508
FXCA62 TJSJ 181754
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
154 PM AST THU JUN 18 2026
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 143 PM AST THU JUN 18 2026
* PERIODS OF MODERATE TO LOCALLY HEAVY RAINFALL, WITH ISOLATED
THUNDERSTORMS ARE STILL EXPECTED FOR THE REST OF TODAY AND LATER
ON FATHER’S DAY WEEKEND, WITH THE HIGHEST CHANCE OF URBAN AND
SMALL STREAM FLOODING ON SUNDAY.
* MODERATE TO HIGH CONCENTRATIONS OF SAHARAN DUST ARE EXPECTED EARLY
FRIDAY INTO FATHER’S DAY WEEKEND, DETERIORATING AIR QUALITY AND
BRINGING HAZY SKIES AND REDUCED VISIBILITY. EXERCISE CAUTION AND
FOLLOW MEDICAL RECOMMENDATIONS.
* SEASONAL TEMPERATURES WILL CONTINUE THIS FATHER’S DAY WEEKEND
THROUGH NEXT WEEK, WITH HEAT INDICES RANGING FROM THE MID 90S
AND MID 100S ACROSS URBAN AND LOW-LYING AREAS OF PUERTO RICO AND
THE U.S. VIRGIN ISLANDS.
SHORT TERM(THIS EVENING THROUGH SATURDAY)
ISSUED AT 143 PM AST THU JUN 18 2026
WHILE A WEAK TROPICAL WAVE IS TRACKING MAINLY SOUTH OF THE
REGION, IT IS ENCOUNTERING A HOSTILE ENVIRONMENT CHARACTERIZED BY
A STRONG TRADE WIND INVERSION NEAR THE 850 MB LAYER AND
SIGNIFICANT MID-TO-UPPER LEVEL DRYING. THE 18/12Z UPPER-AIR
SOUNDING INDICATED A PRECIPITABLE WATER (PWAT) OF 1.37 INCHES,
WELL BELOW SEASONAL CLIMO. WHILE A BRIEF, LOCALIZED BUMP IN LOW-
LEVEL MOISTURE MAY SUPPORT ISOLATED AFTERNOON CONVECTION ACROSS
WESTERN PUERTO RICO TODAY, A SUBSTANTIAL ADVECTION OF DRY AIR WILL
RAPIDLY OVERSPREAD THE ISLANDS TONIGHT THROUGH SATURDAY. TOTAL
PRECIPITABLE WATER IS PROJECTED TO REMAIN SUPPRESSED BETWEEN 1.30
AND 1.60 INCHES, KEEPING SHOWER ACTIVITY LIMITED TO FAST MOVING,
SHALLOW TRADE WIND SHOWERS ACROSS WINDWARD AREAS OVERNIGHT,
FOLLOWED BY DAYTIME DRIVEN CONVECTIVE ACTIVITY OVER WESTERN PUERTO
RICO. HIGH-RES GUIDANCE INDICATES NO SIGNIFICANT WETTING RAINS
FOR MOST OF THE REGION THROUGH THE FIRST HALF OF THE WEEKEND.
THE PRIMARY FEATURE AFFECTING REGIONAL CONDITIONS WILL BE A DENSE
PLUME OF SAHARAN DUST SPREADING ACROSS THE ATLANTIC INTO THE
NORTHEASTERN CARIBBEAN. TOTAL PRECIPITABLE WATER IMAGERY AND
AEROSOL OPTICAL THICKNESS MODELS INDICATE A DEEP LAYER OF
SUSPENDED PARTICULATES ACCOMPANYING A VERY DRY AIR MASS. THIS
DENSE SAHARAN AIR LAYER (SAL) WILL FULLY FILTER INTO THE REGION BY
EARLY FRIDAY AND PERSIST THROUGH SATURDAY, LEADING TO WIDESPREAD
HAZY SKIES, NOTABLY REDUCED HORIZONTAL VISIBILITIES, AND A SEVERE
SUPPRESSION OF VERTICAL CLOUD GROWTH. THEREFORE, RELATIVELY DRY
AND A STABLE WEATHER PATTERN WILL DOMINATE THE LOCAL AREA THROUGH
SATURDAY.
A STRONG SURFACE HIGH PRESSURE OVER THE CENTRAL ATLANTIC WILL
MAINTAIN MODERATE TO FRESH EASTERLY TO EAST-SOUTHEASTERLY TRADE
WINDS AT 15 TO 20 KNOTS, WITH LOCALIZED SEA BREEZE VARIATIONS AND
HIGHER GUSTS UP TO 25–30 KNOTS. SUPPRESSED CLOUD COVER, COMBINED
WITH 0-3 KM STEERING WINDS WITH AN ESE WIND COMPONENT, WILL DRIVE
INTENSE DAYTIME HEATING, PUSHING AFTERNOON HIGH TEMPERATURES INTO
THE LOWER 90S ACROSS COASTAL AND URBAN AREAS, RESULTING IN HEAT
INDICES OF 100–108F. FURTHERMORE, DUE TO A PROLONGED LACK OF
SIGNIFICANT RAINFALL, CRITICALLY DRY FUELS, AND PERSISTENT BREEZY
CONDITIONS, AN ELEVATED WILDFIRE THREAT WILL PERSIST, PARTICULARLY
ACROSS THE SOUTHERN HILLS AND COASTAL PLAINS OF PR.
LONG TERM(SUNDAY THROUGH NEXT WEDNESDAY)
ISSUED AT 303 AM AST THU JUN 18 2026
A TROPICAL WAVE IS EXPECTED TO APPROACH AND MOVE ACROSS THE
NORTHEASTERN CARIBBEAN FROM LATE SUNDAY INTO MONDAY, BRINGING A
SIGNIFICANT INCREASE IN MOISTURE ACROSS THE REGION. MODEL GUIDANCE
INDICATES PRECIPITABLE WATER VALUES RISING TO AROUND 2 INCHES, WITH
SURFACE AND MID-LEVEL RELATIVE HUMIDITY INCREASING TO ABOVE-NORMAL
LEVELS FOR THIS TIME OF YEAR. COMBINED WITH 500 MB TEMPERATURES NEAR
-7 DEGREES CELSIUS, THESE CONDITIONS WILL SUPPORT A MORE UNSTABLE
ATMOSPHERE AND ENHANCE THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS.
AS A RESULT, PERIODS OF MODERATE TO HEAVY RAINFALL ARE EXPECTED FROM
LATE SUNDAY THROUGH LATE MONDAY, WITH THE HIGHEST COVERAGE LIKELY
DURING THE AFTERNOON HOURS ACROSS WESTERN AND INTERIOR PUERTO RICO.
LOCALLY HEAVY DOWNPOURS OR FREQUENT SHOWERS MAY LEAD TO PONDING OF
WATER IN URBAN AND POORLY DRAINED AREAS, AS WELL AS ISOLATED
FLOODING CONCERNS.
BY TUESDAY INTO MIDWEEK, A DRIER AIR MASS WILL GRADUALLY FILTER INTO
THE REGION, IMPROVING WEATHER CONDITIONS. ALTHOUGH PASSING TRADE-
WIND SHOWERS WILL REMAIN POSSIBLE ACROSS WINDWARD AREAS, A RETURN TO
A MORE TYPICAL WEATHER PATTERN IS ANTICIPATED BY MIDWEEK.
THE PRIMARY HAZARDS DURING THE LONG-TERM PERIOD WILL BE PONDING OF
WATER AND FLOODING, ALONG WITH ISOLATED THUNDERSTORMS.
AVIATION
(18Z TAFS)
ISSUED AT 143 PM AST THU JUN 18 2026
MAINLY VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS ALL TERMINALS
DURING THE NEXT 24 HOURS ACROSS ALL TERMINALS. HOWEVER, ISO -TSRA
EXPECTED TO DEVELOP IN AND AROUND TJBQ THRU 18/22Z, WHICH MAY
LEAD TO TEMPO MVFR CONDS. LOW-LEVEL WINDS WILL CONTINUE E-ESE AT
15-20 KT WITH SEA BREEZE VARIATIONS AT TJBQ/TJSJ AND STRONGER
GUSTS THRU 18/21Z. HZ DUE TO SAHARAN DUST WILL GRADUALLY SPREAD
ACROSS THE USVI AND EASTERN PR TERMINALS FROM THIS EVENING THROUGH
FRIDAY, AND VSBY COULD DROP TO NEAR 6 SM.
MARINE
ISSUED AT 143 PM AST THU JUN 18 2026
A BROAD SURFACE HIGH PRESSURE BUILDING OVER THE CENTRAL ATLANTIC
WILL CONTINUE TO PROMOTE MODERATE TO LOCALLY FRESH EAST TO EAST-
SOUTHEAST WINDS OVER THE NEXT SEVERAL DAYS, RESULTING IN CHOPPY SEAS
ACROSS LOCAL WATERS AND CARIBBEAN PASSAGES; SMALL CRAFT MUST
EXERCISE CAUTION. SHOWERS AND ISOLATED THUNDERSTORMS SHOULD MOVE
LATER TODAY AND EARLY FRIDAY, AS A TROPICAL WAVE MOVES ACROSS
CARIBBEAN SEA, RESULTING IN A PERIOD OF LOCALIZED HEAVY RAINFALL,
LIGHTNING ACTIVITY, AND GUSTY WINDS. A DENSE LAYER OF SAHARAN
DUST WILL GRADUALLY FILTER INTO THE REGION LATE TONIGHT INTO EARLY
FRIDAY, RESULTING IN HAZY SKIES, REDUCED VISIBILITY, AND POOR AIR
QUALITY THROUGH FATHER’S DAY WEEKEND. ANOTHER TROPICAL WAVE IS
EXPECTED TO MOVE ACROSS THE CARIBBEAN SEA BY SUNDAY INTO MONDAY.
BEACH FORECAST
ISSUED AT 143 PM AST THU JUN 18 2026
THE BEACH FORECAST REMAINS ON TRACK. THERE’S A MODERATE RISK OF RIP
CURRENTS ACROSS BEACHES OVER NORTH CENTRAL, NORTHWESTERN, AND
SOUTHEASTERN PUERTO RICO, INCLUDING VIEQUES AND CULEBRA, AND ST.
CROIX IN THE U.S. VIRGIN ISLANDS. LOW RISK ELSEWHERE. BEACHGOERS
MUST EXERCISE CAUTION, AS LIFE-THREATENING RIP CURRENTS ARE POSSIBLE
ALONG THE BEACHES UNDER THE MODERATE RISK. AS MENTIONED IN THE
PREVIOUS DISCUSSIONS, THE THREAT SHOULD GRADUALLY SPREAD ACROSS THE
ISLANDS AS WINDS CONTINUE TO STRENGTHEN, LEADING TO BREAKING WAVES
AROUND 4 FEET. IN ADDITION TO RIP CURRENTS, RESIDENTS AND VISITORS
ARE ENCOURAGED TO FOLLOW THE LATEST WEATHER FORECAST, AS AFTERNOON
SHOWERS AND ISOLATED THUNDERSTORMS COULD BE EXPECTED THIS FATHER’S
DAY WEEKEND AND EARLY NEXT WEEK, PARTICULARLY NEAR COASTAL AREAS OF
WESTERN/NORTHWESTERN PUERTO RICO. GUSTY WINDS, ALONG WITH POSSIBLE
LIGHTNING, CAN BE EXPECTED NEAR THUNDERSTORMS. ADDITIONALLY,
MODERATE TO HIGH CONCENTRATIONS OF SAHARAN DUST WILL GRADUALLY
FILTER INTO THE REGION LATE TONIGHT INTO EARLY FRIDAY, RESULTING IN
HAZY SKIES, REDUCED VISIBILITY, AND POOR AIR QUALITY. BEACHGOERS
SENSITIVE TO THESE PARTICLES SHOULD FOLLOW MEDICAL
RECOMMENDATIONS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...DSR
KEY/MARINE/BEACH...MNG
LONG TERM....MMC
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