273
FXCA62 TJSJ 300901
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
501 AM AST WED APR 30 2025
SYNOPSIS
THE WET AND UNSTABLE WEATHER PATTERN WILL CONTINUE THROUGH AT LEAST
THURSDAY EVENING DUE TO A SERIES OF TROUGHS AND ABUNDANT MOISTURE.
SOIL SATURATION AND SOARING RIVERS WILL PROMOTE AN ELEVATED TO
SIGNIFICANT FLOODING THREAT, INCLUDING MINOR FLOODING, FLASH
FLOODING, RIVER FLOODING, AND LANDSLIDES IN STEEP TERRAIN. ALTHOUGH
AN IMPROVEMENT OF WEATHER CONDITIONS IS ANTICIPATED BY THIS
WEEKEND, ABUNDANT MOISTURE WILL TRIGGER SHOWERS AND THUNDERSTORMS
IN THE AFTERNOON.
SHORT TERM...TODAY THROUGH FRIDAY
SHOWERS WILL CONTINUE TO INCREASE THIS MORNING ACROSS THE U.S.
VIRGIN ISLANDS AND EASTERN PUERTO RICO THROUGH THE REST OF THE
MORNING HOURS. PONDING OF WATER ON ROADS AND IN POOR DRAINAGE AREAS
IS EXPECTED WITH THIS SHOWER ACTIVITY. SOME SHOWERS COULD GROW INTO
THUNDERSTORMS BEFORE NOON ACROSS THE MOUNTAIN RANGES OF PR AND LAST
THROUGH THE EVENING HOURS. DUE TO ALREADY SATURATED SOILS AND ABOVE
NORMAL STREAMFLOWS FROM PREVIOUS DAYS HEAVY RAINFALL, QUICK RIVER
RISES, MUDSLIDES, AND FLASH FLOODING IS LIKELY WITH THESE
THUNDERSTORMS.
THE WET WEATHER PATTERN WILL CONTINUE THROUGH THE REST OF THE SHORT-
TERM PERIOD AS ABUNDANT MOISTURE CONTENT(PWAT ABOVE 2.00 INCHES)
LINGERS OVER THE REGION. LATER TODAY, A CUT OFF LOW IS EXPECTED TO
DEVELOP JUST NORTHEAST OF THE LEEWARD ISLANDS FROM A MID-TO UPPER
LEVEL TROUGH OVER THE CENTRAL ATLANTIC. GLOBAL GUIDANCE SUGGEST THAT
ANOTHER BUT WEAK LOW REFLECTED AT THE MID-LEVELS WILL DEVELOP NEAR
CUBA AND HISPANIOLA ON THURSDAY. THESE FEATURES WILL FURTHER ENHANCE
INSTABILITY ACROSS THE NORTHEASTERN CARIBBEAN WITH COLDER THAN
NORMAL 500 MB TEMPERATURES AROUND -9C, AND AS THEY SLOWLY DRIFT
EASTWARD A 75-80 KT JET SEGMENT WILL MEANDER OVER THE ISLANDS
THROUGH FRIDAY. THEREFORE, THUNDERSTORMS OVER THE NEXT FEW DAYS
COULD PRODUCE FREQUENT LIGHTNING, SMALL HAIL, AND STRONG GUSTY WINDS
AS WELL AS FURTHER SUPPORTING LONG LASTING RAINFALL ACTIVITY OVER
THE ISLANDS. RESIDENTS AND VISITORS ARE URGE TO MONITOR THE WEATHER
CONDITIONS AND REMAIN VIGILANT TO TAKE NECESSARY ACTION TO PROTECT
LIFE AND PROPERTY FROM THE EXPECTED FLOODING IMPACTS.
FOR MORE INFORMATION PLEASE REFER TO THE LATEST UPDATES FROM THE
HYDROLOGIC OUTLOOK(ESFSJU).
HTTPS://FORECAST.WEATHER.GOV/WWAMAP/WWATXTGET.PHP?CWA=SJU&WWA
=HYDROLOGIC%20OUTLOOK
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
(06Z TAFS)
MAINLY VFR EARLY IN THE FCST PERIOD. HOWEVER, SHRA INCREASING FROM
THE ATLANTIC AND EASTERN WATERS OF THE ISLANDS WILL MOVE AT TIMES
ACROSS THE USVI/EASTERN PR TERMINALS THRU THE MORNING HOURS. THIS
CAN LEAD TO BRIEF MVFR CIGS. SHRA/TSRA WILL DEVELOP BTW 30/15Z-23Z
OVER THE MOUNTAINS AND DRIFT MAINLY SOUTHWARD UNDER 8-14 KT ENE
WINDS. THEREFORE, EXPECT MTN TOPS OBSCD ACROSS PR AND TEMPO MVFR TO
IFR CONDS MAINLY AT TJPS. ELSEWHERE, -RA/VCTS EXPECTED THRU THE
EVENING HOURS.
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...NONE.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...DS
LONG TERM/MARINE...MNG
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