039
FXCA62 TJSJ 301841
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
241 PM AST FRI MAY 30 2025
KEY MESSAGES
* THE BULK OF A SAHARAN AIR LAYER IS EXPECTED TO ARRIVE BY
TOMORROW EVENING AND EARLY SUNDAY, RESULTING IN HAZY SKIES,
REDUCED VISIBILITIES, AND ADVERSE CONDITIONS FOR SENSITIVE
GROUPS THROUGH AT LEAST MID-NEXT WEEK.
* WARM TO HOT CONDITIONS ARE LIKELY THIS WEEKEND, PARTICULARLY
FOR THE COASTAL AND URBAN AREAS OF THE ISLANDS, AS UP TO BREEZY
EAST TO EAST-SOUTHEAST WINDS CONTINUE.
SHORT TERM...TONIGHT THROUGH SUNDAY
MID TO UPPER LEVEL CLOUDS CONTINUE TO BE STEERED OVER THE LOCAL
ISLANDS, IN PART DUE TO AN UPPER TROUGH WITH AN AXIS NORTHWEST OF
THE REGION. THIS TROUGH WILL CONTINUE GRADUALLY MOVING NORTH-
NORTHEASTWARD DURING THE PERIOD, WHILE ANOTHER ONE TAKES ITS PLACE
AND LINGERS OVER THE ISLANDS. A MID-LEVEL RIDGE IS ALSO PRESENT AND
WILL REMAIN NEARLY STATIONARY OVER THE REGION DURING THE PERIOD.
THIS MORNINGS SOUNDING SHOW A TRADE WIND CAP ABOVE 800MB, WITH DRIER
AIR IN THE MID LEVELS. THIS PATTERN IS FORECAST TO CONTINUE WITH
DRIER AIR IN THE MID LEVELS CUTTING OFF MOIST AIR IN THE UPPER
LEVELS AND MAINTAINING LOW LEVEL MOISTURE BELOW 800MB. A TROPICAL
WAVE IS CURRENTLY WELL SOUTHWEST OF THE LOCAL ISLANDS, OVER THE
CARIBBEAN SEA, MOISTURE FROM THIS WAVE WILL CONTINUE TO FILTER OUT
OF THE REGION, LEAVING PRECIPITABLE WATER (PWAT) VALUES RANGING FROM
1.50 TO 1.85 IN, AT NORMAL VALUES, DURING THE REST OF THE PERIOD. A
WIND SURGE WILL ALSO CROSS THE REGION FROM SATURDAY INTO SUNDAY WILL
INCREASE MOISTURE ADVECTION WHILE ANOTHER INCREASE IN WINDS IS
FORECAST LATE IN THE PERIOD AND INTO THE LONG TERM FORECAST PERIOD.
IN GENERAL UP TO BREEZY EAST TO EAST-SOUTHEAST WINDS WILL CONTINUE.
THE LEADING EDGE OF A DENSE SAHARAN AIR LAYER (SAL), CURRENTLY OVER
THE TROPICAL ATLANTIC AND NEARING THE WINDWARD AND LEEWARD ISLANDS,
IS FILTERING INTO THE LOCAL ISLANDS. CURRENT MODEL GUIDANCE CONTINUE
TO INDICATE THAT THE BULK OF THIS SAL WILL MOVE INTO THE AREA
SATURDAY EVENING DETERIORATING AIR QUALITY AND RESULTING IN HAZY
SKIES, DRIER AIR ALOFT, LOWER VISIBILITIES AND ADVERSE CONDITIONS
FOR IMMUNOCOMPROMISED, VULNERABLE AND SENSITIVE GROUPS. THIS IS A
MODERATE TO HIGH SAL EVENT, PLEASE FOLLOW YOUR DOCTOR'S AND YOUR
HEALTH DEPARTMENT'S RECOMMENDATIONS. DESPITE THE SAHARAN DUST AND
ACCOMPANYING DRY AIR, ABOVE MENTIONED INSTABILITY AND DIURNAL
HEATING CAN CONTINUE TO PROMOTE SHOWER AND ISOLATED THUNDERSTORM
DEVELOPMENT, PARTICULARLY OVER NW PR AND DOWNWIND OF EL YUNQUE AND
THE LOCAL ISLANDS. OVERNIGHT AND EARLY MORNING TRADE WIND SHOWERS
WILL ALSO CONTINUE OVER WINDWARD SECTORS OF THE ISLANDS. A LIMITED
RAINFALL RISK WILL REMAIN FOR NW PR. BREEZY EAST-TO-EAST-SOUTHEAST
WINDS WILL ALSO PROMOTE A LIMITED TO POSSIBLY ELEVATED HEAT THREAT
FOR URBAN AND COASTAL AREAS, THE PRESENCE OF SAHARAN DUST CAN ALSO
CONTRIBUTE TO THIS HEAT THREAT. PLEASE REFER TO THE LATEST HAZARDOUS
WEATHER OUTLOOK (HWOSJU) AND IT'S GRAPHICAL FORMAT
(WEATHER.GOV/ERH/GHWO?WFO=SJU) FOR MORE INFORMATION.
LONG TERM...MONDAY THROUGH FRIDAY
/FROM PREV DISCUSSION
ISSUED AT 350 AM AST FRI MAY 30 2025/
THE FORECAST CONTINUES ON TRACK WITH THE ENTRANCE OF A DENSE PLUME
OF SAHARAN AIR LAYER (SAL) AFFECTING THE NORTHEASTERN CARIBBEAN
THROUGH MID-WEEK. BASED ON THE LATEST MODEL GUIDANCE THE HIGHER
CONCENTRATIONS OF DUST ARE EXPECTED TO PEAK ON MONDAY WITH AEROSOL
OPTICAL THICKNESS OF NEAR 0.5. HAZY SKIES, DETERIORATED AIR QUALITY
AND REDUCED VISIBILITIES WILL CONTINUE THROUGH LATE WEDNESDAY.
DESPITE THE HIGHER CONCENTRATIONS ARE EXPECTED BY EARLY IN THE WEEK,
LOW TO MODERATE CONCETRATIONS OF DUST WILL CONTINUE THROUGH NEXT
WEEKEND. RESIDENTS AND VISITORS ARE URGED TO TAKE THE NECESSARY
HEALTH PRECAUTIONS DURING THIS PERIOD. AT THE SURFACE, A HIGH
PRESSURE SYSTEM WILL PROMOTE SOUTHEASTERLY WINDS THROUGH TUESDAY.
THE, WINDS ARE EXPECTED TO SHIFT FROM THE EAST AS THE SURFACE HIGH
MOVES TOWARDS THE NORTHEAST ATLANTIC. A MID-TO-UPPER LEVEL RIDGE
WILL BUILD OVER THE NORTHEASTERN CARIBBEAN BY MONDAY, PROMOTING
DRIER CONDITIONS AND STABILITY ALOFT. UNDER THESE CONDITIONS, VERY
LIMITED SHOWER ACTIVITY IS ANTICIPATED THROUGHOUT THE PERIOD WITH
PRECIPITABLE WATER VALUES (PWAT) NEAR BELOW-NORMAL CLIMATOLOGICAL
VALUES (1.5 INCHES). HOWEVER, SHOWERS AND ISOLATED THUNDERSTORMS
ARE POSSIBLE OVER WESTERN PUERTO RICO WITH THE COMBINATION OF
DIURNAL HEATING AND LOCAL EFFECTS. WARM TO HOT TEMPERATURES ARE
EXPECTED TOO, WITH TEMPERATURES RISING TO ABOVE NORMAL VALUES FOR
EARLY NEXT WEEK. HIGHS ARE EXPECTED TO BE IN THE UPPER 80S TO LOW
90S IN THE COASTAL AND URBAN AREAS, AND IN THE LOW 80S IN THE
HIGHER ELEVATIONS. HEAT INDICES COULD REACH VALUES OVER 108
DEGREES FAHRENHEIT ON MONDAY AND TUESDAY, PARTICULARLY OVER NORTH-
CENTRAL PUERTO RICO. PLEASE BE AWARE OF THESE CONDITIONS IF
PLANNING TO DO ACTIVITIES OUTDOORS, SCHOOL SUMMER CAMPS OR
CONSTRUCTION.
AVIATION
(18Z TAFS)
MAINLY VFR CONDITIONS ACROSS THE TERMINALS. ANY SHRA WILL MOVE
QUICKLY, WITHOUT SIGNIFICANT IMPACTS TO OPERATIONS FOR MOST
TERMINALS. WINDS FROM THE ESE AT 15-20 KTS, WITH HIGHER GUSTS,
BEFORE DECREASING AFTER 22Z AND INCREASING AGAIN AFTER 31/13Z.
VCSH WILL DEVELOP NEAR TJBQ DURING THE AFTERNOON HOURS. HIGH
CLOUDS WILL CAN CAUSE BKN060-80 SKIES THROUGH THE PERIOD. HZ IS
FORECAST BY TOMORROW EVENING.
MARINE
A SURFACE HIGH PRESSURE BUILDING OVER THE ATLANTIC BASIN WILL
CONTINUE TO PROMOTE MODERATE TO LOCALLY FRESH TRADE WINDS OVER THE
NEXT FEW DAYS. SMALL CRAFT SHOULD EXERCISE CAUTION ACROSS MOST
OFFSHORE WATERS AND LOCAL CARIBBEAN PASSAGES. ISOLATED
THUNDERSTORMS ARE EXPECTED TO AFFECT THE WESTERN COASTAL WATERS OF
PUERTO RICO AND THE MONA PASSAGE EACH AFTERNOON AND EVENING. LOW
CONCENTRATIONS OF SAHARAN DUST WILL REMAIN OVER THE REGION THROUGH
SATURDAY, THEN HAZY SKIES AND REDUCED VISIBILITIES ARE EXPECTED
FROM LATE SATURDAY THROUGH MID-WEEK AS ANOTHER DENSE PLUME OF
SAHARAN DUST MOVES TOWARD THE AREA.
BEACH FORECAST
THERE IS A LOW TO MODERATE RISK OF RIP CURRENTS TONIGHT FOR
NORTHERN BEACHES OF PUERTO RICO, WITH A MODERATE RISK FOR ST.
CROIX. THE REST OF THE AREA, REMAINS UNDER A LOW RISK OF RIP
CURRENTS. ALTHOUGH THE REST OF THE REGION IS UNDER A LOW RISK OF
RIP CURRENTS, THESE LIFE- THREATENING RIP CURRENTS OFTEN OCCUR IN
THE VICINITY OF GROINS, JETTIES, REEFS, AND PIERS. A LOW TO
MODERATE RISK OF RIP CURRENTS IS FORECAST FOR SOUTHERN BEACHES OF
PUERTO RICO, VIEQUES, CULEBRA AND ST. CROIX DURING THE WEEKEND.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM.....MRR
PUBLIC DESK....RVT
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