019
FXCA62 TJSJ 240728
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
328 AM AST WED JUN 24 2026
...NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER...
KEY MESSAGES
ISSUED AT 324 AM AST WED JUN 24 2026
* THE MOISTURE FIELD FROM A WEAK TROPICAL WAVE MOVING ACROSS THE
REGION WILL ENHANCE THE POTENTIAL FOR SHOWERS TODAY AS WELL AS FOR
AFTERNOON SHOWERS AND T-STORMS MAINLY ACROSS INTERIOR TO W-NW PR.
* THE DAY WILL START WITH MODERATE CONCENTRATIONS OF SAHARAN DUST.
HIGH CONCENTRATIONS OF SAHARAN DUST WILL THEN REACH THE USVI THIS
AFTERNOON, CONTINUE MOVING WESTWARD OVER PR THIS EVENING AND
PERSIST OVER THE ISLANDS THROUGH FRIDAY. THIS WILL RESULT IN HAZY
SKIES, REDUCED VISIBILITY AND DETERIORATED AIR QUALITY.
* BREEZY TO LOCALLY WINDY ESE WINDS WILL RESULT IN UP TO A
MODERATE RISK OF RIP CURRENTS ACROSS MOST COASTAL AREAS TODAY AS
WELL AS IN CHOPPY SEAS AND SMALL CRAFT EXERCISE CAUTION
CONDITIONS.
* UP TO AN ELEVATED HEAT RISK WILL PERSIST DURING THE NEXT SEVERAL
DAYS.
* AN UPPER-LEVEL LOW WILL INDUCE A SURFACE TROUGH THAT IS FORECAST
TO CROSS THE REGION ON SATURDAY, PROMOTING LIGHTER WINDS AS WELL
AS A LIMITED FLOODING AND LIGHTNING RISK.
SHORT TERM(TODAY THROUGH FRIDAY)
ISSUED AT 324 AM AST WED JUN 24 2026
A SURFACE HIGH PRESSURE OVER THE ATLANTIC WILL CONTINUE TO RESULT IN
BREEZY, TO LOCALLY WINDY, ESE WINDS THROUGHOUT THE REST OF THE
WORKWEEK. 925 MB WIND SPEEDS ARE FORECAST TO CONTINUE ABOVE
NORMAL VALUES FOR THIS TIME OF THE YEAR, DECREASING TO MORE NORMAL
VALUES ON FRIDAY. PRECIPITABLE WATER (PWAT) SHOULD FLUCTUATE FROM
BELOW NORMAL TO NORMAL VALUES DURING THE FORECAST PERIOD, PEAKING
TODAY (AROUND 1.9 INCHES) AS A TROPICAL WAVE MOVES SOUTH OF THE
ISLANDS AND ITS MOISTURE FIELD MOVES OVER THE REGION. THIS
TROPICAL WAVE WILL ALSO BE EMBEDDED IN SAHARAN DUST CONCENTRATIONS.
ALTHOUGH THE BULK OF THE MOISTURE FROM THIS WAVE WILL STAY OVER
THE CARIBBEAN WATERS, CLOUDINESS AND SHOWERS CAN STILL BE STEERED
TOWARDS THE ISLANDS UNDER THE ESE FLOW BEFORE THE ONSET OF HIGH
CONCENTRATIONS OF SAHARAN DUST LATER THIS AFTERNOON. PWAT VALUES
WILL GRADUALLY DECREASE TO MORE BORDERLINE BELOW-NORMAL TO LOW END
NORMAL VALUES (AROUND 1.5 TO 1.6 INCHES) THURSDAY AND FRIDAY AS
PATCHES OF MOISTURE CONTINUE TO BE STEERED TOWARDS THE ISLANDS. IN
THE MID TO UPPER LEVELS, MID-LEVEL RIDGING WILL CONTINUE, MAINLY
ON THURSDAY AND FRIDAY, ALONG WITH WARM 500 MB TEMPERATURES. THIS,
ALONG WITH THE SAHARAN DUST WILL SERVE TO LIMIT SHOWER AND
T-STORM ACTIVITY, ESPECIALLY TOMORROW, THURSDAY. AN UPPER LOWS
WILL STAY WELL NORTHEAST AND NORTH OF THE REGION DURING THE
PERIOD. TRADE WIND SHOWERS WILL CONTINUE TO REACH WINDWARD SECTORS
FROM TIME TO TIME, ESPECIALLY DURING THE OVERNIGHT AND MORNING
HOURS, BEING SOMEWHAT ENHANCED BY THE MOISTURE FIELD FROM THE
TROPICAL WAVE. TODAY AND POSSIBLY FRIDAY, AFTERNOON SHOWERS AND
ISOLATED T-STORMS WILL AFFECT MAINLY INTERIOR TO W AND NW PUERTO
RICO TODAY AS DIURNAL HEATING AND LOCAL EFFECTS DEVELOP; LINES OF
SHOWERS CAN ALSO DEVELOP DOWNWIND OF EL YUNQUE AND THE LOCAL
ISLANDS. THIS ACTIVITY IS FORECAST TO BE LIMITED, IF ANY, ON
THURSDAY DUE TO HIGH SAHARAN DUST CONCENTRATIONS. AN ELEVATED HEAT
RISK WILL PERSIST DURING THE PERIOD, WITH HEAT INDICES SURPASSING
108 DEGREES FAHRENHEIT. 925 MB TEMPERATURES TODAY SUGGEST NORMAL
TO ABOVE NORMAL TEMPERATURES UNDER E TO ESE FLOW. HEAT ADVISORIES
CAN BE ISSUED LATER TODAY AND/OR DURING THE SHORT TERM PERIOD AS
HIGHS OVER URBAN AREAS AND LOWER ELEVATIONS REACH THE UPPER 80S TO
LOW 90S.
SAHARAN DUST CONCENTRATIONS WILL CONTINUE GRADUALLY INCREASING TODAY.
THE LEADING EDGE OF A SAHARAN AIR LAYER (SAL) WILL INCREASE
CONCENTRATIONS TO MODERATE EARLY TODAY AS IT ARRIVES ALONG WITH THE
TROPICAL WAVE, RESULTING IN HAZY SKIES. AIR QUALITY AND VISIBILITY
ARE PROJECTED TO FURTHER DETERIORATE AS CURRENT MODEL GUIDANCE
SUGGESTS THAT HIGH CONCENTRATIONS OF SAHARAN DUST WILL REACH THE
USVI THIS AFTERNOON AND SPREAD TOWARDS PR DURING THE AFTERNOON AND
EVENING, THESE HIGH CONCENTRATIONS WILL THEN PERSIST THROUGH FRIDAY,
GRADUALLY BECOMING MORE MODERATE FRIDAY AFTERNOON AFTERWARDS. THIS
WILL RESULT IN HAZY SKIES, REDUCED VISIBILITY AND DETERIORATED AIR
QUALITY. SENSITIVE GROUPS SHOULD FOLLOW MEDICAL RECOMMENDATIONS,
PARTICULARLY WEDNESDAY AFTERNOON THROUGH FRIDAY.
LONG TERM(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 324 AM AST WED JUN 24 2026
AT THE BEGINNING OF THE LONG-TERM PERIOD, AN UPPER-LEVEL LOW WILL
INDUCE A SURFACE TROUGH THAT IS EXPECTED TO CROSS THE REGION ON
SATURDAY. THIS FEATURE WILL CAUSE THE SURFACE HIGH PRESSURE OVER THE
CENTRAL ATLANTIC TO WEAKEN, REDUCING THE LOCAL PRESSURE GRADIENT AND
RESULTING IN LIGHTER WINDS THAT WILL GRADUALLY BACK TO THE
NORTHEAST. MOISTURE CONTENT WILL INCREASE TO NEAR-NORMAL LEVELS,
WITH PRECIPITABLE WATER VALUES RANGING FROM 1.60 TO 1.75 INCHES, AND
LOCALLY HIGHER AMOUNTS POSSIBLE. IN ADDITION, SAHARAN DUST
CONCENTRATIONS WILL DECREASE AS THE DUST PLUME MOVES AWAY FROM THE
AREA, LEADING TO IMPROVED AIR QUALITY CONDITIONS. AS A RESULT,
PASSING SHOWERS ARE EXPECTED ACROSS WINDWARD AREAS AND THE VICINITY
OF THE USVI DURING THE EARLY MORNING HOURS, FOLLOWED BY SHOWERS AND
ISOLATED THUNDERSTORMS OVER THE WESTERN SECTORS OF PUERTO RICO
DURING THE AFTERNOON DUE TO THE COMBINATION OF LOCAL EFFECTS AND
DAYTIME HEATING. TEMPERATURES AT 500 MB ARE EXPECTED TO REMAIN ABOVE
NORMAL, AROUND -5 C TO -6 DEGREES C, BUT MAY STILL BE SUFFICIENT TO
SUPPORT A FEW LIGHTNING STRIKES.
ON SUNDAY, DRIER CONDITIONS, WITH BELOW-NORMAL PRECIPITABLE WATER
VALUES, AND LOW CONCENTRATIONS OF SAHARAN DUST WILL BEGIN TO ARRIVE,
ACCOMPANIED BY A SOUTHEAST WIND FLOW. THE PRIMARY HAZARD ON THIS DAY
WILL BE WARM TO HOT CONDITIONS, AS INDICATED BY FORECAST GUIDANCE
SHOWING 925 MB TEMPERATURES AROUND TWO STANDARD DEVIATIONS ABOVE
NORMAL. DAYTIME HIGHS ARE EXPECTED TO REACH THE UPPER 80S TO LOW
90S, AND HEAT INDICES MAY EXCEED 100 DEGREES F, PARTICULARLY ACROSS
COASTAL AND URBAN AREAS. AN ELEVATED HEAT RISK WILL LIKELY PERSIST.
EARLY NEXT WEEK THROUGH MID-WEEK, CURRENT GUIDANCE SUGGESTS THAT A
TROPICAL WAVE MAY APPROACH THE CARIBBEAN BASIN AND INCREASE LOW-
LEVEL MOISTURE ACROSS THE LOCAL ISLANDS. PRECIPITABLE WATER VALUES
ARE FORECAST TO INCREASE TO NEAR-NORMAL OR SLIGHTLY ABOVE-NORMAL
LEVELS BASED ON CLIMATOLOGICAL DATA. THIS WOULD LIKELY ENHANCE
RAINFALL CHANCES, LEADING TO A GREATER FREQUENCY OF SHOWERS AND
AFTERNOON CONVECTION. AT THE SAME TIME, COOLER TEMPERATURES ALOFT
ASSOCIATED WITH LOWER 500 MB TEMPERATURES MAY PROVIDE ADDITIONAL
SUPPORT FOR CONVECTIVE DEVELOPMENT. HOWEVER, SAHARAN DUST IS ALSO
EXPECTED TO BE PRESENT, AND ITS INTERACTION WITH THE INCOMING
MOISTURE REMAINS UNCERTAIN. CONTINUE TO MONITOR THE FORECAST AS
UPDATES BECOME AVAILABLE.
AVIATION
(06Z TAFS)
ISSUED AT 324 AM AST WED JUN 24 2026
A TROPICAL WAVE WILL MOVE SOUTH OF THE REGION TODAY, WITH ITS
MOISTURE FIELD REACHING THE AREA AND PROVIDING SOME RELIEF IN
TERMS OF RH VALUES. NEVERTHELESS, OVER SOUTHERN OF PR, RELATIVE
HUMIDITIES IN THE LOW 50S CONTINUE TO BE POSSIBLE. WINDS WILL BE
FROM THE EAST- SOUTHEAST AT 10 TO 20 MPH, WITH GUSTS UP TO 33 MPH,
ESPECIALLY FROM MID MORNING INTO THE AFTERNOON. ALTHOUGH A
MODERATE FIRE DANGER RISK IS FORECAST, A FIRE DANGER STATEMENT
COULD BE ISSUED LATER TODAY IF THE MOISTURE FIELD FROM THE
TROPICAL WAVE MOVES FURTHER SOUTH, GIVING WAY TO A HIGH FIRE
DANGER RISK. AN ELEVATED HEAT RISK WILL ALSO PERSIST OVER THE AREA
AND SAHARAN DUST CONCENTRATIONS WILL GRADUALLY INCREASE AS THE
DAY CONTINUES.
MARINE
ISSUED AT 324 AM AST WED JUN 24 2026
A BROAD HIGH PRESSURE SYSTEM OVER THE CENTRAL ATLANTIC WILL
MAINTAIN MODERATE TO FRESH EASTERLY WINDS ACROSS THE REGIONAL
WATERS THROUGH THE NEXT SEVERAL DAYS. CHOPPY SEAS AND SMALL CRAFT
EXERCISE CAUTION CONDITIONS ARE EXPECTED ACROSS MOST LOCAL WATERS,
WITH SEAS GENERALLY BETWEEN 4 AND 6 FEET AND OCCASIONALLY UP TO 8
FEET OFFSHORE AND IN LOCAL PASSAGES. MODERATE SAHARAN DUST WILL
PERSIST ACROSS THE REGION, INCREASING WEDNESDAY THROUGH FRIDAY AND
LEADING TO PERIODS OF REDUCED VISIBILITY.
BEACH FORECAST
ISSUED AT 324 AM AST WED JUN 24 2026
A MODERATE RISK OF RIP CURRENTS WILL PERSIST ACROSS MOST NORTH-,
EAST-, AND SOUTH-FACING BEACHES OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS THROUGH THE END OF THE WORKWEEK. BEACHGOERS SHOULD
EXERCISE CAUTION, ESPECIALLY NEAR JETTIES, PIERS, REEFS, AND OTHER
AREAS KNOWN FOR STRONGER CURRENTS. RIP CURRENT CONDITIONS ARE
EXPECTED TO GRADUALLY IMPROVE BY FRIDAY NIGHT, WITH A LOW RISK
FORECAST ACROSS MOST LOCAL BEACHES THROUGH THE WEEKEND.
FIRE WEATHER
ISSUED AT 324 AM AST WED JUN 24 2026
A TROPICAL WAVE WILL MOVE SOUTH OF THE REGION TODAY, WITH ITS
MOISTURE FIELD REACHING THE AREA AND PROVIDING SOME RELIEF IN
TERMS OF RH VALUES. NEVERTHELESS, OVER SOUTHERN OF PR, RELATIVE
HUMIDITIES IN THE LOW 50S CONTINUE TO BE POSSIBLE. WINDS WILL BE
FROM THE EAST- SOUTHEAST AT 10 TO 20 MPH, WITH GUSTS UP TO 33 MPH,
ESPECIALLY FROM MID MORNING INTO THE AFTERNOON. ALTHOUGH A
MODERATE FIRE DANGER RISK IS FORECAST, A FIRE DANGER STATEMENT
COULD BE ISSUED LATER TODAY IF THE MOISTURE FIELD FROM THE
TROPICAL WAVE MOVES FURTHER SOUTH, GIVING WAY TO A HIGH FIRE
DANGER RISK. AN ELEVATED HEAT RISK WILL ALSO PERSIST OVER THE AREA
AND SAHARAN DUST CONCENTRATIONS WILL GRADUALLY INCREASE AS THE
DAY CONTINUES.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
KEY MESSAGES...MRR
SHORT TERM...MRR
LONG TERM....YZR
AVIATION...MRR
MARINE...ICP
BEACH FORECAST...ICP
FIRE WEATHER...MRR
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