National Weather Service Today's Weather Impact Levels

934
FXCA62 TJSJ 131819
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
219 PM AST Fri Mar 13 2026

...New SHORT TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER...

.KEY MESSAGES...
Issued at 218 PM AST Fri Mar 13 2026

* Flooding in urban areas, on roads, and along small streams is
  possible this afternoon across the interior and western Puerto
  Rico.

* Mostly sunny conditions are expected on Saturday, although a few
  localized showers may still develop during the afternoon hours
  across western Puerto Rico.

* Increasing winds are expected on Sunday into next week, leading
  to hazardous marine and beach conditions.

* Across the U.S. Virgin Islands, occasional passing trade-wind
  showers will continue, with a drying trend expected by late
  tonight into Saturday.

&&

.Short Term(This evening through Sunday)...
Issued at 218 PM AST Fri Mar 13 2026

The day began with shower activity across the local waters, with
some showers reaching eastern areas of Puerto Rico due to a patch
of moisture. Based on radar estimates, rainfall accumulations were
minimal across most areas, with the highest amounts observed in
Naguabo, where totals ranged between 0.50 and 0.75 inches in some
locations. Around noon, a streamer developed and produced rainfall
amounts between 0.20 and 0.50 inches across parts of the metro
area, with localized maximums near 0.60 inches. Temperatures along
coastal areas ranged from the low to mid 80s, while interior and
mountainous locations remained in the 70s. Maximum wind gusts
reached the low to mid 20s mph across coastal areas of Puerto Rico
and the U.S. Virgin Islands.

Moving into the afternoon hours, cloudiness has started to
increase across the islands. The morning sounding from San Juan
(TJSJ) showed precipitable water (PWAT) values of 1.40 inches,
while satellite-derived data indicates an area of moisture over
the region near 1.5 inches or slightly higher. These values are
near seasonal levels to slightly above normal based on climatology
for this time of year. This available moisture, combined with
daytime heating and local effects, will promote the continuation
of afternoon convection across the interior and western portions
of Puerto Rico. Periods of moderate rainfall are possible,
increasing the potential for ponding of water on roads and in
poorly drained or urban areas. The flood risk remains limited,
currently at level 2 out of 5 on the graphical hazardous outlook
scale.

Looking ahead to tomorrow, it should be the driest and most
stable day of the short-term period. A noticeable drying trend
will begin late tonight and continue into Saturday. Global
guidance indicates a sharp drop in moisture, with precipitable
water values falling below 1.25 inches. In addition, mid-level
relative humidity (700500 mb) is expected to drop below 20
percent, along with warmer temperatures aloft as a mid-level ridge
establishes itself over the region. As a result, expect mostly
sunny conditions on Saturday, with only localized and shallow
afternoon showers over western Puerto Rico. No flooding risk is
anticipated tomorrow.

On Sunday, precipitable water values are expected to increase
again to around 1.5 inches (near to slightly above normal levels)
as another patch of moisture approaches the region. However,
limited instability is anticipated. As a result, an increase in
occasional trade-wind showers is expected to affect eastern Puerto
Rico and the U.S. Virgin Islands during the overnight and morning
hours, followed by isolated afternoon activity across western
Puerto Rico. The main weather hazard will be increasing winds.
Breezy to windy conditions are expected, so loose objects should
be secured as they may be blown around or damaged.

&&

.LONG TERM(Monday through Friday)...
Issued at 218 AM AST Fri Mar 13 2026

A broad surface high-pressure system over the western Atlantic will
strengthen by early next week, tightening the pressure gradient
across the northeastern Caribbean and promoting a steady increase in
easterly to east-southeasterly low-level flow beginning Monday and
persisting through much of the workweek. Model guidance indicates
925 mb winds increasing well above climatological values, peaking
near or above two standard deviations above normal on Monday. As a
result, breezy to locally windy conditions are expected,
particularly across coastal areas of Puerto Rico, Culebra, Vieques,
and the U.S. Virgin Islands, where a limited to locally elevated
wind threat may develop and unsecured outdoor items could be blown
around or damaged. Although the pressure gradient is expected to
relax slightly after Monday, winds will likely remain above normal
through the remainder of the forecast period.

Mid-level conditions will remain generally stable through the
forecast period. Model guidance continues to show 700500 mb lapse
rates below normal to near the lower end of climatological values,
while 500 mb temperatures remain near climatological normals.
Although a polar trough and its associated frontal boundary are
forecast to move off the eastern seaboard early next week, and an
upper-level trough may develop northeast of the forecast area toward
the end of the period, the local area will remain largely removed
from the strongest dynamical forcing. As a result, most of the
region will continue to experience marginally stable conditions,
limiting deep convective development and favoring mainly shallow
trade wind showers. Relative humidity values in the mid-levels will
also remain modest, further supporting a generally stable pattern.

Moisture levels will remain near climatological normals through most
of the period, with precipitable water generally fluctuating between
around 1.2 and 1.5 inches. Patches of shallow moisture embedded
within the trade wind flow will periodically move across the region,
resulting in brief passing showers across windward sectors,
particularly during the nighttime and morning hours across eastern
Puerto Rico and the U.S. Virgin Islands. During the afternoons,
diurnal heating combined with local effects may support the
development of isolated to scattered showers across interior and
western portions of Puerto Rico. However, the faster steering wind
flow will limit the residence time of showers and keep rainfall
accumulations generally low. Despite this, ponding of water on roads
and in poorly drained areas, along with brief reductions in
visibility, can still occur in areas experiencing the heaviest
showers.

&&

.AVIATION...
(18Z TAFS)
Issued at 218 PM AST Fri Mar 13 2026

Mainly VFR conds across all TAF sites most of the period, except
for some intermittent MVFR over the next hours due to VCSH/SHRA
moving near TJBQ, VCSH in TJSJ and VCSH/-RA in northern USVI.
E-NE winds btwn 10-15 kt with gusts up to 20 kt and sea breeze
variations until 13/23Z, then lighter winds overnight.

&&

.MARINE...
Issued at 218 PM AST Fri Mar 13 2026

A surface high pressure extending over the eastern and central
Atlantic will maintain moderate easterly winds across the local
waters. Under this pattern, seas will remain up to 5 feet, and
between 3 to 4 feet along the nearshore waters. Starting tomorrow,
an increase in the pressure gradient will result in a moderate to
locally fresh easterly wind flow, which will strengthen by
Sunday. This surface change, combined with a diminishing
northeasterly swell, will enhance wind-driven seas, resulting in
choppy conditions across all exposed local waters from late Sunday
into the upcoming workweek. On Monday through midweek, winds will
be the main driver of hazardous marine conditions, with seas up
to 7 feet and winds up to 20 knots. Small boat operators should
stay tuned for further updates in the small craft advisories and
statements.

&&

.BEACH FORECAST...
Issued at 218 PM AST Fri Mar 13 2026

There is a moderate risk of rip currents for the rest
of the day across most of the northern exposed beaches of the
islands, with a low risk of rip currents along the south coast of
Puerto Rico. Similar conditions will persist on Saturday and Sunday
across all coastal areas. Residents and visitors are urged to
exercise caution in exposed coastal areas not designated for
beachgoers, as well as in areas near jetties and rocks. From late
Sunday into the upcoming workweek, a surface high pressure system
will increase surface winds, making them more moderate to strong,
enhancing wind-driven seas and hazardous coastal conditions.
Therefore, the risk of rip currents will increase to high by Monday
along the entire north coast of Puerto Rico, including the
northeastern and northwestern areas, Culebra, and St. Croix.
Beachgoers should continue monitoring the forecast for any updates.
For additional information, please visit: weather.gov/beach/sju.

&&

.FIRE WEATHER...
Issued at 218 PM AST Fri Mar 13 2026

The KBDI in Cabo Rojo it is still above the critical fire weather
threshold. Before noon, RH values decreased to low the low 50s in
Cabo Rojo and some period of gusts up to 20 mph were registered.
For the rest of the afternoon, RH values should increase as
afternoon convection is expected across western PR, keeping the
risk low. At this time an RFD will not be issued, but we encourage
partners to continue monitoring conditions in the coming days,
particularly tomorrow as a drier airmass is expected to arrive.

&&


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

$$

SHORT TERM/AVIATION/FIRE...YZR
LONG TERM...CVB
MARINE/BEACH...LIS

NWS SJU Office Area Forecast Discussion