Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 210925
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
525 AM AST MON APR 21 2014

.SYNOPSIS...MID TO UPPER LEVEL RIDGE OVER THE AREA WILL CONTINUE
TO FLATTEN AS AN UPPER LEVEL TROUGH DOMINATES THE WESTERN ATLANTIC.
THIS UPPER TROUGH IS FORECAST TO DISSIPATE OVER THE NEXT 24-36 HOURS.
THEN...AN INTENSE POLAR LOW WILL EXIT THE EAST COAST OF US BY MID-
WEEK. THE POLAR TROUGH WILL SEND A COUPLE OF UPPER LEVEL PERTURBATIONS
ACROSS THE LOCAL AREA BETWEEN WEDNESDAY AND THURSDAY. THESE PERTURBATIONS
ALOFT WILL HELP TO DESTABILIZE THE ATMOSPHERE AS WELL AS FAVOR MOISTURE
TRANSPORT ACROSS THE ISLANDS. AT LOW LEVELS...LOCAL PRESSURE GRADIENT
WILL CONTINUE TO LOOSE AS SURFACE HIGH PRESSURE NORTHEAST OF THE
REGION WILL PULL FARTHER NORTH INTO THE NORTHEAST ATLANTIC.

&&

.DISCUSSION...TRANQUIL CONDITIONS HAVE BEEN OBSERVED ACROSS THE
ISLANDS OVERNIGHT. SATELLITE AND RADAR IMAGERY DETECTED A FEW
CLOUDS AND SHOWERS OVER THE COASTAL WATERS...HOWEVER MOSTLY CLEAR
AND LITTLE OR NO RAINFALL ACCUMULATIONS HAVE BEEN NOTED OVER THE
ISLANDS SINCE MIDNIGHT. THIS RELATIVELY FAIR WEATHER CONDITIONS ARE
EXPECTED TO CONTINUE THROUGH AT LEAST LATE TONIGHT. THEN...DEEPER
MOISTURE WILL POOL ACROSS THE AREA FROM THE SOUTHEAST ON TUESDAY...
INCREASING THE CLOUDINESS AND THE CHANCES OF SHOWERS ACROSS THE
LOCAL ISLANDS. BY MID WEEK...AFOREMENTIONED POLAR LOW WILL SUPPORT
A WEAKENING COLD FRONT THAT WILL MOVE CLOSE TO THE LOCAL REGION...
ENHANCING THE LOW LEVEL CONVERGENCE ACROSS THE LOCAL ISLANDS WEDNESDAY
AND THURSDAY. THIS FEATURE WILL ALLOW FOR BETTER FORMATION OF EARLY
MORNING SHOWERS ALONG WITH SOME ENHANCED AFTERNOON CONVECTION WHICH
WILL BE MAINLY FORCED BY DIURNAL EFFECTS AND SEA BREEZE CONVERGENCE.
MODEL GUIDANCE SUGGESTS THAT THE MOISTURE WILL DECREASE AGAIN AS
THE POLAR LOW MOVES AWAY INTO THE NORTH ATLANTIC.

&&

.AVIATION...MOSTLY VFR CONDITIONS ARE EXPECTED ACROSS THE LOCAL
FLYING AREA THROUGH THE FORECAST PERIOD. HOWEVER...AFT 21/16Z BRIEF
PERIODS OF MVFR CONDITIONS IN SHRA AND LOCAL MOUNTAIN OBSCURATIONS
WILL REMAIN POSSIBLE ACROSS WESTERN AND INTERIOR PUERTO RICO...
AFFECTING TJMZ AND POSSIBLE TJBQ THROUGH ABOUT 21/22Z. LOW LEVEL
WINDS WILL BE MAINLY EAST SOUTHEAST AT 10 TO 15 KTS.

&&

.MARINE...WINDS OF 14-18 KT AND SEAS OF 4-6 FEET HAVE BEEN MEASURED
BY THE LOCAL BUOYS SINCE MIDNIGHT. THE LATEST WAVE MODEL DATA CONTINUES
TO SHOW A DECREASING TREND IN WINDS AND SEAS ACROSS THE LOCAL WATERS.
BASICALLY...THE SEAS WILL REACH THE MINIMUM BETWEEN WEDNESDAY AND
FRIDAY WITH WAVE HEIGHTS RANGING BETWEEN 2-4 FEET ACROSS MOST OF
THE WATERS. THIS TRANQUIL MARINE CONDITIONS WILL CONTINUE THROUGH
THE END OF THE WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  86  76  87  76 /  30  10  40  30
STT  85  75  86  77 /  20  20  50  40

&&

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

$$

71/11




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