276
FXCA62 TJSJ 121745
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
145 PM AST Wed Nov 12 2025

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

.KEY MESSAGES...
Issued at 130 PM AST Wed Nov 12 2025

* A long-period north-northwesterly swell will worsen marine
  conditions, creating life-threatening rip currents along north-
  and east-facing beaches in Puerto Rico and the US Virgin
  Islands from late this evening to Friday.

* The US Virgin Islands and Puerto Rico are expected to have
  mainly clear skies, with winds bringing patches of moisture and
  clouds, as well as occasional showers, throughout the forecast
  period.

* There is a moderate chance that the weather will become wetter
  and more unstable due to a frontal boundary approaching from
  the western Atlantic, near the northeast Caribbean, around the
  weekend.

&&

.Short Term(This evening through Friday)...
Issued at 130 PM AST Wed Nov 12 2025

The US Virgin Islands and Puerto Rico experienced pleasant weather
conditions during the morning hours, characterized by a mixture of
sunshine and clouds. After mid-morning, the easterlies brought a
patch of moisture, increasing the passing showers, mainly over
PR`s northeast quadrant and across the waters surrounding the US
Virgin Islands. This moisture, combined with the local effects and
sea breezes, results in shallow afternoon convection along and
west of the Cordillera Central. Maximum temperatures reached the
mid-80s, with some coastal areas seeing highs in the upper 80s.
Winds were predominantly from the east to east-northeast, with
speeds ranging from 10 to 20 mph, and higher gusts and variations
in the sea breeze.

The mid-to-upper-level ridge will slowly weaken as an upper-level
trough approaches from the northwest to the Northeast Caribbean,
increasing the probability (40 percent to 50 percent) of observing
afternoon activity with one or two thunderstorms. However, still
a dry air mass above 700 mb will promote subsidence aloft, making
it challenging to form thunderstorms. At the surface, a frontal
boundary moving eastward will interact with the high pressure
across the Central Atlantic, weakening the steering winds,
especially around Friday.

Under the weather pattern expressed above, we can expect a
seasonable weather pattern, consisting of good periods of mostly
clear skies, with occasional clouds and showers arriving each
day, especially overnight. On Thursday and Friday, there is a
better chance (40 to 50 percent) of observing afternoon rain
activity across the interior and western PR, as well as moving
across the USVI, due to the weakening of the mid-level high
pressure. However, 500 mb temperatures are still near normal
values, and the lapse rates at low levels are still below or near
normal, which suggests a challenging situation for the development
of deep convection.

&&

.Long Term(Saturday through next Tuesday)...
Issued at 130 PM AST Wed Nov 12 2025

The islands will be dominated mainly by a pre-frontal trough at
the surface and a trough at the mid-to-upper levels. At the
surface, the surface trough will weaken the pressure gradient,
resulting in variable and light winds from Saturday into Sunday
along the islands. According to the global model guidance, the
frontal boundary will dissipate just north of the region as a
surface high pressure builds just across the western Atlantic,
extending into the Central Atlantic. Although the frontal boundary
will remain to our north, enough deep enough moisture will reach
the islands. The available moisture trapped in the first 300 MB
[1000-700 MB] with precipitable water values from 1.5 to 1.7
inches, which are normal values for this time, will allow the
development of afternoon convection. Isolated thunderstorms are
expected, with the heaviest activity forecasted due to some
instability caused by the presence of the mid-level trough, which
enhances colder temperatures at 500 MB, ranging between -6 and -7
degrees Celsius. Since winds will be variable, the focus of the
showers and the translation movement can contribute to some
isolated urban flooding, with the heaviest showers occurring
during the afternoon hours.

From Monday onwards, as the surface high pressure migrates further
into the Central Atlantic, veering winds from the east-southeast
will again change the weather pattern across the islands.
Therefore, residents can expect a more typical weather pattern,
with an increase in heat indices in some coastal areas and
afternoon convection primarily across eastern sections of Puerto
Rico, specifically in the vicinity of El Yunque, extending to some
metropolitan areas and northwestern Puerto Rico. Rainfall
accumulation is not forecast to be significant; however, some
isolated urban and minor flooding cannot be ruled out in low-
lying areas.

&&

.AVIATION...
(18Z TAFS)
Issued at 130 PM AST Wed Nov 12 2025

Expect VFR conds through the forecast period. Occasional
SHRA/+SHRA will affect local terminals and surrounding waters,
leaving none to minimal impacts to operations. SW-PR afternoon
convection will affect the region thru 12/23z. Winds will remain
mainly from the E to ENE at 10-15 kt, with occasional higher
gusts and sea breeze variations, mainly during the morning and
afternoon hours. Overnight, we expect calm to light and VRB winds.

&&

.MARINE...
Issued at 130 PM AST Wed Nov 12 2025

A frontal boundary moving eastward across the western Atlantic
will linger off to the northwest of the northeast Caribbean
through the rest of the workweek. Therefore, expect moderate to
locally fresh winds through at least Thursday, becoming light to
gentle from Friday into the weekend, as a pre-frontal trough forms
near the islands. Additionally, a long-period north-northwesterly
swell, spreading across the Atlantic Ocean, will reach the local
waters and passages, deteriorating marine conditions. Thus, a
Small Craft Advisory is in effect from late tonight into early
Friday morning.

&&

.BEACH FORECAST...
Issued at 130 PM AST Wed Nov 12 2025

An approaching north-northwesterly swell will spread across the
local Atlantic Waters and Caribbean Passages later this evening,
deteriorating the coastal conditions overnight into Thursday.
Thus, life-threatening rip currents are expected to form from
Rincon to Fajardo and Culebra late tonight or early Thursday
morning, creating a High Risk of rip currents. Meanwhile, the risk
will moderate for the north-facing beaches along St. Thomas, St.
John, and the Adjacent Islands.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory from 6 PM this evening to midnight AST
     Thursday night for AMZ711.

&&

$$

SHORT TERM...CAM
LONG TERM....MNG
AVIATION...ICP