244
FXCA62 TJSJ 281800
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
200 PM AST SUN JUN 28 2026
..NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST
KEY MESSAGES
ISSUED AT 149 PM AST SUN JUN 28 2026
* ABUNDANT TROPICAL MOISTURE WILL ENHANCE SHOWER AND THUNDERSTORM
ACTIVITY LATE TONIGHT AND MONDAY, WITH PONDING OF WATER OVER
ROADWAYS AND POORLY DRAINED AREAS, INCLUDING URBAN AND SMALL
STREAM FLOODING, ACROSS THE ISLANDS.
* WARMER TO HOT CONDITIONS ARE EXPECTED FOR THE NEXT FEW DAYS, WITH
HEAT INDICES EXCEEDING 100 DEGREES FAHRENHEIT ACROSS URBAN AND LOW-
LYING AREAS OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS. STAY
HYDRATED.
* MODERATE TO HIGH CONCENTRATIONS OF SAHARAN DUST WILL LIKELY RETURN
BY EARLY TUESDAY, RESULTING IN HAZY SKIES, REDUCED VISIBILITY, AND
POOR AIR QUALITY. SENSITIVE GROUPS MUST FOLLOW MEDICAL
RECOMMENDATIONS.
SHORT TERM(THIS EVENING THROUGH TUESDAY)
ISSUED AT 149 PM AST SUN JUN 28 2026
A RELATIVELY DRY AND STABLE AIR MASS IS CURRENTLY IN PLACE ACROSS
THE REGION, INFLUENCED BY A MID-LEVEL RIDGE AND A TRADE WIND
INVERSION. THIS WILL KEEP SHOWER ACTIVITY FAIRLY ISOLATED THROUGH
THE REMAINDER OF THE DAY, WITH LOCALLY INDUCED SHOWERS DEVELOPING
BRIEFLY THIS AFTERNOON DUE TO LOCAL EFFECTS. HOWEVER, CONDITIONS
WILL SHIFT GRADUALLY INTO A WETTER PATTERN AS THE LEADING EDGE OF
A TROPICAL WAVE IS CURRENTLY PRODUCING SCATTERED SHOWERS AND BRIEF
ISOLATED THUNDERSTORMS ACROSS THE ANEGADA PASSAGE. THIS SURGE IN
MOISTURE WILL CONTINUE THROUGH MONDAY AS THE TROPICAL WAVE CROSSES
THE REGION. LATEST SATELLITE-DERIVED TOTAL PRECIPITABLE WATER
IMAGERY HIGHLIGHTS THIS DEEP SURGE OF MOISTURE, WITH PWAT VALUES
EXCEEDING 2 INCHES ACROSS PORTIONS OF THE LEEWARD ISLANDS AND THE
SOUTHEASTERN CARIBBEAN.
AS THE AXIS OF THIS DEEP TROPICAL MOISTURE MOVES ACROSS THE
ISLANDS ON MONDAY, WE EXPECT A CONSIDERABLE INCREASE IN THE
COVERAGE AND INTENSITY OF SHOWERS AND THUNDERSTORMS ACROSS THE
U.S. VIRGIN ISLANDS AND PUERTO RICO. THE ACTIVITY WILL GRADUALLY
INCREASE FROM THE LOCAL WATERS INTO THE USVI AND EASTERN PUERTO
RICO DURING THE OVERNIGHT AND EARLY MORNING HOURS. BY MONDAY
AFTERNOON, DAYTIME HEATING AND LOCAL OROGRAPHIC EFFECTS WILL
TRIGGER THUNDERSTORM DEVELOPMENT ACROSS THE EASTERN INTERIOR,
CENTRAL, AND WESTERN SECTIONS OF PUERTO RICO. HIGH-RES MODEL
GUIDANCE SUGGESTS BETWEEN 1 AND 2 INCHES OF RAIN ACROSS THESE
AREAS, WHICH WILL ELEVATE THE THREAT OF URBAN AND SMALL-STREAM
FLOODING.
BY TUESDAY, AS THE TROPICAL WAVE EXITS TO THE WEST, A STRONG
SAHARAN AIR LAYER WITH A DENSE PLUME OF SAHARAN DUST WILL SPREAD
ACROSS THE EASTERN CARIBBEAN. THIS WILL CAUSE RAPID DRYING AND
MORE STABLE CONDITIONS, LIMITING SHOWER ACTIVITY IN GENERAL ACROSS
ALL THE ISLANDS. THE PRIMARY IMPACTS WILL BE NOTICEABLY HAZY SKIES
AND REDUCED AIR QUALITY. ALSO, THE COMBINATION OF SUPPRESSED CLOUD
COVER FROM THE DRY, DUSTY SAHARAN AIR LAYER AND LINGERING SURFACE
HUMIDITY COULD PUSH HEAT INDICES BETWEEN 102F AND 110F ACROSS THE
LOWER ELEVATIONS AND URBAN AREAS OF THE ISLANDS.
LONG TERM(WEDNESDAY THROUGH NEXT SATURDAY)
ISSUED AT 149 PM AST SUN JUN 28 2026
A BROAD SURFACE HIGH PRESSURE SYSTEM CENTERED OVER THE CENTRAL
ATLANTIC AND EXTENDING INTO THE CARIBBEAN WILL REMAIN THE DOMINANT
WEATHER FEATURE THROUGH THE LONG-TERM PERIOD, MAINTAINING A
PREDOMINANTLY SOUTHEASTERLY LOW-LEVEL WIND FLOW ACROSS PUERTO RICO
AND THE U.S. VIRGIN ISLANDS. EMBEDDED PATCHES OF MOISTURE WITH
PRECIPITABLE WATER VALUES FLUCTUATING NEAR CLIMATOLOGICAL NORMALS
WILL CONTINUE TO MOVE ACROSS THE LOCAL AREA FROM WEDNESDAY INTO
THURSDAY, PROMOTING A VARIABLE WEATHER PATTERN. WHILE WIDESPREAD
RAINFALL IS NOT ANTICIPATED, DAYTIME HEATING, LOCAL EFFECTS, AND
AVAILABLE MOISTURE WILL SUPPORT THE DEVELOPMENT OF AFTERNOON SHOWERS
AND ISOLATED THUNDERSTORMS ACROSS PORTIONS OF WESTERN PUERTO RICO
EACH DAY. SOME OF THE STRONGEST SHOWERS COULD PRODUCE LOCALIZED
PONDING OF WATER ON ROADWAYS AND IN POORLY DRAINED AREAS. ALOFT, A
CUTOFF LOW AT 250 MB WILL GRADUALLY APPROACH THE NORTHEASTERN
CARIBBEAN, LOWERING TEMPERATURES NEAR THE 250 MB LEVEL TO AROUND -9
°C. THIS FEATURE WILL PROVIDE MODEST UPPER-LEVEL SUPPORT AND
SLIGHTLY ENHANCE ATMOSPHERIC INSTABILITY, FAVORING LOCALLY STRONGER
CONVECTION DURING THE AFTERNOON HOURS. IN ADDITION, A SMALL AREA OF
SAHARAN DUST IS EXPECTED TO MOVE ACROSS THE REGION ON WEDNESDAY,
RESULTING IN HAZY SKIES AND REDUCED VISIBILITY AT TIMES BEFORE
CONCENTRATIONS GRADUALLY DIMINISH ON THURSDAY.
FROM FRIDAY THROUGH SUNDAY, A MUCH DRIER AIR MASS WILL FILTER INTO
THE REGION FROM THE SURFACE TO AROUND 700 MB, REDUCING MOISTURE
AVAILABILITY AND OVERALL SHOWER COVERAGE. PRECIPITABLE WATER VALUES
ARE EXPECTED TO RANGE BETWEEN 1.5 AND 1.7 INCHES, WHILE RELATIVE
HUMIDITY BETWEEN 850 AND 500 MB WILL REMAIN NEAR TO SLIGHTLY BELOW
CLIMATOLOGICAL NORMALS. ANOTHER PULSE OF SAHARAN DUST IS ALSO
FORECAST TO MOVE ACROSS THE NORTHEASTERN CARIBBEAN DURING THE
WEEKEND, LEADING TO HAZY SKIES AND FURTHER SUPPRESSING SHOWER
ACTIVITY. DESPITE THE DRIER CONDITIONS, ISOLATED AFTERNOON SHOWERS
CANNOT BE COMPLETELY RULED OUT OVER THE WESTERN INTERIOR OF PUERTO
RICO DUE TO LOCAL SEA BREEZE CONVERGENCE AND DAYTIME HEATING. WARM
TO HOT CONDITIONS WILL PERSIST THROUGHOUT THE FORECAST PERIOD, WITH
A DAILY ELEVATED HEAT THREAT EXPECTED ACROSS THE ISLANDS. HEAT INDEX
VALUES WILL GENERALLY RANGE FROM 100 TO 108 DEGREES, WITH ISOLATED
LOCATIONS REACHING AROUND 110 DEGREES, PARTICULARLY ACROSS THE NORTH-
CENTRAL COASTAL PLAIN AND THE WESTERN INTERIOR OF PUERTO RICO DURING
THE PEAK HEATING HOURS BETWEEN 10 AM AND 5 PM EACH DAY.
AVIATION
(18Z TAFS)
ISSUED AT 149 PM AST SUN JUN 28 2026
MAINLY VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS MOST TERMINALS
THROUGH THE REST OF THE DAY. HOWEVER, SHRA AND ISO TSTMS ARE EXPECTED
TO INCREASE FROM THIS EVENING THROUGH MONDAY AS A TROPICAL WAVE
MOVES ACROSS THE REGION. MTN TOPS OBSCD AND BKN CIGS NEAR FL030
ARE EXPECTED WITH THE WAVE PASSAGE. THE 28/12Z TJSJ SOUNDING
INDICATED ESE WINDS UP TO 19 KT BLO FL060.
MARINE
ISSUED AT 149 PM AST SUN JUN 28 2026
A TROPICAL WAVE LOCATED OVER THE LESSER ANTILLES WILL MOVE ACROSS
THE REGION TONIGHT AND MONDAY, INCREASING SHOWER AND THUNDERSTORM
ACTIVITY ACROSS LOCAL WATERS AND CARIBBEAN PASSAGES. SMALL CRAFT
MUST EXERCISE CAUTION NEAR THUNDERSTORMS, AS THEY MAY BRING GUSTY
WINDS, LIGHTNING, AND REDUCE VISIBILITY, CREATING LOCALIZED
HAZARDOUS CONDITIONS. AS THE TROPICAL WAVE CONTINUES ITS WAY INTO
THE CARIBBEAN BASIN, THE SURFACE HIGH PRESSURE LINGERING OVER THE
CENTRAL ATLANTIC WILL INCREASE THE LOCAL PRESSURE GRADIENT, LEADING
TO MODERATE TO LOCALLY FRESH E-ESE WINDS AND CHOPPY SEAS. A BRIEF,
DENSE PLUME OF SAHARAN DUST WILL ARRIVE AND FILTER INTO THE REGION
LATE MONDAY NIGHT INTO TUESDAY, BRINGING HAZY SKIES, REDUCED
VISIBILITY, AND POOR AIR QUALITY.
BEACH FORECAST
ISSUED AT 149 PM AST SUN JUN 28 2026
THE BEACH FORECAST REMAINS ON TRACK, WITH THE LOW RISK OF RIP
CURRENTS PERSISTING ACROSS MOST BEACHES OF PUERTO RICO AND THE U.S.
VIRGIN ISLANDS THROUGH THE FORECAST PERIOD, AS SEAS REMAIN BETWEEN 2
AND 3 FEET BASED ON THE LATEST NEARSHORE BUOY REPORTS. ALTHOUGH THE
RISK WILL REMAIN LOW, LIFE-THREATENING RIP CURRENTS CAN BE PRESENT
IN THE VICINITY OF GROINS, JETTIES, REEFS, AND PIERS. AS WINDS
GRADUALLY STRENGTHEN, THE RISK MAY INCREASE TO MODERATE OVER EXPOSED
BEACHES IN THE NORTHERN/NORTHWESTERN SIDE OF PUERTO RICO, WITH LIFE-
THREATENING RIP CURRENTS POSSIBLE ALONG THE SURF ZONE. IN ADDITION
TO RIP CURRENTS, BEACHGOERS SHOULD REMAIN WEATHER ALERT IF PLANNING
ON GOING TO THE BEACH, PARTICULARLY TONIGHT AND MONDAY, AS SHOWERS
AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE MOVING ACROSS THE
REGION MAY BRING GUSTY WINDS AND LIGHTNING. ON EARLY TUESDAY,
MODERATE TO HIGH CONCENTRATIONS OF SAL WILL RESULT IN HAZY SKIES,
REDUCED VISIBILITY, AND POOR AIR QUALITY.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
AVIATION/SHORT TERM...DSR
LONG TERM...LIS
KM/BEACH/MARINE...MNG
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