194
FXCA62 TJSJ 052051
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
451 PM AST WED MAR 5 2025
SYNOPSIS
AN UNSTABLE WEATHER PATTERN IS EXPECTED TO CONTINUE THROUGH THE
END OF THE WORKWEEK, AS INSTABILITY AND MOISTURE PERSIST OVER THE
REGION. THE MORNINGS WILL BE VARIABLE, FOLLOWED BY AFTERNOON
CONVECTION DEVELOPING ALONG THE MOUNTAINSIDES AND IN THE
NORTHWESTERN QUADRANT. THERE IS AN ELEVATED THREAT OF URBAN
FLOODING, PARTICULARLY IN AREAS THAT HAVE EXPERIENCED RECENT
RAINFALL. A NORTHWESTERLY SWELL IS EXPECTED TO ARRIVE THIS
WEEKEND, LIKELY CREATING HAZARDOUS MARINE CONDITIONS ACROSS THE
ATLANTIC WATERS AND NORTHERN LOCAL PASSAGES.
SHORT TERM...TONIGHT THROUGH FRIDAY
VARIABLY CLOUDY SKIES PREVAILED ACROSS ALL THE ISLANDS THIS
AFTERNOON. SCATTERED TO LOCALLY NUMEROUS SHOWERS DEVELOPED JUST
BEFORE NOON ALONG PORTIONS OF THE CORDILLERA AND WESTERN PUERTO
RICO, AND ACROSS THE U.S. VIRGIN ISLANDS. RAINFALL ACCUMULATIONS
WERE BETWEEN 1.0 TO 3.5 INCHES AS OF 4:30 PM AST WITH THE HEAVIEST
SHOWERS OVER SAN SEBASTIAN, LARES, UTUADO, JAYUYA, CIALES, OROCOVIS,
AND BARRANQUITAS. MAXIMUM TEMPERATURES WERE FROM THE MID 80S TO
90 DEGREES ACROSS THE LOWER ELEVATIONS, TO THE UPPER 70S AND MID
80S ACROSS THE HIGHER ELEVATIONS. WINDS WERE FROM THE EAST BETWEEN
8 AND 12 MPH WITH SEA BREEZE VARIATIONS.
THE MID-TO UPPER-LEVEL TROUGH WILL CONTINUE TO MOVE EASTWARD AND
AWAY OF THE REGION FROM THIS EVENING ONWARDS, WHILE A RIDGE BUILDS
FROM THE WEST. CONDITIONS ALOFT WILL NO LONGER FAVOR THE FORMATION
OF THUNDERSTORMS. HOWEVER, SUFFICIENT SURFACE MOISTURE WILL BRING
ADDITIONAL SHOWERS ACROSS EASTERN PUERTO RICO AND THE U.S. VIRGIN
ISLANDS DURING THE NIGHT AND EARLY MORNING HOURS ON THURSDAY AND
FRIDAY. IN ADDITION, A FRONTAL BOUNDARY NORTHWEST OF PUERTO RICO
WILL APPROACH THE NORTHEASTERN CARIBBEAN. AS IT NEARS, WINDS WILL
SHIFT MORE SOUTHERLY ON THURSDAY, WHILE WIND SPEEDS WILL PLUMMET AS
A COL SETTLES JUST NORTH OF PUERTO RICO. A WEAK SEA BREEZE AND
SOUTHERLY STEERING WINDS WILL CAUSE AFTERNOON SHOWERS TO DEVELOP
MAINLY OVER CENTRAL PR, WHILE SLOWLY DRIFTING NORTHWARDS ON
THURSDAY. ANOTHER UPPER-LEVEL TROUGH AND THE SURFACE FRONT MOVING
FURTHER EASTWARD WILL CAUSE LOW-LEVEL WINDS TO ACQUIRE A
NORTHEASTERLY COMPONENT AND THE AFTERNOON FRIDAY CONVECTION SHOULD
FAVOR THE CORDILLERA AND SOUTHERN SECTIONS OF PR.
AS A RESULT, EXPECT A LIMITED TO ELEVATED FLOODING RISK EACH
AFTERNOON, MOSTLY ACROSS THE INTERIOR OF PUERTO RICO, POTENTIALLY
LEADING TO URBAN AND SMALL-STREAM FLOODING. QUICK RIVER RISES AND
WATER SURGES ARE ALSO ANTICIPATED IN SOME RIVERS.
LONG TERM...SATURDAY THROUGH WEDNESDAY
PREV DISCUSSION
/ISSUED 414 AM AST WED MAR 5 2025
MID-TO UPPER-LEVEL ATMOSPHERIC STABILITY WILL REMAIN IN PLACE
FROM SATURDAY THROUGH WEDNESDAY AS A MID-LEVEL RIDGE BUILDS OVER
THE WESTERN ATLANTIC, EXTENDING INTO THE CARIBBEAN. THIS FEATURE
WILL SUPPORT WARMER-THAN-NORMAL 500 MB TEMPERATURES, SUPPRESSING
DEEP CONVECTIVE DEVELOPMENT ACROSS THE REGION.
A BROAD SURFACE PRESSURE SYSTEM WILL DOMINATE THE REGION THROUGH THE
WEEKEND, MAINTAINING A NORTHEASTERLY WIND FLOW UNTIL SUNDAY MORNING.
UNDER THIS WIND FLOW, MOSTLY SHALLOW PATCHES OF MOISTURE WITH
PRECIPITABLE WATER (PWAT) VALUES BELOW CLIMATOLOGICAL NORMALS
WILL PERSIST. HOWEVER, SURFACE HEATING AND LOCAL EFFECTS WILL
CONTRIBUTE TO SHOWER DEVELOPMENT SHIFTING TOWARD THE SOUTHWESTERN
QUADRANT OF PUERTO RICO. BY LATE SUNDAY, WINDS WILL GRADUALLY
SHIFT FROM THE EAST-SOUTHEAST AS A SURFACE HIGH PRESSURE MOVES
WESTWARD INTO THE CENTRAL ATLANTIC. ACCORDING TO THE MODEL GLOBAL
GUIDANCE, PRECIPITABLE WATER VALUES WOULD REMAIN NEAR OR JUST
BELOW NORMAL. AS A RESULT, SHOWER ACTIVITY WILL FOLLOW A SEASONAL
PATTERN, WITH ISOLATED TO SCATTERED SHOWERS MOVING ACROSS WINDWARD
COASTAL AREAS DURING THE NIGHT AND EARLY MORNING HOURS, FOLLOWED
BY LOCALIZED SHALLOW CONVECTION DEVELOPING ACROSS WESTERN AND SOME
INTERIOR SECTIONS OF PUERTO RICO IN THE AFTERNOONS. GIVEN THE
STABLE CONDITIONS AND LIMITED MOISTURE AVAILABILITY, SIGNIFICANT
RAINFALL ACCUMULATIONS OR WIDESPREAD FLOODING CONCERNS ARE NOT
ANTICIPATED.
BY EARLY NEXT WORKWEEK, DRIER AIR WILL GRADUALLY FILTER INTO THE
REGION. TUESDAY AND WEDNESDAY ARE EXPECTED TO BE THE DRIEST DAYS
UNDER THE INFLUENCE OF THE MID-LEVEL RIDGE AND LIMITED MOISTURE
AVAILABILITY. OVERALL, A QUIET WEATHER PATTERN IS EXPECTED THROUGH
THE LONG-TERM PERIOD, WITH LIMITED SHOWER ACTIVITY AND STABLE
ATMOSPHERIC CONDITIONS DOMINATING THE LOCAL FORECAST.
AVIATION
(18Z TAFS)
SHRA/TSRA EXPECTED OVER THE INTERIOR AND WESTERN PR, AND DOWNWIND
FROM EL YUNQUE THRU 05/23Z. THIS MAY LEAD TO TEMPO MVFR CONDS AT
TJSJ/TJBQ. ACROSS THE USVI, STREAMERS WILL CONTINUE TO PRODUCE -SHRA
AND TEMPO MVFR CIGS THRU AT LEAST 05/22Z. THE 05/12Z TJSJ SOUNDING
INDICATED EAST WINDS UP TO 12 KT BLO FL100.
MARINE
A FADING NORTHERLY SWELL WILL CONTINUE TO SPREAD ACROSS THE
ATLANTIC WATERS THROUGH AT LEAST TONIGHT. A FRONTAL BOUNDARY
APPROACHING FROM THE WESTERN ATLANTIC WILL GRADUALLY WEAKEN THE
PRESSURE GRADIENT ASSOCIATED WITH THE BROAD SURFACE HIGH PRESSURE
EXTENDING FROM THE EASTERN TO CENTRAL ATLANTIC, LEAVING MOSTLY LIGHT
TO MODERATE EASTERLY WINDS. AN UPPER-LEVEL TROUGH AND THE ASSOCIATED
INSTABILITY WILL CONTINUE TO RESULT IN SHOWERS AND SOME ISOLATED
THUNDERSTORMS OVER THE REGIONAL WATERS TONIGHT. ADDITIONALLY, A LONG-
PERIOD NORTHWESTERLY SWELL IS EXPECTED TO ARRIVE THIS WEEKEND,
LIKELY CREATING HAZARDOUS MARINE CONDITIONS ACROSS THE ATLANTIC
WATERS AND NORTHERN LOCAL PASSAGES.
BEACH FORECAST
THE HIGH RIP CURRENT RISK REMAINS IN EFFECT THROUGH AT LEAST LATE
TONIGHT FOR THE NORTHERN BEACHES OF PUERTO RICO, FROM FAJARDO TO
AGUADILLA DUE TO A FADING NORTHERLY SWELL SPREADING ACROSS THE
ATLANTIC WATERS. RESIDENTS AND VISITORS IN THESE AREAS ARE
ENCOURAGED TO TAKE THE NECESSARY PRECAUTIONS AND MONITOR THE
FORECAST FOR ANY UPDATES.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH LATE TONIGHT FOR PRZ001-002-005-
008.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...DS/LIS
LONG TERM...LIS
PUBLIC/MARINE/BEACH FORECAST...YZR
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