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475
FXCA62 TJSJ 130902
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Tue Jan 13 2026

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

.KEY MESSAGES...
Issued at 502 AM AST Tue Jan 13 2026

* Passing trade-wind showers continue: Brief showers will affect
  windward and coastal areas of Puerto Rico and the U.S. Virgin
  Islands, mainly during the morning and evening hours, with limited
  afternoon showers over western Puerto Rico. Periods of sunshine
  will continue between showers.

* Localized flooding remains possible: While widespread flooding is
  not expected, increased moisture later in the week may cause
  ponding on roads and isolated urban or small stream flooding,
  especially across eastern Puerto Rico and the U.S. Virgin Islands.

* Moderate rip current risk: life-threatening rip currents are
  expected along north and east-facing beaches of Puerto Rico and
  the U.S. Virgin Islands through the workweek. The risk may
  increase this weekend, becoming high due to stronger winds and a
  northwesterly swell.

&&

.Short Term(Today through Thursday)...
Issued at 502 AM AST Tue Jan 13 2026

Mainland Puerto Rico experienced calm weather overnight, while a
trade wind disturbance brought passing showers to the U.S. Virgin
Islands, with some reaching eastern Puerto Rico. Winds were from the
east at 5 to 10 mph. Skies were mostly clear in mainland Puerto
Rico, but partly to mostly cloudy in the U.S. Virgin Islands.
Overnight temperatures ranged from the low 70s to the upper 60s
along the coast and from the upper 50s to the low 60s in the
interior valleys and mountains.

Weather conditions across Puerto Rico and the U.S. Virgin Islands
will remain influenced by a broad surface high pressure system
extending from the central Atlantic into the Caribbean, along with a
weak induced surface trough north of the region. This setup will
maintain an east-northeasterly low-level wind flow, allowing shallow
moisture confined mainly below 3 km to advect into the area and
produce passing showers, particularly during the morning and evening
hours.

As the surface trough lifts out, winds will gradually veer to the
east. This will allow modest moisture, with precipitable water
values ranging between 1.3 and 1.5 inches, to continue filtering
into the islands, supporting additional shower activity. However, a
persistent mid-level ridge over the region will limit vertical
development, resulting in a typical trade-wind pattern characterized
by brief showers affecting coastal and windward areas during the
morning and evening hours, followed by limited afternoon convection
mainly across western Puerto Rico.

On Wednesday, low-level winds are expected to veer further as the
surface pattern responds to a frontal boundary exiting the eastern
United States. This change will favor a slight increase in tropical
moisture and cloudiness, with shower activity becoming more
noticeable in the afternoon. Temperatures are expected to remain
near seasonal values.

By Thursday, a deep-layer mid- to upper-level trough will move
further eastward of the Lesser Antilles, while a mid-level ridge
continues to dominate the northeastern Caribbean. Under this
pattern, trade-wind showers will persist across the region as a
surge of moisture increases Precipitable Water to 1.5 to 1.75
inches. Enhanced by low-level convergence and local orographic
effects, this could lead to ponding of water on roads and in
poorly drained areas, particularly across eastern Puerto Rico and
the U.S. Virgin Islands, occasionally throughout the day.

Overall, a limited risk of flooding is expected, though isolated
instances of urban and small stream flooding cannot be ruled out on
any given day. Residents and visitors are encouraged to stay
informed by following the latest forecasts and updates in case
conditions change.

&&

.Long Term(Friday through Tuesday)...
Issued at 502 AM AST Tue Jan 13 2026

On Friday, model guidance indicates that a frontal boundary will
remain north of the region, while a pre-frontal trough may enhance
low-level moisture convergence and atmospheric instability,
supporting a wetter pattern. Friday currently appears to have the
greatest rainfall potential, with a limited flood risk mainly
across western Puerto Rico during the afternoon hours. Isolated
thunderstorms cannot be ruled out. Precipitable water values are
forecast to range between 1.4 and 1.9 inches from Friday through
Saturday, near to above climatological normals for this time of
year.

Low-level winds will generally remain from the east to southeast
at 10 to 15 mph on Friday, then shift to the east to northeast by
Friday night into Saturday while increasing to 15 to 20 mph with
gusts up to 25 to 30 mph. Breezy to locally windy conditions are
expected Saturday and early Sunday, which may lead to loose outdoor
items being blown around, especially across exposed and coastal
areas.

From Sunday through Tuesday, precipitable water values are
expected to decrease to between 1.2 and 1.5 inches, with patches
of near-average moisture moving across the region. This will
support more variable but seasonable conditions, with passing
trade wind showers and limited convective development each
afternoon. No flooding concerns at this time.

A subtropical jet streak near 250 mb will establish a favorable
dynamic pattern from Tuesday night into Wednesday, supporting
upper-level divergence and an induced surface trough. As a result,
an increase in the frequency of showers is expected across the
forecast area under a northeasterly low-level wind flow. Continue
to monitor the forecast updates.

Temperature-wise, ensemble guidance continues to indicate near
seasonal to above-normal temperatures across Puerto Rico and the
U.S. Virgin Islands throughout the long-term period.

&&

.AVIATION...
(06Z TAFS)
Issued at 502 AM AST Tue Jan 13 2026

Expect VFR conds today. SHRA/SHRA may occasionally affect TJSJ,
TIST, and TISX, with brief MVFR conds possible near TJPS in the
afternoon (16-22z). Similar conditions with less activity are likely
for Wednesday. Winds will remain light and variable overnight,
shifting to ENEE at 10 to 15 knots after 13z, with higher gusts and
sea breeze variations.

&&

.MARINE...
Issued at 502 AM AST Tue Jan 13 2026

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

&&

.BEACH FORECAST...
Issued at 502 AM AST Tue Jan 13 2026

A moderate risk of rip currents continues today along the northern
and eastern beaches of Puerto Rico, as well as Culebra and St.
Croix, with breaking waves around 4 feet. Similar conditions are
expected to persist through most of the workweek. A moderate risk
means that life-threatening rip currents are possible within the
surf zone, and beachgoers should exercise caution at all times.

Conditions are likely to deteriorate over the weekend as winds
increase and a long-period northerly swell arrives. This may lead
to a return of a high risk of rip currents across Atlantic exposed
beaches of Puerto Rico and the U.S. Virgin Islands. For more location
specific information, continue to monitor weather.gov/beach/sju.

&&

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

$$

CAM/YZR

NWS SJU Office Area Forecast Discussion