Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 271857
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
257 PM AST TUE JAN 27 2015

.SYNOPSIS...AT UPPER LEVELS...THE RIDGE EXTENDING NORTHEAST ACROSS
THE LEEWARD ISLANDS INTO THE CENTRAL ATLANTIC WILL MOVE EASTWARD
AS A TROUGH PASSES TO THE NORTH AND A SUB TROPICAL JET PASSES OVER
OUR LOCAL ATLANTIC WATERS THURSDAY AND THURSDAY NIGHT. HIGH
PRESSURE WILL THEN SLOWLY RETURN TO THE WESTERN AND CENTRAL
CARIBBEAN.

AT MID LEVELS...HIGH PRESSURE DOMINATES THE CARIBBEAN AS A TROUGH
PASSES TO THE NORTH ON AN EASTWARD TRAJECTORY. HIGH PRESSURE THEN
CONTINUES OVER THE CARIBBEAN AND GREATER ANITLLES THROUGH MUCH OF
NEXT WEEK. AT 700 MB THE RIDGE OF HIGH PRESSURE REMAINS OVER THE
LOCAL AREA THROUGH THE NEXT 10 DAYS.

AT LOWER LEVELS...THE DEEP LOW THAT BROUGHT SO MUCH WIND AND SNOW
TO NEW ENGLAND HAS A TROUGH THAT EXTENDS TOWARD THE LOCAL AREA AND
THAT WILL PASS BY THURSDAY. ALTHOUGH THE COLD FRONT CURRENTLY OVER
HAITI WILL NOT PASS OVER THE AREA THERE WILL BE SOME CONVERGENCE
AND PATCHES OF LOW LEVEL MOISTURE OVER THE LOCAL AREA...THAT WILL BRING
SHOWERS WEDNESDAY THROUGH AND FRIDAY. FLOW TURNS EASTERLY OVER THE
WEEKEND AND SOUTHEASTERLY THEREAFTER WITH MODEST MOISTURE
THROUGHOUT.

&&

.DISCUSSION...SOUTHEAST FLOW PERSISTED THROUGH THE DAY AND THE
MOISTURE GENERATING THE SHOWERS OVER THE CARIBBEAN MOVED OVER THE
LOCAL ISLANDS DURING THE DAY SPAWNING SCATTERED SHOWERS ACROSS A
WIDE AREA...BUT MAINLY WEST OF SAINT THOMAS ANS SAINT CROIX. A
BAND OF DRIER AIR IS EXPECTED TONIGHT WITH ANOTHER BAND OF
MOISTURE ON WEDNESDAY FOLLOWING APPROXIMATELY THE SAME TRAJECTORY
WITH MUCH THE SAME RESULT. A WEAK SHEAR LINE WILL MAKE ITS
PRESENCE FELT OVER THE AREA ON THURSDAY AND...COUPLED WITH THE
JET ALOFT...SHOWER ACTIVITY WILL BE ENHANCED. SURFACE WINDS WILL
BECOME MORE NORTHEASTERLY THURSDAY NIGHT...AFTER THE SHEAR-LINE FROM
THE COLD FRONT TO THE NORTH PASSES OVER THE AREA. BUT...AS THE
WEAK RIDGE TO OUR NORTH EXTENDS FARTHER THE FLOW WILL BECOME EASTERLY
AND MORNING SHOWERS WILL BEGIN TO AFFECT THE NORTHEASTERN COASTS
MORE. FINALLY AS THE RIDGE BUILDS OVER THE EASTERN TROPICAL
ATLANTIC EARLY NEXT WEEK...FLOW WILL AGAIN BECOME MORE SOUTHEASTERLY
AND THE NORTH COAST WILL BE MORE SHELTERED FROM THE PASSING
SHOWERS...WHILE THE SOUTHEAST RECEIVES MORE SHOWERS. SCATTERED
SHOWERS ARE EXPECTED PRETTY MUCH EVERY AFTERNOON IN WESTERN PUERTO
RICO THROUGH THURSDAY OF NEXT WEEK DUE TO MODERATE MOISTURE AND
PRECIPITABLE WATER VALUES BETWEEN 1.4 AND 1.7 INCHES UNTIL
THURSDAY.

&&

.AVIATION...BRIEF MVFR CONDITIONS WILL REMAIN POSSIBLE UNTIL 22Z
AT TJMZ/TJBQ IN SHRA. BKN-OVC LAYER ABOVE FL100 OVER WESTERN
PR...SOME CLOUDINESS SPREADING EASTWARD THRU TONIGHT. SE WINDS AT
10 TO 15 KNOTS. VFR ACROSS THE REST OF THE TERMINALS.

&&

.MARINE...SEAS WILL SLOWLY INCREASE IN THE ATLANTIC THROUGH 2
FEBRUARY...BUT SMALL CRAFT ADVISORIES ARE NOT EXPECTED THIS WEEK.
THE CARIBBEAN WILL BEGIN TO EXPERIENCE A SLIGHT DECREASE IN SEAS
FOR THE NEXT SEVERAL DAYS AS WINDS REMAIN MODERATE.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  73  86  73  85 /  10  40  40  40
STT  74  83  74  84 /  30  40  40  40

&&

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

$$

13/12





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