Area Forecast Discussion
Issued by NWS San Juan, PR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
FXCA62 TJSJ 202110

Area Forecast Discussion
National Weather Service San Juan PR
510 PM AST Sun May 20 2018

.SYNOPSIS...Strong surface high pressure located across the
North-Central Atlantic will continue to influence our local
weather pattern through at least mid-week. A TUTT low located
northeast of the Leeward Islands will move away from the area by
Wednesday and will be replaced by a ridge aloft. This ridge aloft
will remain in place across the forecast area through next


.SHORT TERM...Tonight through Tuesday...The shower activity that
has been affecting western PR as well as the northern half of PR
should dissipate by early this evening. During the evening and
overnight period, mostly clear to partly cloudy skies should
prevail across the forecast area with only a few isolated showers
possible across the USVI and eastern PR. Monday and Tuesday
should feature less shower activity than what has been observed
during this past weekend as a decrease in low-level moisture is
anticipated. The mornings should feature mainly fair weather
conditions with only a few brief passing showers embedded in the
trades affecting the eastern half of PR and the USVI while
locally and diurnally induced showers are expected to develop
across western PR during the afternoon. The thunderstorm coverage
during the next few days should remain very isolated, given that
the mid-levels remain dry.

In terms of the winds, a slight decrease is expected Monday and
Tuesday with easterly winds between 10 and 20 mph with some higher

.LONG TERM...Wednesday through Monday...The aformentioned TUTT low
will begin to move away beginning on Wednesday and this will allow
for a mid to upper-level ridge to establish itself over the
forecast area through next weekend. Under this ridging pattern, a
seasonable and stable weather pattern is expected across the area
with some passing showers affecting eastern PR and the USVI
during the morning hours and convection developing over the
western half of Puerto Rico during the afternoon. Winds will
continue to decrease during the second half of the work week as
the surface high pressure that has been the dominant weather
feature for quite some time shifts eastward and weakens. By late
next weekend into Memorial day, both the GFS and ECMWF models show
another TUTT low sinking southward from the northeast into the
forecast area. As a result, an increase in moisture content as
well as an increase in rain chances is possible.


.AVIATION...Mainly VFR conditions are expected to prevail during the
next 24 hours across all the terminals. SHRA over west PR should end
by 22z. Light passing trade wind showers are possible overnight
across the Leeward/USVI/eastern PR terminals. Surface winds will
continue from the east between 15-20 kts...decreasing 10-15


.MARINE...Hazardous seas up to 8 feet will continue across the
regional waters through tonight. Even though an improvement in
marine conditions is expected across all regional waters by
Monday, seas will remain choppy through at least mid-week due to
easterly winds between 10 and 20 knots continuing. A high rip
current risk continues for the north facing beaches of PR from
northwest to northeast and St. Croix through 6 AM AST Monday while
for the northwest beaches of PR it will continue through Monday


SJU  75  86  76  87 /  20  40  40  40
STT  78  79  78  79 /  20  40  40  40


PR...High Rip Current Risk through 6 AM AST Monday for North Central-
     Northeast-San Juan and Vicinity.

     High Rip Current Risk through Monday afternoon for Northwest-

VI...High Rip Current Risk through 6 AM AST Monday for St Croix.

AM...Small Craft Advisory until 8 PM AST this evening for Anegada
     Passage Southward to 17N-Coastal Waters OF Northwestern
     Puerto Rico out 10 NM-Coastal Waters of Northern USVI and
     Culebra out 10 NM-Coastal Waters of Southern Puerto Rico
     out 10 NM-Coastal Waters of Southern USVI Vieques and
     Eastern Puerto Rico out 10 NM.

     Small Craft Advisory until 8 AM AST Monday for Atlantic Waters
     of Puerto Rico and USVI from 10 NM to 19.5N-Caribbean
     Waters of Puerto Rico from 10 NM to 17N-Mona Passage
     Southward to 17N.

     Small Craft Advisory until 2 AM AST Monday for Coastal Waters of
     Northern Puerto Rico out 10 NM.



LONG TERM....GL is the U.S. government's official web portal to all federal, state and local government web resources and services.