Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 280820
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
420 AM AST SUN DEC 28 2014

.DISCUSSION...COLD FRONT REMNANT NORTH OF PR/USVI APPROACHING
ISLANDS AT ABOUT 12 KNOTS BY EXTRAPOLATION OF SATELLITE IMAGES AND
GFS HAS A GOOD HANDLE...WILL REACH NORTH SHORES AROUND SUNRISE.
SOUNDINGS FROM THIS MODEL HAVE THE MOISTURE LIMITED TO UNDER 650
MB. THAT APPEARS ACCURATE BASED ON IMPLIED CLOUD TOPS FROM IR
IMAGES. BUT THINK GFS MOISTURE LEVELS ARE PROBABLY A LITTLE LOW
ABOVE 800 MB. MOISTURE TO THIS DEPTH IMPLIES QUITE A FEW SHOWERS
THIS MORNING AFTER 600 AM FOR NORTH HALF OF PR AND INTO ST.
THOMAS/VIEQUES/CULEBRA. RADAR CURRENTLY SHOWS THEM SPACED OUT
PRETTY WELL AND MOVING QUICKLY. SHOWERS WILL BE WIDESPREAD BUT NOT
LAST VERY LONG OR BE HEAVY. UNCERTAINTY OVER HOW FAR SOUTH THIS
NARROW BAND OF MOISTURE WILL SAG BY AFTERNOON LEADS TO LOW
CONFIDENCE IN PROBABILITY OF SHOWERS THEN. SUNSHINE ON LAND SHOULD
BE ENOUGH TO CAUSE SOME CONVECTION BUT THE MOISTURE IS PRETTY
SHALLOW ANYWAY SO DO NOT EXPECT IT TO BE WIDESPREAD. FRONTOLYSIS
IS TURNING THIS FRONT INTO A BUNCH OF MINOR EASTERLY WAVES TO
PASS OVER PR/USVI OVER THE NEXT SEVERAL DAYS. THE BEST ONE
PROBABLY ARRIVES TONIGHT. GOOD CONVERGENCE AT 1000-850 MB AS
NOTED ON GFS AT 06Z TONIGHT DEPICTED BETWEEN EASTERN PR AND USVI.
THIS IS A CLIMATOLOGICALLY FAVORED ZONE FOR NIGHTTIME SHOWERS AND
HAVE INCLUDED LIKELY SHOWERS OVERNIGHT THERE.

&&

.AVIATION...A COLD FRONT WILL REACH THE FLYING AREA...CREATING
MVFR/BRIEF IFR CIGS BETWEEN AFT 28/12Z MAINLY AT TJSJ/TJBQ/TNCM...
FOLLOWED BY SCT SHRA ACROSS MOST THE WHOLE AREA LATE IN THE MORNING
AND INTO THE AFTERNOON. INCLEMENT WEATHER IS EXPECTED DURING THE
REST OF THE FORECAST PERIOD. NORTHEASTERLY SFC WINDS AT 10 TO 20 KTS
WITH HIGHER GUSTS ARE EXPECTED TODAY.

&&

.MARINE...LONG PERIOD NORTHEAST SWELLS PEAK TODAY BUT WILL TAKE
SEVERAL DAYS TO DIMINISH. WINDS TO INCREASE SOMEWHAT TODAY WHICH
WILL MAKE THE WAVE GROUPS MORE COMPLEX BETWEEN SHORT PERIOD WIND
WAVE AND SWELL.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  82  70  82  71 /  80  60  50  50
STT  84  74  87  76 /  90  60  50  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...HIGH SURF ADVISORY UNTIL 6 PM AST MONDAY FOR CULEBRA-NORTH
     CENTRAL-NORTHEAST-NORTHWEST-SAN JUAN AND VICINITY-SOUTHEAST-
     WESTERN INTERIOR.

VI...HIGH SURF ADVISORY UNTIL 6 PM AST MONDAY FOR ST CROIX-ST.
THOMAS/ST. JOHN/ADJACENT ISLANDS.


COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 6 PM AST TUESDAY 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 USVI AND CULEBRA 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 NOON AST TUESDAY FOR COASTAL WATERS
     OF NORTHERN PUERTO RICO OUT 10 NM.

     SMALL CRAFT ADVISORY UNTIL MIDNIGHT AST MONDAY NIGHT FOR COASTAL
     WATERS OF NORTHWESTERN PUERTO RICO OUT 10 NM.

&&

$$

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