530
FXCA62 TJSJ 040741
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
341 AM AST Thu Dec 4 2025

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

.KEY MESSAGES...
Issued at 340 AM AST Thu Dec 4 2025

 * An increase in cloudiness and moisture will continue to result
   in showers across eastern sections of Puerto Rico and the U.S.
   Virgin Islands during the morning hours, followed by afternoon
   convection along the western interior.

 * Slightly warmer daytime temperatures will persist over the
   islands, surpassing seasonal normals, especially in urban and
   coastal areas.

 * Improving weather conditions are forecast from Saturday into
   the upcoming workweek due to a more stable pattern.

 * There is a moderate risk of rip currents across all northern
   coastal areas, including St. Thomas and St. Croix.

&&

.Short Term(Today through Saturday)...
Issued at 340 AM AST Thu Dec 4 2025

Overnight weather conditions remained mostly calm under mostly clear
to partly cloudy skies. Doppler radar detected a few quick-moving,
passing showers mainly across portions of eastern and northern
Puerto Rico and the U.S. Virgin Islands, which resulted in minimal
accumulations. Minimum temperatures were observed in the low to mid
60s along the central mountain range of Puerto Rico and in the low
to mid 70s across the lower elevations of the islands. Winds were
light and variable throughout the night.

Today, a surface trough will continue to approach the local area
from the east, increasing the frequency of showers from this morning
into the late afternoon hours. The forecast remains on track, with
the bulk of the moisture associated with this trough remaining south
of the region. However, due to its proximity, there is an enhanced
chance for moderate to heavy showers and a few isolated
thunderstorms across the islands. Consequently, there is a limited
to elevated risk of excessive rainfall, particularly over portions
of central and southwestern Puerto Rico during the afternoon.

From Friday into Saturday, weather conditions are expected to
improve as a mid-to-upper level ridge builds from the west,
promoting the intrusion of drier air and more stable conditions
aloft. Nonetheless, locally induced afternoon showers cannot be
ruled out, mainly over central and western Puerto Rico. This pattern
will likely extend into early next week, bringing limited showers
and great weather conditions for those early Christmas festivities
across the islands during the weekend.

Seasonal temperatures will prevail across the region during the next
few days, ranging from the mid to upper 80s along the lower
elevations of the islands and from the upper 70s to low 80s along
the central mountain range of Puerto Rico.

&&

.Long Term(Sunday through Thursday)...
Issued at 340 AM AST Thu Dec 4 2025

The long-term forecast remains on track. A strong mid to upper-
level ridge will be the main weather feature, mainly resulting in
a stable weather pattern during the period. At 500 MB,
temperatures in the -5 to -6 degree range and the 850 to 700 MB
lapse rate, two standard deviations from the climatological
values, will limit vertical development. Although very stable
conditions will prevail, a strong surface high pressure over the
Central Atlantic will drag patches of trapped moisture at 850 MB.
According to the global model guidance, precipitable water values
associated with the moisture patches will range from 1.4 to 1.6
inches, close to the climatological normals. Therefore, in the
afternoon, brief passing showers are possible due to diurnal
heating and local effects. On Sunday, surface winds will remain
mostly from the east as the surface high pressure remains in the
Central Atlantic. Veering winds are forecast from Monday onwards
as the surface high pressure builds further into the Central and
Eastern Atlantic.

Since the surface winds will remain east-southeasterly and plenty
of sunshine will be present due to the lack of instability,
daytime temperatures will remain just slightly above seasonal
levels across the islands. According to the global model guidance,
925 MB temperatures suggest warmer conditions from Monday
onwards, with Tuesday the warmest day of the long term.

&&

.AVIATION...
(06Z TAFS)
Issued at 340 AM AST Thu Dec 4 2025

Mainly VFR conds across all terminals during the fcst period. The
proximity of a surface trough will result in an increase in SHRA/-
TSRA today, and promoting VCSH at TJSJ/TIST/TISX aft 04/13Z.
Afternoon convection will lead to VCTS at TJPS/TJBQ aft 04/17Z.
Winds will remain from the E-NE at 5 to 8 kt thru 04/13Z, increasing
between 10 to 14 kt thru 04/23Z, with occasional higher gusts near
the strongest shower activity.

&&

.MARINE...
Issued at 340 AM AST Thu Dec 4 2025

An induced surface trough just east of the islands will continue
to result in showers and thunderstorms across eastern local
waters. These showers will result in localized hazardous marine
conditions. On Friday, the islands will be dominated mainly by an
extending surface high pressure under moderate easterly winds,
resulting in seas up to 5 feet. Global model guidance suggests
energy from a northerly swell arriving in the northern offshore
Atlantic waters, probably resulting in high seas and hazardous
marine conditions.

&&

.BEACH FORECAST...
Issued at 340 AM AST Thu Dec 4 2025

An induced surface trough just east of the islands will continue
to result in showers and thunderstorms across the eastern coastal
areas during the morning hours today, and then across the western
side due to the afternoon showers.There is a low to moderate risk
of rip currents across the northern and northeastern coastal areas
of Puerto Rico, Culebra, St. Thomas, and St. Croix.

&&

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

$$

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