Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 080157
Area Forecast Discussion
National Weather Service San Juan PR
957 PM AST Wed Dec 7 2016
.UPDATE...No changes made to the inherited forecast package at
this time which had a good handle on the present and expected
weather conditions overnight through Thursday and the rest of the
.AVIATION UPDATE...Mostly VFR conditions expected at all TAF
sites through 08/18z. Although we expect a dry airmass to remain
in place overnight very isolated showers could affect the Northern
Terminals of Puerto Rico and TIST. Winds will be East between 5-10
kts overnight...but increasing again to around 12-15 kts with sea
breeze variations after 08/14z.
.MARINE...No change to previous marine discussion. Slowly
subsiding north swell and increasing easterly trade winds will
continue to create the risk of strong rip currents along the
Atlantic coastlines of Puerto Rico...Culebra and ST. Thomas.
.PREV DISCUSSION... /issued 131 PM AST Wed Dec 7 2016/
SYNOPSIS...Mid level ridge will continue to suppress the
development of widespread precipitation over the region until at
least Thursday. However, patches of moisture embedded in the trades
are expected to produce few showers across the interior and
western sections of PR in the afternoons. A surface high pressure
north of the region will maintain an East Northeast low level wind
flow over the region. An easterly wave is expected to reach the
region on Friday, but the bulk of the moisture is expected to
remain south of the local islands.
DISCUSSION...Doppler radar detected isolated to scattered showers
across northern and eastern sections of Puerto Rico during the
morning. Few showers are also expected to develop over Western
and interior sections of Puerto Rico late this afternoon. These
showers could cause some ponding of water on roadways and poor
drainage areas since the soils are still very saturated, but in
general not significant accumulations are expected in association
with this activity.
A mid level ridge will remain as the main weather feature over
the region until at least Thursday. This feature will continue to
inhibit the development of significant showers across the local
islands and surrounding waters. However, a surface high pressure
to the north of the region will continue to promote an east
northeast wind flow with few embedded showers across the eastern
sections of Puerto Rico tonight. An easterly wave to the east of
the Lesser Antilles is expected to reach the region Thursday night
and Friday, slightly increasing the chances of showers across the
local islands and surrounding waters, but the bulk of the moisture
will pass mostly south of the region.
AVIATION...Mostly VFR conditions expected at all TAF sites through
08/18z. Will only mention VCSH possible at TJMZ through 07/23Z. This
could result in brief MVFR conds. Expect dry airmass to remain in
place overnight so will not even mention VCSH for any terminal after
08/00z. Winds will be East at around 10-12 kt with sea breeze
variations. Winds should decrease to 5-10 kts overnight...but
increasing again to around 12-15 kts with sea breeze variations
MARINE...Seas of 4-6 feet in subsiding north swells will
continue across the Atlantic waters and the local passages tonight.
Small craft should exercise caution across these areas. Seas
between 3 and 5 feet can be expected elsewhere. A high risk of rip
currents will continue across the Atlantic facing beaches of
Puerto Rico, Culebra and St. Thomas.
.PRELIMINARY POINT TEMPS/POPS...
SJU 76 85 75 87 / 30 30 20 30
STT 76 86 77 86 / 30 30 50 50
PR...High Rip Current Risk through Thursday afternoon for Culebra-
North Central-Northeast-Northwest-San Juan and Vicinity-
VI...High Rip Current Risk through Thursday afternoon for
St.Thomas...St. John.. and Adjacent Islands.
AM...High Rip Current Risk through Thursday afternoon for Coastal
Waters of Northern USVI and Culebra out 10 NM-Coastal
Waters of Southern USVI Vieques and Eastern Puerto Rico out