992
FXCA62 TJSJ 281851
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
251 PM AST SAT JUN 28 2025
KEY MESSAGES
* AN UPPER-LEVEL LOW TO THE NORTHWEST AND A TROPICAL WAVE TO THE
SOUTH WILL PROMOTE INCREASED SHOWERS AND THUNDERSTORM ACTIVITY
THROUGH SUNDAY AFTERNOON, HEIGHTENING THE RISK OF FLOODING.
* SLIGHTLY DRIER AIR, ACCOMPANIED BY MODERATE CONCENTRATIONS OF
SUSPENDED SAHARAN DUST, WILL FOLLOW THE TROPICAL WAVE, LEADING
TO HAZY SKIES AND DEGRADED AIR QUALITY THROUGH EARLY NEXT WEEK.
* BREEZY WINDS WILL SUSTAIN CHOPPY SEAS AND MAINTAIN A MODERATE
RISK OF RIP CURRENTS ALONG EXPOSED BEACHES OVER THE NEXT FEW
DAYS.
SHORT TERM...TONIGHT THROUGH MONDAY
BREEZY TO LOCALLY WINDY CONDITIONS STEERED FREQUENT, FAST-MOVING
SHOWERS INTO EASTERN PUERTO RICO AND THE U.S. VIRGIN ISLANDS THIS
MORNING, RESULTING IN MINIMAL RAINFALL ACCUMULATIONS, THOUGH SOME
AREAS EXPERIENCED PERSISTENT SHOWERS FOLLOWED BY GUSTY WINDS. BY
MIDDAY, DIURNAL HEATING AND LOCAL EFFECTS TRIGGERED ISOLATED
THUNDERSTORMS AND HEAVIER SHOWERS, WITH RADAR ESTIMATES SHOWING UP
TO 2 INCHES OF RAIN BETWEEN ANASCO, MAYAGUEZ, AND LAS MARIAS.
HIGH TEMPERATURES REACHED THE LOWER 90S ACROSS MOST LOWER
ELEVATIONS, WITH 92°F—THE HIGHEST REPORTED SO FAR—OBSERVED IN
SOUTHERN PUERTO RICO AND EASTERN ST. CROIX. SURFACE STATIONS
RECORDED SUSTAINED WINDS OF 24–26 MPH WITH GUSTS UP TO 32 MPH,
MAINLY ALONG THE COAST.
BREEZY EAST-SOUTHEASTERLY WINDS WILL PERSIST THROUGH THE SHORT-
TERM PERIOD, GRADUALLY SHIFTING MORE EASTERLY BY LATE MONDAY. AN
UPPER-LEVEL LOW TO THE WEST-NORTHWEST OF THE REGION WILL MAINTAIN
MARGINAL INSTABILITY OVER THE ISLANDS. MEANWHILE, A TROPICAL WAVE
CROSSING THE EASTERN CARIBBEAN TONIGHT WILL PASS JUST SOUTH OF THE
AREA AND, COMBINED WITH THE LOW, WILL DRAW DEEP TROPICAL MOISTURE
INTO THE REGION. PRECIPITABLE WATER (PWAT) VALUES ARE EXPECTED TO
PEAK BETWEEN 2.1 AND 2.2 INCHES BY MIDDAY SUNDAY, WELL ABOVE
NORMAL FOR THIS TIME OF YEAR. THIS SETUP WILL SUPPORT SCATTERED TO
LOCALLY NUMEROUS OVERNIGHT SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS, MAINLY ACROSS EASTERN PUERTO RICO AND THE U.S.
VIRGIN ISLANDS TONIGHT, FOLLOWED BY MORE WIDESPREAD AFTERNOON
CONVECTION OVER INTERIOR AND NORTHWESTERN PUERTO RICO ON SUNDAY.
THIS OVERALL PATTERN WILL PERSIST THROUGH SUNDAY AFTERNOON.
BY LATE SUNDAY, A TRANSITION BEGINS AS THE UPPER-LEVEL LOW GIVES
WAY TO A BUILDING MID- TO UPPER-LEVEL RIDGE FROM THE EAST,
PROMOTING SUBSIDENCE AND ALLOWING A DRIER AIR MASS TO FILTER INTO
THE REGION. THE TRADE WIND INVERSION WILL BECOME MORE PRONOUNCED,
LIMITING VERTICAL CLOUD DEVELOPMENT AND SUPPRESSING MOST SHOWER
ACTIVITY AS MOISTURE BECOMES TRAPPED BELOW THE 850 MB LAYER.
CONSEQUENTLY, PWAT VALUES WILL GRADUALLY DECREASE, FALLING TO
NORMAL LEVELS BY SUNDAY AFTERNOON AND BELOW TYPICAL VALUES FROM
SUNDAY NIGHT INTO MONDAY. IN THE WAKE OF THE TROPICAL WAVE,
MODERATE CONCENTRATIONS OF SAHARAN DUST ARE EXPECTED TO MOVE IN,
RESULTING IN HAZY SKIES AND POTENTIALLY DEGRADED AIR QUALITY,
ESPECIALLY ON MONDAY.
BREEZY TO LOCALLY WINDY CONDITIONS WILL LIKELY BRING LIMITED NON-
THUNDERSTORM WIND HAZARDS, PARTICULARLY IN COASTAL AND ELEVATED
AREAS DURING PEAK SEA BREEZE INFLUENCE. WHILE LIGHTNING RISKS WILL
REMAIN LIMITED DUE TO EXPECTED ISOLATED THUNDERSTORMS, PERIODS OF
HEAVY RAINFALL FROM THESE STORMS COULD STILL LEAD TO URBAN AND
SMALL STREAM FLOODING, WITH LOCALIZED FLASH FLOODING
POSSIBLE—ESPECIALLY ACROSS INTERIOR AND NORTHWESTERN PUERTO RICO
ON SUNDAY. LIMITED TO ELEVATED EXCESSIVE HEAT RISKS WILL CONTINUE,
PARTICULARLY IN LOWER ELEVATIONS AND URBAN AREAS.
LONG TERM...TUESDAY THROUGH SATURDAY
FROM PREVIOUS DISCUSSION...ISSUED AT 522 AM AST SAT JUN 28 2025
A SEASONAL WEATHER PATTERN WILL INFLUENCE THE METEOROLOGICAL
CONDITIONS, FEATURING A MIX OF CLOUDS AND SUNSHINE, AS WELL AS
CLEAR SKIES FROM TUESDAY TO THURSDAY. ON TUESDAY, WE CAN EXPECT
LINGERING SUSPENDED DUST PARTICLES DUE TO A MID-LEVEL RIDGE.
ADDITIONALLY, EASTERLY TRADE WIND DISTURBANCES, CAUSED BY A TROUGH
LOCATED IN THE MID-TO-UPPER LEVELS OFF THE NORTHEAST OF THE
LESSER ANTILLES, WILL INTRODUCE OCCASIONAL INCREASES IN SHALLOW
MOISTURE ACROSS THE REGION. THESE SURGES OF MOISTURE MAY LEAD TO
BRIEF SHOWERS, PARTICULARLY IN WINDWARD AREAS, FOLLOWED BY
AFTERNOON CONVECTION IN WESTERN LOCATIONS. HOWEVER, THIS ACTIVITY
IS EXPECTED TO BE LIMITED IN INTENSITY DUE TO THE TRADE WIND CAP
AND SUBSIDENCE ALOFT ASSOCIATED WITH THE PERSISTENT MID-LEVEL
RIDGE, WHICH IS ANTICIPATED TO REMAIN IN PLACE THROUGH AT LEAST
WEDNESDAY.
TEMPERATURES ARE EXPECTED TO BE ABOVE NORMAL, PARTICULARLY DUE TO
THE SAL, WHICH WILL HINDER OVERNIGHT COOLING AND RESULT IN WARMER
MINIMUM AND MAXIMUM TEMPERATURES THROUGHOUT THE ISLANDS DURING
THE FIRST HALF OF NEXT WEEK.
CONDITIONS ARE EXPECTED TO CHANGE LATE THURSDAY INTO FRIDAY DUE TO
THE APPROACH OF A RETROGRADING MID- TO UPPER-LEVEL TROUGH/LOW AND
A TROPICAL WAVE. THIS SITUATION MAY LEAD TO INCREASED SHOWER AND
THUNDERSTORM ACTIVITY IN THE US VIRGIN ISLANDS AND PUERTO RICO.
CONDITIONS SHOULD RAPIDLY DRY OUT AFTER THIS WAVE BY LATE FRIDAY
NIGHT INTO NEXT SATURDAY, PROMOTING THE TYPICAL ADVECTIVE PATTERN
OVERNIGHT AND IN THE MORNING, FOLLOWED BY AFTERNOON CONVECTION.
AVIATION
(18Z)
SHRA/TSRA WILL LIKELY AFFECT MOST LOCAL TERMINALS THROUGHOUT THE
FORECAST PERIOD, WITH THE STRONGEST ACTIVITY POSSIBLE NEAR TJUA
AND TJBQ AFTER 29/16Z. THESE SHOWERS AND THUNDERSTORMS MAY CAUSE
BRIEF MVFR CONDITIONS. LOW TO MODERATE CONCENTRATIONS OF SAHARAN
DUST WILL KEEP SKIES HAZY, WITH VISIBILITY OCCASIONALLY REDUCED TO
5–6 STATUTE MILES. BREEZY WINDS OF 15-20 KNOTS ARE EXPECTED
THROUGH 28/23Z AND AGAIN AFTER 29/13Z, DIMINISHING TO 5-10 KNOTS
BETWEEN 28/23Z AND 29/13Z. GUSTY AND VARIABLE WINDS ARE ALSO
POSSIBLE IN AND NEAR STRONGER SHRA/TSRA.
MARINE
MARINERS CAN EXPECT CHOPPY SEAS ACROSS THE LOCAL ATLANTIC AND
CARIBBEAN WATERS DUE PERSISTENT MODERATE TO FRESH EASTERLY WINDS.
A TROPICAL WAVE IS EXPECTED TO MOVE ACROSS THE EASTERN CARIBBEAN
THROUGH SUNDAY, INCREASING THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS ACROSS THE REGION. ANOTHER PULSE WITH SUSPENDED
SAHARAN DUST PARTICLES WILL FOLLOW, MAINTAINING HAZY SKIES
THROUGH EARLY NEXT WEEK.
BEACH FORECAST
WIND-DRIVEN WAVES DUE TO BREEZY EASTERLIES WILL PROMOTE A
MODERATE RISK OF RIP CURRENTS AT SOME EXPOSED BEACHES OF THE
ISLANDS FOR MUCH OF THE FORECAST PERIOD.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...ICP
PUBLIC...LIS
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