558
FXCA62 TJSJ 210936
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
536 AM AST THU NOV 21 2024
SYNOPSIS
SOME MOISTURE PUSHED INTO THE NORTHEAST CORNER OF THE
FORECAST AREA LAST NIGHT AND SHOWERS CONTINUED OVER THE LOCAL
ATLANTIC WATERS, OTHERWISE THE ATMOSPHERE HAS BEEN RELATIVELY DRY
WITH A FEW HEAT-DRIVEN SHOWERS IN THE AFTERNOON. MOISTURE WILL
MOVE INTO THE AREA ON FRIDAY MORNING BRINGING INCREASED SHOWERS
AND THUNDERSTORMS TO THE AREA. A NORTHWESTERLY SWELL WILL INCREASE
THE RIP CURRENT RISK ON SUNDAY. EXCEPT FOR A DRY SLOT THAT CROSSES
MONDAY NIGHT CONDITIONS WILL REMAIN MOSTLY WET AFTER THIS FRIDAY.
SHORT TERM...THURSDAY THROUGH SATURDAY
RELATIVELY CALM AND QUIET WEATHER CONDITIONS PREVAILED DURING THE
OVERNIGHT HOURS ACROSS THE ISLANDS. SATELLITE AND DOPPLER RADAR
OBSERVATIONS INDICATED ISOLATED TO SCATTERED SHOWERS MOSTLY OVER THE
ATLANTIC WATERS WITH NO SIGNIFICANT IMPACT OVER THE REGION. LOWS
WERE IN THE LOW TO MID 60S IN THE CORDILLERA CENTRAL OF PUERTO
RICO AND IN THE MID TO UPPER 70S IN THE COASTAL AND URBAN AREAS OF
THE ISLANDS. WINDS WERE LIGHT AND VARIABLE THROUGH MOST OF THE
NIGHT.
AFTER THE FRONTAL PASSAGE IN THE PREVIOUS DAYS, DRY AND STABLE
CONDITIONS CONTINUED ACROSS THE REGION. TODAY, MOSTLY CALM
WEATHER WILL CONTINUE TO PREVAIL. AFTERNOON SHOWERS MAY DEVELOP
ACROSS THE INTERIOR AND NORTHWESTERN PUERTO RICO DUE TO THE
COMBINATION OF DAYTIME HEATING AND LOCAL EFFECTS. HOWEVER, NO
SIGNIFICANT RAINFALL ACCUMULATIONS ARE ANTICIPATED AT THIS TIME.
BY FRIDAY, A POLAR TROUGH IS EXPECTED TO EXIT THE EASTERN COAST OF
THE UNITED SATES, WHILE A SURFACE HIGH PRESSURE LOCATED NORTH OF
THE AREA CONTINUE TO MOVE EASTWARDS TOWARD THE CENTRAL ATLANTIC.
THIS PATTERN WILL CAUSE THE WINDS TO VEER AND BECOME SOUTHEAST
TODAY AND THEN SOUTH ON FRIDAY. THEREFORE, AN INCREASE IN
MOISTURE CONTENT IS EXPECTED THROUGH THE UPCOMING WEEKEND. THE
LATEST PRECIPITABLE WATER CONTENT ANALYSIS HAS VALUES OF UP TO 2.0
INCHES. THIS ANALYSIS SUGGESTS AN INCREASE IN MOISTURE CONTENT
THAT MAY RESULT IN SHOWER ACTIVITY THROUGH THE REST OF THE SHORT-
TERM PERIOD.
DAYTIME TEMPERATURES WILL REMAIN IN THE MID TO UPPER 80S ALONG THE
COASTAL AND URBAN AREAS OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS,
AND IN THE UPPER 70S TO LOW 80S IN THE CORDILLERA CENTRAL OF PUERTO
RICO. MINIMUM TEMPERATURES WILL DROP TO THE LOW TO MID 60S IN THE
HIGHER ELEVATIONS, AND WILL REMAIN IN THE 70S FOR THE REST OF THE
AREA.
LONG TERM...SUNDAY THROUGH THURSDAY
AT UPPER LEVELS, THE SUB-TROPICAL JET BETWEEN FLORIDA AND HAITI
WILL JOIN THE POLAR JET WELL NORTH OF THE LOCAL AREA, BUT WILL BE
UNABLE TO COME MUCH CLOSER TO THE AREA DUE TO HIGH PRESSURE THAT
STRETCHES FROM THE CENTRAL CARIBBEAN TO THE TROPICAL ATLANTIC
ALONG 20 NORTH WHICH WILL DRIFT A LITTLE SOUTH DURING THE PERIOD.
A DECAYING WAVE WILL APPROACH THE AREA AND CROSS THE WINDWARD
ISLANDS FROM THE EAST EARLY SUNDAY MORNING TO BRING ADDITIONAL
MOISTURE TO THE AREA. THIS MOISTURE WILL MOVE QUICKLY PAST THE
FORECAST AREA TO THE SOUTH AND FEED THE DEVELOPING NORTH-SOUTH
TROUGH NORTH OF PANAMA WHILE PULLING IN DRIER AIR IN FROM THE
EAST OVER US ON MONDAY. AS THE TROUGH DEVELOPS A LOW OVER
JAMAICA, WINDS WILL BECOME MORE SOUTHERLY AND BRING MORE MOISTURE
FROM THE SOUTHEAST CARIBBEAN FOR CONTINUED SHOWER ACTIVITY.
500 MB TEMPERATURES WILL BE MOSTLY MINUS 5 TO MINUS 6 DURING THE
PERIOD, SO THERE WILL PRESENT A CHANCE OF THUNDERSTORMS--MAINLY
DURING THE AFTERNOONS OVER PUERTO RICO AND OVER THE LOCAL WATERS
AT NIGHT. ALTHOUGH SOME LOCAL URBAN AND SMALL STREAM FLOODING
COULD DEVELOP, SHOWERS SHOULD MOVE JUST FAST ENOUGH TO PREVENT
MAJOR RIVER RISES DURING THE PERIOD. NEVERTHELESS MOST AREAS WILL
HAVE AT LEAST SOME RAIN EACH DAY.
AVIATION
(06Z TAFS)
MAINLY VFR CONDS ARE EXPECTED TO PREVAIL ACROSS ALL TERMINALS
THROUGH THE FORECAST PERIOD. AFTN SHRA MAY RESULT IN VCSH AT
TJPS/TJBQ/TIST/TISX BTW 21/16-23Z. VRB AT LESS THAN 5 KTS WILL
CONTINUE THRU 21/14Z. THEN, ESE WINDS AT 10-15 KT WITH HIGHER
GUSTS AND SEA BREEZE VARIATIONS THROUGH 21/22Z.
MARINE
SMALL CRAFT ADVISORIES ARE STILL LIKELY SUNDAY THROUGH TUESDAY--
MAINLY IN THE ATLANTIC WATERS WHEN SEAS BECOME 7 FEET OR MORE.
BEACH FORECAST
CONDITIONS HAVE IMPROVED CONSIDERABLY SINCE YESTERDAY ALLOWING THE
HIGH SURF ADVISORY TO BE DROPPED. BUT THE INCREASING SWELL FROM
THE NORTH NORTHWEST ON SUNDAY WILL ELEVATE THE RIP CURRENT RISK TO
HIGH THROUGH AT LEAST MONDAY.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH THIS AFTERNOON FOR PRZ001-002.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION/PUBLIC...GRS
LONG TERM/MARINE/FIRE WEATHER...WS
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