469
FXCA62 TJSJ 241605
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1205 PM AST SUN MAR 24 2019
UPDATE
DIURNALLY INDUCED SHOWERS ARE DEVELOPING ALONG THE
INTERIOR AND WESTERN SECTIONS OF PUERTO RICO. THESE SHOWERS WILL
CONTINUE THROUGH THE REST OF THE AFTERNOON HOURS AND URBAN AND
SMALL STREAM FLOODING CAN NOT BE RULED OUT WITH THE HEAVIEST
SHOWERS. BETWEEN 1-2 INCHES OF RAINFALL IS POSSIBLE WITH THIS
ACTIVITY. ADDITIONAL CLOUDINESS AND SHOWERS WERE APPROACHING THE
U.S. VIRGIN ISLANDS AND STREAMERS WERE DEVELOPING AS WELL OFF THE
ISLANDS AND MOVING INTO THE NORTHWESTERN WATERS. BUT MOSTLY LIGHT
RAINFALL AMOUNTS ARE EXPECTED WITH THESE SHOWERS. FOR TONIGHT,
SHOWERS CURRENTLY OVER THE LEEWARD ISLANDS ARE EXPECTED TO MOVE
ACROSS THE USVI AND REACH THE EASTERN AND SOUTHEASTERN SECTIONS OF
PUERTO RICO. ELSEWHERE, CLEAR TO PARTLY CLOUDY SKIES ARE EXPECTED
THROUGH THE OVERNIGHT HOURS.
AVIATION
MAINLY VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS
ALL TERMINALS. HOWEVER, SHRA EXPECTED IN AND AROUND TJSJ/TJMZ/TJBQ
THROUGH 23Z. TEMPO MVFR TO BRIEF IFR POSSIBLE AT TJMZ/TJBQ. THE
24/12Z TJSJ UPPER AIR SOUNDING INDICATED ESE WINDS AT 10-30 KT
BLO FL120.
MARINE
SEAS WILL GRADUALLY INCREASE TONIGHT THROUGH MONDAY DUE
TO A COMBINATION OF A SMALL NORTHEASTERLY SWELL AND FRESH TRADES
ACROSS THE ATLANTIC WATERS. SEAS UP TO 7 FEET ARE EXPECTED ACROSS
THE OFFSHORE ATLANTIC WATERS ON MONDAY AND A SMALL CRAFT ADVISORY
WAS ISSUED. ELSEWHERE, SEAS WILL RANGE BETWEEN 3-6 FEET AND EAST
TO SOUTHEAST WINDS WILL PREVAIL BETWEEN 15-20 KNOTS. THEREFORE,
SMALL CRAFTS SHOULD EXERCISE CAUTION.
THERE IS A HIGH RIP CURRENT RISK IN EFFECT FOR THE NORTH CENTRAL
BEACHES OF PUERTO RICO. A MODERATE RISK CONTINUES FOR MOST OF THE
NORTH AND EAST FACING BEACHES OF THE ISLANDS.
PREV DISCUSSION
/ISSUED 523 AM AST SUN MAR 24 2019/
SYNOPSIS...
SURFACE HIGH PRESSURE OVER THE CENTRAL AND NORTHEAST ATLANTIC, AND
A BROAD SURFACE TROUGH OVER THE EASTERN CARIBBEAN WILL CONTINUE TO
PROMOTE MODERATE EAST TO SOUTHEAST WINDS ACROSS THE REGION. OCCASIONAL
BANDS OF TRADE WIND MOISTURE CONTINUED TO TRANSPORT PERIODS OF PASSING
SHOWERS ACROSS THE REGION FROM TIME TO TIME. MODEL GUIDANCE CONTINUED
TO SUGGEST A MUCH WETTER PATTERN DURING THE LATTER PART OF NEXT WEEK
AS THE LONG WAVE TROUGH AND ASSOCIATED FRONTAL BOUNDARY IS FORECAST
TO APPROACH AND EVENTUALLY SINK SOUTHWARDS ACROSS THE REGION.
SHORT TERM...TODAY THROUGH TUESDAY...
A MID LEVEL RIDGE WILL CONTINUE TO HOLD OVER THE CENTRAL ATLANTIC
WATERS THROUGH EARLY NEXT WEEK. PATCHES OF SHALLOW MOISTURE WILL
CONTINUE TO MOVE OVER THE AREA PERIODICALLY, AND INDUCE ISOLATED TO
SCATTERED SHOWERS DURING THE AFTERNOON. ADDITIONALLY, THE SHALLOW
MOISTURE PLUS LOCAL AND DIURNAL EFFECTS WILL PRODUCE LIGHT TO
MODERATE RAINFALL ACROSS PORTIONS OF INTERIOR AND WESTERN AREAS OF
PUERTO RICO. SIMILAR TO YESTERDAY LIGHT LOW-LEVEL WINDS WILL CAUSE
CONTINUOUS LIGHT SHOWERS TO RE-DEVELOP ACROSS THE AREA DURING THE
AFTERNOON. THE TJSJ SKEW-T SHOWS A MOIST PROFILE AT 1000 TO 750 MB,
BUT ABOVE THE 700 MB THERE IS A LARGE LAYER OF DRIER AIR THAT WILL
LIMITED THE VERTICAL DEVELOPMENT OF SHOWERS. THIS MEANS THAT
MOISTURE WILL BE CONFINED TO THE LOWER-LEVEL OF THE ATMOSPHERE.
YESTERDAY SOME AREAS RECEIVED 1.5 TO 2.0 INCHES OF RAIN EXPECT
SIMILAR CONDITIONS TODAY. IF RAIN DEVELOPS TODAY IN THE AREAS THAT
RECEIVED THE 1.5 TO 2.0 INCHES OF RAIN, IT COULD LEAD TO URBAN AND
SMALL STREAM FLOODING; AS WELL AS PONDING OF WATER ON ROADWAYS. THE
GOOD NEWS ABOUT YESTERDAY'S RAINFALL IS THAT RAIN FELL IN BASIN
AREAS THAT NEEDED RAIN. HOWEVER MORE RAIN IS NEEDED FOR MANY AREAS
ACROSS PUERTO RICO.
MONDAY A TROUGH NORTHEAST OF PUERTO RICO WILL IMPINGE ON THE MID-
LEVEL RIDGE AND BEGIN TO WEAKEN IT. THE MID-LEVEL MOISTURE FROM THE
BOUNDARY WILL MOVE NEAR PUERTO RICO LATE MONDAY OR EARLY TUESDAY.
THIS MID-LEVEL MOISTURE WILL MOISTEN THE MID-LEVELS OF THE
ATMOSPHERE AND HELP ADD IN SHOWER DEVELOPMENT ACROSS THE
NORTHWESTERN AREAS OF PUERTO RICO DURING THE AFTERNOON ON LATE
MONDAY AND TUESDAY. BY TUESDAY SURFACE WINDS ARE FORECAST TO BE FROM
THE EAST TO SOUTHEAST, THIS WIND FLOW TYPICALLY LEADS TO WARMER
TEMPERATURES ACROSS THE REGION.
LONG TERM...WEDNESDAY THROUGH SUNDAY
A SLOWLY WEAKENING SHORT-WAVE TROUGH OVER THE EASTERN CARIBBEAN WILL
CONTINUE TO SUPPORT MOISTURE POOLING ACROSS THE REGION THROUGH THE
END OF THE WORK WEEK AND INTO THE WEEKEND AS IT LIFT NORTHWARDS. THE
GRADUAL EROSION OF THE UPPER LEVEL RIDGE IN RESPONSE TO A DEEPENING
LONG WAVE TROUGH ACROSS THE WEST AND SOUTHWEST ATLANTIC WILL WEAKEN
THE TRADE WIND CAP INVERSION AND SUPPORT GOOD LOW LEVEL MOISTURE
CONVERGENCE ACROSS THE FORECAST AREA. IN ADDITION, THE APPROACHING
FRONTAL BOUNDARY AND ASSOCIATED MOISTURE IS FORECAST TO SINK SOUTHWARDS
ACROSS THE AREA BY THE END OF THE WEEK. THEREFORE EXPECT INCREASING
CLOUD COVER AND MORE FREQUENT SHOWER DEVELOPMENT ACROSS THE FORECAST
AREA THROUGH THE END OF THE PERIOD.
RECENT GUIDANCE WAS UNCHANGED AND CONTINUED TO SUGGEST A FAIRLY
MOIST SOUTHEAST WIND FLOW THROUGH MOST OF THE PERIOD. THIS ALONG
WITH THE PROXIMITY OF THE AMPLIFYING LONG WAVE TROUGH AND FRONTAL
BOUNDARY WILL SUPPORT FAVORABLE CONDITIONS FOR CONVECTIVE DEVELOPMENT
WITH ENHANCED SHOWER ACTIVITY ACROSS PORTIONS THE ISLANDS AND COASTAL
WATERS AT LEAST THROUGH SATURDAY. BY SUNDAY THE RETURN FLOW OF MOISTURE
FROM THE FRONTAL BOUNDARY SHOULD BE SUFFICIENT TO SUPPORT EARLY MORNING
AND AFTERNOON CONVECTION ACROSS THE COASTAL WATERS AND LOCAL ISLANDS.
HOWEVER, A GRADUAL IMPROVEMENT IN CONDITIONS IS EXPECTED AS THE UPPER
TROUGH IS EXPECTED TO LIFT NORTHWARDS AND WEAKEN BRINGING STABLE CONDITIONS
ALOFT.
AS PREVIOUSLY MENTIONED, GOOD UPPER LEVEL SUPPORT AND THE FAIRLY
MOIST ENVIRONMENTAL CONDITIONS SHOULD ALL FAVOR ORGANIZED AND
ENHANCED CONVECTION ACROSS PORTIONS OF THE ISLANDS, ESPECIALLY
OVER THE INTERIOR AND NORTHERN SECTIONS OF PUERTO RICO THROUGH
SATURDAY, WITH A GRADUAL IMPROVEMENT EXPECTED BY SUNDAY.
AVIATION...MAINLY VFR/MVFR CONDITIONS ARE EXPECTED ACROSS ALL
TERMINALS DURING THE NEXT 24 HOURS. MVRF CONDS ARE OCCURRING DUE TO
LIGHT -SHRA MAINLY ACROSS PR EASTERN AND THE U.S. VI TERMINALS. BY
24/15Z SHRA WILL DEVELOP ACROSS TJBQ AND TJMZ TERMINALS AND PERSIST
THROUGH 25/01Z. WINDS WILL BE OUT OF THE EAST AT 10 TO 15 KTS WITH
SEA BREEZE VARIATIONS.
MARINE....A NORTHERLY SWELL HAS ARRIVED AND WILL SPREAD ACROSS
THE LOCAL ATLANTIC WATERS AND PASSAGE TODAY THROUGH MONDAY. A
SLIGHT INCREASE IN THE EAST TO SOUTHEAST TRADE WINDS WILL ALSO
BRING MODERATE TO LOCALLY STRONG WINDS BETWEEN 15-20 KNOTS IN SOME
AREAS WITH SEAS UP TO 6 FEET OFFSHORE AND IN THE LOCAL PASSAGES.
SMALL CRAFT OPERATORS SHOULD THEREFORE EXERCISE CAUTION THOUGH
MONDAY.
THERE IS A HIGH RISK OF RIP CURRENT FOR SOME OF THE NORTH CENTRAL
BEACHES OF PUERTO RICO. A MODERATE RISK OF RIP CURRENTS WILL CONTINUE
ACROSS THE REMAINING NORTH FACING BEACHES OF PUERTO RICO, CULEBRA,
EAST VIEQUES, NORTHWESTERN SAINT THOMAS AND NORTH AND EASTERN SAINT
CROIX TODAY. LOW RISK OF RIP CURRENTS ELSEWHERE.
PRELIMINARY POINT TEMPS/POPS
SJU 87 75 88 74 / 40 40 40 40
STT 85 75 85 76 / 30 30 30 40
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH LATE TONIGHT FOR NORTH CENTRAL.
VI...NONE.
AM...SMALL CRAFT ADVISORY FROM 8 AM MONDAY TO 4 AM AST TUESDAY FOR
ATLANTIC WATERS OF PUERTO RICO AND USVI FROM 10 NM TO 19.5N.
SHORT TERM...DS
LONG TERM....99
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