Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 070922
Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Wed Dec 7 2016
.SYNOPSIS...Surface high pressure to the north of the local
islands will be the dominating feature for the next few days in
terms of winds. Winds will be generally from the ene today and
Thursday but then turning mainly easterly for the next several
days thereafter. Ridge in the mid levels will suppress convection
over Puerto Rico but a few showers are still expected to develop
across the interior and western sections of PR with isolated and
brief showers elsewhere. Easterly wave expected to pass through
the area late Thursday into Friday. This will cause an increase in
shower and thunderstorm activity over the area. A more typical
December pattern is expected thereafter with tradewind showers
.DISCUSSION...Isolated to scattered showers were observed across
the local area during the overnight hours which generally left
minimal accumulations across the north and eastern sections of PR.
The USVI, Vieques and Culebra observed even less rain with either
trace amounts of rain or no rain at all. These few and brief
showers are expected to continue affecting the north and eastern
sections of PR through the early morning hours. Afternoon
convection is expected to be modest but a few significant showers
are possible across portions of western PR. These showers could
cause some ponding of water on roadways and poor drainage areas
since the soils are still very saturated in that area of PR. Only
a slight chance of showers for the rest of the forecast area.
Slightly drier air is expected to move in late this afternoon and
tonight with precipitable water values dipping from 1.2 to just under
1 inch across PR and around 1.25 inches across the USVI. Then
staying at around 1.2 inches for Thursday before the easterly wave
moves in late Thursday, causing an increase in moisture and
instability. With the easterly wave there will also be an increase
in shower activity and possibly even some thunderstorms. After the
easterly wave, easterly wind flow will prevail with patches of
higher moisture over the local area. This means that tradewind
showers are expected for the weekend.
.AVIATION...Mostly VFR conditions expected at all TAF sites through
the forecast period with VCSH possible at JSJ/IST/JBQ/ISX through
07/14Z. SHRA to develop over PR after 07/16Z, and may result in
brief MVFR conds at JMZ through 07/22z. Winds will be from the e ast
at around 10 kt with sea breeze variations developing after
.MARINE...Seas of 4-6 feet in subsiding north swells will
continue across the Atlantic waters and the local passages today.
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. Moderate risk of rip currents
across the beaches along the Northwest coast and the eastern tip
of Puerto Rico as well as most of Culebra and Vieques. For the
USVI there is a moderate risk of rip currents from South Central
to Northeast Saint Thomas, Northwest Saint John, and northern and
eastern Saint Croix.
.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 85 75 / 30 30 30 20
STT 87 76 86 77 / 30 30 30 50
PR...High Rip Current Risk through this afternoon for Culebra-North
Central-Northeast-Northwest-San Juan and Vicinity-Southeast-
VI...High Rip Current Risk through this afternoon for St.Thomas...St.
John.. and Adjacent Islands.
AM...High Rip Current Risk through this afternoon for Coastal Waters
of Northern USVI and Culebra out 10 NM-Coastal Waters of
Southern USVI Vieques and Eastern Puerto Rico out 10 NM.