972
FXCA62 TJSJ 310630
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
230 AM AST Tue Mar 31 2026

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

.KEY MESSAGES...
Issued at 230 AM AST Tue Mar 31 2026

* Hazardous beach conditions will continue across Puerto Rico and
  the U.S. Virgin Islands. Life-threatening rip currents and
  dangerous surf are expected along north- and east-facing
  beaches.

* Passing showers overnight and in the morning, with afternoon
  showers and isolated thunderstorms over western to southwestern
  Puerto Rico. Localized flooding is possible; lower risk across
  the U.S. Virgin Islands.

* Isolated thunderstorms may develop, mainly in the afternoon,
  producing lightning, brief heavy rain, and gusty winds.

* Breezy to locally windy conditions will persist, especially in
  coastal and exposed areas, supporting fast-moving showers.

* These conditions may affect outdoor and holiday activities. Plan
  accordingly and stay weather-aware.

&&

.Short Term(Today through Thursday)...
Issued at 230 AM AST Tue Mar 31 2026

Overnight, breezy conditions persisted across the region, with
winds easing slightly from daytime peaks but still ranging around
10 to 15 mph, with higher gusts across the most exposed northern
and eastern areas of Puerto Rico and across the U.S. Virgin
Islands. These winds supported the continued movement of passing
showers inland and, at times, across the entire islands. Some of
these showers produced moderate rainfall, with the highest amounts
observed across northeastern Puerto Rico, including the Sierra de
Luquillo. Additional lighter accumulations were noted across the
interior and southern sections. Temperatures were slightly cooler
than previous nights.

A strong high pressure system over the western Atlantic will
continue to drive breezy conditions and maintain the current trade
wind pattern across Puerto Rico and the U.S. Virgin Islands. Winds
will gradually shift from the northeast to the east by Thursday,
and eventually east-southeast by late Thursday night. Moisture
will fluctuate early, with a brief drier period today, then
increase again from midweek onward. By Wednesday into Thursday, a
more humid and less stable pattern is expected as an upper-level
trough moves near the region. This will support periods of
passing showers, along with afternoon development over interior
and western Puerto Rico.

During this ongoing holiday week, periods of showers and breezy
conditions may lead to interruptions in outdoor activities across
the islands. Showers will be more frequent across northeastern
Puerto Rico during the overnight and morning hours, and across the
interior and southwestern areas during the afternoon. While
showers will move quickly, repeated activity may result in
localized flooding in urban areas, roadways, and poor drainage
locations, especially by midweek as moisture increases. A few
thunderstorms are possible today, mainly across interior and
western Puerto Rico during the afternoon. Breezy to locally windy
conditions will persist, especially across exposed coastal areas
and higher elevations, which may affect outdoor comfort. Residents
and visitors should remain aware of changing weather conditions
while planning outdoor and holiday-related activities.

&&

.Long Term(Friday through Tuesday)...
Issued at 230 AM AST Tue Mar 31 2026

From Friday into Saturday, an evolving pattern under the influence
of an induced surface trough and a shortwave trough will enhance a
more unstable weather pattern across the islands. At the surface,
the induced surface trough, in combination with a surface high
pressure over the Central Atlantic, will promote a northeasterly
wind flow across the area, rapidly shifting to the east-southeast
early Friday as the surface perturbation moves west of the region.
At the upper levels, a shortwave trough will move across the region,
favoring enhanced instability and thunderstorm development. This
pattern will support a high chance of showers across the area;
however, the forecast will be largely dependent on surface
conditions at the time. According to global model guidance and
relative humidity values, a deep upper-level cloud layer may inhibit
the diurnal heating trigger. If sufficient heating does not develop,
widespread shower activity is not anticipated; however, some well-
developed showers are still expected across the northwestern section
and the San Juan Metropolitan area. On Sunday, global model guidance
from the GFS and ECMWF continues to suggest precipitable water
values up to 1.7 inches, which remains near the 75th percentile for
this time of year, consistent with relative humidity values between
850 and 500 mb.

By Monday onward, the main surface weather pattern will be driven by
a broad surface high pressure over the Central Atlantic, resulting
in a tightening of the pressure gradient and increasing winds. Under
this pattern, global model guidance suggests an increase in low-
level moisture across the Caribbean moving into the local islands.
The GFS indicates precipitable water values up to 1.9 inches, which
remains around the 75th percentile through the rest of the period.
Under this setup, reduced upper-level dynamics will limit upper-
level cloudiness, allowing the diurnal heating process to become
more effective. Under this scenario, afternoon convection is likely
to become more widespread and better organized, particularly across
western and interior Puerto Rico, where local effects will enhance
shower and thunderstorm development. This increase in convective
activity, combined with warm and moist conditions, will elevate the
risk of urban and small stream flooding, especially in areas that
experience repeated rainfall. In addition, temperatures are expected
to trend above normal, with coastal highs reaching the low 90s,
further supporting instability and convective potential each
afternoon.

&&

.AVIATION...
(06Z TAFS)
Issued at 230 AM AST Tue Mar 31 2026

SHRA will affect most terminals exposed to the north and across
the islands with MVFR conds (cigs 23 kft, vsby 35 SM) and brief
IFR (cigs 

NWS SJU Office Area Forecast Discussion