National Weather Service Today's Weather Impact Levels

240
FXCA62 TJSJ 150803
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
403 AM AST Fri May 15 2026

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

.KEY MESSAGES...
Issued at 355 AM AST Fri May 15 2026

* Hot and humid conditions will continue across Puerto Rico and
  the U.S. Virgin Islands through much of next week, with elevated
  heat indices likely in urban and coastal areas each day.

* Passing showers will continue across eastern Puerto Rico and
  the U.S. Virgin Islands during the overnight and morning hours,
  followed by afternoon convection across western Puerto Rico.

* A wetter weather pattern is expected to develop next week as
  moisture levels increase and an upper-level trough approaches
  the region. This may result in more frequent showers and
  isolated thunderstorms, especially across western and
  northwestern Puerto Rico and portions of the San Juan metro
  area.

* The main hazards throughout the period will continue to be
  localized flooding from heavy rainfall and excessive heat
  impacts from warm temperatures and high humidity.

* A moderate risk of rip currents will continue along many north-
  and east- facing beaches of Puerto Rico, Vieques, Culebra, and
  the U.S. Virgin Islands through much of the forecast period.
  Beachgoers should swim near lifeguards and follow beach warning
  flags.

&&

.Short Term(Today through Sunday)...
Issued at 355 AM AST Fri May 15 2026

In general, a surge of moisture brought showery weather,
especially across St Croix, and PR`s windward locations, but
with the best activity over the southern USVI and surrounding
waters. This activity produced periods of moderate to locally
heavy rain, reducing visibility and creating water puddles across
roadways and poorly drained areas. Low temperatures ranged from
the mid-70s to the low-80s at urban and coastal sites, to the low
and upper-60s at mountain sites. The winds were primarily from the
east to east- southeast at 10 to 15 mph, with stronger gusts in
windward locations, while leeward sites experienced 5 to 10 mph,
with fluctuations in the land breeze also observed.

A mid- to upper-level ridge will continue to dominate the region
through Saturday, helping to limit widespread thunderstorm
development. However, breezy east-to-east-southeast winds will
continue to move patches of moisture across Puerto Rico and the
U.S. Virgin Islands, resulting in periods of showery weather with
moderate to locally heavy rainfall at times. Because of this
pattern, a limited risk of flooding will remain across windward
areas of Puerto Rico and the U.S. Virgin Islands, particularly
during the overnight and morning hours. During the afternoons,
local effects, sea breeze convergence, and daytime heating will
support the development of showers across interior and western
Puerto Rico.

This overall weather pattern is expected to persist through
Friday and Saturday, with little to no thunderstorm activity
anticipated. However, by Sunday, the ridge is forecast to weaken
as a mid- to upper-level trough approaches from the west. This
will increase instability and improve the chances of thunderstorm
development across the region.

Model guidance also suggests low- to mid-level vorticity moving
across the area, which could help enhance shower and thunderstorm
development, especially early Sunday morning across the U.S.
Virgin Islands and eastern Puerto Rico. Additional afternoon and
evening thunderstorm activity may then develop across interior and
western Puerto Rico due to strong daytime heating, local terrain
effects, and sea breeze interactions. As a result, the flooding
risk is expected to increase on Sunday, especially across interior
and western Puerto Rico, where urban flooding, road ponding, and
isolated small-stream flooding may occur. Residents and visitors
should continue monitoring forecast updates as the weather pattern
evolves.

Although rain is expected each day, above-normal temperatures
will continue across the region. Model guidance indicates warmer-
than-normal temperatures at low levels of the atmosphere, while
sea surface temperatures surrounding the islands remain near or
above 1C above normal. Combined with available moisture, these
factors will continue to produce elevated heat indices across
Puerto Rico and the U.S. Virgin Islands.

At this time, a Heat Advisory has not been issued because patches
of cloud cover and passing showers may help limit the duration of
the hottest conditions in some areas. Nevertheless, residents and
visitors can still expect heat indices up to 111F each day,
especially between 10 AM and 4 PM across urban and coastal areas.
People are encouraged to stay hydrated, limit prolonged sun
exposure, and take frequent breaks if spending time outdoors.

In addition, traces of Saharan dust particles will begin moving
into the region over the next couple of days. The highest
concentrations are expected to remain south of the islands across
the Caribbean Sea, although slight increases in hazy conditions
are possible by Saturday. By Sunday afternoon, most of the dust is
expected to clear from the area, leaving only trace amounts that
could still act as condensation nuclei and support cloud
development.

&&

.Long Term(Monday through Friday)...
Issued at 355 AM AST Fri May 15 2026

A gradual transition toward a wetter weather pattern is expected
across Puerto Rico and the U.S. Virgin Islands through the upcoming
workweek. Surface high pressure over the western Atlantic will
maintain easterly winds early in the period, gradually veering east-
southeasterly by midweek while weakening from fresh to strong speeds
to more moderate to locally fresh conditions late in the week.
Although moisture levels early in the period should remain near to
slightly below seasonal normals, patches of deeper tropical moisture
moving across the region will continue to promote passing showers
across eastern Puerto Rico and the U.S. Virgin Islands during the
overnight and morning hours, followed by afternoon convection across
western Puerto Rico.

At upper levels, model guidance continues to indicate an amplifying
trough north of the northeastern Caribbean, with marginally cooler
mid-level temperatures gradually spreading closer to the local
islands through mid to late week. At the same time, mid-level
conditions are forecast to become less dry, allowing for a somewhat
more favorable environment for shower development. As precipitable
water values gradually increase to near and occasionally above
normal levels, shower activity is expected to become more frequent
by Wednesday and Thursday, particularly across western and
northwestern Puerto Rico and portions of the San Juan metropolitan
area. Although thunderstorms were not explicitly introduced into the
forecast at this time, excessive diurnal heating combined with the
more favorable thermodynamic environment may support one or two very
isolated thunderstorms during the afternoon hours. Hazard risks
remain at medium confidence, primarily associated with localized
excessive rainfall and excessive heat, as warm to hot daytime
temperatures and elevated humidity levels will likely continue
through much of the period.

&&

.AVIATION...
(06Z TAFS)
Issued at 355 AM AST Fri May 15 2026

Expect VFR conditions through much of the forecast period.
However, the advection of SHRA/-SHRA will continue to arrive
affecting windward terminals from time to time. Additional
SHRA/+SHRA will form across the interior and NW-PR btwn 15/16-23z,
probably affecting JBQ and JSJ, which could cause brief MVFR or
IFR conds. Winds will prevail from the E-ESE around 10 kt, then
aft 15/13z winds will range btwn 10-20kt with higher gusts and
sea breeze variations.

&&

.MARINE...
Issued at 355 AM AST Fri May 15 2026

A broad surface high-pressure over the central Atlantic will
continue to promote moderate to locally fresh east to east-
southeasterly winds across the regional waters. These breezy
conditions will maintain somewhat choppy seas, particularly across
the offshore and exposed Atlantic and Caribbean waters. Seas are
forecast to remain between 4 and 5 feet, occasionally up to 6 feet,
through at least the upcoming weekend.

&&

.BEACH FORECAST...
Issued at 355 AM AST Fri May 15 2026

Moderate rip current risk will prevail from Friday onwards along the
northern and eastern beaches of PR, as well as Culebra, Vieques, and
the US Virgin Islands. The long period northerly swell should
gradually subside tonight allowing conditions to gradually improve.
Nevertheless, beachgoers should continue exercising caution
especially near piers and unprotected beaches.

&&

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

$$

KEY MESSAGES/SHORT TERM/AVIATION...CAM
LONG TERM....ICP
MARINE/BEACH FORECAST...MMC

NWS SJU Office Area Forecast Discussion