Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 260259
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1059 PM AST TUE NOV 25 2014

.UPDATE...THE MODEL GUIDANCE SEEMS TO BE WELL INITIALIZED AS
SATELLITE IMAGES AND SOUNDING DATA SUGGESTED. THEREFORE...A DRY
SLOT WILL CONTINUE TO MOVE ACROSS THE LOCAL ISLANDS DIMINISHING
THE SHOWER ACTIVITY OVERNIGHT. HOWEVER...THE SURFACE HIGH PRESSURE
OVER CENTRAL ATLANTIC WILL MAINTAIN A TIGHT PRESSURE GRADIENT
ACROSS THE REGION TO PROMOTE LIGHT TRADE WIND SHOWERS MAINLY OVER
EASTERN PUERTO RICO AND THE NORTHERN U.S. VIRGIN ISLANDS.

&&

AVIATION...VFR CONDS EXPECTED DURG THE FCST PRD. HOWEVER...EXPECT
SCT L/LVL CLD LYRS BLO FL100 WITH FEW PASSING -SHRA EN ROUTE BTW ERN
PR AND NRN LEEWARDS MAINLY OVR COASTAL WATERS FM 26/06Z-26/13Z. NO
SIG CONVECTIVE DVLPMNT EN ROUTE BTW ISLANDS WITH NO SIG RESTRICTIONS
IN VIS ATTM. STRONG PREVAILING EASTERLY TRADES WILL CONTINUE AT
15-25 KTS BLO FL200 THEN BACKING AND BCMG MORE NRLY ABV. NO SIG
OPERATIONAL WX IMPACT AT THIS TIME.

&&

.MARINE...TIGHT PRESSURE GRADIENT ACROSS THE REGION WILL CONTINUE
CREATING CHOPPY TO ROUGH SEAS ACROSS MOST OF THE LOCAL WATERS.
WINDS OF UP TO 22 KNOTS AND SEAS UP TO 8 FEET WILL PREVAIL
OVERNIGHT. THEREFORE...A SMALL CRAFT ADVISORY CONTINUE IN EFFECT
AT LEAST UNTIL WEDNESDAY NIGHT THEN THE WINDS WILL GRADUALLY
DIMINISH BY THURSDAY AS THE HIGH PRESSURE SHIFT EAST AHEAD OF A
COLD FRONT AND THE LOCAL PRESSURE GRADIENT WEAKENS.

&&

.PREV DISCUSSION... /ISSUED 223 PM AST TUE NOV 25 2014/

SYNOPSIS...UPPER LEVEL RIDGE REMAINS FLATTEN TONIGHT AS A
SHORTWAVE TROUGH MOVES ACROSS THE REGION. UPPER LEVEL CONVERGENCE
WILL STRENGTHEN EARLY WEDNESDAY...LEADING TO DRYING AND SUBSIDENCE
PATTERN ACROSS THE REGION. STRONG SURFACE HIGH PRESSURE OVER THE
CENTRAL ATLANTIC WILL MAINTAIN FRESH TO STRONG TRADE WINDS INTO
MIDWEEK.

DISCUSSION...DOPPLER WEATHER RADAR DETECTED ISOLATED TO SCATTERED
PASSING SHOWERS OVER EASTERN AND NORTHERN SECTIONS OF PUERTO RICO
LATE IN THE MORNING AND THIS AFTERNOON. DUE TO THE RAPID MOVEMENT OF
THE SHOWERS THE TOTAL RAINFALL ACCUMULATIONS WERE MINIMAL. STRONG
SURFACE HIGH PRESSURE OVER THE CENTRAL ATLANTIC WILL MAINTAIN BREEZE
CONDITIONS ACROSS THE LOCAL ISLANDS. THESE TRADE WINDS WILL CONTINUE
TO TRANSPORT SMALL PATCHES OF LOW LEVEL MOISTURE FROM TIME TO TIME
TONIGHT AFFECTING MOSTLY THE EASTERN SECTIONS OF PUERTO RICO...
VIEQUES...CULEBRA AND THE U.S. VIRGIN ISLANDS. UPPER LEVEL
CONVERGENCE IS EXPECTED TO STRENGTHENS OVER THE REGION LATE TONIGHT
AND EARLY WEDNESDAY. THIS FEATURE WILL INDUCE A GENERAL DRY AND
STABLE WEATHER PATTERN ACROSS THE LOCAL ISLANDS MOST PART OF
WEDNESDAY AND UNTIL AT LEAST FRIDAY. HOWEVER THE TYPICAL PASSING
SHOWERS OVER EASTERN SECTIONS OF PUERTO RICO DURING THE OVERNIGHT
AND EARLY MORNING HOURS ARE STILL EXPECTED. NOT SIGNIFICANT WEATHER
EVENT IS EXPECTED TO AFFECT THE REGION FOR THE NEXT SEVERAL DAYS.

AVIATION...MOSTLY VCSH EXPECTED ACROSS THE LOCAL FLYING AREA TONIGHT
BRIEF PERIODS OF MVFR CONDITIONS ARE POSSIBLE OVER TIST AND TJSJ.
LATEST TJSJ SOUNDING INDICATED AN EASTERLY WIND FLOW UP TO 30 KNOTS
ALL THE WAY FROM THE SURFACE TO 25K FEET...BECOMING NORTHERLY
ALOFT.

MARINE...WINDS WILL DIMINISH BELOW 20 KT TONIGHT AND WEDNESDAY WITH
MORE RAPID WEAKENING WEDNESDAY NIGHT THROUGH FRIDAY. SEAS WILL
DIMINISH TO 5-7 FT TONIGHT AND WEDNESDAY THEN SUBSIDE RAPIDLY TO 3-5
FT WEDNESDAY NIGHT THROUGH FRIDAY. TRADE WINDS STRENGTHEN AGAIN LATE
SATURDAY THROUGH EARLY NEXT WEEK WITH SEAS GRADUALLY BUILDING TO 5-7
FEET.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  74  85  74  83 /  20  30  30  10
STT  77  86  75  86 /  20  20  20  10

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL MIDNIGHT AST WEDNESDAY NIGHT FOR
     ANEGADA PASSAGE SOUTHWARD TO 17N-ATLC WATERS OF PUERTO RICO
     AND USVI FROM 10NM TO 19.5N-CARIBBEAN WATERS OF PUERTO RICO
     FROM 10 NM TO 17N-COASTAL WATERS OF NORTHERN PUERTO RICO
     OUT 10 NM-COASTAL WATERS OF NORTHERN USVI AND CULEBRA OUT
     10 NM-COASTAL WATERS OF NORTHWESTERN PUERTO RICO OUT 10 NM-
     COASTAL WATERS OF SOUTHERN USVI VIEQUES AND EASTERN PUERTO
     RICO OUT 10 NM-MONA PASSAGE SOUTHWARD TO 17N.

     SMALL CRAFT ADVISORY UNTIL MIDNIGHT AST TONIGHT FOR COASTAL
     WATERS OF SOUTHERN PUERTO RICO OUT 10 NM.

&&

$$

09/27





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