871
FXCA62 TJSJ 162001
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
401 PM AST SAT NOV 16 2024
SYNOPSIS
UNSETTLED WEATHER CONDITIONS AND TWO FRONTAL BOUNDARY ACROSS
NORTHERN OF THE AREA WILL INDUCE A WET PATTERN ACROSS THE REGION
FOR TONIGHT AND TOMORROW. BY MONDAY INTO TUESDAY, A MUCH DRIER
AIRMASS WILL DOMINATE THE PATTERN AND MUCH COLDER TEMPERATURES ARE
EXPECTED, THE FRIITO NAVIDENO IS ON ITS WAY! HAZARDOUS MARINE AND
COASTAL CONDITIONS WILL PERSIST FOR THE REST OF THE WEEKEND.
SHORT TERM...TONIGHT TROUGH MONDAY
A STATIONARY FRONTAL BOUNDARY NORTH OF THE REGION RESULTED IN
SOUTHWESTERLY SURFACE WINDS. UNDER THIS PATTERN, THE ISLANDS
EXPERIENCED SHOWER ACTIVITY ACROSS THE CARIBBEAN WATERS AND THE
SOUTHWESTERN SECTIONS OF PUERTO RICO. AT NOON, SHOWERS START OVER
THE INTERIOR SECTIONS, DRIFTING TOWARD THE NORTHEASTERN QUADRANT
AND AFFECTING THE MUNICIPALITIES OF LUQUILLO, RíO GRANDE, FAJARDO,
AND SURROUNDING AREAS. ACCORDING TO DOPPLER RADAR, SHOWER ACTIVITY
WAS SIGNIFICANT ACROSS NORTHEASTERN SECTIONS OF THE ISLANDS. THIS
ACTIVITY IS LIKELY TO PERSIST FOR THE REST OF THE AFTERNOON,
BECOMING PERSISTENT FOR THE EVENING INTO THE NIGHT HOURS,
ESPECIALLY ACROSS THE NORTHEASTERN SECTIONS OF PUERTO RICO,
CULEBRA VIEQUES, AND ST. THOMAS. DAYTIME TEMPERATURES REMAINED IN
THE LOW TO MID-80S. IN MARINE CONDITIONS, A LONG-PERIOD NORTHERLY
SWELL PRODUCED LARGE BREAKING WAVES ALONG THE NORTHERN COASTS OF
PUERTO RICO, CULEBRA, AND ST. THOMAS. COASTAL FLOODING WAS
REPORTED IN SEVERAL NORTHERN AREAS OF PUERTO RICO.
MOISTURE REMAINS FROM THE FRONT THAT PASSED PUERTO RICO AND THE U.S.
VIRGIN ISLANDS. THE BOUNDARY IS ROUGHLY LOCATED OVER THE SOUTHEAST
CORNER OF THE FORECAST AREA AND WAS HINTED AT IN THE SOUNDING TAKEN
THIS MORNING. A SECOND FRONT IS VISIBLE ON THE SATELLITE IMAGERY AND
WAS SPORTING A ROPE CLOUD AS IT APPROACHES THE AREA. THIS WILL BRING
ADDITIONAL RAINFALL LATE SATURDAY NIGHT AND SUNDAY MORNING. A
SURFACE TROUGH WILL PASS DURING THIS PERIOD AND SURFACE WINDS WILL
TURN FROM SOUTHWEST AND WEST TO NORTH AND NORTHEAST BY LATER ON
SUNDAY. ADDITIONALLY, AN UPPER LEVEL TROUGH WILL INCREASE THE
INSTABILITY, PROMOTING AN UNSETTLED WEATHER CONDITIONS THAT WILL
LEAD TO FLODDING RAINS IN SEVERAL LOCATION ACROSS THE AREA.
ON MONDAY DRIER AIR ABOVE 700 MB WILL ENTER THE AREA AND END
THE LIKELIHOOD OF THUNDERSTORMS. AT THE SAME TIME 500 MB TEMPERATURES
WILL BEGIN WARMING. NEVERTHELESS MOISTURE WILL BE RICH BELOW 700 MB
AND LIGHT RAIN AND MID CLOUD COVER ON THE NORTHERN SIDE OF THE
ISLANDS IS LIKELY. TEMPERATURE-WISE, THE ISLANDS WILL EXPERIENCE
MUCH COLDER CONDITIONS DUE TO THE DRIER AIR AND THE NORTHERN WIND
COMPONENT. THE FRIíTO NAVIDEñO IS ON ITS WAY!
LONG TERM...TUESDAY THROUGH FRIDAY
...FROM PREVIOUS DISCUSSION ISSUED AT 509 AM AST SAT NOV 16,
2024...
A DECREASE IN PRECIPITABLE WATER VALUES (PWAT) IS FORECAST TO
CONTINUE BY THE START OF THE LONG TERM FORECAST PERIOD. 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. 850MB TO 700MB RELATIVE HUMIDITY AND 925MB TEMPERATURES
ARE FORECAST TO BE BELOW NORMAL TO START THE LONG TERM PERIOD. A MID
TO UPPER LEVEL RIDGE WILL MOVE IN FROM THE SOUTHEASTERN UNITED
STATES INTO THE WESTERN CARIBBEAN, MAINTAINING A TRADE WIND CAP
INVERSION AROUND 850 MB, WITH ALL THE LOW LEVEL MOISTURE TRAPPED
BELOW THIS LEVEL. THROUGH WEDNESDAY, GENERALLY LOW PROBABILITY OF
PRECIPITATION (POP) WILL REMAIN, EXCEPT JUST SOUTHEAST OF SAINT
CROIX, WHERE REMNANT MOISTURE OF THE COLD FRONT WILL LINGER.
PWAT VALUES WILL CLIMB BACK UP ONCE WINDS VEER TO BECOME MORE
EASTERLY ON THURSDAY AND GAIN A SOUTHERLY COMPONENT ON FRIDAY. THIS
CHANGE IN WIND DIRECTION WILL BE DUE TO A SURFACE HIGH MOVING FROM
THE EAST TO CENTRAL ATLANTIC. MOISTURE WILL BE BROUGHT IN FROM THE
EAST AND SOUTH, INCREASING THE POTENTIAL FOR SHOWERS AND AFTERNOON
CONVECTION. TEMPERATURES WILL ONCE AGAIN REACH THE UPPER 80S TO LOW
90S ACROSS LOWER ELEVATIONS OF THE ISLANDS.
AVIATION
(18Z)
CONDS ARE MOSTLY VFR, BUT IN AREAS OF SHRA/RA AND ALG THE NORTHERN
FOOTHILLS OF PR MVFR IS SEEN--MAINLY DUE TO CIGS. SHRA HAVE RETURNED
TO THE INTERIOR OF PR MOVG ENE AT ARND 7 KTS. SOME WILL REACH THE
NRN COAST. THE SHRA WILL CONT THRU ABT 17/02Z OVR LAND, BUT PERSIST
OVR THE LCL WATERS THRU 17/15Z. A SECOND FRONT WILL APCH THE AREA.
CONDS TO DETERIORATE MOSTLY ON THE N COAST OF PR, BCMG BY 17/12Z 5SM
-RA WITH CIGS 025-035 AS THE CDFNT APPCHS THE AREA. EXPECT VFR CONDS
SOUTH COAST. LLVL WINDS ARE MOSTLY SW OVER PR/USVI, BUT WINDS WILL
SLOWLY VEER TO THE NNE THRU 17/16Z. MAXIMUM WINDS NW 70 KT ARND
FL435.
MARINE
A FRONTAL BOUNDARY NORTH OF THE REGION WILL CONTINUE TO RESULT IN
GENTLE TO MODERATE WESTERLY WINDS PERSISTING UNTIL TONIGHT,
SHIFTING TO A NORTHERLY FLOW TOMORROW AND BECOMING NORTHEASTERLY
BY MONDAY. THE AVAILABLE MOISTURE WILL ENHANCE SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS THE REGIONAL WATERS AND PASSAGES.
MARINE CONDITIONS WILL REMAIN HAZARDOUS FOR SMALL CRAFT THROUGH
MONDAY DUE TO PULSES OF NORTHERLY SWELLS. SMALL CRAFT ADVISORIES
ARE CURRENTLY IN EFFECT FOR THE COASTAL AND OFFSHORE ATLANTIC
WATERS AND LOCAL PASSAGES. AFTER 6 PM AST TODAY AND CONTINUING
THROUGH NOON AST ON MONDAY, THESE ADVISORIES WILL REMAIN ACTIVE
FOR THE COASTAL AND OFFSHORE ATLANTIC WATERS.
BEACH FORECAST
RECENT BOUY DATA AT SAN JUAN REPORTED 7 FEET AT 13 SECONDS,
PRODUCING LARGE BREAKING WAVES ACROSS NORTHERN SECTIONS OF PUERTO
RICO, CULEBRA, AND ST. THOMAS. GIVEN THE PERSISTENT CONDITIONS AND
THE BREAKING WAVES ACROSS THE NORTH OF THE AREA, A COASTAL FLOOD
ADVISORY WILL BE IN EFFECT UNTIL 6 PM THIS EVENING. BREAKING WAVES
WILL SLIGHTLY DIMINISH DURING THE NIGHT, PERSISTENT UP TO 10 FEET,
WHERE A HIGH SURF ADVISORY WILL REMAIN IN EFFECT UNTIL 6 AM ON
SUNDAY. THERE IS A HIGH RISK OF RIP CURRENTS FOR ALL THE NORTHERN
COASTAL AREAS OF PUERTO RICO, CULEBRA, AND THE U.S. VIRGIN
ISLANDS. FOR MORE DETALIED INFORMATION PLEASE VISIT
WWW.WEATHER.GOV/SJU/MARINE OR THE SURF ZONE FORECAST FOR PUERTO
RICO AND THE U.S. VIRGIN ISLANDS PRODUCT.
SJU WATCHES/WARNINGS/ADVISORIES
PR...COASTAL FLOOD ADVISORY UNTIL 6 PM AST THIS EVENING FOR PRZ001-
005.
HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR PRZ001-002-
005-008-010-012.
HIGH SURF ADVISORY UNTIL 6 AM AST SUNDAY FOR PRZ001-002-005-008-
012.
HIGH SURF ADVISORY UNTIL 6 PM AST THIS EVENING FOR PRZ010.
HIGH RIP CURRENT RISK UNTIL 6 PM AST THIS EVENING FOR PRZ013.
VI...HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR VIZ001.
HIGH SURF ADVISORY UNTIL 6 AM AST SUNDAY FOR VIZ001.
AM...SMALL CRAFT ADVISORY UNTIL NOON AST MONDAY FOR AMZ711-712-716.
SMALL CRAFT ADVISORY UNTIL 6 PM AST THIS EVENING FOR AMZ723.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT AST TONIGHT FOR AMZ741-742.
SHORT TERM...WS/LIS
MARINE...CAM
AVIATION...WS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page