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Area forecast discussion 
National Weather Service San Juan PR
516 am AST Sat Apr 18 2015

Synopsis...middle to upper level trough will linger across the northeastern
Caribbean today then gradually fill while lifting northward on Sunday
and Monday. Surface high pressure north of the region will continue
to shift eastward into the central Atlantic...then lift farther
north into the northeast Atlantic by Sunday. This will maintain
light to moderate east southeast trade winds across the northeastern
Caribbean through the weekend and into early next week. An induced
low level trough will continue to move across the region today
and bring a slight increase in low level moisture.


Discussion...moisture accompanying the induced low level trough
along with sufficient instability created by the proximity of the
upper trough will aid in shower and isolated thunderstorm
development across the islands and coastal waters today. As the
prevailing winds become more east southeast...expect convective
activity to be focused more across the north central and northwest
sections of Puerto Rico...with possible streamer like convection
forming across parts of the eastern interior...then training over
portions of the san Jun metropolitan later in the day. Some streamer
formation will also be possible across Culebra and Vieques as well
as over portions of the U.S.Virgin Islands during the rest of the

Lesser activity expected on Sunday and Monday as the low level trough
will weaken along with decreasing moisture advection. In upper level ridge will build overhead once again by
Monday and Tuesday allowing for more stable and subsident
conditions aloft.


Aviation...brief periods of MVFR conditions expected to
continue across tisx...tist and tisj until 18/14z with vcsh possible
across tncm and tkpk. Rain showers/thunderstorms and rain are expected to develop across the
northwest quadrant of Puerto Rico after 18/17z...producing at least
vcsh/thunderstorms in the vicinity with possible MVFR conditions due to reduced visibility
and ceilings at tjmz and tjbq. Low level winds will continue from
the east to east southeast at 10 to 15 knots becoming westerly and
stronger aloft.


Marine....conditions remain below Small Craft Advisory levels
through early next week. Seas may however reach 6 feet in the
northeastern local outer Atlantic waters later next week based on
the latest forecast model guidance.


Preliminary point temps/pops...
sju 88 77 90 77 / 30 40 40 30
stt 84 76 85 77 / 30 40 40 50


Sju watches/warnings/advisories...



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