284
FXCA62 TJSJ 011809
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
209 PM AST THU MAY 1 2025
SYNOPSIS
ONCE AGAIN, UNSETTLED WEATHER IS EXPECTED OVER THE NEXT SEVERAL
DAYS DUE TO A COMBINATION OF ABUNDANT TROPICAL MOISTURE AND A
SERIES OF UPPER- LEVEL TROUGHS. THE FLOOD WATCH REMAINS IN EFFECT
FOR PUERTO RICO UNTIL FRIDAY MORNING BUT WE ENCOURAGE PEOPLE TO
STAY UPDATED FOR ANY CHANGES REGARDING THE FLOOD WATCH. THE
COVERAGE AND INTENSITY OF THESE SHOWERS ARE EXPECTED TO DECREASE
SOMEWHAT DURING THE UPCOMING WEEKEND. WET AND UNSETTLED WEATHER
CONDITIONS MAY RETURN NEXT WEEK (AROUND WEDNESDAY).
SHORT TERM...TONIGHT THROUGH SATURDAY
CALM CONDITIONS PREVAILED OVER LAND ACROSS PUERTO RICO AND THE
U.S. VIRGIN ISLANDS DURING THE MORNING HOURS. HOWEVER, RAINFALL
AND THUNDERSTORM ACTIVITY DEVELOPED OVER THE CARIBBEAN, ATLANTIC
WATERS, AND NEAR THE COASTAL WATERS OF SAINT THOMAS, PROMPTING THE
ISSUANCE OF MARINE WEATHER STATEMENTS SINCE THE EARLY MORNING
HOURS. BY LATE MORNING INTO THE AFTERNOON, HEAVY SHOWERS AND
THUNDERSTORMS DEVELOPED ACROSS EASTERN AND NORTH-CENTRAL PUERTO
RICO, AS WELL AS THE CORDILLERA CENTRAL, WHERE CONSIDERABLE
RAINFALL WAS OBSERVED IN PAST DAYS. THESE REGIONS, PARTICULARLY
THE INTERIOR SECTIONS OF PUERTO RICO, REMAIN HIGHLY VULNERABLE TO
LANDSLIDES DUE TO SATURATED SOILS, ALONG WITH POTENTIAL WATER
SURGES, AS RIVERS CONTINUE TO RUN HIGH AND RESPOND RAPIDLY TO
ADDITIONAL RAINFALL. TEMPERATURES REMAINED IN THE 80S ACROSS
COASTAL AREAS AND THE 70S ACROSS MOUNTAINOUS REGIONS THROUGHOUT
THE DAY.
TONIGHT INTO EARLY FRIDAY, UNSTABLE WEATHER CONDITIONS WILL DOMINATE
THE U.S. VIRGIN ISLANDS AS FAVORABLE DYNAMICS AND A PREVAILING
TROUGH ENHANCE ATMOSPHERIC INSTABILITY. MODEL GUIDANCE SUGGESTS
UPPER- LEVEL JET SUPPORT WITH WINDS RANGING BETWEEN 60 AND 80
KNOTS. ALSO, SHOWERS ARE ANTICIPATED ACROSS EASTERN PUERTO RICO.
ON FRIDAY AND SATURDAY, SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS ARE FORECAST ACROSS PUERTO RICO AND THE U.S. VIRGIN
ISLANDS, ESPECIALLY DURING THE AFTERNOON AND EARLY EVENING HOURS.
A MOIST TROPICAL AIR MASS, COMBINED WITH UNSTABLE UPPER-LEVEL
CONDITIONS, WILL SUSTAIN AN ELEVATED RISK OF EXCESSIVE RAINFALL,
MAINLY ACROSS THE CENTRAL INTERIOR OF PUERTO RICO.
RESIDENTS AND VISITORS ARE URGED TO STAY ALERT AND TAKE NECESSARY
PRECAUTIONS TO PROTECT LIFE AND PROPERTY FROM POTENTIAL FLASH
FLOODING AND LANDSLIDES. CONTINUE TO MONITOR UPDATES FROM THE
NATIONAL WEATHER SERVICE, INCLUDING ANY CHANGES TO THE FLOOD WATCH
(FFASJU), WHICH MAY BE EXTENDED IF CONDITIONS WARRANT. REGARDLESS
OF THE WATCH STATUS, ACTIVE WEATHER IS EXPECTED EACH AFTERNOON.
FOR MORE DETAILED INFORMATION, REFER TO EXPERIMENTAL GRAPHICAL
HAZARDOUS WEATHER OUTLOOK.
LONG TERM...SUNDAY THROUGH THURSDAY
//FROM PREVIOUS DISCUSSION//
THE FORECAST FOR THE BEGINNING OF THE WEEK REMAINS ON TRACK. WINDS
SHOULD REMAIN FROM THE SOUTHEAST, DUE TO THE HIGH SURFACE PRESSURE
BUILDING IN THE WESTERN ATLANTIC AND THE DEEP LAYERED TROUGH
NORTHEAST OF THE CWA. BASED ON THE LATEST MODEL GUIDANCE, PWAT
VALUES WILL REMAIN ABOVE NORMAL (1.8 - 2.0 INCHES) DUE TO HIGH
LOW TO MID-LEVEL MOISTURE CONTENT. THE RIDGING IN THE MID TO HIGH
LEVELS IS STILL EXPECTED, FILTERING DRIER AIR. HOWEVER, THE 500 MB
TEMPERATURES SHOULD CONTINUE BETWEEN -7 AND -8 CELSIUS, COLDER
BASED ON CLIMATOLOGY. ADDITIONALLY, STRONG UPPER-LEVEL WINDS COULD
BRING VENTILATION ALOFT AND CONSEQUENTLY INCREASE INSTABILITY.
THE COMBINATION OF AVAILABLE MOISTURE, LOCAL EFFECTS, SLOWING
WINDS, AND DAYTIME HEATING WILL BRING LIGHT TO MODERATE SHOWERS
AND ISOLATED THUNDERSTORMS DURING THE AFTERNOON, MAINLY OVER
INTERIOR PUERTO RICO. A TRANSITION TO A MORE UNSETTLED AND WET
PATTERN BY THE SECOND PART OF THE WEEK IS STILL EXPECTED, WITH
ANOTHER DEEP MID TO UPPER LEVEL TROUGH APPROACHING THE LOCAL AREA
BY TUESDAY INTO WEDNESDAY. THE LATEST MODEL GUIDANCE SOLUTION SHOW
A DRIER AIR MASS FILTERING INTO THE REGION. HOWEVER, THE
AVAILABLE MOISTURE REMAINS ABOVE CLIMATOLOGICAL NORMALS. GLOBAL
MODELS STRONGLY SUGGEST WELL ABOVE NORMAL MOISTURE CONTENT POOLING
INTO THE REGION BEGINNING ON WEDNESDAY. ADDITIONALLY, EXTREME
FORECAST INDEXES (EFI) CONTINUE HIGHLIGHTING THE SIGNIFICANT
WEATHER CLOSER TO THE REGION DURING THAT PERIOD. THERE'S
CONFIDENCE THAT THE ABOVE NORMAL MOISTURE AND MID TO UPPER- LEVEL
DYNAMICS SHOULD BE ENOUGH TO ENHANCE DEEP AFTERNOON CONVECTION
FOR THE SECOND PART OF THE NEXT WORKWEEK.
DUE TO SATURATED SOILS, ABOVE NORMAL STREAMFLOWS, AND THE
EXPECTED WEATHER, THE FLOOD THREAT WILL REMAIN ELEVATED EACH DAY,
MAINLY FOR THE INTERIOR OF PUERTO RICO.
THE TENDENCY OF OBSERVING NEAR ABOVE-NORMAL TEMPERATURES IN THE
DAYTIME CONTINUES, BUT THE HEAT RISK WILL REMAIN LOW FOR THE LONG
TERM FORECAST.
AVIATION
(18Z TAFS)
MVFR TO BRIEFLY IFR CONDITIONS WILL PERSIST ACROSS MOST OF THE TAF
SITES MVFR UNTIL 01/23Z WITH TSRA RESULTING LOWER CEILINGS AND
REDUCTION IN VIS. MTN TOPS OBSCD AND BKN/OVC LYRS BTW FL040-200
EXPECTED TO CONTINUE. WINDS WILL REMAIN LIGHT FROM THE E-NE AT 10
KNOTS OR LESS WITH GUSTY WINDS NEAR SHRA, DIMINISHING EVEN MORE AT
01/23. WINDS WILL PEAK UP AGAIN AT 02/15Z. VCSH WILL REMAIN PRESENT
ACROSS THE USVI TAF SITES FROM 02/06Z TO 02/15Z.
MARINE
A SURFACE HIGH PRESSURE BUILDING IN THE WESTERN ATLANTIC AND A
DEEP LAYERED TROUGH NORTHEAST OF THE REGION WILL CONTINUE
PROMOTING LIGHT TO MODERATE EAST- NORTHEAST TO NORTHEAST WINDS FOR
THE NEXT FEW DAYS. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
DEVELOP ACROSS THE LOCAL WATERS, PRODUCING LOCALLY HIGHER WINDS
AND SEAS. SMALL CRAFT SHOULD EXERCISE CAUTION AND STAY WEATHER
ALERT.
BEACH FORECAST
THE MODERATE RISK OF RIP CURRENTS WILL CONTINUE FOR THE BEACHES IN
NORTHERN PUERTO RICO, CULEBRA, AND NOW FOR ST. THOMAS AND ST. JOHN
IN THE U.S. VIRGIN ISLANDS. BEACHGOERS MUST EXERCISE CAUTION DUE
TO POSSIBLE LIFE- THREATENING RIP CURRENTS ALONG THE SURF ZONE AND
STAY WEATHER ALERT.
THE RIP CURRENT RISK WILL BE LOW FOR THE LOCAL ISLANDS BY THE END
OF THE WEEKEND.
SJU WATCHES/WARNINGS/ADVISORIES
PR...FLOOD WATCH THROUGH FRIDAY MORNING FOR PRZ001>013.
VI...NONE.
AM...NONE.
SHORT TERM/MARINE/BEACH FORECAST...MMC
LONG TERM...MNG
AVIATION...LIS
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