Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 021535
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1135 AM AST WED SEP 2 2015

.UPDATE...
DRY AIR ADVECTION WAS OBSERVED WITH THE AVAILABLE SATELLITE
IMAGES ACROSS THE LOCAL. TJSJ 02/12Z SOUNDING SHOWS A TPW OF 1.72
INCHES...A VALUE AROUND THE PERCENTILE 25TH FOR SEPTEMBER. THE
COMBINATION OF THE LINGERING MOISTURE ASSOCIATED WITH YESTERDAYS
WAVE...LOW LEVEL INSTABILITY AND THE LOCAL EFFECT WILL BE ENOUGH
TO PRODUCE SOME CONVECTIVE ACTIVITY MAINLY ACROSS THE INTERIOR AND
NORTHWESTERN PUERTO RICO DURING THE AFTERNOON HOURS. IN
ADDITION...SOME SHOWERS ARE POSSIBLE TO DEVELOP IN THE WAKE OF EL
YUNQUE TOO. MINOR CHANGES WERE INTRODUCE TO THE PREVIOUS FORECAST.

&&

.AVIATION...
VFR CONDITIONS DURING MOST OF THE FORECAST PERIOD...HOWEVER SOME
SHRA/TSRA CAN BE EXPECTED OVER TJMZ...TJBQ DURING THE AFTERNOON
HOURS. ALSO SOME SHRA ARE POSSIBLE FROM TIME TO TIME ACROSS TJSJ.
AFTER SUNSET...MOST OF THE SHRA/TSRA ACTIVITY ARE EXPECTED TO
DECREASE. WINDS AT 5 TO 10 KNOTS INCREASING AT 10 TO 15 WITH
HIGHER GUST MAINLY NEAR TSRA/SHRA.

&&

.MARINE...SEAS WILL REMAIN BELOW 4 FEET WITH WINDS UP TO 15
KNOTS. SHOWER AND THUNDERSTORM ACTIVITY CAN PRODUCE HAZARDOUS
MARINE CONDITIONS MAINLY ACROSS THE NORTHWESTERN SECTIONS OF
PUERTO RICO.

&&

.PREV DISCUSSION... /ISSUED 542 AM AST WED SEP 2 2015/

SYNOPSIS...TUTT WILL LINGER OVER THE FORECAST AREA FOR THE NEXT
SEVERAL DAYS. MID LEVEL RIDGE WILL MOVE OVER THE ISLANDS LATER
TODAY...CONTINUING FOR THE REST OF THE WEEK. LINGERING MOISTURE
ASSOCIATED TO A TROPICAL WAVE WILL COMBINE WITH DIURNAL EFFECTS TO
INDUCE AFTERNOON SHOWERS AND THUNDERSTORMS TODAY. FAIR WEATHER
CONDITIONS EXPECTED FOR THE NEXT SEVERAL DAYS WITH AFTERNOON
CONVECTION OVER WESTERN PR.

DISCUSSION...SHOWERS AND THUNDERSTORMS WERE OBSERVED OVERNIGHT
MAINLY OVER THE ATLANTIC WATERS WITH A FEW OF THEM REACHING PARTS
OF THE NORTHERN U.S. VIRGIN ISLANDS AND NORTHEASTERN PR.
HOWEVER...THE HEAVIEST RAINFALL WAS OVER THE COASTAL WATERS. FOR
THE REST OF THE MORNING HOURS THERE IS STILL A CHANCE THE SAME
AREAS EXPERIENCE SOME RAINFALL ACTIVITY...ALTHOUGH NOT SIGNIFICANT
AS MID LEVEL DRY AIR WILL FILTER ACROSS THE REGION FROM THE EAST
LATER TODAY. HOWEVER...CONDITIONS ARE FAVORABLE FOR SHOWERS AND
THUNDERSTORMS TO DEVELOP WITH HEAVY RAINFALL THAT CAN LEAD TO
URBAN AND SMALL STREAM FLOODING THIS AFTERNOON NORTH OF THE
CORDILLERA CENTRAL AND THE SAN JUAN METRO AREA.

AFTER TODAY...FAIR WEATHER CONDITIONS ARE EXPECTED AS TUTT IS
FORECAST TO BE ON ITS UNFAVORABLE SIDE TO ENHANCE CONVECTION AND
THE DUE TO THE INTRUSION OF MID LEVEL DRY AIR. HOWEVER...PASSING
LIGHT SHOWERS ARE EXPECTED TO REACH SECTIONS OF THE USVI AND EASTERN
PUERTO RICO DURING THE OVERNIGHT AND EARLY MORNING HOURS WITH
DIURNAL INDUCED SHOWER AND THUNDERSTORM ACTIVITY OVER THE INTERIOR
AND WESTERN SECTIONS OF PR EACH AFTERNOON.

AVIATION...VFR CONDS EXPECTED THROUGH THE MORNING HOURS WITH
VCSH/VCTS AT TJSJ THROUGH AROUND 02/11Z. AFTERNOON CONVECTION WILL
LIKELY DEVELOP SHRA/TSRA IN AND AROUND TJSJ/TJBQ/TJMZ AFTER
02/16Z...LINGERING TROUGH THE AFTERNOON UNTIL 02/23Z. MVFR CONDS ARE
POSSIBLE AT TJMZ AND TJBQ...MTN OBSCURATIONS ARE LIKELY. WINDS WILL
BE FROM THE EAST TO E-SE AT ABOUT 10 KNOTS TODAY...GUSTY NEAR
SHRA/TSRA. WINDS WILL DIMINISH AFTER 02/23Z.

MARINE...SEAS WILL REMAIN AT 4 FEET OR LESS FOR THE NEXT SEVERAL
DAYS AND LIGHT TO MODERATE EAST-SOUTHEAST WINDS ARE ALSO EXPECTED
TO PREVAIL THRU THE WEEKEND.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  92  79  93  79 /  50  20  10  10
STT  89  81  88  79 /  40  20  10  10

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
AM...NONE.
&&

$$

27/71


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