Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 010846
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
446 AM AST TUE SEP 1 2015

.SYNOPSIS...AT UPPER LEVELS...WEAK LOW PRESSURE WILL DRIFT SOUTH
OVER THE AREA THROUGH WEDNESDAY...AND THEN HOVER NEARBY THROUGH
THE END OF THE WEEK. WEAK HIGH PRESSURE WILL BUILD IN EARLY NEXT
WEEK.

AT MID LEVELS...HIGH PRESSURE PERSISTS THROUGH MUCH OF NEXT WEEK.
FIRST NORTH OF THE AREA AND THEN MAINLY OVER OR JUST EAST OF THE
AREA. MID LEVELS MOISTEN CONSIDERABLY TONIGHT AND THEN DRY OUT
SLOWLY ON FRIDAY. MID LEVELS ARE GENERALLY DRY THROUGH NEXT
TUESDAY.

AT LOWER LEVELS...A TROPICAL WAVE WILL MOVE THROUGH THE AREA THIS
AFTERNOON SPREADING SHOWERS AND SCATTERED THUNDERSTORMS ACROSS THE
AREA. ALTHOUGH A FEW PATCHES OF MOISTURE COME IN FROM THE
NORTHEAST OVER THE WEEKEND NEITHER STRONG FEATURES NOR DEEP
MOISTURE ARE EXPECTED UNTIL AFTER THE END OF THIS FORECAST PERIOD.

&&

.DISCUSSION...LIGHT TO MODERATE SHOWERS FELL ACROSS SAINT THOMAS
AND SAINT CROIX LEAVING SEVERAL HUNDREDTHS AND ONE TENTH INCH
RESPECTIVELY. AND...SHOWERS HAVE ALREADY BEGUN TO MOVE IN ACROSS
EASTERN PUERTO RICO...WITH HEAVIER SHOWERS MOVING INTO HUMACAO AND
YABUCOA. SHOWERS WILL CONTINUE TO INCREASE SPORADICALLY ACROSS THE
AREA THIS MORNING AND THEN FORM ACROSS WESTERN PUERTO RICO WITH
SCATTERED THUNDERSTORMS. WOULD EXPECT SOME POSSIBILITY FOR GUSTY
WINDS AND LOCAL URBAN AND SMALL STREAM FLOODING TODAY. MOISTURE
CONTINUES ACROSS THE AREA TONIGHT...ALTHOUGH AMOUNTS WILL NOT BE
VERY HEAVY ACROSS WESTERN PUERTO RICO...THEN...TOMORROW...SHOWERS
WILL BEGIN TAPERING OFF IN THE U.S. VIRGIN ISLANDS AND EASTERN
PUERTO RICO...BUT THE BACK OF THE WAVE WILL STILL PRODUCE SHOWERS
AND SCATTERED THUNDERSTORMS IN NORTHWEST PUERTO RICO WEDNESDAY.

ACCORDING TO THE GFS THIS IS THE BEST MOISTURE THAT WILL OCCUR FOR
THE NEXT 10 DAYS. FLOW AT MID LEVELS BECOMES NORTHEAST AROUND HIGH
PRESSURE JUST NORTH OF THE AREA AND WEAK BANDS OF MOISTURE DO MOVE
ACROSS THE AREA THROUGH THE WEEKEND...BUT OTHERWISE SIGNIFICANT
FEATURES ARE NOT SEEN UNTIL AFTER THE FRIDAY AFTER NEXT...WHEN A
STRONG TROPICAL WAVE IS SEEN APPROACHING THE LEEWARD ISLANDS. IT
WILL PROBABLY NOT ARRIVE UNTIL 13 SEPTEMBER AND HAS NOT YET COME
OUT OF AFRICA. SOME AREAS OF SAHARAN DUST WERE SEEN IN THE AREAS
OF DRIER AIR...BUT THE BULK OF THE DUST IS TO MOVE SOUTH OF PUERTO
RICO AND THE U.S. VIRGIN ISLANDS.

&&

.AVIATION...SCT SHRA/TSRA ARE EXPECTED TO AFFECT THE FLYING AREA
THRU THE FCST PERIOD AS A TROPICAL WAVE MOVES OVER THE LOCAL
ISLANDS. MAINLY VFR WITH TEMPO MVFR CONDITIONS SPREADING FM
LEEWARD TERMINALS THRU USVI/EASTERN PR TERMINALS BY NOON
AST...THEN OVER THE INTERIOR AND WESTERN PR WITH MTN TOPS OBSCD
ALONG ALL MTN RANGES OF MAINLAND PR AFT 01/16Z. EASTERLIES BLO
FL200 AT 10-20 KTS...HIGHER GUSTS NEAR TSRA.

&&

.MARINE...WINDS AND SEAS ARE SLOWLY SUBSIDING AND ARE EXPECTED TO
CONTINUE TO DO SO THROUGH THE NEXT 5 TO 7 DAYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  90  79  91  78 /  60  50  40  20
STT  88  80  88  79 /  60  40  40  10

&&

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

$$

13/12


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