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Area forecast discussion...updated 
National Weather Service San Juan PR
948 PM AST Wed Oct 26 2016

Update...evening sounding came in above 2 inches of precipitable
water and was still unstable except for shallow inhibiting layer
near the surface. Lower level wind flow was still northeasterly.


Discussion...few changes to the forecast were considered. Shower
activity is sparse for the amount of moisture available but there
is little in the way of triggering activity. Showers are expected
to increase tomorrow morning on the north coast. Temperatures are
in accordance with the onshore flow from the north and will slowly
warm as they become more easterly. This will also increase the
shower activity over the western sections of Puerto Rico as
previously forecast.


Aviation...VFR conds expected through the local terminals with
passing -shra at tjsj/tist. Passing vcsh possible for the rest of
the local terminals. Afternoon rain showers/thunderstorms and rain are likely btwn 27/16z-
23z across the interior and across the west half portion of PR.
This activity could produce brief MVFR conds at tjps/tjmz/tjbq.
Elsewhere frequent vcsh are possible. Winds continuing from the
NE, however overnight calm to light and vrb winds expected,
increasing at about 10kt with sea breeze variations after 27/13z.


Marine...models were underforecasting a wind wave out of the
front north of the area, but this has subsided slightly and model
have come up slightly. Nevertheless have augmented wave height
somewhat during the first 18 hours of the forecast...mainly based
on The Rincon buoy which has been running 4.5 to 4.9 feet much of
the day. Seas will increase somewhat Thursday night, but newest
model runs refrain from Small Craft Advisory conditions. After
Friday small craft advisories are not expected through at least
early next week.


Previous discussion... /issued 151 PM AST Wed Oct 26 2016/

Synopsis...another short wave trof is forecast to move aloft
from the western Atlantic by early next week. At lower levels,
frontal boundary to the north of the area and troughiness will
continue to keep a moist environment for the next couple of days.
An easterly wave will move mainly south of the area through
Thursday. Surface high across the western Atlantic will maintain
an east to northeast wind flow through the end of the work week.
East to southeast winds return during the weekend. area of moderate to heavy showers moved across
the San Juan metropolitan area this morning. Around one inch of
rainfall was observed. A slot of drier air can be seen on
satellite images late this morning and early this afternoon. This
area of drier air has limited the shower and thunderstorm
development compared to yesterday. However, by noon showers and
thunderstorms started to develop across the southern slopes of
Puerto Rico as available moisture combined with daytime heating
and local effects. Therefore, scattered to numerous showers are
expected the rest of this afternoon across these areas. For
tonight, some passing showers are expected to affect mainly the
north and east sections of Puerto Rico and the northern U.S.
Virgin Islands.

For the weekend an upper level ridge will dominates the local
area, which will limit somewhat the chances for showers and
thunderstorms across the area. For the long term, although the GFS
is showing a very wet pattern by the end of next week, still too
early to know if this solution will verify or not.

Aviation...VFR conds expected through the local terminals with
persistent vcsh/thunderstorms in the vicinity at tjmz and tjps after 26/18z as rain showers/thunderstorms and rain is
expected across the interior, west, and south PR. Passing vcsh
possible for the rest of the local terminals. Winds continuing from
the NE at about 10kt with sea breeze variations through today.
Weather conditions to improve after 27/00z. Winds becoming lighter

Marine...seas up to 5 feet and winds up to 15 knots are expected.
Seas are expected to increase by late Thursday into Friday across
the offshore Atlantic waters.


Preliminary point temps/pops...
sju 78 88 79 89 / 30 30 40 40
stt 79 88 78 88 / 30 30 40 40


Sju watches/warnings/advisories...



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