452
FXCA62 TJSJ 020758
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
358 AM AST THU JAN 2 2025
SYNOPSIS
THE CITIZENS AND VISITORS OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS SHOULD EXPERIENCE LIMITED SHOWER ACTIVITY AND PLEASANT
TEMPERATURES FOR THE NEXT FEW DAYS. BY NEXT WEEKEND,CONDITIONS
WILL BECOME MORE WET AND UNSTABLE WITH THE POTENTIAL APPROACH OF
ANOTHER COLD FRONT WITH A PRE- FRONTAL TROUGH NEAR THE REGION.
MARINE AND COASTAL CONDITIONS ARE EXPECTED TO DETERIORATE BY LATE
FRIDAY AND EARLY NEXT WEEK DUE TO THE ARRIVAL OF ANOTHER LONG-
PERIOD NORTHEASTERLY SWELL.
SHORT TERM...TODAY THROUGH SATURDAY
OVERNIGHT, A SLOT OF DRY AIR LIMITED RAIN ACTIVITY TO THE
SURROUNDING WATERS, AND PR AND THE USVI OBSERVED PLEASANT
TEMPERATURES WITH CLEAR SKIES. THE WINDS WERE FROM THE NORTHEAST,
AND LOW TEMPERATURES WERE IN THE LOW 70S ALONG THE COAST TO THE LOW
60S OR EVEN THE 50S ACROSS MOUNTAINS AND VALLEYS.
A SURFACE HIGH PRESSURE NORTH OF THE ISLANDS MOVING INTO THE CENTRAL
ATLANTIC WILL PROMOTE A NORTHEASTERLY WIND FLOW THROUGH AT LEAST
FRIDAY. THE WIND FLOW WILL MAINTAIN PLEASANT TEMPERATURE ACROSS PR
AND THE USVI, WITH THE ARRIVAL OF POCKETS OF MOISTURE AT TIMES. THIS
MOISTURE EMBEDDED IN THE TRADES WILL RESULT IN OCCASIONAL QUICK
PASSING SHOWERS, MAINLY ACROSS THE WINDWARD LOCATIONS. THE INTERIOR
AND WESTERN SECTIONS OF PR WILL SEE SOME SHOWERS IN THE AFTERNOON,
ESPECIALLY TODAY. ON FRIDAY, MOISTURE BELOW NORMAL WILL LIMIT RAIN
ACTIVITY, LEAVING A MIX OF CLOUDS AND SUNSHINE OR CLEAR SKIES.
A COLD FRONT BEHIND THE SURFACE HIGH PRESSURE WILL APPROACH THE
NORTHEAST CARIBBEAN AROUND SATURDAY AFTERNOON, INDUCING A PRE-
FRONTAL TROUGH AND POOLING ABOVE-NORMAL MOISTURE OVER PR AND THE
USVI. GFS SUGGESTS STEEP LAPSE RATE AT LOW-LEVELS, WHICH, COMBINED
WITH LOCAL EFFECTS, COULD PROMOTE WIDESPREAD RAINS. UNDER THIS
WEATHER PATTERN, WE CAN ANTICIPATE A MIGRATION TO A WET AND
UNSETTLED PATTERN WITH SCATTERED TO WIDESPREAD SHOWERS AND A SLIGHT
CHANCE OF ISOLATED TO SCATTERED THUNDERSTORMS, ESPECIALLY FROM
SATURDAY AFTERNOON INTO SUNDAY. URBAN AND SMALL STREAM FLOODING
CAN BE OBSERVED WITH THE MOST INTENSE RAIN ACTIVITY.
LONG TERM...SUNDAY THROUGH THURSDAY
AT THIS TIME, BOTH THE GLOBAL FORECAST SYSTEM (GFS) AND EUROPEAN
CENTRE FOR MEDIUM-RANGE WEATHER FORECASTS (ECMWF) MODELS AGREE ON A
COLD FRONT MOVING ACROSS THE NORTHEASTERN CARIBBEAN INDUCING A PRE-
FRONTAL TROUGH NEAR PUERTO RICO AND THE U.S. VIRGIN ISLANDS,
PARTICULARLY ON SUNDAY. THE LATEST GUIDANCE SUGGEST PRECIPITABLE
WATER VALUES ABOVE THE 75TH PERCENTILE OR ABOVE NORMAL VALUES FOR
THIS TIME OF THE YEAR, WITH VALUES RANGING AROUND 1.5 TO 2.0
INCHES. ALSO, THE GALVEZ-DAVISON INDEX (GDI)SUGGEST THUNDERSTORM
ACTIVITY ACROSS THE ISLANDS THROUGH SUNDAY AFTERNOON. THE SURFACE
MOISTURE IS FORECAST TO LIFT AND REACH THE 500 TO 700 MB THROUGH
THE BEGINNING OF THE WORKWEEK. THIS INCREASE IN PRECIPITABLE WATER
VALUES AND INSTABILITY LEANS TOWARDS HAVING AN ACTIVE WEATHER DAY
WITH AN INCREASE IN SHOWER ACTIVITY AND A SLIGHT TO MODERATE
CHANCE FOR ISOLATED TO SCATTERED THUNDERSTORMS BY THE END OF THE
WEEKEND, POSSIBLY EXTENDING TOWARDS THE BEGINNING OF THE
WORKWEEK. THEREFORE, URBAN AND SMALL STREAM FLOODING CAN BE SEEN
WITH THE HEAVIEST RAINFALL ACTIVITY.
WEATHER CONDITIONS SHOULD SLIGHTLY IMPROVE BY TUESDAY INTO
WEDNESDAY WITH COOLER TEMPERATURES AND SOMEWHAT DRIER AIR.
HOWEVER, THE WET PATTERN WILL RETURN BY THURSDAY WHEN ANOTHER COLD
FRONT APPROACHES THE REGION.
AVIATION
(06Z TAF)
VFR CONDS WILL PREVAIL TODAY UNDER A NORTHEAST WIND FLOW. EXPECT
CALM TO LIGHT AND VRB WINDS THRU 02/13Z, THEN WINDS WILL RANGE
BETWEEN 10-15 KT WITH HIGHER GUSTS AND SEA BREEZES. A PATCH OF
CLOUDS WILL BRING SHRA/-SHRA ACROSS JSJ/IST/ISX BTWN 02/10-18Z, AND
WE CANNOT RULE OUT BRIEF PERIODS OF MVFR CONDS. SHRA WILL DEVELOP
INTO PR'S INTERIOR AND SOUTHWEST SECTIONS BTWN 02/15-22Z, WHICH
COULD IMPACT THE JPS'S VICINITY.
MARINE
MODERATE NORTHEASTERLY WINDS WILL CONTINUE TO PREVAIL THIS WEEK
UNDER THE INFLUENCE OF A SURFACE HIGH PRESSURE MOVING INTO THE
CENTRAL ATLANTIC AND SURFACE LOW OVER THE EASTERN ATLANTIC. ANOTHER
FRONT FROM THE EASTERN US COAST WILL APPROACH THE NORTHEAST CARIBBEAN
BY THE WEEKEND. ANOTHER LONG PERIOD NORTHERLY SWELL WILL PROMOTE
HAZARDOUS SEAS BY THE END OF THIS WEEK THROUGH THE WEEKEND.
BEACH FORECAST
PULSES OF A FADING NORTHEASTERLY SWELL, MOVING ACROSS THE ATLANTIC
WATERS AND CARIBBEAN PASSAGES, WILL PROMOTE A MODERATE RISK OF RIP
CURRENTS ALONG THE NORTH AND EAST-FACING BEACHES OF PR/USVI,
INCLUDING CULEBRA. MEANWHILE, THE SOUTHERN PROTECTED BEACHES OF PR
REMAIN UNDER A LOW RISK OF RIP CURRENTS.
COASTAL CONDITIONS WILL DETERIORATE AGAIN BY FRIDAY NIGHT THROUGH
THE WEEKEND WITH THE ARRIVAL OF ANOTHER LONG-PERIOD NORTHERLY
SWELL.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...CAM
LONG TERM/BEACH FORECAST/MARINE...MMC
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