190
FXCA62 TJSJ 042117
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
517 PM AST SAT JAN 4 2025
KEY MESSAGES
* UNSETTLED AND WET CONDITIONS (INCREASED SHOWER ACTIVITY) WILL
CONTINUE THROUGH SUNDAY, WITH ISOLATED THUNDERSTORMS POSSIBLE,
POTENTIALLY LEADING TO LOCALIZED FLOODING IMPACTS.
* NORTHERLY SWELLS AND STRENGTHENING NORTHEASTERLY WINDS WILL CREATE
CHOPPY TO HAZARDOUS SEAS FOR SMALL CRAFT OVER THE HOLIDAY WEEKEND.
* LIFE-THREATENING RIP CURRENTS WILL CONTINUE THROUGH AT LEAST EARLY
NEXT WEEK ACROSS THE NORTHERN AND EASTERN EXPOSED BEACHES.
* BREEZY TO LOCALLY WINDY CONDITIONS ARE ANTICIPATED FOR TONIGHT AND
SUNDAY.
SHORT TERM...TONIGHT THROUGH MONDAY
RADAR AND SATELLITE ANALYSIS TODAY INDICATED PRIMARILY FAIR WEATHER,
WITH ISOLATED TO SCATTERED SHOWERS GRADUALLY INCREASING AFTER
MIDDAY. HOWEVER, SURFACE OBSERVATIONS AND RADAR ESTIMATES SHOWED
MINIMAL RAINFALL ACCUMULATIONS SINCE 8 AM AST. TEMPERATURES PEAKED
IN THE MID-70S ACROSS HIGHER ELEVATIONS AND AROUND 87F IN COASTAL
AND URBAN AREAS OF PUERTO RICO, WHILE THE U.S. VIRGIN ISLANDS AND
NEARBY ISLANDS REPORTED HIGHS IN THE LOWER TO MID-80S. NOTABLY,
PONCE (MERCEDITA AIRPORT) RECORDED HIGHS OF 90-91°F. WINDS WERE
PREDOMINANTLY EAST-NORTHEASTERLY AT 5-10 MPH BUT PRIMARILY
INFLUENCED BY SEA BREEZE PATTERNS.
MARGINALLY UNSTABLE AND WETTER CONDITIONS WILL PERSIST THROUGH
SUNDAY, TRANSITIONING TO NEAR-FAIR WEATHER BY MONDAY, COINCIDING
WITH THREE KINGS DAY. THIS PATTERN IS DRIVEN BY A MID-TO-UPPER-LEVEL
TROUGH, A DISSIPATING FRONTAL BOUNDARY AND ASSOCIATED PRE-FRONTAL
TROUGH, AND A DEVELOPING SURFACE HIGH OVER THE SOUTHWESTERN
ATLANTIC, SUSTAINING ABOVE-NORMAL TO WELL-ABOVE NORMAL MOISTURE
LEVELS (PWAT VALUES ABOVE 1.8 INCHES) THROUGH SUNDAY NIGHT. MODERATE
TO FRESH NORTHEASTERLY WINDS OF 15-25 MPH WILL ENHANCE INLAND
MOISTURE AND SHOWER ACTIVITY.
INSTABILITY WILL ALSO PEAK TONIGHT INTO SUNDAY, SUPPORTING SCATTERED
TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS, MAINLY OVER NORTHERN
AND NORTHEASTERN PUERTO RICO, VIEQUES, CULEBRA, AND THE U.S. VIRGIN
ISLANDS, WITH SECONDARY SHOWER CLUSTERS ACROSS SOUTHERN AND
SOUTHWESTERN PUERTO RICO BY SUNDAY AFTERNOON. 12-HOUR RAINFALL
ACCUMULATIONS MAY REACH AN INCH WITH ISOLATED HIGHER AMOUNTS THROUGH
THE NEXT 24-36 HOURS, LEADING TO PONDING ON ROADWAYS AND LOCALIZED
FLOODING IMPACTS. THE MOST ACTIVE PERIOD IS EXPECTED AFTER MIDNIGHT
INTO SUNDAY MORNING.
CONDITIONS WILL IMPROVE LATE SUNDAY NIGHT INTO MONDAY AS RIDGING
REESTABLISHES AND MOISTURE DECREASES. HOWEVER, THE TYPICAL SEASONAL
PATTERN OF TRADE WIND SHOWERS AND LIMITED AFTERNOON DEVELOPMENT WILL
PERSIST. TEMPERATURES WILL REMAIN NEAR OR SLIGHTLY BELOW NORMAL,
MAINTAINING THE "FRIíTO NAVIDEñO." FOR UPDATES, VISIT THE
EXPERIMENTAL GRAPHICAL HAZARD WEATHER OUTLOOK:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=SJU.
LONG TERM...TUESDAY THROUGH SATURDAY
OVERALL, FAIR WEATHER CONDITIONS WILL PREVAIL OVER THE LONG-TERM
PERIOD. THE PRECIPITABLE WATER CONTENT WILL FLUCTUATE BETWEEN NORMAL
AND BELOW-NORMAL LEVELS (1.0-1.5 INCHES), WITH UPPER-LEVEL HIGHS
BUILDING OVER THE SOUTHEASTERN CARIBBEAN. TWO WEAK COLD FRONTS ARE
FORECAST TO REACH THE LOCAL AREA AT THE END OF THE WORKWEEK AND LATE
SUNDAY, WITH ASSOCIATED UPPER-LEVEL TROUGHS PASSING MAINLY NORTH OF
THE AREA, PROVIDING ONLY SLIGHT INSTABILITY OVER THE ISLANDS.
HOWEVER, BY MIDWEEK, AS THE SURFACE HIGH OVER THE CENTRAL ATLANTIC
MOVES FURTHER EAST AND THE PRESSURE GRADIENT RELAXES OVER THE
EASTERN CARIBBEAN, A PRE-FRONTAL TROUGH SHOULD DEVELOP MAINLY EAST
OF THE LEEWARD ISLANDS, CAUSING WINDS BRIEFLY TO ACQUIRE AN EAST TO
SOUTHEASTERLY DIRECTION AND BECOME LIGHT TO CALM EARLY IN THE
PERIOD. MOISTURE ADVECTION SHOULD FAVOR SHOWERS OVER THE USVI, BUT
MINOR RAINFALL AMOUNTS ARE EXPECTED WITH THIS ACTIVITY. MODERATE TO
FRESH NE TO NNE WINDS WILL RETURN BY THURSDAY AND FRIDAY AS THE
FRONT APPROACHES THE LOCAL AREA.
A SIMILAR WEATHER PATTERN IS EXPECTED DURING THE WEEKEND, AS THE
PRESSURE GRADIENT RELAXES AGAIN ON SATURDAY BEFORE THE ARRIVAL OF
THE NEXT FRONT ON SUNDAY. PLEASANT TEMPERATURES WILL CONTINUE DURING
THE FORECAST PERIOD, ESPECIALLY DURING CLEAR NIGHTS WITH CALM WINDS
AND AFTER THE FRONTAL PASSAGES.
AVIATION
(18Z TAFS)
FRONTAL BOUNDARY AND ELEVATED MOISTURE LEVELS WILL CONTINUE TO
SUPPORT SHRA AND POSSIBLE TSRA ACROSS THE REGION. THIS ACTIVITY IS
EXPECTED TO IMPACT MOST TAF SITES OVER THE NEXT 12-24 HOURS, WITH
PEAK ACTIVITY ANTICIPATED AFTER 04/22Z AND LASTING THROUGH THE
FORECAST PERIOD. THIS SETUP COULD LEAD TO BRIEF MVFR CONDITIONS
WITH SCT-BKN CEILINGS BETWEEN FL020-040. THE GENERAL WIND FLOW
WILL REMAIN FROM THE EAST-NORTHEAST AT 6-10 KNOTS, BUT WILL BE
STRONGLY INFLUENCED BY SEA BREEZES AT TAF SITES. AFTER 04/22Z,
WINDS WILL SHIFT TO NNE-N AND INCREASE TO 10-15 KNOTS WITH HIGHER
GUSTS, PARTICULARLY NEAR THE SHRA/TSRA.
MARINE
A COLD FRONT WITH ASSOCIATED SHEARLINE APPROACHING THE AREA FROM THE
NORTHWEST WILL PROMOTE MODERATE TO FRESH NORTHEASTERLY WINDS THROUGH
AT LEAST MONDAY. A LONG-PERIOD NORTHEAST SWELL WILL CONTINUE TO
SPREAD ACROSS THE ATLANTIC WATERS AND PASSAGES THROUGH THE REST OF
THE WEEKEND. A LARGER NORTHWEST SWELL WILL ARRIVE LATE SUNDAY AND
LINGER THROUGH EARLY NEXT WEEK. THE COMBINATION OF THE SWELLS WITH
INCREASING WINDS WILL PROMOTE SMALL CRAFT ADVISORY CONDITIONS DUE TO
HAZARDOUS SEAS ACROSS THE LOCAL WATERS THROUGH AT LEAST TUESDAY.
BEACH FORECAST
A LONG-PERIOD NORTHEASTERLY SWELL CONTINUES TO PROMOTE LIFE-
THREATENING RIP CURRENTS. A LARGER LONG-PERIOD NORTHWESTERLY SWELL
WILL ARRIVE LATE ON SUNDAY AND LINGER THROUGH EARLY NEXT WEEK,
CAUSING LARGE BREAKING WAVES THAT WILL LEAD TO HIGH SURF ADVISORY
CONDITIONS, MINOR BEACH EROSION, AND LIFE-THREATENING RIP
CURRENTS, PARTICULARLY ALONG THE ATLANTIC COASTLINE OF PUERTO RICO
FROM RINCON TO FAJARDO.
ACROSS THE U.S. VIRGIN ISLANDS, LIFE-THREATENING RIP CURRENTS
WILL PREVAIL ACROSS ALL NORTHERN EXPOSED BEACHES DUE TO THE LONG
PERIOD SWELLS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH LATE MONDAY NIGHT FOR PRZ001-002-
005-008-010-012-013.
HIGH SURF ADVISORY FROM 6 AM SUNDAY TO 6 PM AST MONDAY FOR
PRZ001-002-005-008-010.
VI...HIGH RIP CURRENT RISK THROUGH LATE MONDAY NIGHT FOR VIZ001-002.
AM...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO NOON AST TUESDAY
FOR AMZ711.
SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM AST TUESDAY
FOR AMZ712-741-742.
SMALL CRAFT ADVISORY FROM 6 AM SUNDAY TO NOON AST TUESDAY FOR
AMZ716-723.
SHORT TERM/AVIATION...ICP
LONG TERM/MARINE...DSR
PUBLIC...MNG
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