALLY WINDY.
HOWEVER, MOISTURE CONTENT WILL REMAIN ABOVE AVERAGE AND, WHEN
COMBINED WITH LOCAL EFFECTS AND DIURNAL HEATING, WILL LIKELY SUPPORT
OVERNIGHT AND MORNING WINDWARD SHOWERS, FOLLOWED BY AFTERNOON
CONVECTION ACROSS THE INTERIOR AND WESTERN PORTIONS OF PUERTO RICO.
THE FLOOD THREAT DURING THESE DAYS IS CURRENTLY EXPECTED TO BE MORE
LIMITED AND MAINLY CONFINED TO NORTHWESTERN PUERTO RICO, WITH
PONDING OF WATER ON ROADS AND IN POORLY DRAINED AREAS BEING THE
PRIMARY CONCERN. THIS FORECAST WILL CONTINUE TO BE REFINED WITH EACH
UPDATE AS CONFIDENCE INCREASES.
DRIER AIR WILL BEGIN FILTERING INTO THE AREA FROM WEDNESDAY NIGHT/
THURSDAY THROUGH FRIDAY, ACCOMPANIED BY SOME SAHARAN DUST. AS PWAT
VALUES DECREASE TO NEAR SEASONAL LEVELS, ISOLATED TRADE WIND SHOWERS
WILL CONTINUE DUE TO THE PRESENCE OF PATCHES OF MOISTURE EMBEDDED IN
THE TRADES, BUT OVERALL SHOWER COVERAGE IS EXPECTED TO BE MORE
LIMITED THAN DURING THE PREVIOUS DAYS. THROUGHOUT MOST OF THE
FORECAST PERIOD, AVAILABLE MOISTURE AND SOUTHEASTERLY WIND FLOW,
PARTICULARLY FROM WEDNESDAY ONWARD, WILL MAINTAIN WARM TO HOT
CONDITIONS, RESULTING IN AN ELEVATED HEAT RISK ACROSS COASTAL AND
URBAN AREAS.
AVIATION
(18Z TAFS)
ISSUED AT 143 PM AST FRI JUL 24 2026
VFR CONDITIONS WILL PERSIST ACROSS ALL TAF SITES DURING THE
PERIOD. HZ WILL CONTINUE TO RESULT IN LIMITED VIS AT LEAST UNTIL
25/10Z FOR EASTERN-LOCATED SITES AND THEN FOR THE REST OF THE
SITES. VCSH AND -VCTS ARE POSSIBLE FROM 24/19Z TO 24/21Z NEAR THE
VICINITY OF TJBQ, AND AFTER THAT AT 25/06Z ACROSS TIST & TISX.
WINDS WILL CONTINUE FROM THE E AT 15 KNOTS AND GUSTY WINDS UP TO
25 KNOTS, DECREASING AT 24/23Z AND INCREASING AGAIN AT 25/13Z FROM
THE E.
MARINE
ISSUED AT 143 PM AST FRI JUL 24 2026
A BROAD SURFACE HIGH PRESSURE WILL MAINTAIN MODERATE TO LOCALLY
FRESH EAST-SOUTHEAST WINDS THROUGH AT LEAST SATURDAY, BECOMING
MODERATE ON SUNDAY. MODERATE TO HIGH CONCENTRATIONS OF SAHARAN DUST
WILL CONTINUE TO SPREAD ACROSS THE REGION FOR THE REST OF TODAY,
SLIGHTLY REDUCING VISIBILITY, DIMINISHING ON SATURDAY. SHOWER
ACTIVITY SHOULD GRADUALLY INCREASE THIS AFTERNOON AS A WEAK TROPICAL
WAVE MOVES ACROSS THE REGION. A VIGOROUS TROPICAL WAVE IS EXPECTED
TO REACH THE NORTHEASTERN CARIBBEAN FROM LATE SUNDAY INTO MONDAY,
INCREASING MOISTURE AND THE POTENTIAL FOR THUNDERSTORM ACTIVITY OVER
THE LOCAL CARIBBEAN WATERS, WHICH WILL RESULT IN LOCALIZED HAZARDOUS
MARINE CONDITIONS.
BEACH FORECAST
ISSUED AT 143 PM AST FRI JUL 24 2026
THE BEACH FORECAST REMAINS ON TRACK. THE MODERATE RISK OF RIP
CURRENTS CONTINUES ACROSS NORTHERN AND EASTERN BEACHES OF PUERTO
RICO, INCLUDING VIEQUES AND CULEBRA, AND ST. CROIX IN THE U.S.
VIRGIN ISLANDS, WITH LOW RISK ELSEWHERE. ALTHOUGH THERE IS A
MODERATE RISK, BEACHGOERS MUST EXERCISE CAUTION AS LIFE-THREATENING
RIP CURRENTS REMAIN POSSIBLE ALONG THE SURF ZONE. AS WINDS WEAKEN BY
SUNDAY, THE RISK MAY BE LOWERED IN SOME AREAS, THOUGH BEACHGOERS
MUST REMAIN AWARE OF ISOLATED LIFE-THREATENING RIP CURRENTS IN THE
VICINITY OF GROINS, JETTIES, REEFS, AND PIERS. AS WINDS GRADUALLY
STRENGTHEN, THE MODERATE RISK SHOULD SPREAD ACROSS THE ISLANDS AND
PERSIST FOR THE REST OF THE FORECAST PERIOD. BESIDES RIP CURRENTS,
BEACHGOERS SHOULD CONTINUE TO MONITOR WEATHER CONDITIONS, AS
AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS MAY MOVE NEAR COASTAL
AREAS OF WESTERN PUERTO RICO, INCLUDING EASTERN PUERTO RICO ON
SUNDAY AND MONDAY. IN ADDITION, MODERATE TO HIGH CONCENTRATIONS WILL
LINGER ACROSS THE REGION THROUGH SATURDAY, DETERIORATING AIR
QUALITY.
FIRE WEATHER
ISSUED AT 143 PM AST FRI JUL 24 2026
SURFACE CONDITIONS REMAINED ON THE DRIER SIDE AS A DRIER AIRMASS
DOMINATED THE REGION RESULTING IN RH VALUES DROPPING INTO THE LOW
50S ACROSS STATIONS ALONG THE SOUTHERN COASTAL PLAINS. FOR
TOMORROW SURFACE WINDS WILL REMAIN FROM THE EAST PEAKING UP AT
AROUND 10 AM AST UP TO 15 KNOTS AND SLIGHTLY HIGH IN LOCALIZED
AREAS. RH VALUES FOR TOMORROW WILL RANGE BETWEEN THE MID 50S TO
UPPER 60S DUE TO SOME MOISTURE ASSOCIATED WITH THE PREVIOUS
TROPICAL WAVE.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM...LIS
LONG TERM....YZR
AVIATION...LIS
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