138
FXCA62 TJSJ 142001
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
401 PM AST MON APR 14 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
REMNANTS OF THIS ACTIVITY WILL LIKELY LINGER THROUGH THE EVENING
HOURS. OTHER HAZARD RISKS INCLUDE LIGHTNING OVER THE NEXT FEW
DAYS, WITH NON- THUNDERSTORM WIND RISKS ANTICIPATED ON TUESDAY.
THE RISK OF LIFE-THREATENING RIP CURRENTS WILL RISE TO MODERATE BY
TUESDAY 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 WEDNESDAY
FAIR WEATHER CONDITIONS WITH VARIABLY CLOUDY SKIES PREVAILED ACROSS
THE ISLANDS DURING THE MORNING HOURS TO EARLY AFTERNOON HOURS.
CURRENT SATELITE DERIVED PRECIPITABLE WATER (PWAT) VALUES INDICATE
AROUND 2 INCHES (ABOVE NORMAL VALUES) OVER PUERTO RICO AND ITS
NORTHERN, WESTERN AND SOUTHWESTERN WATERS, AND 1.6 TO 1.78 INCHES
(AT NORMAL TO ABOVE NORMAL VALUES) OVER THE U.S. VIRGIN ISLANDS.
THIS INCREASE IN PRECIPITABLE WATER IS DUE TO A FRONTAL BOUNDARY
DISSIPATING BUT MOVING OVER OUR REGION. SHOWERS PRODUCED BY THIS
FRONTAL BOUNDARY STAYED MOSTLY OVER THE WATERS. HOWEVER, THIS
FRONTAL BOUNDARY AND ASSOCIATED TROUGH, ALONG WITH PREDOMINANT
NORTHEASTERLY WINDS, DIURNAL HEATING AND LOCAL EFFECTS PROMOTED
AFTERNOON CONVECTIVE SHOWERS AND ISOLATED THUNDERSTORMS MAINLY OVER
THE INTERIOR TO SOUTH AND SOUTHWESTERN PR. RAINFALL ACCUMULATIONS
UNTIL NOW HAVE REACHED UP TO 2.0-2.5 INCHES. THIS ACTIVITY WILL
GRADUALLY DISSIPATE AND/OR MOVE OFFSHORE DURING THE LATE AFTERNOON
TO EVENING HOURS. REPORTED HIGHS WERE IN THE MID TO UPPER 80S
ACROSS COASTAL AREAS OF THE ISLANDS, WITH SOME AREAS REACHING THE
LOW 90S.
PWAT VALUES WILL GRADUALLY DECREASE OVERNIGHT AND REMAIN AT
OR ABOVE 1.5 INCHES DURING THE REST OF THE PERIOD AS THE FRONT
DISSIPATES. A SURFACE HIGH WILL 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
GRADUALLY BECOME EASTERLY TOMORROW AND THEN EAST-SOUTHEASTERLY BY
WEDNESDAY. THIS WILL CONTINUE TO BRING FRAGMENTED MOISTURE FROM THE
FRONTAL BOUNDARY TO THE LOCAL ISLANDS, RESULTING IN POSSIBLE PASSING
SHOWERS ALONG WINDWARD SECTIONS OF THE ISLANDS. THE WIND SHIFT,
COMBINED WITH AVAILABLE MOISTURE AND LAPSE RATES AT NORMAL VALUES,
WILL MAINTAIN THE POTENTIAL FOR AFTERNOON CONVECTIVE SHOWERS AND
POSIBLE THUNDERSTORMS, ACROSS INTERIOR AND WESTERN PUERTO RICO ON
TUESDAY AND OVER THE INTERIOR TO NORTHWESTERN PUERTO RICO ON
WEDNESDAY. ON WEDNESDAY, A DEVELOPING SURFACE TROUGH WEST OF THE
ISLANDS WILL ALSO BE PRESENT REPLACING A MID LEVEL RIDGE PATTERN ON
TUESDAY. WITH MORE SOUTHEASTERLY WINDS, WARMER TEMPERATURES ARE
FORECAST. 925 MB TEMPERATURES ARE FORECAST TO BE AT NORMAL TO ABOVE
NORMAL VALUES DURING THE PERIOD. 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.
LONG TERM...THURSDAY THROUGH MONDAY
FROM PREVIOUS DISCUSSION ISSUES AT 447 AM AST MON APR 14 2025
THE OVERALL FORECAST SCENARIO REMAINS CONSISTENT WITH THE PREVIOUS
DISCUSSION. ON THURSDAY, WINDS WILL WEAKEN AS A POLAR TROUGH
APPROACHES FROM THE WESTERN ATLANTIC. AT THE SAME TIME, ENHANCED
MOISTURE FROM THE CARIBBEAN WILL MOVE OVER THE REGION, DRIVEN BY A
SOUTHEASTERLY WIND FLOW. THESE FEATURES WILL SUPPORT THE DEVELOPMENT
OF SHOWERS AND THUNDERSTORMS, PARTICULARLY ACROSS THE INTERIOR,
WESTERN, AND NORTHERN PORTIONS OF PUERTO RICO DURING THE AFTERNOON
AND EARLY EVENING HOURS. THE IMPACTS ASSOCIATED WITH THIS WEATHER
PATTERN WILL BE THE URBAN AND SMALL STREAM FLOODING, RAPID RIVER
RISES, MUDSLIDES, AND FREQUENT LIGHTNING ASSOCIATED WITH
THUNDERSTORM ACTIVITY. FRIDAY WILL BRING SIMILAR CONDITIONS,
ALTHOUGH WINDS ARE FORECAST TO GRADUALLY VEER TOWARD THE EAST. THE
APPROACHING TROUGH WILL BE ACCOMPANIED BY A COLD FRONT, WHICH IS
EXPECTED TO MOVE INTO THE AREA BY SATURDAY. AS THE FRONT CROSSES THE
ISLANDS, WINDS WILL SHIFT TO THE NORTHEAST, CONTINUING TO SUPPORT
MOISTURE IN SOME AFTERNOON CONVECTION, ESPECIALLY OVER THE
CORDILLERA CENTRAL. WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS
REMAIN LIKELY DURING THIS PERIOD. BY SUNDAY INTO MONDAY, A DRIER AND
COOLER AIR MASS IS FORECAST TO MOVE INTO THE REGION IN THE WAKE OF
THE FRONT. THIS TRANSITION WILL BRING BREEZY NORTHEAST WINDS, LOWER
HUMIDITY, AND REDUCED RAIN CHANCES, SIGNALING A RETURN TO MORE
STABLE AND SEASONABLE WEATHER CONDITIONS.
OVERALL, UNSETTLED WEATHER CONDITIONS ARE EXPECTED TO PERSIST ACROSS
THE LOCAL ISLANDS THROUGH AT LEAST SATURDAY, WITH GRADUAL
IMPROVEMENT ANTICIPATED LATE IN THE WEEKEND AND INTO EARLY NEXT WEEK.
AVIATION
(18Z TAFS)
VFR CONDITIONS WILL CONTINUE TO PREVAIL AT ALL TAF SITES DURING THE
FORECAST PERIOD WITH BRIEF PERIODS OF MVFR CONDS IN SHRA/VCTS AT JPS
THROUGH AT LEAST 14/22Z. WINDS WILL REMAIN FROM THE NE AT 15 MPH,
WITH GUSTY WINDS NEAR THE SHOWERS, BECOMING AT 10 KNOTS OR LESS
OVERNIGHT.
MARINE
A HIGH PRESSURE SYSTEM BUILDING OVER THE WESTERN ATLANTIC WILL
PROMOTE MODERATE TO LOCALLY FRESH EAST TO NORTHEAST WINDS, GRADUALLY
VEERING TO BECOME EASTERLY TOMORROW AND EAST-SOUTHEASTERLY ON
WEDNESDAY. THIS HIGH WILL PUSH THE REMNANTS OF A FRONTAL BOUNDARY
ACROSS THE REGION, LEADING TO INCREASED SHOWERS AND THUNDERSTORMS.
AFTERNOON CONVECTION WILL ALSO AFFECT PORTIONS OF THE COASTAL WATERS.
ANY THUNDERSTORM ACTIVITY WILL LIKELY GENERATE LOCALLY HAZARDOUS
MARINE CONDITIONS FOR SMALL CRAFT. INCREASING WINDS AND A NORTHERLY
SWELL WILL LIKELY DETERIORATE MARINE CONDITIONS OVER THE WEEKEND.
BEACH FORECAST
LIGHT WINDS WILL MAINTAIN THE RISK OF RIP CURRENTS LOW. HOWEVER,
INCREASING WINDS ON TUESDAY WILL LEAD TO MODERATE RISK FOR MOST
NORTH- AND EAST-FACING BEACHES. 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
AVIATION...OMS/ICP
MARINE...ICP
PUBLIC/UA...MRR/MNG
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