629
FXCA62 TJSJ 150626
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
226 AM AST Mon Dec 15 2025

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

.KEY MESSAGES...
Issued at 214 AM AST Mon Dec 15 2025

* A surge in moisture associated with a pre-frontal trough moving
  to the north of the area will promote more unstable and wet
  conditions during the first half of the workweek across the U.S.
  Virgin Islands and Puerto Rico.

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

* A northwesterly swell is forecast to arrive by midweek,
  deteriorating marine and coastal conditions through the upcoming
  weekend.

&&

.Short Term(Today through Wednesday)...
Issued at 214 AM AST Mon Dec 15 2025

A surge in moisture associated with a pre-frontal trough moving to
the north is expected in the short-term period. The precipitable
water content (PWAT) is expected to increase to near 1.75 inches
late today, with no significant change in moisture levels through
the rest of the short-term period. Latest satellite imagery
indicates an area of cloudiness and showers moving over the Leeward
Islands into the Anegada Passage. This area will then reach the USVI
early this morning and spread across PR throughout the day. As the
local area lies between the front and a distant surface high
pressure, winds will generally persist from the east to southeast at
5 to 15 knots. For Tuesday and Wednesday, no significant variations
in moisture content are expected. However, the 500mb temperatures
are forecast to be the coldest on Tuesday afternoon, around -6.5C,
which should favor heavier showers and isolated thunderstorm
development. Ponding of water in roads and other poor drainage areas
can be expected each day across the islands, with a higher chance of
urban and small stream flooding on Tuesday in PR.

&&

.Long Term(Thursday through Monday)...
Issued at 214 AM AST Mon Dec 15 2025

The forecast remains on track with previous discussions. A
building surface high-pressure system over the western Atlantic
will continue to push lingering moisture from a frontal boundary
into the local area from Thursday into Friday. This will increase
the frequency of passing showers across Puerto Rico and the U.S.
Virgin Islands, particularly during the morning hours across the
windward portions. As the surface high continues to move over the
Atlantic Ocean, another frontal boundary will move east of the
eastern coast of the CONUS, promoting a northeasterly wind flow
across the area. Under this pattern, cooler temperatures will be
felt across the region during the upcoming weekend. By Sunday,
another surface high pressure behind the front is expected to
strengthen north of the local area, bringing slightly drier
conditions; nonetheless, patches of moisture will continue to move
into the islands, promoting showers from time to time.

&&

.AVIATION...
(06Z TAFS)
Issued at 214 AM AST Mon Dec 15 2025

Mainly VFR conditions are expected early in the fcst period.
However, SHRA en route from the Leeward Islands will reach the USVI
terminals btw 15/12-16z, this may lead to tempo MVFR conds,
particularly at TIST. Additional SHRA is expected to develop in and
around TJSJ and TJBQ btw 15/16-22z, which could lead to brief MVFR
cigs. Winds will increase 8-12 kt from the ESE, with sea breeze
variations at TJSJ/TJBQ aft 15/14z.

&&

.MARINE...
Issued at 214 AM AST Mon Dec 15 2025

A surface high-pressure system across the eastern into central
Atlantic will continue to promote moderate to locally fresh east to
southeast winds across the local waters today. Wind-driven seas
are promoting hazardous marine conditions for small craft
operators across the offshore Atlantic waters, where a Small Craft
Advisory remain in effect at least through Monday morning. A cold
front and another surface high-pressure system will move from the
western Atlantic into the central Atlantic over the next few
days, weakening the pressure gradient and allowing for gentle to
moderate winds from late today and Tuesday. By midweek,
increasing winds and a northwesterly swell will likely deteriorate
marine conditions once again.

&&

.BEACH FORECAST...
Issued at 214 AM AST Mon Dec 15 2025

A moderate risk of rip currents will continue along most beaches
of the islands through mid-week. This means that life-threatening
rip currents are possible in the surf zone, and beachgoers are
encouraged to exercise caution. The moderate risk of rip currents
is expected to prevail across north-facing beaches of Puerto
Rico, Culebra, and the U.S. Virgin Islands, with a low risk
elsewhere. Remember that even when the risk is low, life-
threatening rip currents can still occur, especially near groins,
jetties, reefs, and piers.

By midweek, beach conditions are anticipated to deteriorate again
due to increasing winds and a northwesterly swell spreading across
the local Atlantic waters. Stay tuned to the forecast! For specific
location information, please visit weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until noon AST today for AMZ711.

&&

$$

MIDNIGHT CREW...DSR/GRS

NWS SJU Office Area Forecast Discussion