365
FXCA62 TJSJ 170846
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
446 AM AST SUN NOV 17 2024
SYNOPSIS
A COLD FRONT NORTH OF THE AREA, WILL MAINTAIN WET AND UNSETTLED
CONDITIONS AND WILL CONTINUE TO PROMOTE SHOWERS AND THUNDERSTORMS
TODAY AS IT CROSSES THE ISLANDS. AFTER THE FRONTAL PASSAGE, A
DRIER AND COOLER AIR MASS WILL REACH THE AREA BY MONDAY AND LINGER
THROUGH MIDWEEK. THIS WILL BRING "EL FRIITO NAVIDENO"! A
NORTHERLY SWELL WILL CONTINUE TO REACH THE REGIONAL WATERS,
DETERIORATING MARINE AND COASTAL CONDITIONS THROUGH TOMORROW.
SMALL CRAFT ADVISORIES, COASTAL FLOOD ADVISORIES, HIGH SURF
ADVISORIES AND HIGH RISK OF RIP CURRENTS ARE IN EFFECT.
SHORT TERM...TODAY THROUGH TUESDAY
THE EVENING HOURS WERE VERY ACTIVE ACROSS EASTERN PUERTO RICO, WHERE
FLASH FLOODING, MUDSLIDES, AND RIVERS REACHING FLOOD STAGES WERE
OBSERVED. RAINFALL ACCUMULATIONS RANGED FROM 3 TO 6 INCHES, WITH THE
HIGHEST ACCUMULATIONS IN HUMACAO. LATER AT NIGHT, THE HEAVIEST
ACTIVITY MOVED OVER SAINT CROIX, WITH HEAVY RAIN AND REDUCED
VISIBILITIES. ADDITIONALLY, NEW SHOWERS DEVELOPED OVER THE ATLANTIC
AND CARIBBEAN WATERS, AND ARE EXPECTED TO REACH THE VIRGIN ISLANDS,
NORTHERN AND WESTERN PUERTO RICO.
ANOTHER COLD FRONT IS ANALYZED NORTH OF THE ISLANDS TODAY, AND IT IS
EXPECTED TO PUSH DOWN INTO THE AREA TODAY. THE HIGH RESOLUTION AND
GLOBAL MODELS SHOW MORE SHOWERS AND THUNDERSTORMS DEVELOPING TODAY,
MAINLY IN THE AFTERNOON AND EVENING HOURS FOR NORTHERN, WESTERN, AND
EASTERN PUERTO RICO, AS WELL AS FOR THE VIRGIN ISLANDS. WITH RIVERS
RUNNING HIGH AND SOILS SATURATED, THE RISK OF FLOODING WILL BE
ELEVATED (LOCALLY HIGH, ESPECIALLY ACROSS EASTERN PUERTO RICO). THE
THUNDERSTORMS MAY ALSO BRING GUSTY WINDS AND LIGHTNING ACTIVITY.
THE RAIN WILL GRADUALLY TAPER OFF IN THE OVERNIGHT HOURS, GIVING WAY
TO A DRIER AND COOLER PATTERN. A HIGH PRESSURE SYSTEM WILL ROLL FROM
THE WEST INTO THE BAHAMAS, WITH DRIER AIR ESTABLISHING ABOVE 850 MB.
DURING THE FIRST COUPLE OF DAYS OF THE WORKWEEK, GENERALLY FAIR
WEATHER WILL PREVAIL. THE ONLY EXCEPTION WILL BE THE VICINITY OF
SAINT CROIX, WHERE THE REMNANTS OF THE FRONT WILL HANG AROUND. ALSO,
TEMPERATURES WILL COOL DOWN BELOW THE CLIMATOLOGICAL VALUE FOR A
CHANGE, SO IT WILL FEEL COOLER TOO.
LONG TERM...WEDNESDAY THROUGH SATURDAY
BELOW NORMAL PRECIPITABLE WATER VALUES (PWAT) ARE FORECAST TO
CONTINUE BY MIDWEEK. CURRENT MODEL GUIDANCE HAS PWAT VALUES OF 0.9
TO 1.2 INCHES, WELL BELOW TO BELOW NORMAL VALUES FOR THIS TIME OF
THE YEAR. THIS IS DUE TO A COOLER AND DRIER AIR MASS FILTERING
INTO THE REGION UNDER NORTHERLY FLOW BEHIND THE FRONTAL BOUNDARY
MENTIONED AT THE END OF THE SHORT TERM PERIOD. MID TO UPPER LEVEL
RIDGING WILL MOVE IN FROM THE SOUTHEASTERN U.S. INTO THE WESTERN
CARIBBEAN, MAINTAINING A TRADE WIND CAP INVERSION AROUND 850 MB,
WITH ALL THE LOW LEVEL MOISTURE TRAPPED BELOW THIS LEVEL. THIS LOW
LEVEL MOISTURE AS WELL AS 925MB TEMPERATURES ARE FORECAST TO BE
BELOW NORMAL TO START THE PERIOD. GENERALLY LOW PROBABILITY OF
PRECIPITATION (POP) WILL REMAIN, EXCEPT JUST SOUTHEAST OF SAINT
CROIX, WHERE REMNANT MOISTURE OF THE COLD FRONT WILL LINGER.
INCREASING MOISTURE WILL THEN BE EXPERIENCED THURSDAY THROUGH
SATURDAY AS WINDS VEER TO BECOME MORE EASTERLY ON THURSDAY AND
GAIN A SOUTHERLY COMPONENT FRIDAY AND SATURDAY. THIS CHANGE IN
WIND DIRECTION WILL BE DUE TO A SURFACE HIGH MOVING FROM THE EAST
TO CENTRAL ATLANTIC. A MOISTURE PLUME WILL BE BROUGHT IN FROM THE
EAST AND SOUTH, INCREASING THE POTENTIAL FOR SHOWERS AND
AFTERNOON CONVECTION. MODEL GUIDANCE SUGGEST THAT THE TRADE CAP
WILL NOT BE PRESENT BY LATE FRIDAY AND SATURDAY LEAVING HIGH
RELATIVE HUMIDITIES AT ALL LEVELS. PWAT VALUES ARE FORECAST TO BE
AT AROUND 2.25 IN. HIGHS WILL ONCE AGAIN REACH THE UPPER 80S TO
LOW 90S ACROSS LOWER ELEVATIONS OF THE ISLANDS.
AVIATION
(06Z TAFS)
MAINLY VFR CONDITIONS EXPECTED TO PREVAIL BEFORE 15Z TODAY. THEN,
SHRA AND TSRA WILL WILL DEVELOP, BRINGING PERIODS OF REDUCED VIS AND
LOW CEILINGS FOR TJSJ AND THE USVI TERMINALS. AFTER 18Z, THIS
ACTIVITY COULD SPREAD INTO TJBQ AND TJPS AS WELL. THE WINDS WILL BE
FROM THE NORTH AT 5-8 KTS.
MARINE
GENTLE TO MODERATE NORTHERLY WINDS WILL PREVAIL THROUGH LATE
WEDNESDAY WHEN EASTERLY WINDS RETURN. MARINE CONDITIONS WILL BE
UNFAVORABLE FOR SMALL CRAFT THROUGH TOMORROW DUE TO PULSES OF
NORTHERLY SWELLS. A COLD FRONT NORTH OF THE REGION AND ASSOCIATED
MOISTURE, IS FORECAST TO MOVE THROUGH THE ISLANDS TODAY. THIS WILL
INCREASE THE CHANCE FOR SHOWERS AND SCATTERED THUNDERSTORMS ACROSS
THE REGIONAL WATERS AND PASSAGES. A DRIER PATTERN IS FORECAST TO
START THE WORKWEEK.
BEACH FORECAST
A LONG PERIOD NORTHERLY SWELL WILL CREATE HAZARDOUS COASTAL
CONDITIONS ALONG THE NORTH-FACING BEACHES OF PR AND THE US VIRGIN
ISLANDS THROUGH AT LEAST TOMORROW, MONDAY. THE EXPOSED ATLANTIC
COASTLINE WILL BE IMPACTED BY BREAKING WAVES BETWEEN 8 AND 15 FEET.
ADDITIONALLY, THE FULL MOON PHASE WILL EXACERBATE THE HIGH TIDES,
WHERE ISOLATED COASTAL FLOODING IS EXPECTED ALONG THE MOST
VULNERABLE BEACHES OF NORTHERN PR THROUGH AT LEAST NOON ON SUNDAY.
THE COASTAL HAZARDS THAT WILL IMPACT THE NORTH-FACING BEACHES ARE
LIFE-THREATENING RIP CURRENTS AND BREAKING WAVES.
SJU WATCHES/WARNINGS/ADVISORIES
PR...COASTAL FLOOD ADVISORY UNTIL NOON AST TODAY FOR PRZ001-002-005-
008.
HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR PRZ001-002-
005-008-010-012.
HIGH SURF ADVISORY UNTIL 6 PM AST THIS EVENING FOR PRZ001-002-
005-008.
HIGH SURF ADVISORY UNTIL 6 AM AST EARLY THIS MORNING FOR PRZ010-
012.
HIGH RIP CURRENT RISK THROUGH THIS AFTERNOON FOR PRZ013.
VI...HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR VIZ001.
HIGH SURF ADVISORY UNTIL 6 AM AST EARLY THIS MORNING FOR VIZ001.
AM...SMALL CRAFT ADVISORY UNTIL NOON AST MONDAY FOR AMZ711-712-716-
741-742.
SMALL CRAFT ADVISORY UNTIL 6 AM AST EARLY THIS MORNING FOR
AMZ723.
SMALL CRAFT ADVISORY UNTIL NOON AST TODAY FOR AMZ726.
SHORT TERM...ERG
LONG TERM....MRR
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