440  
FXCA62 TJSJ 101749  
AFDSJU  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN JUAN PR  
149 PM AST THU JUL 10 2025  
   
KEY MESSAGES
 
 
 
* HAZY SKIES AND POOR AIR QUALITY DUE TO SAHARAN DUST WILL  
PERSIST THROUGH THE WEEKEND, ESPECIALLY IMPACTING SENSITIVE  
GROUPS.  
 
* WARMER-THAN-NORMAL NIGHTS AND HOT DAYTIME TEMPERATURES WILL  
CONTINUE, WITH HEAT INDICES REACHING LEVELS THAT MAY WARRANT  
HEAT ADVISORIES OR EXTREME HEAT WARNINGS—PARTICULARLY IN URBAN  
AND COASTAL AREAS.  
 
* A MODERATE RISK OF RIP CURRENTS CONTINUES ALONG NORTH- AND EAST-  
FACING BEACHES OF PUERTO RICO AND PARTS OF THE U.S. VIRGIN  
ISLANDS.  
 

 
   
SHORT TERM...TONIGHT THROUGH SATURDAY
 
 
AFTER THE SURGE OF MOISTURE THAT BROUGHT SCATTERED TO WIDESPREAD  
SHOWERS ACROSS THE ISLANDS, A SLOT OF DRY AIR LIMITS RAIN ACTIVITY  
AND PRODUCES HAZY SKIES. MAXIMUM TEMPERATURES WERE IN THE LOW AND  
MID-90S ALONG THE URBAN COASTAL AREAS, WITH WARM TO HOT MAXIMUM  
HEAT INDICES. AT THE SAME TIME, THE MOUNTAIN ZONES OBSERVED  
MAXIMUM TEMPERATURES BETWEEN THE MID-80S AND LOW 80S DEGREES  
FAHRENHEIT. WINDS WERE FROM THE EAST TO EAST NORTHEAST AT 15 TO  
25 MPH, WITH HIGHER GUSTS AND VARIATIONS DUE TO SEA BREEZES.  
 
FOLLOWING THE PASSAGE OF TODAY’S PERTURBATION, STRONGER EAST-  
SOUTHEASTERLY WINDS WILL PROMOTE BREEZY CONDITIONS AND USHER IN A  
MUCH DRIER AIR MASS, WITH PRECIPITABLE WATER VALUES EXPECTED TO  
FALL BETWEEN 1.15 AND 1.35 INCHES. THIS DRIER ENVIRONMENT WILL  
COINCIDE WITH MODERATE TO HIGH CONCENTRATIONS OF SAHARAN DUST,  
SIGNALING THE ONSET OF A HAZY, WARMER, AND MORE STABLE WEATHER  
PATTERN ACROSS PUERTO RICO AND THE US VIRGIN ISLANDS, EXPECTED TO  
PREVAIL THROUGH THE WEEKEND. AT THE MID-TO-UPPER LEVELS, A TROUGH  
LOCATED TO THE NORTHEAST OF THE REGION WILL GRADUALLY REPLACE THE  
RETREATING MID-LEVEL RIDGE, SETTLING NORTHWEST OF THE ISLANDS BY  
SATURDAY. HOWEVER, THE EXTENSIVE MID-LEVEL DRY AIR MASS WILL  
MINIMIZE THE IMPACTS OF THIS TROUGH ALOFT BY PROMOTING SUBSIDENCE  
ALOFT IN THE AREA.  
 
TONIGHT MARKS A TRANSITIONAL PERIOD, WITH RESIDUAL AFTERNOON AND  
EVENING CONVECTION ACROSS WESTERN PUERTO RICO GIVING WAY TO  
INCREASINGLY DRY AND HAZY CONDITIONS THAT WILL SUPPRESS ADDITIONAL  
SHOWER DEVELOPMENT. AS A RESULT, VISIBILITY AND AIR QUALITY WILL  
DETERIORATE, ESPECIALLY FOR SENSITIVE POPULATIONS. FAIR AND DRY  
WEATHER WILL DOMINATE ACROSS THE US VIRGIN ISLANDS AND EASTERN  
PUERTO RICO. REGARDLESS OF THESE CONDITIONS, WE CANNOT RULE OUT  
THE POSSIBILITY OF A POCKET OF MOISTURE ARRIVING, RESULTING IN A  
FEW PASSING SHOWERS ACROSS THE WINDWARD LOCATIONS. THEN, DIURNAL  
HEATING AND LOCAL EFFECTS MAY PRODUCE REDUCED AFTERNOON CONVECTION  
EACH DAY.  
 
WARMER-THAN-NORMAL MINIMUM TEMPERATURES ARE EXPECTED TO RETURN  
DUE TO THIS CONCENTRATION OF SAL, WHICH WILL REDUCE NIGHTTIME  
COOLING. AS DAYS BEGIN WARMER THAN NORMAL, MAXIMUM TEMPERATURES  
WILL REACH ABOVE NORMAL LEVELS, WHICH, COMBINED WITH THE AVAILABLE  
LOW-LEVEL MOISTURE, WILL RESULT IN WARM TO HOT HEAT INDICES.  
THESE HEAT INDICES MAY REACH LEVELS THAT PROMPT HEAT ADVISORIES OR  
EXTREME HEAT WARNINGS, PARTICULARLY IN URBAN AND LOWER-ELEVATION  
AREAS OF PUERTO RICO.  
 
RESIDENTS AND VISITORS, AS WELL AS THE SENSITIVE COMMUNITIES, ARE  
ADVISED TO TAKE APPROPRIATE PRECAUTIONS DURING THIS PERIOD,  
PARTICULARLY THOSE WHO ARE SENSITIVE TO REDUCED AIR QUALITY AND  
HEAT.  
   
LONG TERM...SUNDAY THROUGH THURSDAY...FROM PREV DISCUSSION
 
 
ON SUNDAY, SAHARAN DUST CONCENTRATIONS WILL BEGIN TO DIMINISH.  
HOWEVER, WE STILL ANTICIPATE HAZY SKIES ACROSS THE U.S. VIRGIN  
ISLANDS AND PUERTO RICO. THE LATEST MODEL GUIDANCE CONTINUES TO  
INDICATE A TROPICAL UPPER-TROPOSPHERIC TROUGH (TUTT) SHIFTING  
WESTWARD TOWARDS HISPANOLA AND LINGERING THERE THROUGH THE  
BEGINNING OF THE WORKWEEK WEAKENING THE HIGH PRESSURE SYSTEM AT  
THE SURFACE AND FORCING THE BREEZY TO LOCALLY WINDY CONDITIONS TO  
DIMINISH.  
 
ON MONDAY AND TUESDAY, THE APPROACH OF EASTERLY TRADE WIND  
PERTURBATIONS WILL GRADUALLY ENHANCE MOISTURE LEVELS ACROSS THE  
REGION. AS ATMOSPHERIC MOISTURE INCREASES, SO WILL THE POTENTIAL  
FOR SHOWER AND THUNDERSTORM ACTIVITY, PARTICULARLY DURING THE  
AFTERNOON HOURS OVER WESTERN AND SOUTHWESTERN PUERTO RICO, WITH  
POCKETS OF SHOWERS OVER EASTERN PUERTO RICO IN THE MORNING HOURS.  
ADDITIONALLY, MODEL GUIDANCE INDICATE THAT MOISTURE WILL EXTEND  
FROM THE SURFACE THROUGH THE MID AND UPPER LEVELS OF THE  
ATMOSPHERE, SUPPORTING INCREASED ATMOSPHERIC INSTABILITY AND  
ENHANCING THE POTENTIAL FOR CONVECTIVE DEVELOPMENT DURING THIS  
PERIOD.  
 
BY MIDWEEK, A TROPICAL WAVE IS EXPECTED TO APPROACH THE FORECAST  
AREA, BRINGING INCREASED TROPICAL MOISTURE. HOWEVER, THE MOST  
INTENSE PART OF THE WAVE IS EXPECTED TO PASS SOUTH OF PUERTO RICO  
AND THE U.S. VIRGIN ISLANDS. NEVERTHELESS, SCATTERED SHOWERS AND  
THUNDERSTORMS ARE ANTICIPATED EACH AFTERNOON, ESPECIALLY ACROSS  
INTERIOR AND WESTERN AREAS. WE WILL CONTINUE TO MONITOR CONDITIONS  
CLOSELY FOR ANY SIGNIFICANT CHANGES.  
 

 
   
AVIATION
 
 
SHRA WILL LIKELY FORM NEAR OR OVER TJBQ BTWN THRU 10/23Z,  
POSSIBLY CAUSING BRIEF MVFR CONDS. VCSH ARE ALSO POSSIBLE AROUND  
TJSJ AND USVI TERMINALS THROUGHOUT THE PERIOD, ESPECIALLY AFTER  
10/23Z. WE EXPECT HAZY SKIES WITH VISIBILITIES REDUCED BETWEEN  
5-6SM DUE TO THE ARRIVAL OF MODERATE TO HIGH CONCENTRATIONS OF  
SUSPENDED SAHARAN DUST PARTICLES. BREEZY TO LOCALLY WINDY WINDS OF  
16-22 KT THRU 10-23Z, DIMINISHING TO 10-15 KT AFT 10/23Z, BUT  
RETURNING TO SIMILAR SPEEDS TOMORROW AFT 11/13Z.  
 

 
   
MARINE
 
 
MARINERS CAN EXPECT MODERATE TO FRESH EASTERLY WINDS AND CHOPPY  
SEAS ACROSS THE ISLANDS THROUGH THE WEEKEND. AN EXTENSIVE SAHARAN  
AIR LAYER WILL MOVE ACROSS THE NORTHEASTERN CARIBBEAN LINGERING  
THROUGH THE WEEKEND, AND LEAVING A TROPICAL WAVE WELL SOUTH OF THE  
ISLANDS.  
 

 
   
BEACH FORECAST
 
 
MODERATE TO HIGH RIP CURRENT RISK CONTINUES ALONG NORTH- AND EAST-  
FACING BEACHES OF PUERTO RICO AND PARTS OF THE USVI. ALWAYS SWIM  
NEAR LIFEGUARDS AND OBEY POSTED WARNINGS. CONDITIONS MAY BE  
DANGEROUS FOR INEXPERIENCED SWIMMERS.  
 
EXPECT HOT AND HAZY CONDITIONS THROUGH THE WEEKEND, WITH  
EXCESSIVE HEAT POSING A RISK—ESPECIALLY IN URBAN AND COASTAL  
AREAS. HEAT INDICES MAY EXCEED 108°F, SO STAY HYDRATED, SEEK  
SHADE, AND AVOID PEAK SUN HOURS.  
 

 
   
SJU WATCHES/WARNINGS/ADVISORIES
 
 
PR...HEAT ADVISORY UNTIL 5 PM AST THIS AFTERNOON FOR PRZ001>005-007-  
008-010-011.  
 
VI...NONE.  
AM...NONE.  

 
 

 
 
SHORT TERM...CAM  
LONG TERM....YZR  
AVIATION...YZR  
 
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