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Area forecast discussion 
National Weather Service San Juan PR
305 PM AST Sat Jul 30 2016

Synopsis...vigorous tropical wave east of the Lesser Antilles
will bring heavy rainfall and gusty winds to the forecast area
tonight into Sunday. This moist and unstable pattern will prevail
through at least Monday afternoon. Drier and more stable air mass
is expected Tuesday through early Thursday. Then...another
tropical wave will reach the local region producing another round
of showers and thunderstorms Thursday night into Friday.

&&

Discussion...satellite imagery shows a strong tropical wave
approaching the leewards islands this afternoon. A large area of
showers and thunderstorms accompanied this wave. Due to the rapid
movement of this feature...the leading edge of the wave will
likely reach the Anegada Passage and the U.S. Virgin Islands later
this afternoon and tonight. Shower and thunderstorm activity will
spread over Puerto Rico late tonight into Sunday. At this time...
the best moisture convergence and vorticity advection will move
over the local islands during the day on Sunday. Therefore...a
Flash Flood Watch has been issued for all Puerto Rico and the
U.S. Virgin Islands due to the high risk of flooding rains. The
watch is in effect from Sunday morning to Sunday night.

Although the tropical wave will move away from region on Monday
morning...residual moisture in the wake of the wave will keep the
atmosphere relatively unstable through at least Monday afternoon.
Conditions will improve on Tuesday as drier air will filter in
from the east. Weather pattern will remain generally tranquil
through Thursday. Then...another tropical wave will bring showers
and thunderstorms over the local islands late Thursday into Friday.

&&

Aviation...an approaching tropical wave will increase rain showers and thunderstorms and rain
activity across the waters and local islands thru Sunday. MVFR
ceilings/visibilities likely across the leeward, USVI and east PR overnight and
Sunday morning, spreading to the west PR terminals by Sunday morning
and afternoon. Mtn obscurations likely. Windy cond expected at 10-20
kts with periods of gusts of 25-35 kts.

&&

Marine...marine conditions will deteriorate rapidly later this
afternoon into the evening hours as the tropical wave moves over
the regional waters. Seas will build to 6-8 feet and winds will
increase to around 20 knots with wind gust in excess of 30 knots
possible with the showers and thunderstorms. The most intense
thunderstorms are capable of producing strong gusty winds...
lightning strikes and locally higher waves.

&&

Preliminary point temps/pops...
sju 80 86 76 88 / 80 80 80 50
stt 80 86 77 89 / 80 80 50 50

&&

Sju watches/warnings/advisories...
PR...Flash Flood Watch from Sunday morning through Sunday evening for
central interior-Culebra-eastern interior-Mayaguez and
vicinity-north Central-Northeast-northwest-Ponce and
vicinity-San Juan and vicinity-southeast-southwest-Vieques-
western interior.

Vi...Flash Flood Watch from Sunday morning through Sunday evening for
St Croix-St... John.. and adjacent islands.

Small Craft Advisory from 8 PM this evening to 8 PM AST Sunday
for St... John.. and adjacent islands.

Am...Flash Flood Watch from Sunday morning through Sunday evening for
coastal waters of southwestern Puerto Rico out 10 nm-
coastal waters of northern USVI and Culebra out 10 nm-
coastal waters of southern Puerto Rico out 10 nm-coastal
waters of southern USVI Vieques and eastern Puerto Rico out
10 nm.

Small Craft Advisory from 8 PM this evening to 8 PM AST Sunday
for Caribbean waters of Puerto Rico from 10 nm to 17n-
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.

Small Craft Advisory from 2 am to 8 PM AST Sunday for coastal
waters of northern Puerto Rico out 10 nm.

Small Craft Advisory until 8 PM AST Sunday for Anegada Passage
southward to 17n-Atlantic waters of Puerto Rico and USVI
from 10 nm to 19.5n.

&&

$$

05/11

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