Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 240047

Area Forecast Discussion
National Weather Service San Juan PR
847 PM AST Sun Oct 23 2016

.UPDATE...Shower and thunderstorm activity dissipated across the
east and southeast interior sections of the Puerto Rico during the
early evening, but as the local winds shifted and became more
northeasterly, the local land and seas breeze interaction gave
way to more showers and thunderstorm activity across parts of the
north coastal areas of Puerto Rico and also around parts of the
northern U.S. Virgin Islands.

Expect the thunderstorms activity to diminish during the next
couple of hours, however the prevailing low level northeasterly
wind flow should bring periods of passing showers across parts of
the north and east coastal sections of the islands through the
early morning hours.

Otherwise no change to the previous forecast discussion. Sufficient
available low level moisture and instability during the day for
afternoon convection but activity should be focused across parts
of the southern slopes and southwest sections of Puerto Rico and
down wind of the remainder of the islands.


.AVIATION UPDATE...A broad band of moist air is slowly moving
trough the area. Brief periods of MVFR conditions are possible
across all taf sites except TJPS and TJMZ in SHRA with mtn
obscurations. Aft 24/16z SHRA/TSRA will develop arnd the
Cordillera Central and downstream from El Yunque. Brief MVFR
expected at TJMZ. Mtn obscurations are expected. Winds NE 5 to 15
kt up through FL200 byd 25/00Z.


.MARINE UPDATE...No change to previous marine forecast package at
this time based on recent marine observation and latest forecast
guidance. Fairly tranquil conditions during the next few days
with wind of 5-15 knots and Seas of 4 feet or less though Monday.
A slight increase in the east to northeast trade winds expected
during the latter parts of the work week as the local pressure
gradient tightens.


.PREV DISCUSSION... /issued 139 PM AST Sun Oct 23 2016/

SYNOPSIS...Ridge pattern aloft continues to weaken, as a polar
trough moves across the Western Atlantic. At lower levels, a
frontal system is expected to moves across the Western Atlantic
and remain to the north of the local islands through mid week. As
a result, moisture is expected to pool across the local area.

DISCUSSION...Partly to mostly sunny skies prevailed across the
local area late this morning. Limited shower activity was
observed. However, early this afternoon, a line of showers and
thunderstorms affected the U.S. Virgin Islands and eastern Puerto
Rico. This area of moisture will continue to move across Puerto
Rico the rest of this afternoon. This moisture in combination with
daytime heating and local effects will produce a round of showers
and thunderstorms over central interior sections of Puerto Rico
this afternoon. Showers and thunderstorms should last longer due
to the light winds across the region.

For the rest of the week, as ridge pattern aloft continues to
weaken, an increase in shower and thunderstorm activity is
expected. Trade winds are expected to shift more northeasterly by
Tuesday, which will bring patches of low level moisture across the
region. In the long term, no significant weather events are
forecast to affect the region at this time.

AVIATION...Mostly VFR conditions will prevail across the Leeward
taf sites with only vcsh expected. Brief periods of MVFR conditions
are possible across the USVI taf sites as well as across all PR TAF
sites in SHRA/isolated TSRA until 23/23Z under a light and variable
wind flow at 10 knots or less. Mountain obscurations across central
PR expected.

MARINE...Tranquil marine conditions are expected to continue
through mid this week with seas below 5 feet and winds around 15
knots. Today`s rip currents risk is low across the local beaches.


SJU  79  89  79  88 /  50  50  50  50
STT  79  89  78  89 /  50  50  50  50




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