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Area forecast discussion 
National Weather Service San Juan PR
1054 am AST Friday Sep 30 2016

Update...Doppler weather radar detected scattered showers and
isolated thunderstorms mostly across the surrounding coastal
waters this morning. Some of these showers also affected the
eastern and northern sections of Puerto Rico as well as the U.S.
Virgin Islands. However, due to the rapid movement of the showers
the total rainfall amounts associated with this activity were
generally minimal so far this morning. All this activity was
associated with the lingering moisture left behind the Hurricane
Matthew moving across the central Caribbean. This lingering
moisture in combination with daytime heating, local and diurnal
effects will produce a round of showers and thunderstorms mainly
over the central interior and western sections of Puerto Rico this
afternoon. Similar weather conditions are expected for Saturday as
Matthew moves across the central Caribbean. The GFS model guidance
suggest a sharp increase in moisture across the region early next
week as the tail of Matthew moves close across the region.

&&

Aviation...trade wind showers could briefly affect the
leeward/USVI and east/northern PR terminals through the rest of
the morning hours. Then between 16z-22z, thunderstorms and rain/rain showers developing
along the interior and western portions of PR will create tempo
MVFR conditions, impacting mainly tjmz and the vcty of
jbq/jps/jsj. Low level east winds will continue at 15-25 kt.

&&

Marine...marine conditions will continue to improve as Matthew
moves across the central Caribbean and further away from the local
islands. Seas up to 10 feet across the offshore Caribbean waters
and subsiding with winds 15-20 knots.



&&

Previous discussion... /issued 535 am AST Friday Sep 30 2016/

Synopsis...Hurricane Matthew will continue to move across the
central Caribbean and away from the local islands today. Ridge
aloft will hold through the end of week with trofiness returning
to the forecast area sun-Mon. Surface high north of the area and
Hurricane Matthew southwest of the forecast area will continue to
promote moderate to fresh easterly winds through Saturday. Surface
winds are expected to become southerly early next week as Matthew
moves northward and crosses into the southwest Atlantic.

Discussion...partly to variably cloudy skies prevailed across
the local islands during the overnight and early morning hours.
Passing showers were observed mainly over the offshore waters
with some of them affecting the northern and eastern coasts of
the islands. Minimum temperatures were in the mid 70s to around 80
degrees across lower elevations.

Under weak ridge aloft...moderate to fresh easterly winds and
precipitable water near normal values, a few showers embedded in
the trades will continue to affect the coastal areas in the
morning followed by locally induced showers and thunderstorms
across west PR. This weather pattern is expected through at least
Saturday. Surface winds are expected to become southerly early
next week as Matthew moves northward and crosses into the
southwest Atlantic.

Weather conditions across the forecast area are highly dependent
on Matthew trajectory. Based on the latest guidance as winds
shift southerly, deep tropical moisture will be advected across
the local islands. This moisture will then combine with trofiness
aloft from the east to result in a better chance for shower and
thunder late sun-Tue. A weak ridge will build across the local
islands by midweek. However, locally induced afternoon showers
and thunderstorms still expected Wed-Fri.

Aviation...mainly VFR conditions expected across much of the
terminals today. However, trade wind showers with tops around
fl250 with possible thunderstorm across the Atlantic waters could briefly
affect the leeward/USVI and east/northern PR terminals through the
morning hours. Then between 16z-22z, thunderstorms and rain/rain showers developing along
the interior and western portions of PR will create tempo MVFR
conditions, impacting mainly tjmz and the vcty of jbq/jps/jsj.
Low level east winds will continue at 15-25 kt.

Marine...marine conditions will continue to slowly improve
as Matthew moves across the central Caribbean and further away
from the local islands. Seas up to 12 feet across the offshore
Caribbean waters and subsiding with winds 20-25 knots.

&&

Preliminary point temps/pops...
sju 89 78 90 77 / 40 20 30 20
stt 90 79 90 79 / 30 30 30 20

&&

Sju watches/warnings/advisories...
PR...high rip current risk until 6 PM AST this evening for central
interior-Culebra-northeast-northwest-Ponce and vicinity-
southeast-southwest-Vieques-western interior.

Vi...high rip current risk until 6 PM AST this evening for St Croix.

Am...high rip current risk until 6 PM AST this evening for coastal
waters of southwestern Puerto Rico out 10 nm-coastal waters
of southern Puerto Rico out 10 nm.

Small Craft Advisory until 10 PM AST this evening for Atlantic
waters of Puerto Rico and USVI from 10 nm to 19.5n-
Caribbean waters of Puerto Rico from 10 nm to 17n-Mona
Passage southward to 17n.

&&

$$

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