Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 261002
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
602 AM AST FRI DEC 26 2014

.SYNOPSIS...UPPER LEVEL RIDGE WILL REMAIN OVER THE LOCAL AREA FOR
THE NEXT SEVERAL DAYS. SURFACE HIGH PRESSURE WILL EXIT THE EAST
COAST OF THE U.S. AND THEN SLOWLY MOVE EAST THROUGH THE ATLANTIC
FOR THE NEXT FEW DAYS. COLD FRONT EXPECTED OVER THE LOCAL ISLANDS
ON SUNDAY.

&&

.DISCUSSION...PASSING SHOWERS HAVE BEEN OBSERVED THROUGH THE NIGHT
ACROSS THE LOCAL AREA. SATELLITE DERIVED PRECIPITABLE WATER AND
LATEST GUIDANCE SUGGESTS THAT MOISTURE WILL REMAIN CONSTANT TODAY
AT ABOUT 1.3 INCHES OF P-WAT BUT DRIER AIR IS MOVING IN LATE TODAY
INTO SATURDAY. THIS MEANS THAT SCATTERED SHOWERS MAY CONTINUE IN
THE MORNING THEN SHOWERS MAY DEVELOP ACROSS THE INTERIOR AND
SOUTHWESTERN PORTIONS OF PR IN THE AFTERNOON. THE SHOWERS IN THE
AFTERNOON ARE NOT EXPECTED TO BE HEAVY OR LONG LASTING AS THE
MOISTURE IS LIMITED. SATURDAY...IS EXPECTED TO BE A VERY NICE DAY
WITH LITTLE TO NO SHOWER ACTIVITY. NORTHEASTERLY WINDS AND DRY AIR
APPROACHING WILL LIKELY KEEP FAIR WEATHER CONDITIONS THROUGH THE
LOCAL AREA...ONLY A SLIGHT CHANCE OF LIGHT SHOWERS FOR SATURDAY.

COLD FRONT IS EXPECTED TO APPROACH THE LOCAL ISLANDS ON SUNDAY.
THIS SHOULD SIGNIFICANTLY INCREASE MOISTURE...CLOUD COVER AND SHOWER
ACTIVITY. HOWEVER THE TIMING OF THE FRONTAL PASSAGE HAS NOT BEEN
THAT CONSISTENT BETWEEN MODEL RUNS...SO POPS WERE KEPT A BIT
CONSERVATIVE UNTIL MORE CONSISTENCY IS SEEN IN THE TIMING.

FROM MONDAY ON...FAIR WEATHER IS EXPECTED ON MONDAY AND TUESDAY
BEHIND THE FRONT WITH EAST NORTHEAST WINDS AND PATCHES OF MOISTURE
MOVING THROUGH ON WEDNESDAY.

MARINE CONDITIONS THOUGH WILL NOT BE SO GOOD THIS WEEKEND. DETAILS
IN THE MARINE SECTION BELOW.

&&

.AVIATION...ACT SHRA ACROSS THE LOCAL AREA IS CAUSING VCSH ACROSS
MOST OF THE LOCAL TERMINALS...THIS SHOULD IMPROVE BY 26/14Z.
AFTERNOON SHRA MAY CAUSE VCSH AT TJMZ BUT CONDITIONS OVERALL
SHOULD BE VFR. NORTHEAST WINDS TODAY AT AROUND 10-15 KTS.


&&

.MARINE...MARINE CONDITIONS ARE EXPECTED TO START DETERIORATING
TONIGHT. NORTHEASTERLY SWELL WILL INVADE THE LOCAL WATERS AND
CAUSE HAZARDOUS MARINE CONDITIONS. LATEST MARINE GUIDANCE WAS
RATHER BULLISH IN THE WAVE HEIGHTS BUT WE DECIDED TO CAP THE WAVE
HEIGHTS AT 8 FEET STARTING ON SATURDAY NIGHT. THIS WAS BECAUSE THE
SWELL HAS YET TO PASS THROUGH ANY OF THE BUOYS THAT ARE CLOSER TO
THE LOCAL AREA SO THERE IS STILL SOME UNCERTAINTY ON MODEL
GUIDANCE PERFORMANCE. THE MARINE FORECAST WAS UPDATED AFTER
CONSIDERING THE LATEST OBSERVATIONS AND THE LATEST GUIDANCE. SMALL
CRAFT ADVISORIES TO GO INTO EFFECT STARTING LATE TONIGHT.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  82  71  83  71 /  20  10  20  30
STT  85  73  85  74 /  20  10  30  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...NONE.
&&

$$

27/25




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