Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 230121
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
921 PM AST MON DEC 22 2014

.UPDATE...SATELLITE TPW ANALYSIS SHOWS A MOISTURE BAND APPROACHING
TO THE LEEWARD ISLANDS THIS EVENING. AS A RESULT...MOISTURE CONTENT
WILL INCREASE TO SLIGHTLY ABOVE NORMAL LEVELS DURING THE NEXT 12-18
HOURS. PRECIPITABLE WATER VALUES WILL INCREASE FROM 1.10 INCHES
TONIGHT TO 1.55 BY 18Z ON TUESDAY. THIS WILL RESULT IN A FEW ROUNDS
OF SCATTERED SHOWERS AFFECTING THE REGIONAL WATERS AND PORTIONS OF
THE LOCAL ISLANDS OVERNIGHT AND TUESDAY. MOISTURE LEVELS WILL DROP
RAPIDLY LATE TUESDAY AND CHRISTMAS EVE AS DRY AND STABLE AIR
ENCOMPASS THE REGION. NO CHANGES WERE NECESSARY TO THE FORECAST
PACKAGE THIS EVENING.

&&

.AVIATION...VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS WITH
A CHANCE OF PASSING SHRA ACROSS THE LOCAL TAF SITES. EASTERLY SFC
WINDS AT 5 TO 10 KTS ARE EXPECTED TONIGHT...INCREASING TO 10 TO 15
KTS AND GUSTY AFTER 23/14Z.

&&

.MARINE...WINDS OF 15-20 KT AND SEAS OF 3-5 FT EXPECTED OVER THE
NEXT FEW DAYS.

&&

.PREV DISCUSSION... /ISSUED 306 PM AST MON DEC 22 2014/

SYNOPSIS...RIDGE ALOFT WILL BE THE DOMINANT WEATHER FEATURE OVER
THE NEXT SEVERAL DAYS. WEAK SURFACE TROUGH WILL MOVE ACROSS THE
LOCAL ISLANDS LATE THURSDAY INTO FRIDAY.

DISCUSSION...MOSTLY SUNNY SKIES PREVAILED ACROSS THE LOCAL ISLANDS
THROUGH THE DAY. WINDS WERE FROM THE EAST AT 10 TO 15 MPH WITH SOME
SEA BREEZE VARIATIONS. THE MAXIMUM TEMPERATURES WERE IN THE MID 80S
AT LOWER ELEVATIONS AND IN THE 70S AT HIGHER ELEVATIONS. A GENERALLY
FAIR AND MAINLY STABLE WEATHER PATTERN WILL CONTINUE TO PREVAIL ACROSS
THE LOCAL ISLANDS DURING THE NEXT FEW DAYS UNDER RIDGE ALOFT/ASSOCIATED
SUBSIDENCE AND BELOW TO NORMAL PRECIPITABLE WATER.

LATEST MODEL GUIDANCE CONTINUED TO INDICATE BEST MOISTURE ADVECTION
TUESDAY MORNING THROUGH TUESDAY AFTERNOON. THEREFORE AN INCREASE
IN SHOWER ACTIVITY IS THEN EXPECTED...WITH PASSING SHOWERS ACROSS
WINDWARD AREAS IN THE MORNING HOURS FOLLOWED BY LIMITED AFTERNOON
CONVECTION...IF ANY...OVER AND WEST OF THE CORDILLERA CENTRAL. A
DRIER AIR MASS WILL MOVE IN FROM THE EAST WEDNESDAY MORNING TO
COMBINE WITH SUBSIDENCE ALOFT. AS A RESULT...LIMITED SHOWER ACTIVITY
IS EXPECTED WEDNESDAY AND EARLY THURSDAY. ALTHOUGH MOISTURE WILL
REMAIN NEAR NORMAL VALUES THURSDAY AND FRIDAY...A WEAK SURFACE
WILL MOVE ACROSS THE LOCAL AREA. THIS MAY INCREASE A BIT THE CHANCE
OF PASSING SHOWERS ACROSS WINDWARD AREAS. MODERATE TO FRESH TRADE
WINDS WILL CONTINUE TO PROMOTE NEAR NORMAL TEMPERATURES ACROSS
LOCAL ISLANDS.

AVIATION...MOSTLY VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS
WITH A SLIGHT CHANCE OF PASSING -SHRA ACROSS THE LOCAL TAF SITES.
AN INCREASE IN SHOWERS ACTIVITY OVER TIST/TISX/TJSJ/TNCM/TKPK IS
EXPECTED AFT 23/00Z WHEN A BAND OF MOISTURE IS EXPECTED TO REACH
THE ISLANDS. EASTERLY SFC WINDS AT 10 TO 15 KTS WITH HIGHER GUSTS...
DECREASING AT 5 TO 10 OVERNIGHT.

MARINE...MODERATE TO FRESH EASTERLY TRADE WINDS WILL PREVAIL
THROUGH TUESDAY. NORTHEASTERLY WINDS WILL RETURN BY THE END OF
THE WEEK ALONG WITH NORTHEAST SWELLS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  84  75  84 /  30  30  10  20
STT  75  85  75  86 /  40  40  20  20

&&

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

$$

25/11





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