688
FXCA62 TJSJ 301826
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
226 PM AST WED APR 30 2025
SYNOPSIS
UNSETTLED WEATHER IS EXPECTED OVER THE NEXT SEVERAL DAYS DUE TO A
COMBINATION OF ABUNDANT TROPICAL MOISTURE AND A SERIES OF UPPER-
LEVEL TROUGHS. ACCORDING TO THE LATEST FORECASTS, WIDESPREAD
SHOWERS AND THUNDERSTORMS ARE ANTICIPATED TODAY AND THURSDAY, FOR
WHICH A FLOOD WATCH IS IN EFFECT FOR PR. THE COVERAGE AND
INTENSITY OF THESE SHOWERS ARE EXPECTED TO DECREASE SOMEWHAT
DURING THE UPCOMING WEEKEND. THE MODEL GUIDANCE SUGGESTS ANOTHER
PERIOD WITH VERY WET AND UNSTABLE WEATHER CONDITIONS FOR THE
MIDDLE OF NEXT WEEK (AROUND WEDNESDAY).
SHORT TERM
THE MAXIMUM TEMPERATURES OBSERVED RANGED IN THE LOW 90S NEAR ST
CROIX AND SOUTHWEST PR TO THE MID TO UPPER 80S ACROSS URBAN
SECTIONS NEAR LOWER ELEVATIONS AND THE LOW 80S IN THE MOUNTAINS.
WINDS ARE NOW FROM THE NORTHEAST TO EAST-NORTHEAST AT 10 MPH OR
LESS, WITH THE INFLUENCE OF THE SEA BREEZE BUT GUSTY NEAR SHOWERS
AND THUNDERSTORMS. SHOWERS BEGAN TO IMPACT THE USVI AROUND MIDDAY,
PRODUCING PONDING OF WATER IN ROADS AND POORLY DRAINED AREAS, AS
WELL AS ACROSS THE ISLANDS OF VIEQUES AND CULEBRA, SOME MOUNTAIN
AREAS OF PR (IN THE NORTHEAST AND FROM THE SOUTHWEST TO SOUTH).
ACTIVITY WILL AGGRAVATE LATER THIS AFTERNOON INTO THIS EVENING AS
OTHER ROUNDS OF THUNDERSTORMS DEVELOP. GIVEN THE SATURATION OF
SOILS AND THE SOARING RIVERS, THE THREAT OF FLOODING THE REST OF
TODAY AND THROUGH MUCH OF THE FORECAST PERIOD IS SIGNIFICANT.
ADDITIONALLY, THERE IS A MODERATE TO HIGH CHANCE OF OBSERVING
SUDDEN LANDSLIDES, ESPECIALLY ALONG STEEP TERRAINS UNDER PROLONGED
PERIODS OF RAIN.
AS WE MENTIONED IN THE FLOOD WATCH, ATMOSPHERIC CONDITIONS FAVOR
OBSERVING RAINFALL AMOUNTS BETWEEN 2 AND 4 INCHES, ESPECIALLY
ACROSS MOUNTAIN AREAS EACH DAY (THE REST OF TODAY AND THURSDAY),
WITH ISOLATED HIGHER AMOUNTS. ELSEWHERE, EXPECT BETWEEN 1 AND 2
INCHES. AS A RESULT, THE THREAT OF FLOODING WILL BE SIGNIFICANT
THROUGH AT LEAST EARLY FRIDAY MORNING. ALTHOUGH INSTABILITY WILL
SLOWLY DIMINISH, THE TYPICAL MAY CONVECTIVE ACTIVITY WILL IMPACT
THE ALREADY VULNERABLE PORTIONS.
LONG TERM...SATURDAY THROUGH WEDNESDAY
THE LONG-TERM FORECAST SUFFERED SOME CHANGES. WINDS ON SATURDAY
WILL REMAIN FROM THE NORTHEAST, AND WILL SHIFT FROM THE SOUTHEAST
DUE TO A SURFACE HIGH PRESSURE BUILDING IN THE WESTERN ATLANTIC
AND THE INDUCED LOW IN THE CENTRAL ATLANTIC MOVING SOUTHWARD. THE
LATEST MODEL ENSEMBLE MEMBERS ARE SHIFTING TO A WETTER SCENARIO
THIS WEEKEND, WITH PWAT VALUES ABOVE CLIMATOLOGICAL NORMAL (1.8 -
2.0 INCHES). THE 500 MB TEMPERATURES SHOULD REMAIN COLDER (-7 TO
-8 CELSIUS), AND THE LATEST MODEL GUIDANCE KEEPS SUGGESTING THAT
THE UPPER DYNAMICS WILL REMAIN STRONGER WITH WINDS IN THE 250 MB
LAYER AROUND 70 KNOTS, PROVIDING VENTILATION ALOFT. ADDITIONALLY,
THE GALVEZ-DAVISON INDEX (GDI) ALSO DISPLAYS THE POTENTIAL OF
ISOLATED THUNDERSTORMS MAINLY IN THE AFTERNOONS. ALTHOUGH MODEL
GUIDANCE KEEPS SUGGESTING DRIER AIR FILTERING IN THE UPPER LEVELS
DUE TO RIDGING, ABOVE-NORMAL LOW TO MID-LEVEL MOISTURE CONTENT IN
THE REGION WILL TRIGGER SHOWER AND THUNDERSTORM ACTIVITY IN THE
AFTERNOONS ALONG INTERIOR PUERTO RICO, MOVING INTO NORTHERN/WESTERN
PUERTO RICO IN THE EARLY EVENINGS. DUE TO THE HEAVY RAINFALL,
SATURATED SOILS, AND SOARING RIVERS, THE RISK OF FLOODING WILL
REMAIN LIMITED, WITH MOSTLY PONDING OF WATER IN ROADWAYS, URBAN,
AND POORLY DRAINED AREAS, ALONG URBAN AND SMALL STREAM FLOODING.
ANOTHER MID TO UPPER-LEVEL TROUGH SHOULD MOVE NORTH OF THE
CARIBBEAN, AND INDUCE A SURFACE LOW. THE INTERACTION OF THIS LOW AND
A SURFACE HIGH PRESSURE IN THE CENTRAL ATLANTIC COULD PROMOTE
SOUTHERLY WINDS THROUGHOUT THE PERIOD. WITH THIS PATTERN, WINDS
MAY POOL WELL ABOVE-NORMAL MOISTURE CONTENT INTO THE REGION BY
LATE TUESDAY, WITH PWAT VALUES AROUND 2.0 - 2.2 INCHES FOR THE
REST OF THE FORECAST PERIOD. THE BEST MOISTURE CONTENT MIGHT STAY
IN THE EAST SIDE OF THE CWA, IMPACTING EASTERN SECTIONS OF PUERTO
RICO, VIEQUES, CULEBRA, AND THE U.S. VIRGIN ISLANDS. HOWEVER,
DEEPER AFTERNOON CONVECTION SHOULD DEVELOP OVER INTERIOR PUERTO
RICO, ELEVATING ONCE AGAIN THE FLOODING POTENTIAL.
WITH THE SOUTHERLY COMPONENT IN THE WINDS AND ABUNDANT MOISTURE,
IS LIKELY TO OBSERVE NEAR ABOVE-NORMAL TEMPERATURES DURING THIS
PERIOD. HOWEVER, THE HEAT RISK WILL REMAIN LOW FOR THE REST OF THE
FORECAST PERIOD.
AVIATION
(18Z) TAFS
SHRA/TSRA WILL CONTINUE TO AFFECT THE LOCAL FLYING AREA
THROUGHOUT THE FCST PRD. THIS ACTIVITY WILL LEAD TO PERIODS OF
MVFR OR IFR CONDITIONS THROUGH THIS EVENING. ANOTHER PERIOD WITH
SHRA/TSRA WILL IMPACT THE EASTERN SECTIONS DURING THE OVERNIGHT
HOURS, WHERE MVFR OR EVEN IFR CONDS CAN BE EXPECTED IF THE
ACTIVITY AFFECTS THE LOCAL TERMINAL. WINDS WILL GENERALLY BE
AROUND 12 KT, PRIMARILY FROM THE ENE/NE, WITH VARIATIONS DUE TO
SEA BREEZES. AFTER 30/23, WINDS WILL BECOME CALM TO LIGHT AND
VARIABLE, THEN RETURN FROM THE NE AT ABOUT 10 KNOTS AFTER 01/13Z,
ALSO INFLUENCED BY SEA BREEZES.
MARINE
A SURFACE HIGH PRESSURE BUILDING IN THE WESTERN ATLANTIC AND A
DEEP LAYERED TROUGH WILL PROMOTE 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
NO SIGNIFICANT SWELL EVENTS IS ANTICIPATED FOR THE NEXT FEW DAYS.
HOWEVER, THE MODERATE RISK OF RIP CURRENTS WILL CONTINUE FOR THE
BEACHES IN NORTHERN PUERTO RICO, AND POSSIBLY FOR CULEBRA AND THE
NORTHERN USVI BY TOMORROW INTO THE WEEKEND.
SJU WATCHES/WARNINGS/ADVISORIES
PR...FLOOD WATCH THROUGH FRIDAY MORNING FOR PRZ001>013.
VI...NONE.
AM...NONE.
SHORT TERM...CAM
LONG TERM....GRS
AVIATION...ERG
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page