985
FXCA62 TJSJ 070900
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
500 AM AST MON JUL 7 2025
KEY MESSAGES
* NORMAL TO ABOVE-NORMAL TEMPERATURES WILL PERSIST, WITH A LIMITED
HEAT RISK DAILY ACROSS LOWER ELEVATIONS AND URBAN AREAS, POSING
RISKS TO VULNERABLE GROUPS.
* AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS ARE LIKELY DAILY,
DRIVEN BY LOCAL EFFECTS AND DIURNAL HEATING, EVEN DURING DRIER
PERIODS. STAY ALERT FOR LIGHTNING AND SUDDEN DOWNPOURS.
* BREEZY TO LOCALLY WINDY CONDITIONS WILL CAUSE CHOPPY SEAS AND A
MODREATE RISK OF RIP CURRENTS OVER THE NEXT FEW DAYS. THESE MAY
CREATE HAZARDOUS CONDITIONS. STAY CAUTONS AND FOLLOW SAFETY
ADVISE.
* MODERATE CONCENTRATIONS OF SAHARAN DUST ARE EXPECTED TO RETURN
LATER THIS WEEK, RESULTING IN HAZY SKIES AND REDUCED VISIBILITY,
WHICH MAY MINIMIZE OUTDOOR VISIBILITY AND AFFECT WEATHER
OBSERVATIONS.
SHORT TERM...TODAY THROUGH WEDNESDAY
A VARIABLE WEATHER PATTERN PREVAILED DURING THE NIGHT INTO THE
EARLY MORNING HOURS. DOPPLER RADAR DETECTED SOME PASSING SHOWERS
OVER THE ATLANTIC WATERS OVERNIGHT. AS THE NIGHT PROGRESSED,
ADDITIONAL SHOWERS WERE STEERED ACROSS THE REGION BY NORTHEASTERLY
WINDS, AFFECTING NORTHERN AND NORTHEASTERN SECTIONS OF PUERTO
RICO. AROUND 2 AM, ISOLATED TO SCATTERED SHOWERS WERE OBSERVED
ACROSS THE METROPOLITAN AREA, IMPACTING MUNICIPALITIES SUCH AS
CAROLINA, SAN JUAN, CANOVANAS, CATANO, BAYAMON, AND GUAYNABO.
THESE SHOWERS DEVELOPED AS A RESULT OF COLD-AIR ADVECTION, WHICH
ENHANCED SHALLOW CONVECTIVE ACTIVITY. RAINFALL ACCUMULATIONS WERE
MINIMAL. WINDS WERE FROM THE EAST-NORTHEAST AT 10 MPH OR LESS.
OVERNIGHT TEMPERATURES RANGED FROM THE MID TO UPPER 70S IN COASTAL
AREAS TO THE UPPER 60S AND LOW 70S ACROSS THE MOUNTAINS.
FOR THIS MORNING, A VARIABLE WEATHER PATTERN WILL PERSIST ACROSS
THE ISLANDS AS WINDS MAINTAIN A NORTHEASTERLY COMPONENT. BY LATE
MORNING, WINDS ARE EXPECTED TO SHIFT TO A MORE EASTERLY DIRECTION
AS THE SURFACE HIGH PRESSURE SYSTEM EXTENDS INTO THE WESTERN
ATLANTIC. AS THIS TRANSITION OCCURS, TRAPPED MOISTURE WITH
PRECIPITABLE WATER VALUES BETWEEN 1.40 AND 1.60 INCHES WILL BE
TRANSPORTED TOWARD THE ISLANDS BY THE PREVAILING FLOW. UNDER THIS
PATTERN, ISOLATED TO SCATTERED SHOWERS ARE EXPECTED ACROSS COASTAL
AREAS AND LOCAL WATERS IN THE MORNING, FOLLOWED BY INCREASED
CONVECTIVE ACTIVITY OVER WESTERN AND INTERIOR PUERTO RICO IN THE
AFTERNOON DUE TO LOCAL AND DIURNAL EFFECTS. WHILE THE U.S. VIRGIN
ISLANDS SHOULD EXPERIENCE MOSTLY FAIR WEATHER, BRIEF TRADE WIND
SHOWERS MAY DEVELOP, WITH LOCALIZED PONDING POSSIBLE IN AREAS
WHERE SHOWERS BRIEFLY INTENSIFY.
FROM TUESDAY INTO WEDNESDAY, THE UPPER-LEVEL RIDGE WILL SHIFT
FARTHER EAST OF THE LEEWARD ISLANDS, LEAVING THE ISLANDS UNDER A
STABLE PATTERN. THIS FEATURE WILL PROMOTE SUBSIDENCE ALOFT, ENHACING
DRIER AIR ALOFT AND SUPPRESSING DEEP CONVECTION ACROSS THE REGION.
HOWEVER, AT THE SURFACE, MOISTURE CONTENT WILL INCREASE AS A
TROPICAL WAVE AND AN EASTERLY DISTURBANCE ENHANCE CONVECTIVE
POTENTIAL ACROSS THE LOCAL FORECAST AREA. THESE COMBINED DYNAMICS
WILL SUPPORT SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS
EASTERN PUERTO RICO AND THE SURROUNDING WATERS BEGINNING TUESDAY
EVENING, WITH ACTIVITY SPREADING INTO INTERIOR AREAS AND THE U.S.
VIRGIN ISLANDS BY EARLY WEDNESDAY. ACCORDINGLY, THE FORECAST WAS
ADJUSTED TO REFLECT AN INCREASE IN THE PROBABILITY OF ISOLATED TO
SCATTERED SHOWERS BEGINNING AROUND 16Z TUESDAY OVER THE OFFSHORE
NORTHEASTERN ATLANTIC WATERS, PROGRESSING INTO NORTHEASTERN PUERTO
RICO, ST. THOMAS, AND ST. CROIX BY 20Z TUESDAY. THIS WILL LEAVE
EARLY WEDNESDAY UNDER A VARIABLE WEATHER PATTERN WITH INCREASED
CLOUDINESS AND PASSING SHOWERS. ADDITIONALLY, LOW CONCENTRATIONS
OF SAHARAN DUST WILL BE PRESENT FROM TUESDAY AND CONTINUE INTO
WEDNESDAY.
LONG TERM...THURSDAY THROUGH MONDAY
A WEAK TROPICAL WAVE IS EXPECTED TO MOVE THROUGH THE REGION ON
THURSDAY, STEERED BY A STRONG BERMUDA-AZORES HIGH, MAINTAINING
NEAR-NORMAL MOISTURE LEVELS. A SURFACE WIND SURGE WILL ARRIVE ON
FRIDAY, INITIALLY ENHANCING LOW-LEVEL MOISTURE BEFORE A
SIGNIFICANTLY DRIER AIR MASS SETTLES IN THROUGH THE WEEKEND. MID-
TO UPPER-LEVEL DRY AIR AND A TRADE WIND CAP INVERSION—REINFORCED
BY A TROPICAL UPPER-TROPOSPHERIC TROUGH (TUTT) TO THE
NORTHEAST—WILL LIMIT DEEP CONVECTION DURING THIS PERIOD. MORE
FAVORABLE CONDITIONS ARE LIKELY SUNDAY INTO EARLY NEXT WEEK AS THE
TUTT SHIFTS OVER HISPANIOLA AND EASTERLY TRADE WIND DISTURBANCES
APPROACH THE AREA.
LINGERING MOISTURE WILL SUPPORT ISOLATED TO SCATTERED SHOWERS
EARLY IN THE PERIOD, WITH SIGNIFICANT DRYING EXPECTED FROM FRIDAY
THROUGH SUNDAY, REDUCING RAINFALL POTENTIAL. EVEN DURING THE
DRIEST PERIODS, AFTERNOON CONVECTIVE DEVELOPMENT—DRIVEN BY DIURNAL
HEATING AND LOCAL TERRAIN EFFECTS—REMAINS LIKELY EACH DAY. BREEZY
TO WINDY CONDITIONS WILL PREVAIL THROUGH THE WEEKEND, WITH
SOUTHEASTERLY WINDS SUPPORTING ABOVE-NORMAL TEMPERATURES,
ESPECIALLY BETWEEN THURSDAY AND SATURDAY, WHEN VALUES ARE FORECAST
TO EXCEED TYPICAL SEASONAL THRESHOLDS. COOLER AIR ALOFT MAY
ARRIVE FRIDAY AND PERSIST INTO SATURDAY; HOWEVER, LIMITED MOISTURE
WILL LIKELY PREVENT WIDESPREAD CONVECTION. RAIN CHANCES ARE
EXPECTED TO INCREASE AGAIN FROM SUNDAY AFTERNOON INTO MONDAY.
A SAHARAN AIR LAYER SPREADING OVER THE REGION BEGINNING THURSDAY
WILL CONTRIBUTE TO HAZY SKIES, REDUCED VISIBILITY, AND CONTINUED
SUPPRESSION OF WIDESPREAD CONVECTION THROUGH AT LEAST SATURDAY.
WHILE EXCESSIVE RAINFALL IS NOT A CONCERN UNTIL SUNDAY, OTHER
WEATHER HAZARDS—INCLUDING PERIODS OF EXCESSIVE HEAT, GUSTY WINDS,
AND ISOLATED AFTERNOON LIGHTNING—REMAIN POSSIBLE THROUGHOUT THE
LONG-TERM PERIOD.
AVIATION
(06Z TAF)
VFR CONDITIONS WILL PERSIST FOR THE UPCOMING HOURS, WITH BRIEF
MVFR CIGS ACROSS TJSJ AND TJBQ IN THE AFTERNOON HOURS DUE TO LOWER
CEILINGS AND A REDUCTION IN VIS. WINDS WILL CONTINUE FROM THE
E-NE AT 10 KNOTS, BACKING TO E AT AROUND 07/12Z, AND INCREASING UP
TO 15 KNOTS WITH GUSTY WINDS. VCTS ARE FORECAST AT 07/18Z FOR
TJBQ.
MARINE
MODERATE TO LOCALLY FRESH WINDS WILL CREATE CHOPPY SEAS ACROSS
LOCAL WATERS OVER THE NEXT SEVERAL DAYS, PROMPTING CAUTION FOR
SMALL CRAFT OPERATORS. AFTERNOON THUNDERSTORMS MAY IMPACT COASTAL
WATERS AND LOCAL PASSAGES, PARTICULARLY OVER WESTERN PUERTO RICO
AND THE MONA PASSAGE EACH DAY. SHOWERS AND THUNDERSTORM CHANCES
INCREASE ON TUESDAY AND THURSDAY WITH THE PASSAGE OF TROPICAL
WAVES. SAHARAN DUST IS EXPECTED TO RETURN LATER IN THE WORKWEEK.
BEACH FORECAST
WITH STRENGTHENING WINDS OVER THE NEXT SEVERAL DAYS, A MODERATE
RIP CURRENT RISK IS EXPECTED TO GRADUALLY EXPAND ACROSS MOST LOCAL
BEACHES—FROM NORTHWESTERN PUERTO RICO, CULEBRA, AND ST. CROIX
TODAY, TO ALL OF NORTHERN PUERTO RICO, PARTS OF SOUTHEASTERN
PUERTO RICO, AND VIEQUES BY TONIGHT. BEACHGOERS ARE ADVISED TO
EXERCISE CAUTION, MAINLY ALONG EXPOSED NORTHERN AND EASTERN
SHORELINES. FOR THE LATEST DETAILED UPDATES ON RIP CURRENT RISKS,
PLEASE REFER TO THE SURF ZONE FORECAST (SRFSJU).
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...LIS
LONG TERM....ICP
PUBLIC...ICP/LIS
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