516
FXCA62 TJSJ 151533 AAA
AFDSJU
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
1133 AM AST FRI NOV 15 2024
UPDATE
CONVECTION JUST NORTH OF THE COAST OF PUERTO RICO WAS
SLOWLY DISSIPATING WHILE THE SHOWERS OVER THE NORTHERN U.S. VIRGIN
ISLANDS WERE DISSOLVING AND MOVING EAST. MEANWHILE DURING THE LAST
HOURS MINOR SHOWERS WERE FORMING IN A LINE UPSTREAM FROM SAINT
CROIX. THIS HAS MAINTAINED GENERALLY CLOUDY SKIES AND COOLER
TEMPERATURES FOR THE DAY. AN AREA OF HEAVIER SHOWERS WAS ALSO
CONSOLIDATING SOUTH OF SALINAS AS THEY MOVED EAST.
FLOW IS GENERALLY FROM THE WEST UP THROUGH 16 KFT. STABILITY HAS
BEEN LIMITED AND FEW--IF ANY--THUNDERSTORMS HAVE FORMED SINCE THE
SOUNDING WAS TAKEN AT SAN JUAN, PUERTO RICO THIS MORNING AT
15/12Z. THAT SOUNDING SHOWED ONLY WEAK BUOYANCY WITH A CAPE OF
1128 J/KG. THE FRONTAL BOUNDARY IS STILL IN BALANCE WITH OPPOSING
FLOWS AND SO IS SHOWING VERY LITTLE MOVEMENT. HOWEVER, THE GFS
SHOWS THAT IT IS LIKELY TO MOVE OVER PUERTO RICO TONIGHT AND THEN
MOVE BACK TO THE NORTH AS SOUTHERLY FLOW SETS IN. THIS WILL BRING
ANOTHER REPEAT OF SHOWERS OVER THE AREA.
AVIATION
CONDS ARE MOSTLY VFR, BUT IN AREAS OF SHRA AND ALG THE
NORTHERN COAST OF PUERTO RICO MVFR IS SEEN--MAINLY DUE TO CIGS.
SHRA WERE DISSIPATING, BUT ARE EXPECTED TO REFORM IN THE INTERIOR
OF PR AFT 15/16Z AND LAST THRU 15/21Z. LLVL WINDS ARE MOSTLY W
OVER PUERTO RICO AND MOSTLY VRB OVR THE USVI, BUT WINDS ARE NE
NORTH OF THE FRONT WHICH HAS BEEN HOLDING N OF THE ISLANDS.
MAXIMUM WINDS NW 60 KTS ARND 180 MB.
PREV DISCUSSION
/ISSUED 656 AM AST FRI NOV 15 2024/
SYNOPSIS...
A COLD FRONT NEAR THE AREA WILL CONTINUE TO PRODUCE SHOWERS ACROSS
THE ISLANDS. ANOTHER FRONTAL BOUNDARY IS EXPECTED TO REACH THE
ISLANDS ON SATURDAY AND SUNDAY, FOLLOWED BY DRIER CONDITIONS FOR
THE FIRST HALF OF THE NEXT WORKWEEK. MARINE AND BEACH CONDITIONS
WILL BE HAZARDOUS THROUGH EARLY NEXT WEEK AS A NORTHERLY SWELL
ARRIVES.
SHORT TERM...TODAY THROUGH SUNDAY...
OVERNIGHT RADAR AND SATELLITE IMAGERY INDICATED GENERALLY CALM
CONDITIONS OVER LAND, WITH SHOWER ACTIVITY ASSOCIATED WITH A FRONTAL
BOUNDARY FOCUSED OVER THE ATLANTIC WATERS FOR MOST OF THE NIGHT.
BASED ON RADAR ESTIMATES, SAN JUAN AREA AND EASTERN PUERTO RICO HAD
AROUND 0.02 TO 0.30 OF RAIN. TEMPERATURES OVERNIGHT RANGED FROM
THE MID TO UPPER 70S ALONG COASTAL AND URBAN AREAS, AND FROM THE
60S TO LOW 70S ACROSS THE MOUNTAINOUS REGIONS. LIGHT AND VARIABLE
WINDS DOMINATED THE REGION.
THE UNSTABLE AND WET PATTERN WILL PERSIST THROUGHOUT THE SHORT-TERM
FORECAST. FOR TODAY, LIGHT AND VARIABLE WINDS AHEAD OF THE STALLED
FRONTAL BOUNDARY TO THE NORTH WILL PREVAIL ACROSS OUR REGION. THIS
BOUNDARY WILL MAINTAIN ABOVE-NORMAL PRECIPITABLE WATER VALUES,
OF AROUND 2 INCHES. BECAUSE OF THIS MOST OF THE RAIN ACTIVITY
WILL STAY OVER THE ATLANTIC WATERS AND MORNING SHOWERS ARE
EXPECTED TO CONTINUE AND MOVE INLAND, PRIMARILY OVER THE NORTHERN
COAST OF PUERTO RICO, EASTERN MUNICIPALITIES, AND SURROUNDING
ISLANDS. AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS, DRIVEN BY
DIURNAL AND LOCAL EFFECTS, WILL SPREAD INTO THE INTERIOR AND
COASTAL SECTORS LATER TODAY.
TONIGHT, A CHANGE IN THE WIND PATTERN IS EXPECTED. WINDS WILL SHIFT
TO A SOUTHERLY COMPONENT, DRIVEN BY SURFACE RIDGING OVER THE
NORTHEASTERN ATLANTIC. THE CURRENT FRONTAL BOUNDARY AND ITS
ASSOCIATED MOISTURE FIELD ARE EXPECTED TO BE PUSHED TO THE NORTH.
THIS WILL ENHANCE SHOWERS SATURDAY MORNING ACROSS SOUTHWESTERN AND
WESTERN PUERTO RICO. ADDITIONALLY, A POLAR TROUGH OVER THE NORTHEAST
U.S. AND ITS ASSOCIATED COLD FRONT WILL BEGIN TO MOVE INTO THE
WESTERN ATLANTIC WATERS.
BY SATURDAY, STRONG HIGH PRESSURE BUILDING ACROSS THE WESTERN
ATLANTIC WILL CONTINUE TO PUSH THE COLD FRONT TOWARD THE CARIBBEAN.
ACCORDING TO THE LATEST MODEL GUIDANCE, THE FRONT IS EXPECTED TO
CROSS OUR REGION BY SATURDAY NIGHT INTO SUNDAY. SUFFICIENT MOISTURE
AND INSTABILITY WILL REMAIN IN PLACE, MAKING SUNDAY THE MOST ACTIVE
DAY OF THIS PERIOD. AFTER THE FRONT PASSES, A MUCH DRIER AIR MASS
WILL DOMINATE THE REGION, LEADING TO A MORE STABLE WEATHER PATTERN
STARTING SUNDAY NIGHT.
OVERALL, THE FLOOD THREAT WILL REMAIN ELEVATED THROUGH SUNDAY ACROSS
THE ISLANDS WITH THE RISK TO OBSERVE URBAN AND SMALL STREAM FLOODING
AND QUICK RIVER RISES. THE POTENTIAL FOR MUDSLIDES AND UNSTABLE
TERRAIN WILL ALSO PERSIST DUE TO CONTINUED SATURATED SOIL CONDITIONS
ACROSS MUCH OF THE FORECAST AREA. RESIDENTS AND VISITORS ARE
ENCOURAGED TO CONTINUE MONITOR THE FORECAST AND ANY ADVISORY OR
WARNING FOR THEIR AREA.
LONG TERM...MONDAY THROUGH FRIDAY...
AFTER THE COLD FRONT PASSES THROUGH THE ISLANDS, A COOLER AND
DRIER AIR MASS WILL FILTER INTO THE REGION, WITH TEMPERATURES
DROPPING A LITTLE BELOW NORMAL. A MID TO UPPER LEVEL RIDGE WILL
ROLL FROM THE SOUTHEASTERN UNITED STATES INTO THE WESTERN
CARIBBEAN. THIS FEATURE WILL MAINTAIN A TRADE WIND CAP INVERSION
AROUND 850 MB, WITH ALL THE LOW LEVEL MOISTURE TRAPPED BELOW THIS
LEVEL. DURING THE FIRST HALF OF THE WORKWEEK, THE PROBABILITY OF
PRECIPITATION WILL BE GENERALLY LOW, EXCEPT JUST SOUTHEAST OF
SAINT CROIX, WHERE THE REMNANTS OF THE COLD FRONT WILL LINGER.
AS THE HIGH PRESSURE SYSTEM MIGRATES TOWARD THE EAST AND MOVES
INTO THE CENTRAL ATLANTIC, THE WINDS WILL SHIFT FROM THE SOUTHEAST
ON THURSDAY AND FROM THE SOUTH ON FRIDAY. THIS WILL ONCE AGAIN
PULL MOISTURE FROM THE CARIBBEAN INTO THE LOCAL ISLANDS,
INCREASING THE POTENTIAL FOR SOME SHOWERS. TEMPERATURES WILL
BOUNCE BACK, AND HIGHS ARE EXPECTED TO REACH THE UPPER 80S AND LOW
90S ONCE AGAIN, ESPECIALLY FOR THE LOW-ELEVATED AND URBAN AREAS.
AVIATION...
(06Z TAFS)
VFR CONDITIONS ACROSS MOST OF THE TAF SITES ARE EXPECTED TO PERSIST
THROUGH THE NEXT FEW HOURS. A COLD FRONT STALLED TO THE NORTH WILL
KEEP CLOUDINESS, SHOWERS, AND ISOLATED THUNDERSTORMS THIS MORNING,
TJSJ AND TIST HAVING THE BEST CHANCE TO OBSERVE RAIN. AFTERNOON
SHOWERS AND ISOLATED THUNDERSTORMS, DRIVEN BY DIURNAL AND LOCAL
EFFECTS, WILL SPREAD INTO THE INTERIOR AND COASTAL SECTORS AFTER
18Z. THIS COULD RESULT IN INTERMITTENT MVFR CONDITIONS AND MOUNTAIN
OBSCURATIONS. WINDS WILL REMAIN LIGHT, LESS THAN 10KT WITH
TYPICAL VARIATIONS EXCEPT IN THE VICINITY OF ANY MODERATE TO
HEAVY RAIN DEVELOPMENT. A MORE SOUTHERLY COMPONENT IS EXPECTED TO
DEVELOP TONIGHT.
MARINE...
VARIABLE GENTLE TO MODERATE WINDS WILL PREVAIL OVER THE NEXT FEW
DAYS. MARINE CONDITIONS WILL BECOME UNFAVORABLE FOR SMALL CRAFT
STARTING ON FRIDAY MORNING AS PULSES OF NORTHERLY SWELLS ARRIVE
AND CREATE HAZARDOUS SEAS TODAY, STRETCHING INTO THE
WEEKEND. ALSO, MOISTURE REMNANTS ALONG A COLD FRONTAL BOUNDARY
WILL SINK SOUTHWARD ACROSS THE REGION. THIS WILL INCREASE THE
CHANCE FOR SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE REGIONAL
WATERS AND PASSAGES.
BEACH FORECAST...
PULSES OF NORTHERLY SWELL WILL MAINTAIN A HIGH RIP CURRENT RISK
FOR THE BEACHES OF NORTHERN PUERTO RICO FROM RINCON TO FAJARDO,
CULEBRA, AND SAINT THOMAS AND ST. JOHN. THESE CONDITIONS COULD
DETERIORATE FURTHER TOMORROW AND SUNDAY, WITH HIGHER BREAKING
WAVES ANTICIPATED.
BREAKING WAVES WILL BE LOWER IN THE BEACHES OF THE CARIBBEAN SEA
IN SOUTHERN PUERTO RICO, WHERE THE RIP CURRENT RISK IS LOW.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH LATE SUNDAY NIGHT FOR PRZ001-005-
008.
HIGH RIP CURRENT RISK FROM 6 PM AST THIS EVENING THROUGH LATE
SUNDAY NIGHT FOR PRZ002-010-012.
VI...HIGH RIP CURRENT RISK FROM 6 PM AST THIS EVENING THROUGH LATE
SUNDAY NIGHT FOR VIZ001.
AM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT AST SATURDAY NIGHT FOR
AMZ711.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT AST
SATURDAY NIGHT FOR AMZ712-716.
SHORT TERM/AVIATION...WS
UPPER AIR/PUBLIC...CAM
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