538
FXCA62 TJSJ 032054
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
454 PM AST FRI JAN 3 2025
KEY MESSAGES
* FAIR WEATHER CONDITIONS ARE EXPECTED TO CONTINUE TONIGHT.
* SHOWER ACTIVITY IS LIKELY TO INCREASE TOMORROW INTO SUNDAY, WITH
ISOLATED THUNDERSTORMS POSSIBLE, POTENTIALLY LEADING TO LOCALIZED
FLOODING IMPACTS.
* NORTHERLY SWELLS AND STRENGTHENING NORTHEASTERLY WINDS WILL CREATE
CHOPPY TO HAZARDOUS SEAS FOR SMALL CRAFT OVER THE WEEKEND.
* A HIGH RISK OF LIFE-THREATENING RIP CURRENTS IS IN EFFECT THROUGH
AT LEAST EARLY NEXT WEEK.
SHORT TERM...TONIGHT THROUGH SUNDAY
A NICE DAY WITH CALM WEATHER CONDITIONS WAS OBSERVED ACROSS THE
ISLANDS, WITH A MIX OF MOSTLY CLEAR SKIES AND JUST A FEW HIGH CLOUDS
STREAMING IN. PLEASANT TEMPERATURES PREVAILED ACROSS THE AREA, WITH
SURFACE OBSERVATIONS RECORDING MINIMUM TEMPERATURES IN THE LOW 70S
ALONG THE COAST AND IN URBAN AREAS, WHILE TEMPERATURES IN THE
MOUNTAINS WERE MOSTLY IN THE LOW 60S. DAYTIME HIGHS PEAKED IN THE
MID TO UPPER 80S ALONG THE COAST AND URBAN AREAS, AND IN THE MID-70S
IN THE MOUNTAINOUS REGIONS. NORTHEASTERLY WINDS AT AROUND 8 TO 16
MPH PREVAILED.
THIS AFTERNOON AND EVENING, STABLE CONDITIONS ARE EXPECTED TO
CONTINUE, WITH A DRY AIR MASS AND A RIDGE DOMINATING THE UPPER
LEVELS OF THE ATMOSPHERE.
THE REST OF THE SHORT-TERM FORECAST REMAINS ON TRACK. A SURFACE HIGH-
PRESSURE SYSTEM OVER THE CENTRAL ATLANTIC WILL CONTINUE TO PUSH A
FRONTAL BOUNDARY TOWARD THE REGION. AS IT APPROACHES FROM THE WEST,
IT WILL INDUCE A PRE-FRONTAL TROUGH AND INCREASE MOISTURE CONTENT
THROUGH THE WEEKEND. BASED ON THE LATEST MODEL GUIDANCE,
PRECIPITABLE WATER (PWAT) VALUES WILL RISE FROM BELOW NORMAL TO
SEASONAL, AND EVEN ABOVE NORMAL VALUES. PWAT SHOULD PEAK NEXT
SUNDAY, REACHING UP TO 2 INCHES, WHICH IS TWO STANDARD DEVIATIONS
ABOVE NORMAL FOR THIS TIME OF YEAR. INSTABILITY WILL ALSO INCREASE
FROM TOMORROW INTO SUNDAY, AS INDICATED BY COOLER 500 MB
TEMPERATURES AND INCREASING GALVEZ-DAVIDSON INDEX VALUES. THIS WILL
BRING A SHIFT IN THE WEATHER PATTERN, WITH SCATTERED TO NUMEROUS
SHOWERS EXPECTED PRIMARILY ACROSS NORTHERN AND NORTHEASTERN PUERTO
RICO, VIEQUES, CULEBRA, AND THE U.S. VIRGIN ISLANDS IN THE MORNINGS,
ALONG WITH A SLIGHT TO MODERATE CHANCE OF ISOLATED THUNDERSTORMS.
ADDITIONAL ACTIVITY IS ALSO EXPECTED ACROSS THE WEST-CENTRAL AND
SOUTHWESTERN SECTIONS OF PUERTO RICO AS THE DAY PROGRESSES. AS A
RESULT, A LIMITED TO LOCALIZED ELEVATED RISK OF FLOODING WILL BE IN
PLACE DUE TO THE POSSIBILITY OF PONDING WATER ON ROADWAYS AND POORLY
DRAINED AREAS, AS WELL AS URBAN AND SMALL STREAM FLOODING. FROM
SUNDAY NIGHT ONWARD, SEASONAL PWAT VALUES WILL RETURN WITH THE
ARRIVAL OF A SLIGHTLY DRIER AIR MASS AND THE RETURN OF A RIDGE
ALOFT. PLEASANT TEMPERATURES ARE EXPECTED TO PREVAIL OVER THE COMING
DAYS, ACCOMPANIED BY NORTHEASTERLY WINDS.
LONG TERM...MONDAY THROUGH FRIDAY
//...FROM PREVIOUS DISCUSSION...//
THE LATEST WEATHER FORECASTS SUGGEST THAT PRECIPITABLE WATER VALUES
WILL GRADUALLY DECREASE FROM ABOVE-NORMAL LEVELS TO AROUND NORMAL BY
MONDAY. WE EXPECT THAT THE AVAILABLE MOISTURE WILL REMAIN CONFINED
BELOW 700MB, MEANING ANY RAINFALL THAT DEVELOPS IS UNLIKELY TO GROW
SIGNIFICANTLY IN VERTICAL DEPTH. THIS REDUCES THE LIKELIHOOD OF
HEAVY RAINFALL OR INTENSE THUNDERSTORMS.
AS THREE KINGS DAY APPROACHES, IT IS WORTH NOTING THAT IT IS
UNLIKELY THE DEVELOPMENT OF SIGNIFICANT DISRUPTIVE WEATHER EVENTS
DURING THE CELEBRATIONS. ON THE MORNING OF JANUARY 6TH, BOTH
RESIDENTS AND VISITORS IN PUERTO RICO AND THE U.S. VIRGIN ISLANDS
CAN EXPECT SOME PASSING SHOWERS, PRIMARILY DRIVEN BY RESIDUAL
MOISTURE FROM A RECENT COLD FRONT AND THE ASSOCIATED PRE-FRONTAL
TROUGH THAT PASSED CLOSE TO THE REGION. COOLER TEMPERATURES ARE ALSO
EXPECTED AS A RESULT OF THE COLD FRONT'S PASSAGE. HOWEVER,
CONDITIONS ARE ANTICIPATED TO IMPROVE GRADUALLY THROUGHOUT THE DAY.
LIGHT, INTERMITTENT SHOWERS MAY STILL OCCUR, CONSISTENT WITH THE
TYPICAL TROPICAL WINTER WEATHER PATTERN AND THE AVAILABLE MOISTURE
ACROSS THE AREA.
OVERALL, WE EXPECT THIS WEATHER PATTERN, CHARACTERIZED BY SPORADIC
SHOWERS AND SLIGHTLY COOLER TEMPERATURES, TO PERSIST ACROSS THE
ISLANDS DURING THE LONG TERM. THE FORECAST SUGGESTS THAT PUERTO RICO
AND THE U.S. VIRGIN ISLANDS WILL CONTINUE TO EXPERIENCE RELATIVELY
CALM CONDITIONS WITH BRIEF EPISODES OF LIGHT PRECIPITATION, WHICH IS
TYPICAL DURING WINTER IN THIS TROPICAL CLIMATE.
AVIATION
(18Z TAFS)
VFR CONDITIONS WILL PREVAIL THROUGH 03/23Z ACROSS ALL TAF SITES. AS
A FRONTAL BOUNDARY AND ASSOCIATED FEATURES APPROACH THE AREA, EXPECT
INCREASING SHRA ACROSS TJSJ, TJBQ, AND THE USVI TAF SITES
AFTERWARDS, WITH SHRA AFFECTING TJPS AFTER 04/16Z. THIS COULD RESULT
IN BRIEF VFR CONDITIONS WITH SCT-BKN CEILINGS BELOW FL020-030. WINDS
WILL REMAIN FROM THE EAST-NORTHEAST AROUND 10-15 KNOTS, WITH HIGHER
GUSTS AND SEA BREEZE VARIATIONS. BETWEEN 03/23Z AND 04/14Z, WINDS
WILL BECOME LIGHT TO CALM AND VARIABLE, BUT GUSTY NEAR THE SHRA.
MARINE
MODERATE EAST TO NORTHEASTERLY WINDS WILL PREVAIL THROUGH SATURDAY
UNDER THE INFLUENCE OF A WEAK SURFACE HIGH PRESSURE OVER THE
CENTRAL ATLANTIC. A COLD FRONT WILL APPROACH THE NORTHEAST CARIBBEAN
LATE IN THE WEEKEND, AS A STRONGER SURFACE HIGH DEVELOPS OVER THE
WESTERN ATLANTIC. THIS WILL PROMOTE FRESH NORTHEASTERLY WINDS ON
SUNDAY AND MONDAY. A LONG PERIOD NORTHEAST SWELL WILL SPREAD ACROSS
THE ATLANTIC WATERS AND PASSAGES FROM TODAY ONWARDS. A LARGER
NORTHWEST SWELL WILL ARRIVE LATER ON SUNDAY AND LINGER THROUGH EARLY
NEXT WEEK. THE COMBINATION OF THE SWELLS WITH INCREASING WINDS WILL
PROMOTE HAZARDOUS SEAS ACROSS THE LOCAL WATERS THROUGH AT LEAST
TUESDAY.
BEACH FORECAST
A LONG-PERIOD NORTHEASTERLY SWELL WILL GRADUALLY SPREAD ACROSS
THE LOCAL WATERS TODAY. THIS SWELL WILL INCREASE THE RISK OF LIFE-
THREATENING RIP CURRENTS THROUGH THE WEEKEND WITH ROUGH SURF
CONDITIONS ALONG THE NORTHERN EXPOSED BEACHES OF THE ISLANDS. IN
ADDITION, A LARGER LONG-PERIOD NORTHWESTERLY SWELL WILL ARRIVE ON
SUNDAY AND LINGER THROUGH EARLY NEXT WEEK, CAUSING LARGE BREAKING
WAVES THAT WILL LEAD TO HIGH SURF ADVISORY CONDITIONS, MINOR BEACH
EROSION, AND LIFE- THREATENING RIP CURRENTS, PARTICULARLY ALONG
THE ATLANTIC COASTLINE OF PUERTO RICO FROM RINCON TO FAJARDO, AND
CULEBRA. ACROSS THE U.S. VIRGIN ISLANDS, LIFE-THREATENING RIP
CURRENTS WILL PREVAIL ACROSS ALL NORTHERN EXPOSED BEACHES DUE TO
THE LONG PERIOD SWELLS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR PRZ001-002-
005-008-012.
HIGH RIP CURRENT RISK FROM SATURDAY MORNING THROUGH MONDAY
AFTERNOON FOR PRZ010.
VI...HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR VIZ002.
HIGH RIP CURRENT RISK FROM SATURDAY MORNING THROUGH MONDAY
AFTERNOON FOR VIZ001.
AM...NONE.
SHORT TERM...YZR/DSR
LONG TERM...MMC
AVIATION...ICP
PUBLIC DESK/UPPER AIR...GRS
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