Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
531 am AST Sat Dec 3 2016
a ridge pattern aloft is forecast to slowly erode during the next
few days. However, a surface perturbation and enough surface
moisture will result in passing showers across the local waters,
the U.S. Virgin Islands and east Puerto Rico this morning.
Followed by afternoon showers mainly over the interior and west
sections of Puerto Rico and downwind from the U.S. Virgin Islands.
Sunday and into midweek, the prevailing winds are to become more
northeasterly as a surface high pressure builds across the western
Atlantic. This weather pattern is forecast to increase the chance
of frequent passing showers along the northern and eastern sections
of Puerto Rico, as well as across the U.S. Virgin Islands.
a surface trough and easterly trades provided sufficient moisture
transport to support isolated to scattered showers across the
local waters, eastern PR and the U.S. Virgin Islands overnight.
This surface perturbation is expected to continue enhancing this
activity across the islands today. During the afternoon, showers
development is expected across most of the islands, but more
frequent across the interior and west sections of Puerto Rico. In
addition, due to the east southeast wind flow, showers are
possible across the San Juan metropolitan area.
The upper level ridge pattern is forecast to slowly erode into the
upcoming week. At low levels, winds are forecast to become more
easterly as a high pressure builds over the Atlantic waters. Also,
a frontal boundary is forecast to moves to the north and near the
local region. Due to the proximity of this frontal boundary and
under the prevailing northeasterly wind flow the chance of early
morning cloudiness and quick passing showers along the north and
east coastal section of the islands is expected to increase at
least until midweek.
VFR conditions are expected across all taf sites through
at least 03/16z. Brief periods of MVFR conditions with mountain
obscurations can be expected over tjmz and tjbq from 03/16z through
03/22z. Low level winds will be mainly east at 10 kts except for sea
breeze variations in coastal areas.
mariners can expect seas up to 5 and winds at 10 knots or less. A
northerly swell is forecast to move across the Atlantic waters and
Caribbean passages late Monday or Tuesday.
Preliminary point temps/pops...
sju 87 77 86 76 / 50 20 20 20
stt 85 76 86 74 / 50 20 20 20