Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 201744

Area Forecast Discussion
National Weather Service San Juan PR
144 PM AST Mon Feb 20 2017

.SYNOPSIS...Trough pattern aloft and a surface trough across the
western Atlantic will continue to approach the local region the
rest of this afternoon and tonight. Low level winds will be
variable and are expected to shift to the north and northeast by
Tuesday as a high Pressure system builds across the western


.DISCUSSION...A very dry and stable air mass moved across the
region this morning. No shower activity was observed over land
areas. A very dry and stable air mass encompassed the local region
this morning and early afternoon which kept the local area under
mostly sunny skies. However, this could change in the next few
hours as a surface trough in combination with trough pattern
aloft are expected to destabilize the local atmosphere which will
result in better chance for showers and even thunderstorms later
this afternoon and tonight. The shower and thunderstorm activity
is expected to occur mainly across the Atlantic waters and along
the north and east sections of Puerto Rico, and later tonight over
the U.S. Virgin Islands.

This slightly wetter pattern is expected to linger through
Tuesday morning. Global models indicated a very dry air mass will
move behind the trough Tuesday afternoon as an upper level ridge
builds across the western Atlantic. As a result, a return to a
normal weather pattern for the month of February is then expected
from Tuesday afternoon and beyond.


.AVIATION...VFR conds across the local terminals. Developing SHRA
could affect the vicinity of TJSJ after 20/19Z. Southwesterly wind
is expected this afternoon across most of the terminals except for
the terminals of northern PR where westerly winds are expected. SCT
SHRA activity moving in tonight. So VCSH is expected through many of
the local terminals after 21/00Z. Winds are expected to gradually
become WNW for the overnight hours at 10-15KT.


.MARINE...Seas will continue to improve across the local waters
through Tuesday. Seas up to 5 feet diminishing to 4 feet are
expected over the coastal waters.


SJU  74  82  73  83 /  40  40  30  30
STT  73  82  72  83 /  60  50  30  30




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