384
FXCA62 TJSJ 070852
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
452 AM AST Sun Dec 7 2025

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

.KEY MESSAGES...
Issued at 449 AM AST Sun Dec 7 2025

* Mostly fair and stable conditions will continue through the
  period, with brief overnight and morning showers on windward sides
  and isolated afternoon showers across the interior and west. No
  flooding impacts are expected.

* Winds will increase late in the week, leading to breezy to windy
  conditions across coastal and elevated areas by Thursday and
  Friday. Lightweight outdoor items may be blown around in exposed
  locations.

* For the U.S. Virgin Islands, fair weather will prevail, with a
  few quick passing showers mainly during the night and early
  morning. Winds will become noticeably stronger late in the week.

* Marine and beach conditions will deteriorate mid- to late week as
  increasing winds and an incoming long-period northerly swell raise
  seas and rip current risks. Hazardous surf and Small Craft
  Advisories are likely.

&&

.Short Term(Today through Tuesday)...
Issued at 449 AM AST Sun Dec 7 2025

A variable weather pattern prevailed during the night into the early
morning hours, with abundant cloud cover and isolated to scattered
showers across the eastern section of Puerto Rico and the U.S.
Virgin Islands. Rainfall activity was frequent, diminishing at 2 AM,
and rainfall accumulations were less than 0.5 inches. The rest of
the morning, cloudiness prevailed across the area as the surface
disturbance moved more westward into the Mona Passage. Overnight
temperatures remained in the mid to upper 70s across the coastal and
urban areas and in the 60s across the mountains.

For today, a similar weather pattern is expected, mostly due to a
mid- to upper-level broad ridge anchored in the central Atlantic.
This main weather feature will maintain very stable conditions
aloft, resulting in drier conditions, warmer temperatures at 500 MB,
and a drastically stable 850-700 MB lapse rate. At the surface, a
moderate easterly wind flow will remain in place as the broad
surface high pressure extending from the eastern Atlantic into the
Caribbean continues to result in a tight pressure gradient.
Therefore, today residents can expect breezy conditions across
coastal areas and local waters. Under the easterly wind flow, a
drier airmass will filter in, with precipitable water values of 1.1
in, as indicated by GOES-derived satellite imagery.

From Monday into Tuesday, a more east-southeasterly wind flow is
expected as the surface high pressure establishes across the central
Atlantic. Similar to previous days, precipitable water values will
remain quite low relative to the seasonal average, enhancing mostly
stable weather conditions with little rainfall activity. Although
excellent weather conditions will persist, diurnal heating at the
local level may enhance short-lived afternoon showers across the
western interior and northwestern sections. This shower activity is
not expected to pose a flooding threat across the affected areas.
Also, the wind component can help keep temperatures within seasonal
climatological normals and even slightly warmer in some coastal
areas.

&&

.Long Term(Wednesday through Sunday)...
Issued at 449 AM AST Sun Dec 7 2025

A persistent and increasingly dominant mid-level ridge will govern
the period, maintaining well-below-normal mid-level moisture. Recent
model cycles show 700-500 mb relative humidity frequently dipping
below 20 percent and at times near 10 percent, supporting a strong
and persistent inversion based near 850 mb through most of the
forecast period. This pattern will continue to favor stable
conditions and suppress deep convection for the most part. However,
occasional shallow moisture surges embedded in the trade winds will
periodically lift the inversion height above the 700 mb layer,
allowing for an uptick in passing showers. These events will favor
the overnight and morning hours across windward coastal areas.
During the afternoons, isolated to scattered showers remain possible
across the interior and western Puerto Rico, but any thunderstorms
that develop will be short-lived and very isolated. No significant
flooding threat is expected.

Toward the latter part of the period, surface high pressure over the
central Atlantic is forecast to strengthen while a frontal boundary
approaches from the northwest. This will tighten the pressure
gradient across the northeastern Caribbean and result in breezy to
windy conditions, especially across coastal and elevated areas from
late week into the weekend. These winds may cause unsecured or
lightweight outdoor items to blow around and could produce localized
minor impacts in areas exposed to stronger gusts.

Overall, conditions will remain largely stable with shallow
convection, limited rainfall amounts, and a notable increase in
winds late in the workweek into the weekend.

&&

.AVIATION...
(06Z TAFS)
Issued at 449 AM AST Sun Dec 7 2025

VFR conditions will persist throughout the period at all TAF sites.
Winds will remain from the east at 10 knots or less, increasing at
07/14Z up to 15 knots with gusty winds. Some brief RA to SHRA until
07/15z might continue to result in lower ceilings and a slight
reduction in VIS across TJSJ, TIST & TISX.

&&

.MARINE...
Issued at 449 AM AST Sun Dec 7 2025

Marine conditions will remain moderate through early in the week,
with moderate easterly trades maintaining choppy seas across the
offshore waters and local passages. By midweek, strengthening high
pressure north of the region will tighten the pressure gradient and
increase easterly winds, allowing seas to build across the Atlantic
waters and exposed passages. At the same time, a long-period
northerly swell arriving midweek will further worsen conditions.
Hazardous seas and moderate to fresh winds are expected Thursday
into Friday, with Small Craft Advisories likely. A gradual
improvement remains possible over the weekend as winds and swell
ease.

&&

.BEACH FORECAST...
Issued at 449 AM AST Sun Dec 7 2025

A low to moderate rip current risk will persist across the region
through the start of the week, primarily affecting the northern and
eastern exposed beaches of the islands, where weak northeasterly
swells and local winds are keeping the nearshore waters slightly
rougher. Conditions will start to change by midweek as a long-period
northerly swell moves into the area, which is expected to increase
wave energy and significantly raise the rip current risk along north-
facing beaches of Puerto Rico and the U.S. Virgin Islands. Some
uncertainty remains regarding the exact timing and strength of this
swell, but the overall trend suggests a more hazardous setup from
Wednesday onward. Beachgoers should stay updated, since conditions
could deteriorate quickly once the swell arrives.

For localized and updated risk levels, visit weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM & AVIATION...LIS
LONG TERM, MARINE & BEACH FORECAST....CVB