Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 161606
Area Forecast Discussion
National Weather Service San Juan PR
1206 PM AST Mon Jan 16 2017
.UPDATE...Prevailing east to northeast winds 15 to 20 knots below
500 millibars with dry and stable air mass aloft as indicated by
the recent TJSJ 16/12z upper air sounding. Precipitable water now
down to near one inch as depicted by the upper air sounding.
Recent satellite imagery showed patches of shallow moisture below
5 KFT moving across the region in the prevailing northeast wind
flow. Shower activity was mainly across the offshore Atlantic
waters and between PR and the Virgin Islands particularly the
island of Saint Croix. Passing shower activity along the north
coastal areas of PR and the adjacent islands diminished by late
morning leaving mostly sunny skies. No changes expected for the
rest of the day as some showers embedded in the prevailing winds
may reach the north coast once again as well as parts of the west
and southwest sections of Puerto Rico. Few passing showers may
also continue to affect some of the U.S Virgin Islands from time
to time but overall fair skies and pleasant weather conditions
will prevail. No changes made to the inherited forecast package at
.AVIATION...No chg to previous avn discussion. VFR...SCT-BKN low
cld lyrs nr FL025...FL040...mostly CLR abv. Few -SHRA/SHRA en route
.MARINE...Recent buoy data suggest winds at 15-20 knots while NE
swell continue to slowly subside across the coastal waters and local
passages. Seas of up to 8 feet will remain possible in some areas
and small craft advisories will continue in effect today for most
of the coastal waters, except for the near shore waters of west
PR, where small craft should exercise caution due to moderate to
fresh trade winds.
High risk of rip currents remain in effect most of northwest to
north and east facing beaches of PR, vieques, Culebra and the
.PREV DISCUSSION... /issued 555 AM AST Mon Jan 16 2017/
SYNOPSIS...High pressure across the western Atlantic will
maintain a fresh northeast wind flow across the local region
through Wednesday. High pressure will weaken at the end of the
week as a deep surface low pressure moves across the western
DISCUSSION...Passing showers were observed across the local area
overnight. Most shower activity was observed across the Caribbean
coastal waters. Local area continue to be dominated by a surface
high pressure system which is located across the western Atlantic.
This high pressure system will continue to produce fresh northeast
winds across the local area through at least Wednesday. Therefore,
passing showers will continue to affect the local area from time
By the later part of the work week, the aformentioned high
pressure system is expected to weaken, which will allow for a
relax in the pressure gradient. As a result, winds will diminish
considerably by Friday. Under a mid to upper level ridge,
relatively fair weather conditions are expected without any
significant weather events affecting the region. Temperatures will
remain very pleasant, with minimum temperatures expected to drop
to the mid to upper 50s by the later part of the work week, as
clear skies are anticipated and winds will be light and variable.
AVIATION...Mostly VFR conditions expected through the forecast
period. Some passing showers are expected over TIST and TJSJ from
time to time. Low level winds will continue mainly ENE at 10 to 15
kts with higher gusts, mainly in showers.
MARINE...Latest buoy observations are showing seas between 5 to 7
feet with occasional seas up to 8 feet mainly across the offshore
Atlantic waters. Seas are expected to diminish gradually next few
days. However, marine conditions will continue hazardous through
at least Wednesday. High Surf advisory was cancelled as breaking
waves of 10 feet are no longer expected. Small Craft advisories
will continue in effect through at least Wednesday.
.PRELIMINARY POINT TEMPS/POPS...
SJU 82 74 82 73 / 40 30 30 20
STT 84 72 83 71 / 40 30 30 20
PR...High Rip Current Risk through Tuesday afternoon for Culebra-
Mayaguez and Vicinity-North Central-Northeast-Northwest-San
Juan and Vicinity-Southeast-Vieques-Western Interior.
Small Craft Advisory until 6 AM AST Wednesday for Northeast.
VI...High Rip Current Risk through Tuesday afternoon for St Croix-
St.Thomas...St. John.. and Adjacent Islands.
AM...High Rip Current Risk through Tuesday afternoon for Coastal
Waters of Northern USVI and Culebra out 10 NM-Coastal
Waters of Southern USVI Vieques and Eastern Puerto Rico out
Small Craft Advisory until 6 AM 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-Coastal Waters of Northern Puerto Rico
out 10 NM-Coastal Waters of Northern USVI and Culebra out
10 NM-Mona Passage Southward to 17N.
Small Craft Advisory until 2 AM AST Tuesday for Coastal Waters
OF Northwestern Puerto Rico out 10 NM-Coastal Waters of
Southern USVI Vieques and Eastern Puerto Rico out 10 NM.