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160
FXCA62 TJSJ 311832
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
232 PM AST Wed Dec 31 2025

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

.KEY MESSAGES...
Issued at 217 PM AST Wed Dec 31 2025

* The north-facing beaches from Rincon/Anasco to Fajardo,
  Culebra, St. Thomas, St. John, and adjacent islands have a high
  risk of life-threatening rip currents through late tonight. The
  risk will turn moderate from tomorrow onward.

* An unstable and wet pattern will prevail from New Year`s Eve
  into the first days of the New Year, especially for the western
  portion of Puerto Rico. Meanwhile, the US Virgin Islands can
  expect calm weather conditions with a few quick passing showers.

* Model guidance indicates a possibility of moving into an unsettled
  weather pattern around Three Kings Day for the region.


&&

.Short Term(This evening through Friday)...
Issued at 217 PM AST Wed Dec 31 2025

The US Virgin Islands and Puerto Rico observed tranquil weather
conditions with pleasant winter tropical temperatures through the
morning. Cloud cover began to slowly increase from the west across
the islands by mid-morning as an approaching mid- to upper-level
trough moved closer to the region. Additionally, the Doppler Radar
briefly detected some showers affecting the southeast coast of
PR. Winds were mainly from east-southeast at less than 10 mph.

The mid- to upper-level trough will continue to approach the
Northeast Caribbean, with its axis moving over Puerto Rico and the
US Virgin Islands around Friday. At the same time, as a cold
front extending from the North Atlantic into the western Caribbean
moves eastward toward the local islands, it will induce a frontal
trough, mainly over Hispaniola and the Mona Passage late tonight
into Thursday or Friday.

Under this weather pattern, we expect a chance (20-50%) to
observe periods of showers over the region from late this
afternoon into the overnight hours. This activity could spread
from the Mona Passage into the western half of Puerto Rico,
creating ponding of water in roads and poorly drained areas as
early as this evening. There is a limited chance to observe
lightning activity as well.

The most unstable pattern is possible from Thursday (New Year`s
Day) afternoon into the early Friday morning, as a pre-frontal
trough interacting with the trough aloft creates favorable
conditions to have a chance (30-50%) to likely (60-70%) rain
activity over portions of west, interior, and north PR. As a
result, there is an elevated risk of flooding rains across
portions of western and northern PR during that period.

Temperature-wise, there is a high (>70%) chance of temperatures
below 65% in the interior sections of PR. Meanwhile, the coastal
sections of the USVI/PR will have a high (>80%) chance of
observing low temperatures below 75 degrees Fahrenheit in the
early morning hours of the first day of 2026.

&&

.Long Term(Saturday through next Tuesday)...
Issued at 424 AM AST Wed Dec 31 2025

From Saturday into Sunday, weather conditions will remain
dependent on a high-pressure system building over the central
Atlantic. On Saturday, surface winds will remain from the east,
veering on Sunday more from the southeast to south, and eventually
from the west with the approach of a pre-frontal boundary late.
At the upper levels, conditions will rapidly improve as the
subsidence side of the upper-level trough moves eastward, allowing
a more stable pattern to dominate. At 500 mb, a ridge will move
in, allowing warmer temperatures of 6 to -5 degrees. Although
stable conditions will persist at the mid to upper levels, at the
surface, as surface winds vary, shallow patches of moisture will
support some morning showers across the eastern sections, with
afternoon showers developing across the interior and western
Puerto Rico. According to the global model guidance, precipitable
water values will remain within the climatological normals,
ranging from 1.5 to 1.7 inches. These surface conditions and the
local mountain effect might aid some very short-lived showers at
the peak of the afternoon on Saturday and Sunday.

Conditions will rapidly deteriorate from late Monday into Tuesday
as a deep mid- to upper-level trough moves across the forecast
area. This mid- to upper-level feature will enhance very unstable
weather conditions across the islands, with colder mid-level
temperatures ranging from 9 to 10 degrees. In addition to these
very favorable conditions for thunderstorm activity, the GDI index
also shows an increase in the potential for scattered showers
late Monday into Tuesday. Furthermore, 850500 mb relative
humidity values will spike well above climatological norms,
surpassing two standard deviations by Tuesday. Although changes
are highly likely, residents and visitors are urged to stay tuned
for further updates, especially given the Three Kings Day
celebration on Tuesday.

&&

.AVIATION...
(18Z TAFS)
Issued at 217 PM AST Wed Dec 31 2025

Mainly VFR conds exp across all TAF sites thru this evening. We
cannot rule out a few SHRA/isold TSRA this afternoon. However,
there is a chance that SHRA/TSRA moving eastward from the Mona
Passage spread over the western half of PR from around 31/22z
onward. Followed by another round of SHRA/TSRA tomorrow afternoon
into the evening. Expect E-SE winds at 8-13 kt, becoming calm to
light and variable aft 31/23z, returning from the E-ESE aft 01/13z
with higher gusts and sea breeze variations.

&&

.MARINE...
Issued at 217 PM AST Wed Dec 31 2025

A frontal boundary approaching the northeastern Caribbean will
promote a moderate east-southeast wind flow across the region
through at least Friday. Then, as the front interacts with a
surface high pressure building over the central Atlantic, winds
will return from the east to northeast Friday into the weekend.
Additionally, a long-period northerly swell will slowly dissipate
across the local waters through late tonight. Also, frontal
proximity will support the development of showers and
thunderstorms, especially across the Mona Passage and Atlantic
Waters through at least Friday.

&&

.BEACH FORECAST...
Issued at 217 PM AST Wed Dec 31 2025

Beachgoers, a long-period northerly swell will continue to spread
across the north-facing beaches, resulting in life-threatening
rip currents, especially from Rincon along the Atlantic Coastline
to Fajardo, Culebra, St Thomas, St John, and the Adjacent Islands.
Vieques and St Croix have a moderate risk of rip currents, and
the rest of the western and southern beaches have a low risk. From
Thursday onward, the risk will turn moderate for the north-facing
beaches.

There is a limited chance of lightning across the western and
northern beaches of Puerto Rico, particularly this evening and
again from Thursday afternoon into Friday. Remember that lightning
can strike several miles away from a thunderstorm. If you hear
thunder, seek shelter immediately.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for PRZ001-002-005-
     008-010-012.

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

AM...None.
&&

$$

MORNING CREW...CAM/GRS
EVENING CREW...DS/MRR

NWS SJU Office Area Forecast Discussion