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389
FXCA62 TJSJ 140821
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
421 AM AST Sun Dec 14 2025

...New SHORT TERM, LONG TERM, AVIATION...

.KEY MESSAGES...
Issued at 403 AM AST Sun Dec 14 2025

* A drier and stable air mass will continue to move across the
  islands today, promoting limited showers.

* Choppy to rough seas are expected to continue across the
  offshore Atlantic waters through at least Monday morning.

* For the U.S. Virgin Islands, mainly fair weather conditions are
  expected with few passing showers moving into the area.

* The approach of a frontal system and its associated upper-level
  trough over the western Atlantic will promote unstable conditions
  during the first half of the workweek.

&&

.Short Term(Today through Tuesday)...
Issued at 403 AM AST Sun Dec 14 2025

A drier and more stable air mass will continue to gradually fill
over the region today. This will promote mostly fair weather
conditions across the islands, with limited shower development this
afternoon over land areas. On Monday and Tuesday, global model
guidance continues to suggest a wet period, as an approaching cold
front and associated upper level trough from the western Atlantic
induces a pre-frontal trough near the local area. The precipitable
water content is expected to increase near 1.75 inches, which is
above normal levels. This pooling of moisture will allow for weak
surface troughs to move from the east, increasing the chance of
showers between 50-70% each day across the islands, with a slight
chance of thunderstorm development over western PR in the afternoon
hours. As the front remains north of the region, and the area sits
between two areas of high pressure over the Azores and behind the
front over western Atlantic, a southeasterly wind flow will prevail.
This will lead to warmer than normal temperatures before the onset
of afternoon showers.

&&

.Long Term(Wednesday through Sunday)...
Issued at 403 AM AST Sun Dec 14 2025

The inherited forecast remains on track. Instability is expected
to arrive in the area on Wednesday, driven by an upper-level
trough positioned along a frontal boundary north of the region.
At the surface, a building high-pressure system over the western
Atlantic will begin to push moisture associated with this front
into the local area, promoting wetter conditions by the latter
part of the week. As this surface high strengthens, winds will
shift to the northeast, pushing slightly cooler air into the area.
Under this pattern, frequent passing showers are expected during
the morning hours across portions of eastern Puerto Rico and the
U.S. Virgin Islands, followed by afternoon showers over portions
of central and western Puerto Rico. During this period,
precipitable water content values are expected to range from 1.6
to 1.8 inches, suggesting normal to near-above-normal values for
the season. At the 500 mb level, temperatures are expected to
remain around -6C; however, isolated thunderstorms cannot be ruled
out, particularly with the afternoon activity over western Puerto
Rico. Furthermore, the increasing pressure gradient force driven
by the strengthening high pressure will result in breezy
conditions during the latter half of the week, with wind speeds
sustained between 15 to 20 knots.

&&

.AVIATION...
(06Z TAFS)
Issued at 403 AM AST Sun Dec 14 2025

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. Mostly VCSH expected at times across the
area terminals. Winds will prevail from the east at 15-20 kt with
sea breeze variations and stronger gusts aft 14/14z.

&&

.MARINE...
Issued at 403 AM AST Sun Dec 14 2025

A surface high-pressure system will continue to build near the
Azores, promoting moderate to fresh east to southeast winds
across the local waters. Increasing winds and a fading long-period
northerly swell will result in choppy to rough seas, mainly
across the Atlantic waters. Small Craft Advisories remain in
effect at least through Monday morning across the offshore
Atlantic waters. A cold front and another surface high- pressure
system will move from the western Atlantic into the central
Atlantic early next week, weakening the pressure gradient and
allowing for gentle to moderate winds through Tuesday. By midweek,
increasing winds and a northwesterly swell will deteriorate
marine conditions once again.

&&

.BEACH FORECAST...
Issued at 403 AM AST Sun Dec 14 2025

A fading, long-period northerly swell will create life-threatening
rip currents along the north and east facing beaches of the
islands, where a Rip Current Statement remains in effect at least
through early this morning. Beachgoers are urged to avoid
swimming under these conditions. For the rest of the area, a low
to moderate risk of rip currents is expected to dominate from
today onwards, with beach conditions deteriorating again by
midweek as a northwesterly swell spreads across the local Atlantic
waters. For specific location information, please visit
weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 AM AST early this morning for
     PRZ001-002-005-008.

VI...None.
AM...Small Craft Advisory until 6 AM AST Monday for AMZ711.

&&

$$

MIDNIGHT CREW...DSR/GRS

NWS SJU Office Area Forecast Discussion