National Weather Service Today's Weather Impact Levels

828
FXCA62 TJSJ 170932
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
532 AM AST Wed Dec 17 2025

...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST...

.KEY MESSAGES...
Issued at 429 AM AST Wed Dec 17 2025

* Life-threatening breaking waves and rip currents will impact the
  north-facing beaches of PR from Rincon to Fajardo and Culebra.

* Life-threatening rip currents will form along the exposed north-
  facing beaches in St Thomas and St John.

* Showers and isolated thunderstorms this afternoon may lead to a
  slight chance of flooding and thunderstorm impacts, extending
  from El Yunque into the San Juan metropolitan area and into the
  interior, north- central, and northwest PR.

* Dangerous marine conditions for small craft operators will
  prevail today across the local Atlantic Waters, and Caribbean
  Passages.

&&

.Short Term(Today through Friday)...
Issued at 429 AM AST Wed Dec 17 2025

Although we observed calm weather with pleasant overnight low
temperatures, a pre- frontal trough brought passing showers across
the windward locations in PR and the US Virgin Islands overnight.
Additionally, a long- period north- northwesterly swell promoted
the formation of life- threatening rip currents along the north-
facing beaches in PR and the US Virgin Islands early this morning.
Winds were calm to light and variable, allowing the land breeze
to form overnight. However, the passing showers lead to occasional
gusty winds.

We have moderate/high confidence that a long-period northwesterly
swell will create life-threatening breaking waves and rip
currents, and minor coastal flooding at the most vulnerable
coastal locations from Rincon to Fajardo, especially this morning
around high tide. Also, life-threatening rip currents will form on
the north-facing beaches in Culebra, St. John, and St. Thomas.

There is a high confidence (60-80%) of mostly calm and stable
conditions across the interior, western, and southern plains of
Puerto Rico during the early morning hours, resulting in limited
weather impacts in those areas. In contrast, a pre-frontal trough
is expected to increase the likelihood of passing showers across
the U.S. Virgin Islands and the windward sections of Puerto Rico
this morning, with a moderate probability (30-50%) of brief
moderate to locally heavy rainfall.

As the day progresses, east to east-southeast winds associated
with the pre-frontal trough will likely favor the development of
El Yunque Streamer, extending into the San Juan Metropolitan
Area, and afternoon convection over portions of the interior,
north-central, and northwest Puerto Rico. In these areas, there
is a moderate to high chance (4070%) of periods of moderate to
locally heavy rainfall, which could lead to localized ponding of
water in poor drainage areas and brief reductions in visibility,
especially during the afternoon commute, as well as isolated urban
and small stream flooding.

The proximity of an upper-level trough and a jet streak will
introduce marginal instability, resulting in a slight chance of
isolated thunderstorms during the afternoon and evening hours
across parts of Puerto Rico and the surrounding U.S. Virgin
Islands waters. However, most model guidance indicates that the
strongest dynamical support will remain north of the region,
limiting thunderstorm coverage and keeping the overall flooding
risk low, with only a localized and brief flooding threat in areas
experiencing repeated heavy showers.

Looking ahead to Thursday and Friday, confidence is high that a
mid- to upper-level ridge will build over the Northeast Caribbean,
promoting subsidence and drier air aloft. Despite this,
strengthening easterly trade winds will maintain a moderate to
high chance (3060%) of passing showers across windward locations
of Puerto Rico and the U.S. Virgin Islands. These showers will be
most frequent during the overnight and early morning hours, with
some activity likely spreading into the interior and western
Puerto Rico during the afternoon, resulting in generally minor but
recurrent wet-weather impacts.

&&

.Long Term(Saturday through Wednesday)...
Issued at 429 AM AST Wed Dec 17 2025

Saturday through Wednesday...

A mid-to-upper-level ridge will dominate local weather for the first
half of the period, maintaining stable conditions aloft. During this
time, precipitable water (PWAT) values will remain below the
seasonal climatological values, ranging from 1.2 to 1.5 inches. At
the surface, patches of low-level moisture will continue to drift
into the area, bringing passing showers to windward sections of the
islands. Rainfall accumulations will stay limited, though localized
afternoon showers are possible across western Puerto Rico. Overall
impacts are expected to remain minimal.

Transitioning into the second half of the period and through
Christmas Eve, a wetter pattern will evolve. The mid-level ridge
will erode as a polar trough, exiting the eastern U.S. coast,
approaches from the northwest. This will increase instability, with
500mb temperatures dropping to between -6 and -8C. At the surface,
an associated frontal boundary is forecast to approach late Tuesday
into Wednesday. During this period moisture will increase, with PWAT
values reaching 1.5 to 1.75 inches. This combination of cooling
aloft and increased moisture suggests an unsettled pattern for the
Christmas holiday, potentially bringing isolated thunderstorms and
locally heavy rainfall that could increase the risk of flooding in
prone areas starting late Tuesday or Wednesday.

&&

.AVIATION...
(06Z TAFS)
Issued at 429 AM AST Wed Dec 17 2025

Passing SHRA/+SHRA will impact JSJ/IST and ISX throughout the day.
Then, between 17/16-23z, we have a moderate confidence that TSRA
will form near JSJ and JBQ, when MVFR conditions could develop.
Winds will prevail calm to light and VRB thru 17/13z, then we
expect E-ESE winds at 10 to 15 kt with higher gusts and sea breeze
variations. Calm to light/VRB winds will return aft 17/23z. There
is a slight chance that TSRA could develop during the evening
along the PR`s Atlantic Coastline.

&&

.MARINE...
Issued at 429 AM AST Wed Dec 17 2025

A cold front extending from around Turks and Caicos to the
northeastern Atlantic and a pre-frontal trough will promote moderate
to locally fresh east to east-southeast winds across the islands
today. Meanwhile, a long-period north-northwesterly swell will create
hazardous marine conditions for small craft throughout the day. Thus,
a Small Craft Advisory is in effect for the Atlantic and Caribbean
Passages. The frontal boundary will linger off to the northwest as an
occluded low form over the Central Atlantic, far to the northeast of
the region, Thursday and Friday.

&&

.BEACH FORECAST...
Issued at 429 AM AST Wed Dec 17 2025

A long period north to northwesterly swell will create life-
threatening breaking waves and rip currents along the north-facing
beaches in Puerto Rico from Rincon to Fajardo, and Culebra.
Meanwhile, the north- facing beaches in the US Virgin Islands can
expect life- threatening rip currents throughout the day. By this
evening the risk will spread to the southwest of Puerto Rico and
Vieques. We encourage beachgoers to avoid visiting these beaches.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for PRZ001-002-005-
     008.

     Coastal Flood Advisory until 6 PM AST this evening for PRZ001-
     002-005-008-010.

     High Surf Advisory until 6 AM AST Thursday for PRZ001-002-005-
     008-010.

     High Rip Current Risk through late tonight for PRZ010-012.

     High Rip Current Risk from this evening through late tonight for
     PRZ011-013.

VI...High Rip Current Risk through late tonight for VIZ001.

AM...Small Craft Advisory until 6 AM AST Thursday for AMZ711-712-716-
     723-741-742.

     Small Craft Advisory from noon today to 6 AM AST Thursday for
     AMZ726.

&&

$$

SHORT TERM...CAM
LONG TERM....GRS
AVIATION...CAM

NWS SJU Office Area Forecast Discussion