793  
FXCA62 TJSJ 192158  
AFDSJU  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN JUAN PR  
558 PM AST WED MAR 19 2025  
   
SYNOPSIS  
 
WEATHER CONDITIONS WILL IMPROVE GRADUALLY ON THURSDAY. HOWEVER,RAINFALL  
ACTIVITY IS ANTICIPATED BY THE WEEKEND WITH PWAT VALUES  
INCREASING FROM FRIDAY INTO SATURDAY. A LONG- PERIOD NORTHWESTERLY  
SWELL WILL CREATE HAZARDOUS MARINE AND COASTAL CONDITIONS FROM  
THURSDAY ONWARD. THEREFORE, WE URGE PEOPLE TO STAY INFORMED WITH  
THE LATEST UPDATES.  
 
 
   
SHORT TERM...TONIGHT THROUGH FRIDAY  
 
AS A COLD FRONT MOVES THROUGH OUR AREA TODAY, SOME SHOWERS HAVE BEEN  
OBSERVED DURING THE MORNING HOURS ACROSS THE NORTHWEST AND, DURING  
THE EARLY AFTERNOON, FURTHER INLAND AND TO THE EAST. RADAR ESTIMATES  
INDICATE MINIMAL ACCUMULATIONS, JUST LOCALIZED AREAS IN THE  
INTERIOR OBSERVED AROUND 0.25 INCH OF RAIN. DAYTIME HIGH  
TEMPERATURES REACHED THE LOW TO MID 80S, PARTICULARLY ACROSS  
COASTAL AREAS OF THE ISLANDS, AND STAYED MAINLY IN THE 70S ACROSS  
THE MOUNTAINS. MINIMUM TEMPERATURES THIS MORNING FELT COOLER THAN  
NORMAL, WITH SOME STATIONS ACROSS THE INTERIOR DROPPING EVEN INTO  
THE MID 50S TO LOW 60S, AND MAINLY LOW 70S ALONG COASTAL AREAS.  
 
TONIGHT INTO THURSDAY, WEATHER CONDITIONS ARE EXPECTED TO REMAIN  
STABLE AND PLEASANT FOR MOST OF THE FORECAST AREA, WITH LIGHTER  
WINDS FROM THE NORTH-NORTHEAST TO KIND OF VARIABLE. DRIER AIR IN  
THE WAKE OF THE FRONTAL PASSAGE WILL CAUSE A SHARP DECLINE IN  
MOISTURE CONTENT TO AROUND 0.7 INCHES. ADDITIONALLY, AS SUGGESTED  
BY BELOW-NORMAL 925 MB TEMPERATURES, COOLER-THAN-NORMAL  
TEMPERATURES ARE EXPECTED DURING THIS OVERNIGHT PERIOD AND  
THURSDAY MORNING.  
 
THEN, THE LINGERING FRONT WILL INTERACT WITH AN INDUCED DISTURBANCE  
NEAR THE SOUTHEAST CARIBBEAN FROM THURSDAY NIGHT INTO FRIDAY,  
LIFTING ABUNDANT MOISTURE NEAR ST. CROIX AND SPREADING INTO THE REST  
OF THE ISLANDS AS EARLY AS THURSDAY AFTERNOON INTO FRIDAY. AS A  
RESULT, PWAT VALUES WILL GRADUALLY INCREASE TO NEAR CLIMATOLOGICAL  
LEVELS BY THURSDAY NIGHT LIKELY ENHANCING SHOWER ACTIVITY ACROSS THE  
REGION, WITH THE POTENTIAL FOR ISOLATED FLOODING IMPACTS ONCE  
AGAIN.  
 
 
   
LONG TERM...SATURDAY THROUGH WEDNESDAY  
 
//FROM PREVIOUS DISCUSSION//  
 
A SURFACE-INDUCED TROUGH WILL PROMOTE WET AND UNSTABLE WEATHER  
CONDITIONS ON SATURDAY. A GRADUAL INCREASE IN MOISTURE IS EXPECTED  
FROM SATURDAY ONWARDS WITH PRECIPITABLE WATER VALUES (PWAT) FROM 1.4  
TO 1.8 INCHES. THEREFORE, THE MOISTURE INCREASE IN COMBINATION WITH  
DAYTIME HEATING AND LOCAL EFFECTS WILL FAVOR THE DEVELOPMENT OF  
SHOWER ACTIVITY ACROSS PORTIONS OF THE INTERIOR AND WESTERN PUERTO  
RICO DURING THE AFTERNOON HOURS. WITH THE EXPECTED ACTIVITY, THERE  
IS AN INCREASED POTENTIAL OF ISOLATED FLOODING IMPACTS MAINLY IN  
URBAN AND LOW-LAYING AREAS.  
 
A STRONG SURFACE HIGH PRESSURE MOVING FROM THE WESTERN ATLANTIC INTO  
THE CENTRAL ATLANTIC WILL PROMOTE AN EASTERLY WIND FLOW THROUGH AT  
LEAST WEDNESDAY WHEN WINDS WILL BECOME FROM THE SOUTHEAST. IN THE  
MID-LEVELS A RIDGE WILL BUILD OVER THE NORTHEASTERN CARIBBEAN REGION  
PROMOTING DRIER AIR INTRUSION AND STABLE CONDITIONS ALOFT. HOWEVER,  
PATCHES OF LOW-LEVEL MOISTURE WILL CONTINUE TO MOVE INTO THE AREA  
FROM THE EAST PROMOTING PASSING TRADE WIND SHOWERS DURING THE  
MORNING HOURS ACROSS THE U.S. VIRGIN ISLANDS AND EASTERN PUERTO  
RICO. THE 925 MB TEMPERATURES WILL GRADUALLY INCREASE OVER THE  
WEEKEND WITH TEMPERATURES AT NORMAL AND ABOVE-NORMAL  
CLIMATOLOGICAL VALUES. AT THIS TIME HIGHS ARE EXPECTED TO RANGE  
FROM UPPER 80S TO LOW 90S ALONG THE COASTAL AND URBAN AREAS, AND  
FROM THE UPPER 70S TO THE LOW TO MID 80S IN THE MOUNTAINS AND  
HIGHER TERRAINS.  
 
 
   
AVIATION  
 
(18Z TAFS)  
 
MAINLY VFR CONDITIONS ARE EXPECTED THIS FORECAST PERIOD. ADDITIONAL  
VCSH TO -SHRA ARE LIKELY MAINLY ACROSS TJPS AND AND USVI TERMINALS  
TONIGHT, AND DRIER CONDITIONS ARE FORECAST FOR TOMORROW. NW TO N  
WINDS ARE EXPECTED AT AROUND 10 KNOTS OR LESS, WITH SEA BREEZE  
VARIATIONS BTWN 20/14-19/23Z.  
 
 
   
MARINE  
 
A SERIES OF SURFACE LOW PRESSURE SYSTEMS OVER THE NORTH ATLANTIC  
WILL CONTINUE TO BRING NORTHERLY SWELLS ACROSS THE LOCAL WATERS OVER  
THE NEXT FEW DAYS. THESE SWELLS WILL CREATE HAZARDOUS SEAS FOR SMALL  
CRAFT THROUGH THE END OF THE WORKWEEK. IN THE MEANTIME, AS A FRONTAL  
BOUNDARY CROSSES THE LOCAL AREA, EXPECT WINDS TO STRENGTHEN AND TURN  
FROM THE NORTHWEST.  
 
 
   
BEACH FORECAST  
 
LIFE-THREATENING RIP CURRENTS WILL CONTINUE ACROSS THE NORTH-FACING  
BEACHES OF THE ISLANDS THROUGH THE REST OF THE WEEK DUE TO PULSES OF  
LONG PERIOD NORTHERLY SWELLS. A LARGER, NORTHWESTERLY SWELL WILL  
ARRIVE ON THURSDAY, BUILDING SEAS BETWEEN 8 AND 12 FEET AT 13 TO 15  
SECONDS. THIS WILL LIKELY RESULT IN COASTAL FLOOD AND HIGH SURF  
ADVISORY CONDITIONS, PARTICULARLY FROM THE WEST/NORTHWEST TO  
NORTHEAST COAST OF PUERTO RICO FROM THURSDAY THROUGH FRIDAY.  
THEREFORE, A COASTAL FLOOD ADVISORY AND A HIGH SURF ADVISORY ARE NOW  
IN EFFECT, STARTING ON THURSDAY MORNING AND CONTINUING THROUGH AT  
LEAST FRIDAY. FOR THE NORTHERN USVI AND CULEBRA, A HIGH SURF  
ADVISORY AND A HIGH RIP CURRENT RISK ARE IN EFFECT. FOR THE  
SOUTHWEST COAST OF PUERTO RICO, PARTICULARLY FOR THE WEST FACING  
BEACHES, A HIGH RIP CURRENT RISK IS IN EFFECT.  
 
 
   
SJU WATCHES/WARNINGS/ADVISORIES  
 
PR...HIGH RIP CURRENT RISK THROUGH LATE FRIDAY NIGHT FOR PRZ001-002-  
005-008-012.  
 
COASTAL FLOOD ADVISORY FROM 6 AM THURSDAY TO 6 AM AST FRIDAY FOR  
PRZ001-002-005-008-010.  
 
HIGH SURF ADVISORY FROM 6 AM THURSDAY TO 6 PM AST FRIDAY FOR  
PRZ001-002-005-008-010-012.  
 
HIGH RIP CURRENT RISK FROM THURSDAY MORNING THROUGH LATE FRIDAY  
NIGHT FOR PRZ010-011.  
 
VI...HIGH RIP CURRENT RISK THROUGH LATE FRIDAY NIGHT FOR VIZ001.  
 
HIGH SURF ADVISORY FROM 6 AM THURSDAY TO 6 PM AST FRIDAY FOR  
VIZ001.  
 
HIGH RIP CURRENT RISK UNTIL 6 PM AST THIS EVENING FOR VIZ002.  
 
AM...SMALL CRAFT ADVISORY UNTIL 6 PM AST FRIDAY FOR AMZ711-712-741.  
 
SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 6 PM AST FRIDAY FOR  
AMZ716-742.  
 
SMALL CRAFT ADVISORY FROM 6 PM THURSDAY TO 6 PM AST FRIDAY FOR  
AMZ745.  
 
 
 
 
 
SHORT TERM...YZR/MMC  
LONG TERM...GRS  
AVIATION...YZR/DSR  
MARINE/BEACH FORECAST...DSR  
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