Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service San Juan PR
1023 PM AST Tuesday Apr 15 2014

Update...afternoon showers continued through late tonight...affecting
mainly Ponce and vicinity. At 1000 PM...most of the shower
activity move offshore and only light passing showers were noted.
Partly cloudy skies are expected to prevail across Puerto Rico and
the U.S. Virgin Islands tonight...with passing showers possible
over the U.S. Virgin Islands and eastern Puerto Rico. Forecast is
on track with ongoing weather situation.


Aviation...VFR conditions will continue to prevail at all taf
sites through at least 16/15z with a few passing showers possible
in and around jsj/ist/isx and ncm/kpk. After 16/15z...showers will
develop once again across west PR and may affect jmz resulting in brief
MVFR conds and mountain obscurations. Low level winds of 10-20 knots will
continue mainly from the east below 10k feet.

&& changes to previous discussion.


Previous discussion... /issued 307 PM AST Tuesday Apr 15 2014/

Synopsis...upper level trough northeast of the forecast area will
be replaced by an upper level ridge over the next 24 hours. This
ridge aloft will hold to through at least Saturday. Then...another
upper level trough moves into the SW North Atlantic destabilize our
atmosphere...promoting moisture transport across the local region
Sunday through early next week. Although...low level moisture will
gradually increase through the rest of the widespread
rain is expected across the forecast area.

Discussion...strong diurnal heating and good sea breeze convergence
have combined to produce showers across portions of the Cordillera
Central and western Puerto Rico this afternoon. This shower activity
will start to diminish near sunset. For the rest of the week...mid-
upper level ridge will dominate the local area through at least
Saturday. Although...operational models suggest a gradual increase
in low level moisture across the synoptic forcing
will be present to produce widespread rainfall. As a result...
shallow cloud clusters and trade wind showers across the islands
at night and early in the morning...followed by a round of
scattered convection over western PR in the afternoon. Then...a
wetter and more unstable pattern is expected from Sunday through
early next week as another upper level trough moves across the SW
North Atlantic. This upper level perturbation will favor moisture
transport and the cloud and shower development across the local
area...especially early next week.

Aviation...MVFR ceilings at jmz with showers. Otherwise...VFR at all
other sites. Low level winds of 10-20 knots will continue mainly from the
east below 10k feet.

Marine...tranquil marine conditions expected through Wednesday
with seas 3-5 feet. Winds strengthen Thursday through Saturday
with seas building 6-8 feet. Small craft advisories will be required
for most of the waters. These strong winds may generate rip currents
especially across the east facing coasts.


Preliminary point temps/pops...
sju 75 85 75 84 / 20 20 50 50
stt 75 85 76 87 / 30 30 50 50


Sju watches/warnings/advisories...
Coastal waters...none.