Area Forecast Discussion
National Weather Service San Juan PR
331 AM AST Sat Feb 17 2018
.SYNOPSIS...Surface high pressure continues to the north of the
local islands, causing moderate east to east northeast winds
across the local area. The local pressure gradient will tighten
early in the workweek as a stronger surface high pressure
develops across the northwestern Atlantic. This will cause the
local winds to increase and the marine conditions to become
hazardous once again. Overall available moisture will remain
below normal, but patches of low level moisture will pass through
occasionally, causing brief showers across the islands. An upper
low pressure could approach the local area late in the upcoming
workweek but it is not expected to have a significant impact in
the local weather, therefore no major change in the weather
conditions is anticipated for the next several days.
.SHORT TERM...Today through Monday...
Moderate east northeast trade winds winds will persist across the
local area through the weekend and into early next week. Breezy
conditions are therefore expected today through Monday, as the
surface high pressure ridge across the Atlantic will strengthen
north of the region leading to increasing trade winds between
15-25 mph with more frequent gusty winds.
Patches of low level moisture and associated trade wind showers will
continue to make their way and increase in frequency across the
region by Sunday, as the pressure gradient tightens and trade winds
increase. These showers and clouds will affect the local waters,
U.S. Virgin Islands, Vieques and Culebra, and the north and eastern
sections of PR, especially during the evening and early morning
hours. During the day, most of the cloud and shower development is
then expected to form and stream across the interior into west
sections of PR during the afternoons. Elsewhere and over the USVI,
mostly sunny fair weather skies and breezy to windy conditions will
prevail during the period with no significant rainfall or weather
feature anticipated at this time.
.LONG TERM...Tuesday through Sunday...
Patches of moisture will pass through at times, causing brief
showers over the local area. These showers will mainly be observed
across the local waters, USVI, Vieques and Culebra as well as
northern and eastern PR, especially during the nighttime and early
morning hours. A strong SFC high pressure across the northwestern
Atlantic will cause the local pressure gradient to tighten early
in the workweek, which will cause windy conditions locally. These
winds will likely inhibit the usual sea breeze convergence in the
afternoon hours across western PR, which means that the areas that
could be affected by rain will probably be the local islands and
north and eastern PR, even during the daytime hours. Wednesday
looks to be the day with the best moisture so it is the day, in
the long term range of the forecast, that will likely observe the
best rainfall coverage, however, it is still expected to be
somewhat windy so the showers observe should be very brief. No
major change in the overall pattern is expected other than maybe
the wind speeds decreasing by Thursday.
.AVIATION...SCT-BKN cld lyrs nr FL025...FL050...FL080. -SHRA/SHRA en
route btw islands and over coastal waters. VCSH with ocnl -RA at
TJSJ/TJBQ/TIST/TISX/TNCM TIL 17/14Z. Sfc wnds 10kts or less,
increasing 15 to 25 kts with occasionally higher gusts aft 16/14z.
Low level wnds fm NE 15-25 KTS. VCSH and BKN nr FL040-FL080 at TJMZ
and ctrl mtn range of PR 16/18-16/22z.
.MARINE...Small craft operators are urged to exercise caution
across the local waters since seas will be up to 6 feet and the
local winds will be up to 20 knots, with the exception of the
coastal waters of southwestern Puerto Rico where the winds will be
up to 15 knots and the seas up to 4 feet. There is a moderate to
high risk of rip currents across most of the local beaches, please
refer to the local surf zone forecast for the details in your
.PRELIMINARY POINT TEMPS/POPS...
SJU 82 74 83 74 / 50 30 30 30
STT 83 73 84 73 / 40 30 30 30