904
FXCA62 TJSJ 020913
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
500 AM AST SUN MAR 2 2025
SYNOPSIS
DRIER AIR HAS MOVED INTO THE ISLANDS, WITH ONLY ISOLATED SHOWERS
EXPECTED TODAY. AN INCREASE IN SHOWERS IS EXPECTED BY MIDWEEK DUE
TO THE PROXIMITY OF A TROUGH, WITH THE STRONGEST ACTIVITY ACROSS
THE INTERIOR AND NORTHWESTERN PUERTO RICO. A COLD FRONT IS
EXPECTED TO LINGER NORTH OF THE AREA BY THE END OF THE WEEK.
SHORT TERM...TODAY THROUGH TUESDAY
CURRENT SATELLITE DERIVED PRECIPITABLE WATER (PWAT) IMAGERY SHOW A A
DRY AIR MASS OVER THE ISLANDS WITH VALUES RANGING FROM 0.90 TO 1.10
INCHES, 0.90 INCHES OF PWAT IS 2 STANDARD DEVIATIONS BELOW NORMAL
FOR THIS TIME OF THE YEAR. DURING THE OVERNIGHT HOURS, LIGHT TO
LOCALLY MODERATE SHOWERS STEERED BY EAST-SOUTHEAST WINDS AFFECTED
SECTORS OF THE ISLANDS. RADAR ESTIMATED RAINFALL TOTALS SINCE
MIDNIGHT INDICATE LOW ACCUMULATIONS OVER SOUTHEASTERN TO EASTERN AND
EASTERN INTERIOR PUERTO RICO, VIEQUES, ST. CROIX, ST. THOMAS AND ST.
JOHN. STATIONS REPORTED MINIMUM TEMPERATURES IN THE UPPER 60S TO LOW
70S (SOME ISOLATED MID 70S) AT LOWER ELEVATIONS OF PUERTO RICO, IN
THE MID 70S OVER VIEQUES, CULEBRA AND THE USVI, AND IN THE UPPER 50S
TO LOW 60S AT HIGHER ELEVATIONS OF PUERTO RICO.
LOW CONCENTRATIONS OF SAHARAN DUST WILL FILTER INTO THE REGION
DURING THE PERIOD, PROMOTING HAZY SKIES. PASSING SHOWERS WILL MOVE
INTO THE EASTERN REGION DURING THE MORNING HOURS AS PATCHY FOG OVER
SOME AREAS DISSIPATES. DURING THE AFTERNOON, CONVECTIVE SHOWER
ACTIVITY WILL CONCENTRATE AGAIN OVER NORTHWESTERN PUERTO RICO,
HOWEVER PWAT VALUES TODAY WILL BE GENERALLY LESS THAN DURING THE
REST OF THE PERIOD. DURING THE OVERNIGHT HOURS, A PATCH OF MOIST
AIR WILL MOVE IN FROM THE SOUTHEAST, PASSING ADVECTIVE SHOWERS
WILL AFFECT WINDWARD SECTORS OF THE ISLANDS. AN AREA OF MOISTURE
(PWAT VALUES AT 1.5 OR MORE) IS EXPECTED TO MOVE SOUTH OF THE AREA
TOMORROW AS A TROUGH DEVELOPS NORTH OF THE AREA AND A COLD FRONT
APPROACHES FROM THE WEST. IF THE TROUGH MOVES IN DURING THE
AFTERNOON HOURS, THE SHIFTING STEERING FLOW FROM THE EAST TO
NORTHEAST CAN FOCUS AFTERNOON SHOWERS OVER WEST TO SOUTHWEST PR. A
DRY AIR MASS WITH PWAT VALUES AROUND AN INCH WILL AFFECT THE
ISLANDS TOMORROW NIGHT.
AFTER THIS, A WETTER AND MORE UNSTABLE PATTERN IS FORECAST FOR
TUESDAY AND INTO THE LONG TERM PERIOD. A MID TO UPPER LEVEL TROUGH
WILL APPROACH THE ISLANDS BY TUESDAY. WITH AN AREA OF THE JET STREAM
REACHING THE ISLANDS AND 500 MB TEMPERATURES COOLING DOWN,
INSTABILITY WILL INCREASE AND ENHANCE THE POTENTIAL FOR STRONGER
AFTERNOON CONVECTION, LEADING TO A LIMITED TO ELEVATED EXCESSIVE
RAINFALL RISK OVER INTERIOR TO NORTHWESTERN PUERTO RICO. A LIMITED
LIGHTNING RISK WAS KEPT IN THE FORECAST, AS DIURNAL HEATING AND
THE PRESENCE OF SAHARAN DUST CAN ALSO AID IN THUNDERSTORM
FORMATION. A LIMITING FACTOR IS THE MOISTURE CONTENT AS PWAT
VALUES WILL BE AT AROUND 1.5 INCHES.
UP TO BREEZY E-SE FLOW WILL CONTINUE TODAY DUE TO A SURFACE HIGH
OVER THE EASTERN ATLANTIC. THIS WILL PROMOTE WARMER THAN NORMAL
TEMPERATURES, PARTICULARLY DURING THE AFTERNOONS. TEMPERATURES AT
925MB WILL FLUCTUATE BETWEEN 1 TO 2 STANDARD DEVIATIONS ABOVE THE
CLIMATOLOGICAL MEAN. MAXIMUM TEMPERATURES WILL REACH THE LOW TO
MID 80S, SOME AREAS IN THE UPPER 80S, AT LOWER ELEVATIONS OF THE
ISLANDS, AND IN THE UPPER 70S TO LOW 80S AT HIGHER ELEVATIONS OF
PUERTO RICO.
LONG TERM...WEDNESDAY THROUGH SUNDAY
A SURFACE HIGH PRESSURE OVER THE CENTRAL ATLANTIC WILL MAINTAIN
THE TRADE WINDS FROM THE SOUTHEAST AT MODERATE SPEEDS. AT THE MID
TO UPPER LEVELS, THE AXIS OF THE TROUGH WILL BE POSITIONED JUST TO
THE NORTHEAST OF THE ISLANDS. EVEN THOUGH, SOME INSTABILITY WILL
REMAIN OVER THE ISLANDS, WITH MID-LEVEL TEMPERATURES A LITTLE
COOLER THAN NORMAL. A SURFACE REFLECTION OF THE TROUGH WILL ALSO
MOVE OVER THE ISLANDS, BRINGING SOME SHOWERS OVER THE VIRGIN
ISLANDS AND EASTERN PUERTO RICO. HOWEVER, THE STRONGEST SHOWERS
ARE EXPECTED FOR THE INTERIOR AND NORTHWEST OF PUERTO RICO, WHERE
THERE IS ALSO A CHANCE OF LIGHTNING.
BY THE END OF THE WEEK, THE WINDS WILL GAIN A SOUTHERLY COMPONENT
DUE TO A COLD FRONT THAT EXITS THE EASTERN COAST OF THE UNITED
STATES. AS THE FRONT APPROACHES, THE WINDS WILL BECOME LIGHT AND
VARIABLE. THE MOISTURE AND SHOWERS ASSOCIATED WITH THIS FRONT WILL
LIKELY REACH THE ISLANDS AS FRAGMENTED PATCHES OF CLOUDS, SO A
SIGNIFICANT INCREASE IN SHOWERS IS NOT EXPECTED. HOWEVER, WITH
LIGHT WINDS, ANY EPISODE OF RAIN THAT DEVELOPS WILL LIKELY LINGER,
RESULTING IN AN ELEVATED RISK OF URBAN AND SMALL STREAM FLOODING.
ADDITIONALLY, WITH THESE SOUTHERLY WINDS ON THURSDAY AND FRIDAY,
IT IS LIKELY THAT TEMPERATURES WILL FEEL ABOVE NORMAL, WITH HIGHS
IN THE UPPER 80S FOR COASTAL AREAS.
THE FORECAST IS A LITTLE MORE UNCERTAIN BY LATE SATURDAY AND
SUNDAY. THERE ARE DISCREPANCIES ON HOW MUCH MOISTURE WILL REACH
THE ISLANDS BY THEN. FOR NOW, A WETTER SOLUTION IS SHOWN, WITH A
40-50% CHANCE OF SHOWERS INCREASING ACROSS THE ATLANTIC WATERS,
THE NORTHERN AND EASTERN MUNICIPALITIES OF PUERTO RICO, AND ALSO
FOR THE VIRGIN ISLANDS.
AVIATION
(06Z TAFS)
MAINLY VFR CONDITIONS EXPECTED. VCSH WILL AFFECT TJSJ/TJPS/TIST/TISX
DURING THE MORNING HOURS. AFTER 02/17Z, SHOWERS WILL ALSO DEVELOP
OVER NW PR AND AFFECT TJBQ, POSSIBLY LEADING TO BRIEF PERIODS OF
REDUCED VIS AND LOW CEILINGS. ESE WINDS AT 10-15 KTS, WITH STRONGER
GUSTS, AFTER 02/13Z. THE PRESENCE OF SAHARAN DUST WILL PROMOTE SOME
HZ, BUT VISIBILITIES WILL BE P6SM.
MARINE
A BROAD SURFACE HIGH PRESSURE OVER THE EASTERN ATLANTIC WILL PROMOTE
MODERATE TO LOCALLY FRESH SOUTHEASTERLY WINDS THROUGH TOMORROW.
MODERATE EAST TO NORTHEAST TRADES RETURN ON TUESDAY. A COLD FRONT
WILL MOVE ACROSS THE WESTERN ATLANTIC, APPROACHING THE ISLANDS FROM
THE WEST MONDAY AND TUESDAY. ADDITIONALLY, A SURFACE TROUGH WILL
BRING PASSING SHOWERS ACROSS THE LOCAL WATERS.
BEACH FORECAST
THE RIP CURRENT RISK WILL BE MODERATE FOR THE NORTH, EAST,
SOUTHEAST COAST OF PUERTO RICO, AND ALSO FOR VIEQUES, CULEBRA,
SAINT THOMAS, SAINT JOHN, AND SAINT CROIX. THIS RISK IS EXPECTED
TO CONTINUE FOR THE NEXT SEVERAL DAYS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM...MRR
LONG TERM....ERG
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