800
FXCA62 TJSJ 122102
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
502 PM AST SAT APR 12 2025
SYNOPSIS
SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP EACH AFTERNOON
ACROSS THE ISLANDS, ENHANCING THE RISK FOR URBAN AND SMALL STREAM
FLOODING, AS WELL AS MUDSLIDES AND RAPID RIVER RISES. THE HEAVIEST
ACTIVITY IS EXPECTED ACROSS NORTH, WEST AND THE INTERIOR OF PUERTO
RICO, BUT SHOWERS WILL ALSO REACH THE VIRGIN ISLANDS AND EASTERN
PUERTO RICO AT TIMES.
SHORT TERM...TONIGHT THROUGH MONDAY
SUNNY TO PARTLY CLOUDY SKIES PREVAILED ACROSS PUERTO RICO AND THE US
VIRGIN ISLANDS IN THE MORNING, BECOMING VARIABLY CLOUDY ACROSS MOST
OF PUERTO RICO IN THE AFTERNOON. PASSING SHOWERS WERE NOTED ACROSS
THE EAST AND SOUTHEAST COASTAL AREAS OF PUERTO RICO DURING THE LATE
MORNING HOURS; HOWEVER, RAINFALL TOTALS ASSOCIATED WITH THESE
SHOWERS WERE MINIMAL. AS EXPECTED, SHOWERS AND ISOLATED
THUNDERSTORMS ALSO DEVELOPED OVER PORTIONS OF THE INTERIOR AND NORTH-
WEST PUERTO RICO IN THE AFTERNOON. MAXIMUM RAINFALL ACCUMULATIONS
WERE BETWEEN 1.5 AND 2 INCHES IN LARES AND SAN SEBASTIAN. MAXIMUM
TEMPERATURES WERE FROM THE MID TO HIGH 80S ACROSS THE LOWER
ELEVATIONS OF THE ISLANDS TO THE UPPER 70S AND MID-80S ACROSS THE
HIGHER ELEVATIONS. THE WIND WAS FROM THE EAST TO SOUTHEAST AT 10 TO
15 MPH WITH OCCASIONAL HIGHER GUSTS.
A WEAK COLD FRONT AND ASSOCIATED LOW LEVEL MOISTURE WILL CONTINUE TO
MOVE ACROSS THE SW NORTH ATLANTIC, REACHING THE LOCAL ISLANDS ON
SUNDAY. ONCE THIS FEATURE MOVES EAST OF THE AREA, A SURFACE HIGH
PRESSURE WILL ESTABLISH NORTH OF THE LOCAL ISLANDS MONDAY THROUGH AT
LEAST TUESDAY. ALTHOUGH THE BEST UPPER LEVEL DYNAMICS ASSOCIATED
WITH THE FRONT WILL REMAIN NORTH OF THE AREA AND CLOSE TO AN AREA OF
LOW PRESSURE (22N72W), THERE IS ENOUGH INSTABILITY ACROSS THE
FORECAST AREA TO RESULT IN PERIODS OF SHOWERS AND THUNDERSTORMS
TONIGHT AND SUNDAY. AS A RESULT, UNDER THE PREVAILING SOUTHEAST WIND
FLOW, EXPECT PASSING SHOWERS AND ISOLATED THUNDERSTORMS POSSIBLE
ACROSS EAST AND SOUTHEAST PUERTO RICO TONIGHT AND SUNDAY MORNING,
WITH SHOWERS AND THUNDERSTORMS DEVELOPING ACROSS THE NORTHERN SLOPES
OF PUERTO RICO ON SUNDAY AFTERNOON. THE SOUTHEAST WIND FLOW WILL
ALSO GRANT MAXIMUM TEMPERATURES IN THE UPPER 80S ACROSS THE NORTH
COAST OF PUERTO RICO ON SUNDAY. DUE TO THE BUILDING SURFACE HIGH
PRESSURE NORTH OF THE AREA EARLY THE UPCOMING WORKWEEK, WINDS ARE
EXPECTED TO BECOME MORE NORTHEASTERLY ON MONDAY. THEREFORE,
AFTERNOON SHOWERS ARE EXPECTED TO DEVELOP ACROSS CENTRAL AND
SOUTHWEST PUERTO RICO, WITH SOME RELIEF IN MAXIMUM TEMPERATURES
ALONG THE NORTH COAST AS WELL.
OVERALL, PLENTY OF MOISTURE WILL PREVAIL OVER THE NORTHEASTERN
CARIBBEAN OVER THE NEXT SEVERAL DAYS, WITH PRECIPITABLE WATER VALUES
EXCEEDING THE NORMAL RANGE FOR THE SEASON. THEREFORE THE RISK FOR
URBAN AND SMALL STREAM FLOODING CONTINUES EACH DAY. IN FACT, THERE
IS A MODERATE TO HIGH CHANCE OF EXCEED 1 INCH OF RAINFALL
ACCUMULATION EACH AFTERNOON DURING THE FORECAST CYCLE.
LONG TERM...TUESDAY THROUGH SATURDAY
/PREV DISCUSSION... /ISSUED 358 AM AST SAT APR 12 2025/
A SURFACE HIGH PRESSURE WILL ROLL EASTWARD FROM THE WEST, FORCING
THE FRONTAL BOUNDARY TO LIE DOWN ACROSS THE REGION, AND THUS
PROVIDING PLENTY OF MOISTURE THROUGH MUCH OF THE FORECAST PERIOD.
AT THE SURFACE, A TROUGH WILL ALSO DEVELOP ON TUESDAY, WHILE
ANOTHER MID TO UPPER LEVEL TROUGH WILL APPROACH FROM THE WEST ON
WEDNESDAY AND THURSDAY. AS THESE SYSTEM INTERACT, YET ANOTHER
SURFACE TROUGH WILL DEVELOP NORTH OF THE REGION. ALL THIS
INSTABILITY AND MOISTURE WILL RESULT IN ACTIVE AFTERNOONS, WITH
SHOWERS AND THUNDERSTORMS DEVELOPING, MOSTLY ACROSS THE INTERIOR,
WESTERN AND NORTHERN PUERTO RICO. SOMETHING ELSE TO CONSIDER IS
THAT WINDS WILL BE MOSTLY FROM THE SOUTHEAST...ON TUESDAY, AROUND
10-15 MPH, AND SLOWING DOWN AFTER WEDNESDAY, BELOW 10 MPH. AFTER
A COUPLE DAYS OF RAIN, SOILS WILL BE SATURATED, AND RIVERS WILL BE
RUNNING HIGH. THEREFORE, THE RISK FOR URBAN FLOODING, RAPID RIVER
RISES, AND MUDSLIDES WILL INCREASE.
BY THE END OF THE WEEK, THE UNCERTAINLY INCREASE, MOSTLY BECAUSE
THE ECMWF MODEL SHOWS A DEEPER TROUGH REACHING THE REGION, BUT THE
GFS DOES NOT HAVE SUCH A DEFINE FEATURE. THE FORECAST WAS ADJUSTED
FOR THIS PERIOD, SHOWING HIGHER PROBABILITY OF PRECIPITATION AND
AMOUNT OF RAINFALL. AS IS USUAL, SHOWERS WILL REACH EASTERN
PUERTO RICO AND THE VIRGIN ISLANDS PERIODICALLY, BUT THE STRONGEST
ACTIVITY WILL IMPACT THE INTERIOR, WESTERN AND NORTHERN PORTIONS
OF PUERTO RICO.
AVIATION
(18Z TAFS)
BRIEF PERIODS OF MVFR CONDITIONS WILL REMAIN POSSIBLE AT JSJ AND JBQ
THROUGH ABOUT 12/22Z IN SHRA/TSRA. WINDS WILL PREVAIL FROM THE SE AT
10-15 KTS WITH STRONGER GUSTS, BECOMING LIGHT AND VARIABLE OVERNIGHT.
MARINE
A BROAD SURFACE HIGH PRESSURE WILL REMAIN ANCHORED OVER THE CENTRAL
ATLANTIC PROMOTING LIGHT TO MODERATE EAST TO SOUTHEAST WINDS THROUGH
THE WEEKEND. HOWEVER, ANOTHER SURFACE HIGH PRESSURE WILL BUILD OVER
THE WESTERN ATLANTIC AND PUSH THE FRONT OVER THE LOCAL AREA BY EARLY
NEXT WEEK, PROMOTING MODERATE TO FRESH NORTHEAST WINDS. SHOWER AND
THUNDERSTORM ACTIVITY WILL DEVELOP EACH DAY, MAINLY ACROSS THE
ATLANTIC WATERS AND THE MONA PASSAGE. A COLD FRONT ACROSS THE
WESTERN ATLANTIC WILL CONTINUE TO APPROACH THE NORTHEASTERN
CARIBBEAN OVER THE NEXT FEW DAYS.
BEACH FORECAST
THE RISK OF RIP CURRENTS WILL REMAIN MODERATE TONIGHT FOR EASTERN
BEACHES OF PUERTO RICO, CULEBRA, AND ST. CROIX. BEACH CONDITIONS
WILL CONTINUE IMPROVING TONIGHT INTO EARLY NEXT WEEK. HOWEVER,
THE RISK WILL INCREASE ONCE AGAIN BY TUESDAY AND REMAIN MODERATE
THROUGH THE REST OF THE WORKWEEK.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...OMS/ICP
LONG TERM....ERG
MARINE...MNG
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