Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 010246 AAA
AFDSJU

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
1046 PM AST SAT FEB 28 2015

.UPDATE...A SURPRISING SOUNDING THIS EVENING 01/00Z...WITH 38
KNOTS OF WIND AS LOW AS 2 KFT. A SLIGHT INVERSION AT 1000 MB
PROTECTS THE LOWEST LAYER FROM MUCH OF THE STRONGER VELOCITIES.
ADIABATIC BETWEEN 1200 TO 3200. MOST OF THE PATCHES OF RAIN HAVE
MOVED THROUGH THE AREA AND SATELLITE IMAGERY INDICATED THAT THE
BACK EDGE OF THE BEST MOISTURE IS NOW MOVING THROUGH THE GREATER
METROPOLITAN AREA OF SAN JUAN. THE NEXT AREA OF MOISTURE AND
SHOWERS...AND THEY ARE LIGHT...IS MOVING INTO SAINT THOMAS FROM
BEEF ISLAND WITH THE CENTER OF THE BAND NEAR SAINT MARTIN.


&&

.DISCUSSION...SHOWERS IN THIS BAND HAVE LESS MOISTURE AND ARE
SPOTTY. OTHERWISE NO CHANGES TO DISCUSSION BELOW. HAVE RAISED POPS
ON EAST SIDE OF PUERTO RICO AND THE OVER THE U.S. VIRGIN ISLANDS
TO THE LOW SCATTERED CATEGORY...FOR LATE TONIGHT AND TOMORROW.


&&

.AVIATION...FAST MOVING LIGHT RAIN IS STILL PASSING OVER THE LOCAL
ISLANDS. BKN/OVC CLOUD COVER AT ABOUT FL050 IMPROVING AFTER
01/06Z...LEAVING SCT CLOUDS PASSING OVER THE AREA OVERNIGHT. WINDS
WILL BE FROM THE EAST AT AROUND 10 KNOTS OVERNIGHT...INCREASING TO
15-20 KNOTS AND GUSTY AFTER 01/14Z. ALTHOUGH SOUNDING HAD LLWS FOR AN
INCREASE OF 31 KNOTS FROM THE EAST IN THE LOWEST 2 KFT...MOST
FLIGHTS ARE REPORTING LESS WINDS THAN LLWS CRITERIA IN THE LOWEST
2 KFT AND SO WILL NOT BE ADDING IT TO THE TAFS.

&&

.MARINE...WINDS AND SEAS CONTINUE TO BE STRONGER THAN USUAL AND SO
WILL KEEP SMALL CRAFT ADVISORIES. WITH SUCH STRONG WINDS JUST
ABOVE THE SURFACE LAYER STRONG GUSTS IN THE 30 TO 40 KNOT RANGE
WITH SHOWERS ARE LIKELY.

&&

.PREV DISCUSSION... /ISSUED 254 PM AST SAT FEB 28 2015/

SYNOPSIS...UPPER LEVEL TROUGH ACROSS THE TROPICAL ATLANTIC INTO
THE EASTERN CARIBBEAN WILL ERODE TONIGHT AND SUNDAY...AS RIDGE
PATTERN AMPLIFIES ACROSS THE CARIBBEAN BASIN. HOWEVER...THIS FEATURE
WILL QUICKLY ERODE EARLY NEXT WEEK AS A DEEP TROUGH AMPLIFIES
ACROSS THE CENTRAL ATLANTIC INTO THE EASTERN CARIBBEAN. MID LEVEL
RIDGE CONTINUES TO HOLD ACROSS THE AREA DURING THE NEXT SEVERAL
DAYS. MIGRATORY SURFACE HIGHS WILL CONTINUE TO PROMOTE FRESH TO
LOCALLY STRONG TRADE WINDS THIS WEEKEND AND EARLY NEXT WEEK.

DISCUSSION...VARIABLY CLOUDY SKIES WITH PASSING SHOWERS PREVAILED
FROM TIME TO TIME ACROSS THE USVI AND EASTERN PUERTO RICO TODAY.
SKIES BECAME PARTLY CLOUDY ACROSS WESTERN PUERTO RICO IN THE LATE
AFTERNOON HOURS WITH LIMITED SHOWER ACTIVITY OBSERVED SO FAR.
COASTAL TEMPERATURES WERE IN THE MID 80S...ALONG WITH A FRESH TO
LOCALLY STRONG EASTERLY WIND FLOW.

UNDER WEAK RIDGE PATTERN ALOFT AND BREEZY/WINDY CONDITIONS...TRADE
WIND SHOWERS WILL CONTINUE TO PREVAIL ACROSS THE FORECAST AREA
TONIGHT THRU MONDAY. A DEEP UPPER LEVEL TROUGH IS THEN EXPECTED TO
AMPLIFY ACROSS THE CENTRAL ATLANTIC INTO THE EASTERN CARIBBEAN
EARLY NEXT WEEK WITH LOCAL ISLANDS REMAINING UNDER ITS CONVERGENT
SIDE. THEREFORE EXPECT A GENERALLY FAIR WEATHER PATTERN MUCH OF
NEXT WEEK WITH SEASONABLE TEMPERATURES UNDER EAST NORTHEAST WINDS
AND NEAR TO BELOW NORMAL PRECIPITABLE WATER. HOWEVER...PASSING
SHOWERS CANT BE RULED OUT FROM TIME TO TIME AS THIS EASTERLY WIND
FLOW CONTINUES TO BRING PATCHES OF CLOUDINESS EMBEDDED IN THE
FLOW.

AVIATION...IN GENERAL FAST MOVG -SHRA WILL CONT AT TIMES THROUGH AT
LEAST MIDNIGHT. STRONG WINDS IN/AROUND SHRA ARE POSSIBLE DURING
THE FCST PERIOD. XPCT VFR EVEN IN MOST SHRA BUT WITH THE POTENTIAL
OF HAVING GUSTS AROUND 30 KT. 28/12Z TSJU DATA...HAVE EASTERLY
WINDS BETWEEN 15 AND 30 KNOTS UP TO 2KFT. AFT 28/22Z WINDS BCMG
ENE AT 5 TO 15 KT.

MARINE...STRONG ATLANTIC SURFACE HIGH PRESSURE RIDGE WILL REMAIN
ACROSS THE REGION OVER THE NEXT SEVERAL DAYS. THIS WILL RESULT IN
A FRESH TO LOCALLY STRONG TRADE WIND FLOW WITH STEEP WAVES UP TO 7
FEET THROUGH AT LEAST LATE SUNDAY NIGHT.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  85  75  85 /  30  30  20  20
STT  74  85  74  85 /  30  30  20  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL NOON AST MONDAY 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 PUERTO RICO OUT 10 NM-
     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.

&&

$$

25/12




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