302
FXCA62 TJSJ 121821
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
221 PM AST Mon Jan 12 2026

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

.KEY MESSAGES...
Issued at 202 PM AST Mon Jan 12 2026

 * A seasonal pattern is forecast for tonight into tomorrow with
   patches of moisture and cloudiness moving across the area. Therefore,
   residents of the eastern side of the islands can expect some
   brief passing showers.

 * For the upcoming weekend, the approach of a frontal boundary will
   result in an increase in the frequency of the showers along
   the islands.

 * There is a moderate risk of rip currents across all northern-
   exposed beaches, increasing to high by the upcoming weekend.

&&

.Short Term(This evening through Wednesday)...
Issued at 202 PM AST Mon Jan 12 2026

A variable weather pattern persisted across the local islands
during the day as shallow patches of cloudiness and moisture moved
into the region. The showers peaked mostly over the Atlantic
offshore waters; however, some passing showers affected eastern
sections of Puerto Rico and the U.S. Virgin Islands. Although
showers were observed on the eastern side, the western side
enjoyed a mostly sunny morning with minimal cloudiness. Daytime
temperatures were mostly seasonal, ranging from the lower 80s to
mid-80s across coastal areas and up to the upper 80s in some urban
coastal areas. at 12 PM, Doppler Radar and satellite imagery
showed the increase of Claudine`s and showers along the interior
sections. Rainfall accumulations were minimals, however, some
showers were moderate to locally strong.

Tonight, surface conditions will continue to be influenced by a
broad surface high pressure extending from the Central Atlantic
into the Caribbean, and by an induced surface trough about 300
miles north of the islands. The combination of this surface
pattern will continue to result in an east-northeast wind flow
across the islands. Under these conditions, shallow moisture
trapped in the 0-3 km layer will filter into the islands during
the rest of the night. Rapidly, surface conditions will change as
the surface trough moves out and a more easterly wind flow
returns. Under this pattern, enough trapped moisture, with
Precipitable Water values of 1.3 to 1.5 inches, will filter in,
enhancing shower development. Although surface conditions will
remain favorable for some showers, the limiting factor will be the
mid-level ridge stall just over the islands. Therefore, the
forecast mostly calls for variable morning and evening with the
typical pattern of showers briefly impacting the coastal areas and
then limited showers in the afternoon. On Wednesday, veering winds
are forecast as the surface pattern changes due to a frontal
boundary exiting the eastern coast of the United States. This
surface change will slightly shift seasonal temperatures and bring
tropical moisture over the islands, increasing cloudiness, mostly
in the afternoon hours.

&&

.Long Term(Thursday through next Sunday)...from previous
discussion Issued at 507 AM AST Mon Jan 12 2026

During Thursday, a deep-layer mid to upper-level trough will be
well east of the Lesser Antilles, while a mid level ridge persists
over the northeastern Caribbean. Trade wind showers will continue
to affect the region on Thursday, with limited afternoon convection
expected across western and northwestern Puerto Rico. On Friday,
model guidance suggests a frontal boundary will remain north of
the region, while a pre-frontal trough may enhance moisture
convergence and atmospheric instability, supporting a wetter
pattern on Friday. At this time, Friday appears to present the
highest rainfall potential, with a limited flood risk mainly
across western Puerto Rico during the afternoon hours. Isolated
thunderstorm activity cannot be ruled out as mid-level temperatures
cool, with 500 mb temperatures decreasing from near -4 degrees C
on Wednesday to around -7 degrees C by latter part of the week.
Precipitable water values are forecast to range between 1.5 and
1.8 inches from Thursday through Saturday, near to above
climatological normal for this time of year, with peak moisture
expected on Friday.

Low-level winds will generally remain from the east to southeast
at 10 to 15 mph with gusts up to 20 mph through Friday, then shift
to the east-northeast from Saturday through Monday while increasing
to 15 to 25 mph with gusts up to 30 mph. Breezy to locally windy
conditions are anticipated, particularly on Saturday, which may
result in loose outdoor items being blown around, especially
across exposed and coastal areas.

From Sunday through Monday, precipitable water values are expected
to decrease to between 1.1 and 1.5 inches, with patches of near-
average moisture moving across the region, promoting variable but
seasonable weather conditions with passing trade wind showers and
limited convective development.

Ensemble guidance continues to indicate slightly above-normal
temperatures across Puerto Rico and the U.S. Virgin Islands
throughout the long-term period.

&&

.AVIATION...
(18Z TAFS)
Issued at 202 PM AST Mon Jan 12 2026

VFR conditions will persist across all TAF sites during the
period. Winds will continue from the E at 12 knots or less, with
sea-breeze variations, diminishing around 12/23Z. VCSH will
persist across TJSJ, TISX & TIST, then SHRA to TSRA, affecting
the interior and possibly resulting in a VIS & Cigs reduction near
TJBQ and TJPS.

&&

.MARINE...
Issued at 202 PM AST Mon Jan 12 2026

A surface high pressure moving eastward across the central Atlantic,
combined with a weak surface trough northeast of the region, will
maintain gentle to moderate east to northeast winds through mid-
week, then shifting from the east to southeast by Thursday and
Friday. This pattern will support passing trade-wind showers, mainly
across the Atlantic waters, with occasional showers also moving
through the Caribbean passages. By the end of the week into the
weekend, strengthening northeasterly winds and the arrival of a
long-period northerly swell will likely result in choppy and
potentially hazardous marine conditions. Mariners are advised to
continue monitoring the forecast.

&&

.BEACH FORECAST...
Issued at 202 PM AST Mon Jan 12 2026

There is a moderate risk of rip currents for tonight into the
upcoming workweek days for the northern exposed beaches including,
Culebra, Vieques and the U.S. Virgin Islands. A moderate risk
indicates that life- threatening rip currents are possible within
the surf zone, and beachgoers should exercise caution at all
times. By next weekend, conditions will likely deteriorate due to
increasing winds and the arrival of a long-period northerly
swell, with the potential for a high risk of rip currents to
return across most local beaches of Puerto Rico and USVI.

&&

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

$$

SHORT TERM & AVIATION...LIS
LONG TERM & MARINE....YZR

NWS SJU Office Area Forecast Discussion