599
FXCA62 TJSJ 040910
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
510 AM AST SUN MAY 4 2025
SYNOPSIS
A SIGNIFICANT FLOODING THREAT CONTINUES ACROSS PUERTO RICO DUE TO
THE EXCESSIVE RAINFALL ACTIVITY EXPECTED FOR TODAY IN COMBINATION
WITH THE OBSERVED ACTIVITY OVER THE PAST WEEK. THE FLASH FLOOD
WATCH HAS BEEN EXTENDED THROUGH THIS EVENING. STRONG THUNDERSTORMS
AND ADDITIONAL HEAVY RAINFALL ARE EXPECTED, ESPECIALLY DURING THE
AFTERNOON, RESULTING IN HAZARDOUS CONDITIONS FOR FLASH FLOODING,
LANDSLIDES, QUICK RIVER RISES, AND WATER SURGES. RESIDENTS AND
EMERGENCY MANAGEMENT PARTNERS ARE URGED TO REMAIN VIGILANT,
ESPECIALLY IN FLOOD-PRONE AND STEEP TERRAIN AREAS.
SHORT TERM...TODAY THROUGH TUESDAY
...A FLASH FLOOD WATCH REMAINS IN EFFECT FOR PUERTO RICO THROUGH
THIS EVENING...
LATE SATURDAY NIGHT, A LINE OF HEAVY RAIN IMPACTED THE NORTHERN
COASTLINE OF PR, BUT IT DISSIPATED BY MIDNIGHT. ON THE OTHER HAND, A
LINE OF THUNDERSTORMS MOVED OVER ST CROIX AFTER MIDNIGHT, PRODUCING
BETWEEN 1 AND 2 INCHES OF RAIN OVER PORTIONS OF THE VICINITY OF THE
ISLANDS. ADDITIONALLY, RIVER SENSORS ALONG THE RIO GUANAJIBO, RIO
LA PLATA, AND RIO GRANDE DE MANATI SURPASSED THE FLOODING STAGE
OVERNIGHT. HOWEVER, AT THE MOMENT OF THIS DISCUSSION, RIVERS HAVE
RETURNED BELOW THE FLOOD STAGE. WINDS ARE MAINLY FROM THE EAST TO
EAST-SOUTHEAST AT LESS THAN 10 MPH, BUT LOCALLY HIGHER NEAR
THUNDERSTORMS. MINIMUM TEMPERATURES ALONG THE INTERIOR HIGHER
PORTIONS OF PUERTO RICO ARE IN THE LOW 60S, WHILE ALONG THE US
VIRGIN ISLANDS ARE IN THE LOW 70S IN COTTON VALLEY, ST CROIX.
A SIGNIFICANT FLOODING THREAT PERSISTS ACROSS PUERTO RICO DUE TO THE
EXCESSIVE RAINFALL ACTIVITY OBSERVED OVER THE PAST WEEK. RADAR
ESTIMATED RAINFALL ACCUMULATIONS HAVE SURPASSED 15 INCHES IN SOME
AREAS, ESPECIALLY ALONG THE INTERIOR AND MOUNTAIN SECTIONS, WHERE
SOILS ARE SATURATED AND RIVER LEVELS ARE RUNNING HIGH. DUE TO THESE
PREEXISTING HAZARDOUS CONDITIONS, THE FLASH FLOOD WATCH HAS BEEN
EXTENDED THROUGH THIS EVENING, AS WE EXPECT ANOTHER ROUND WITH
WIDESPREAD RAIN ACTIVITY, ESPECIALLY ALONG AND TO THE NORTH OF
CORDILLERA CENTRAL AND LA SIERRA DE LUQUILLO. THE PRIMARY WEATHER
THREATS INCLUDE URBAN AND SMALL STREAM FLOODING, RIVER FLOODING,
FLASH FLOODING, MUDSLIDES, AND LANDSLIDES, PARTICULARLY IN
MOUNTAINOUS, STEEP TERRAINS. ADDITIONALLY, STRONG THUNDERSTORMS
CAPABLE OF PRODUCING STRONG WINDS, FREQUENT LIGHTNING, AND EVEN HAIL
ARE EXPECTED, ESPECIALLY DURING THE AFTERNOON. RESIDENTS AND
EMERGENCY MANAGEMENT PARTNERS ARE URGED TO REMAIN VIGILANT,
ESPECIALLY IN FLOOD-PRONE AND STEEP TERRAIN AREAS. CONTINUE TO
MONITOR OFFICIAL UPDATES AND BE PREPARED TO TAKE IMMEDIATE ACTION
SHOULD FLASH FLOOD OR FLOOD WARNINGS BE ISSUED.
THE TYPICAL MAY CONVECTIVE PATTERN WILL PREVAIL ON MONDAY AND
TUESDAY. DUE TO THE VULNERABLE PREEXISTING ENVIRONMENTAL CONDITIONS,
WE MIGHT CONTINUE TO SEE FLOODING AND LANDSLIDES OVER AREAS WHERE
THE AFTERNOON CONVECTION DEVELOPS. ALSO, AN EAST-NORTHEAST WIND FLOW
EXPECTED TO RETURN AROUND MONDAY AND TUESDAY, COMBINED WITH THE LAND
BREEZE, WILL PROMOTE LOW-LEVEL CONVERGENCE ALONG THE NORTHERN
SECTIONS OF PR AND NEAR THE US VIRGIN ISLANDS, WHERE WE MIGHT SEE
PERIODS OF MODERATE TO LOCALLY HEAVY RAIN IN THE EVENINGS, TOO.
LONG TERM...WEDNESDAY THROUGH SUNDAY
A LOW PRESSURE SYSTEM NORTH OF THE AREA WILL PROMOTE EAST TO
NORTHEASTERLY WINDS TROUGH THE FIRST HALF OF THE LONG TERM PERIOD.
HOWEVER, WINDS ARE EXPECTED TO SHIFT FROM THE SOUTHEAST AS THE
LOW PRESSURE MIGRATES WESTWARDS OVER THE ATLANTIC. THE LATEST
MODEL GUIDANCES HAVE BEEN CONSISTENT WITH PREVIOUS MODEL RUNS ON
THE ENTRANCE OF A RELATIVELY DRIER AIRMASS INTO THE REGION,
PROMOTING STABLE CONDITIONS OVER THE ISLANDS. THE PRECIPITABLE
WATER CONTENT (PWAT) WILL REMAIN WITHIN NORMAL CLIMATOLOGICAL
VALUES OF 1.6 TO 1.8 INCHES THROUGH MUCH OF THE FORECAST PERIOD.
NONETHELESS, AT THE 500 MB LEVEL THE TEMPERATURES WILL DROP INTO
-9 TO -10 DEGREES CELSIUS SUGGESTING THE POTENTIAL TO SUPPORT
CONVECTIVE ACTIVITY DURING THE AFTERNOON HOURS OVER THE ISLANDS.
UNDER THE AFOREMENTIONED PATTERN, TYPICAL SEASONAL WEATHER
CONDITIONS ARE ANTICIPATED WITH SUNNY TO PARTLY CLOUDY MORNINGS
ACROSS PUERTO RICO AND THE U.S. VIRGIN ISLANDS. THEN, FOLLOWED BY
AFTERNOON CONVECTIVE ACTIVITY OVER PORTIONS OF CENTRAL AND WESTERN
PUERTO RICO EACH AFTERNOON. WITH THE RAINFALL ACTIVITY FROM PREVIOUS
DAYS/WEEKS, IT IS IMPORTANT TO REMEMBER TO STAY WEATHER ALERT DUE TO
ABOVE-NORMAL STREAMFLOWS AND SATURATED SOILS THAT MAY RESULT IN
LOCALIZED FLOODING ACROSS PORTIONS OF PUERTO RICO. THE 925 MB
TEMPERATURES WILL REMAIN AT NORMAL OR BELOW-NORMAL VALUES DURING THE
WEEK. HIGHS ARE ANTICIPATED IN THE LOW TO MID 80S ACROSS THE
COASTAL AND URBAN AREAS, AND IN THE MID TO UPPER 70S.
AVIATION
(06Z TAFS)
SHRA/TSRA CONTINUES TO AFFECT THE LOCAL FLYING AREA, THIS WILL
LEAD TO PERIODS OF MVFR OR IFR CONDS. AFTERNOON CONVECTION WILL
DEVELOP FROM 4/15 TO 4/22Z. PERIODS WITH SHRA/TSRA WILL IMPACT THE
EASTERN SECTIONS OF PR AND THE USVI, WHERE MVFR OR EVEN IFR CONDS
CAN BE EXPECTED IF THE ACTIVITY AFFECTS THE LOCAL TERMINAL. WINDS
WILL GENERALLY BE CALM TO LIGHT AND VRB THRU AT LEAST 4/13Z, WHEN
THEY WILL RETURN FROM THE E-ESE AT AROUND 10 KT, WITH SEA
BREEZES, BECOMING CALM TO LIGHT AND VARIABLE AFT 4/23Z ONCE AGAIN.
MARINE
A SURFACE HIGH PRESSURE BUILDING ACROSS THE WESTERN ATLANTIC AND A
DEEP LAYERED TROUGH NORTHEAST OF THE REGION WILL PROMOTE LIGHT TO
MODERATE EAST TO NORTHEAST WINDS FOR THE NEXT FEW DAYS. SHOWERS AND
THUNDERSTORMS WILL CONTINUE TO DEVELOP ACROSS THE LOCAL WATERS TODAY,
PRODUCING LOCALLY HIGHER WINDS AND SEAS.
BEACH FORECAST
THERE IS A MODERATE RISK OF RIP CURRENTS FOR THE BEACHES OF PUERTO
RICO FROM AGUADILLA TO FAJARDO. BEACHGOERS MUST EXERCISE CAUTION
DUE TO POSSIBLE LIFE- THREATENING RIP CURRENTS ALONG THE SURF ZONE
AND STAY WEATHER ALERT. THE RIP CURRENT RISK IS STILL EXPECTED TO
GRADUALLY DECREASE BY EARLY THIS WEEK.
SJU WATCHES/WARNINGS/ADVISORIES
PR...FLOOD WATCH THROUGH THIS EVENING FOR PRZ001>013.
VI...NONE.
AM...NONE.
SHORT TERM...CAM
LONG TERM....GRS
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