Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 270135
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
935 PM AST Sun Feb 26 2017

.UPDATE...Showers developed across the southwest section of Puerto
rico late this afternoon and early this evening. This activity
lingered through around 9 pm. An area of cloudiness and showers
will affect the local islands overnight into early Monday.
Therefore, and increase in shower activity is expected. This area
of moisture will move west and will exit the local area by Monday
afternoon. No changes were made to forecast grids tonight.

&&

.AVIATION...Mainly VFR early in the forecast period. However, trade
wind shower activity expected to increase from 27/02z-12z across the
USVI and eastern PR terminals. SCT/BKN cigs btw FL030-FL070 with
SHRA that could also result in brief tempo MVFR conds. Max tops
around FL200. Latest 27/00z TJSJ upper air sounding indicated low
level E-ENE winds at 10-18 kts.

&&

.MARINE...Marine conditions are expected to deteriorate Monday
night as winds will increase across the local waters. A small
craft advisory will be in effect from Monday night through at
least Wednesday night. Seas up to 6 feet and winds up to 20 knots
are expected overnight.


&&

.PREV DISCUSSION... /issued 154 PM AST Sun Feb 26 2017/

SYNOPSIS...Mid-upper level ridge will hold through at least
midweek. Surface high pressure will exit the Eastern US on Monday
tightening the pressure gradient across the region. The strong
high pressure will bring breezy to windy conditions across Puerto
Rico and the U.S. Virgin Islands most of the week as moves eastward
through the North Atlantic.

DISCUSSION...A relatively stable conditions have been observed
across the local islands today. Morning TJSJ sounding indicated
normal moisture levels and strong subsidence cap around 775mb.
Satellite imagery is showing sea breeze convergence along the
Interior and West Puerto Rico. This convergence will likely result
in scattered showers across these areas later this afternoon.
However...no significant rainfall accumulations are expected with
this activity as mid-upper level ridge will inhibit the vertical
development of the showers.

The next band of moisture will reach the USVI and eastern PR
after 27/06Z. This band of moisture is associated with an easterly
pertubation that will enhance the moisture convergence across the
islands early Monday. In the wake of the low level pertubation...
a patch of drier air will spread over the USVI/PR late Monday
afternoon and evening. This drier air mass will be short-lived as
another area of moisture will move over the islands on Tuesday.

A trade wind pattern will persist most of the week as fresh to
strong trades will bring passing showers at times. All in all...
expect breezy conditions with a mixture of sunshine and clouds as
well as scattered showers from time to time dominating the local
islands for the next several days.

AVIATION...VFR conds expected through the fcst period. SHRA and
Clouds are expected across the interior and west PR, as a result
SHRA can affect TJMZ btwn 26/18-22z. Then showers en route btw PR
and the Northern Leeward islands expected btwn 27/00-12Z. The
frequency of showers is possible across E-PR and USVI terminals
btwn 27/06-12z. Low levels E-NE winds at 15 to 25 knots.

MARINE...Strong surface high pressure will move north of the
islands over the next few days increasing the trade winds around
20 kts. Fresh to strong winds will lead to choppy seas across the
local waters most of next week. Seas are forecast to build up to
8 feet across the offshore waters. Seas of 5-7 feet are expected
across the near-shore wates. Small Craft Advisories will likely
begin tonight and continue through the end of the work week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  74  84  74  85 /  50  50  30  30
STT  74  85  74  85 /  40  40  30  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory from 8 PM Monday to 8 PM AST Wednesday for
     Anegada Passage Southward to 17N-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.

&&

$$

13/71


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