902
FXCA62 TJSJ 152107
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
507 PM AST TUE APR 15 2025
SYNOPSIS
THE REMNANTS OF THIS SHOWER ACTIVITY WILL LIKELY LINGER THROUGH
THIS EVENING. OTHER HAZARD RISKS INCLUDE LIGHTNING OVER THE NEXT
FEW DAYS, WITH NON- THUNDERSTORM WIND RISKS ANTICIPATED TOMORROW.
THE RISK OF LIFE- THREATENING RIP CURRENTS WILL CONTINUE MODERATE
FOR MOST NORTH- AND EAST- FACING BEACHES. INCREASING WINDS AND A
NORTHERLY SWELL WILL LIKELY DETERIORATE MARINE AND SURF ZONE
CONDITIONS OVER THE WEEKEND.
SHORT TERM...TONIGHT THROUGH THURSDAY
VARIABLE TO SHOWERY WEATHER CONDITIONS PREVAILED FOR MUCH OF THE
REGION DURING THE LATE MORNING TO AFTERNOON HOURS. SINCE MIDNIGHT,
RADAR ESTIMATED ACCUMULATIONS SHOW AT LEAST MINIMAL ACCUMULATIONS
OVER ALL BUT SOUTHERN TO SOUTHWESTERN MOST PR AS WELL AS OTHER
ISOLATED AREAS. CURRENT SATELITE DERIVED PRECIPITABLE WATER (PWAT)
VALUES INDICATE AROUND 1.74 INCHES (JUST ABOVE NORMAL VALUES)
OVER THE ISLANDS AS MOISTURE REMNANTS FROM A PAST FRONTAL BOUNDARY
CONTINUE TO REACH THE REGION. UNDER VEERING EAST-NORTHEAST TO
EASTERLY WINDS, SHOWERS CONTINUED TO REACH WINDWARD SECTORS AND,
DURING THE AFTERNOON, DIURNAL HEATING AND LOCAL EFFECTS PROMOTED
SHOWER AND THUNDERSTORM DEVELOPMENT OVER WESTERN PUERTO RICO. THIS
ACTIVITY WILL GRADUALLY DISSIPATE AND/OR MOVE OFFSHORE DURING THE
LATE AFTERNOON TO EVENING HOURS. RADAR ESTIMATED RAINFALL
ACCUMULATIONS UNTIL NOW HAVE REACHED 2.0 TO 2.5 INCHES OVER
PORTIONS OF THE SAN JUAN METROPOLITAN AREA, AND 1.0 TO 1.5 INCHES
OVER THE WESTERN INTERIOR TO NORTHWESTERN PUERTO RICO. REPORTED
HIGHS WERE IN THE MID TO UPPER 80S ACROSS COASTAL AREAS OF THE
ISLANDS, WITH SOME ISOLATED AREAS REACHING THE LOW 90S.
PWAT VALUES WILL GRADUALLY DECREASE OVERNIGHT AND REMAIN AT OR ABOVE
1.5 INCHES TONIGHT. DRIER AIR WILL FILTER IN AT TIMES (ESPECIALLY
LATE WEDNESDAY TO EARLY TUESDAY) BUT, FOR MOST OF THE PERIOD PWAT
VALUES WILL CONTINUE AT OR ABOVE 1.5 IN. A SURFACE HIGH WILL
CONTINUE TO BUILD OVER THE SOUTHWESTERN ATLANTIC TONIGHT, GRADUALLY
MOVING EASTWARD DURING THE PERIOD. THIS WILL RESULT IN VEERING WINDS
DURING THE NEXT FEW DAYS, STEERING FLOW WILL BECOME MORE EAST-
SOUTHEASTERLY ON WEDNESDAY, AND CONTINUE THROUGH THURSDAY. THIS WILL
CONTINUE TO BRING FRAGMENTED MOISTURE TO THE LOCAL ISLANDS,
RESULTING IN PASSING SHOWERS ALONG WINDWARD SECTIONS. ON WEDNESDAY,
A DEVELOPING SURFACE TROUGH WEST OF THE ISLANDS WILL ALSO BE
PRESENT. INSTABILITY WILL INCREASE AS WE CONTINUE INTO THE WEEK AS
AN UPPER TROUGH ALSO MOVES INTO THE AREA FROM THE WEST. THIS,
DIURNAL HEATING AND LOCAL EFFECTS WILL CONTINUE THE POTENTIAL FOR
AFTERNOON CONVECTIVE SHOWERS AND POSIBLE THUNDERSTORMS, ACROSS
INTERIOR AND WEST-NORTHWEST PUERTO RICO ON WEDNESDAY AND THURSDAY,
AS WELL AS LINES OF SHOWERS AND POSIBLE T-STORMS ALSO DEVELOPING
FROM VIEQUES, CULEBRA, THE USVI AND EL YUNQUE AND MOVING
NORTHWESTWARD. A LIMITED TO ELEVATED FLOODING RISK WILL BE PRESENT
EACH AFTERNOON RESULTING FROM PONDING OF WATER OVER ROADS AND POORLY
DRAINED AREAS TO FLOODING IN URBAN AREAS, ROADS, SMALL STREAMS AND
WASHES. WITH SOUTHEASTERLY WINDS, 925 MB TEMPERATURES ARE FORECAST
TO BE AT NORMAL TO ABOVE NORMAL VALUES DURING THE PERIOD.
LONG TERM...FRIDAY THROUGH TUESDAY
/PREV DISCUSSION... /ISSUED 428 AM AST TUE APR 15 2025/
UNSETTLED WEATHER CONDITIONS WILL DOMINATE THE FORECAST AREA AS
LOW PRESSURE OVER THE NORTH-NORTHWESTERN ATLANTIC CONTINUES TO
DRAW MOISTURE FROM THE CARIBBEAN. TOWARD THE END OF THE WORKWEEK
AND INTO THE WEEKEND, WINDS ARE EXPECTED TO SHIFT GRADUALLY FROM
THE EAST- SOUTHEAST TO THE NORTHEAST.
THE LATEST MODEL GUIDANCE CONTINUES TO INDICATE THE APPROACH OF A
TROUGH ACCOMPANIED BY A COLD FRONT, WHICH IS EXPECTED TO MOVE INTO
THE REGION ON SATURDAY. THESE FEATURES WILL ENHANCE THE POTENTIAL
FOR SHOWER AND THUNDERSTORM DEVELOPMENT, PARTICULARLY ACROSS THE
INTERIOR AND SOUTHWESTERN PORTIONS OF PUERTO RICO DURING THE
AFTERNOON AND EARLY EVENING HOURS. MODEL DATA SUGGESTS PRECIPITABLE
WATER VALUES RANGING FROM 1.8 TO 1.9 INCHES, 500 MB TEMPERATURES
BETWEEN -8 AND -9 DEGREES CELSIUS, AND DEEP-LAYER MOISTURE EXTENDING
FROM THE SURFACE UP TO AROUND 500 MB. THESE CONDITIONS WILL SUPPORT
THE POTENTIAL FOR URBAN AND SMALL STREAM FLOODING, RAPID RIVER
RISES, MUDSLIDES, AND FREQUENT LIGHTNING ASSOCIATED WITH
THUNDERSTORM ACTIVITY. AT THIS TIME, SATURDAY IS THE WETTEST DAY OF
THE LONG-TERM PERIOD.
A GRADUAL IMPROVEMENT IN WEATHER CONDITIONS IS ANTICIPATED FROM
SUNDAY THROUGH TUESDAY AS A DRIER AND COOLER AIR MASS IS FORECAST TO
MOVE INTO THE REGION BEHIND THE FRONT. THIS TRANSITION WILL BRING
LOWER HUMIDITY AND REDUCED RAIN CHANCES, SIGNALING A RETURN TO MORE
STABLE AND SEASONABLE CONDITIONS. LATE SATURDAY WINDS WILL INCREASE
AND BECOME BREEZY THROUGH AT LEAST TUESDAY.
AVIATION
(18Z TAFS)
MOSTLY VFR CONDS WILL BE PRESENT ACROSS THE TAF SITES DURING THIS
PERIOD. HOWEVER, TSRA AND SHRA ARE EXPECTED ACROSS TJBQ AND POSSIBLY
TJSJ/TJPS THROUGH 15/23Z, RESULTING IN LOWER VIS AND CIGS IN THE TAF
SITE AND MTN OBSC OVR INTERIOR PUERTO RICO. WINDS WILL REMAIN FROM
THE ESE AT 12-18 KNOTS, WITH HIGHER GUSTS NEAR SHOWERS.
MARINE
A HIGH PRESSURE SYSTEM BUILDING OVER THE WESTERN ATLANTIC WILL
PROMOTE MODERATE TO LOCALLY FRESH EASTERLY WINDS, GRADUALLY VEERING
TO BECOME EAST-SOUTHEASTERLY TOMORROW. THIS HIGH WILL PUSH THE
REMNANTS OF A FRONTAL BOUNDARY ACROSS THE REGION, LEADING TO
INCREASED SHOWERS AND THUNDERSTORMS ACROSS LOCAL WATERS. ANY
THUNDERSTORM ACTIVITY WILL LIKELY GENERATE LOCALLY HAZARDOUS MARINE
CONDITIONS, SMALL CRAFT SHOULD EXERCISE CAUTION. INCREASING WINDS AND
A WEAK NORTHERLY SWELL WILL LIKELY DETERIORATE MARINE CONDITIONS
OVER THE WEEKEND.
BEACH FORECAST
INCREASING WINDS WILL PROMOTE A MODERATE RISK FOR MOST NORTH- AND
EAST- FACING BEACHES OF PUERTO RICO AND ST. CROIX IN THE U.S.
VIRGIN ISLANDS. THESE CONDITIONS ARE EXPECTED THROUGH THURSDAY,
IMPROVING BY FRIDAY. HOWEVER, DETERIORATING MARINE CONDITIONS
WILL BRING THE RISK OF RIP CURRENTS TO HIGH DURING THE WEEKEND. BE
AWARE THAT AFTERNOON THUNDERSTORMS POSE A THREAT OF LIGHTNING,
MOSTLY FOR THE BEACHES IN THE WEST AND SOUTHWESTERN COAST OF
PUERTO RICO.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM...MRR/ICP
LONG TERM....MMC
AVIATION...CVB
MARINE...MNG
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