433
FXCA62 TJSJ 131902
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
302 PM AST Wed May 13 2026

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

.KEY MESSAGES...
Issued at 259 PM AST Wed May 13 2026

 * Heat indices between 100 and 110 degrees are expected across
   urban and coastal areas each day, especially during the late
   morning and afternoon hours. Residents and visitors should stay
   hydrated, limit prolonged outdoor activities, and take frequent
   breaks in shaded or air-conditioned areas.

 * A moderate to high risk of rip currents will persist through
   the period across several north-facing beaches of Puerto Rico.
   Life-threatening rip currents are possible, particularly in
   areas exposed to the incoming northeasterly swell.

 * Breezy to locally windy conditions will continue through at
   least the weekend due to strong high pressure over the central
   Atlantic, promoting choppy marine and coastal conditions.

 * A wetter and more unstable weather pattern may develop early
   next week as an upper-level trough approaches the region,
   increasing the potential for more frequent showers and isolated
   thunderstorms.

&&

.Short Term(This evening through Friday)...
Issued at 259 PM AST Wed May 13 2026

A moisture surge triggered fast-moving showers across eastern and
northeastern Puerto Rico this morning, including the San Juan
metropolitan area, with rainfall accumulations generally remaining
below 0.5 inches. Southeast winds prevailed at 15 to 20 mph,
accompanied by higher gusts and localized sea breeze variations
across Puerto Rico and the U.S. Virgin Islands.

For the remainder of the day, showers will continue to develop along
the central mountain range and drift into northwestern Puerto Rico.
Meanwhile, the San Juan metropolitan area, eastern Puerto Rico, and
Vieques will experience passing showers driven by daytime heating
and orographic lifting. These conditions are expected to persist
through the end of the workweek as a tight pressure gradient
maintains a steady southeasterly flow at 15 to 20 mph, before
shifting more east-southeasterly by the weekend.

Throughout the week, a mid-to-upper-level ridge will promote dry air
and subsidence across the region, limiting widespread thunderstorms.
However, available moisture combined with sea breeze convergence
will drive daily afternoon convection over the interior and western
areas, maintaining a limited risk of localized flooding and ponding.
Precipitable water (PWAT) values will remain near seasonal normals,
ranging from 1.45 to 1.70 inches, resulting in frequent, fast-moving
showers across the islands.

Model guidance indicates a warming trend through Sunday, potentially
leading to elevated heat indices across urban and coastal areas,
particularly between 9 AM and 4 PM AST. This heat could pose a risk
to sensitive individuals and impact local infrastructure.
Additionally, trace to minor concentrations of Saharan dust are
expected to arrive, which may slightly impact visibility and air
quality. Residents and visitors are urged to stay hydrated, seek
shade, and monitor local weather conditions to ensure personal
safety during peak temperature hours.

&&

.Long Term(Saturday through next Tuesday)...
Issued at 259 PM AST Wed May 13 2026

A drier to seasonal weather pattern is anticipated over the long-
term forecast.  A surface high pressure building over the Western
Atlantic should maintain E-SE winds throughout the period, promoting
breezy to locally windy conditions across the islands. The mid-level
ridge should keep dominating the weather pattern on Saturday and
Sunday, bringing subsidence and promoting stability aloft.
Nevertheless, as mentioned in the previous discussion, an upper-
level trough will likely extend into the tropics and is likely to
become a cut-off low over the Bahamas by Tuesday. From the latest
model guidance, 250 mb heights star to drop Sunday onwards, with 500
mb temperatures cooling (around - 7 degrees Celsius). Additionally,
PWAT values will likely increase up to 1.75 inches (typical for this
time of the year), with a low chance of reaching 2.0 inches. The
most likely scenario is to expect shower activity each day, with
afternoon shallow convection across western/northwestern Puerto Rico
on Saturday and Sunday. Although no flooding impacts are expected,
expect puddles over the road, slippery pavement, and reduced
visibility. On Monday onwards, the frequency of showers will
increase and may produce minor flooding over windward sections, with
afternoon showers and isolated thunderstorms over western and
northwestern Puerto Rico, including the San Juan Metropolitan Area.
Hence, the flooding threat will remain limited over the
aforementioned areas for the rest of the forecast period.

As southeasterly winds will prevail, warmer-than-normal temperatures
and the available moisture will result in heat indexes exceeding 100
degrees Fahrenheit, with a limited to elevated heat risk. Residents
and visitors should stay tuned to further updates, as Heat Advisory
issuances cannot be ruled out.

Minor concentrations of SAL will linger through the weekend,
according to the latest NASA DUex. Although the highest
concentrations should remain well south of the region, individuals
sensitive to these particles should exercise caution.
&&

.AVIATION...
(18Z TAFS)
Issued at 259 PM AST Wed May 13 2026

Mainly VFR conds will prevail across all TAF sites through the
forecast period. However, passing VCSH/SHRA embedded in the trade
winds will result in brief periods of MVFR conds due to reduced VIS
and lower CIGs FL020 and FL030. -SHRA with isolated VCTS may develop
in the vicinity of TJSJ/TJBQ thru 13/22Z. Southeast winds will
prevail btw 10-15 knots, with higher gusts and sea breeze
variations. Winds are expected to diminish after 14/03Z.

&&

.MARINE...
Issued at 259 PM AST Wed May 13 2026

A surface high-pressure system over the Central Atlantic will
continue to produce a moderate to locally fresh east-to-
southeasterly wind flow across the region. These breezy conditions
will turn slightly choppy, especially across the offshore, exposed
waters of the Atlantic and Caribbean. Later today into tomorrow,
some energy from the northeasterly weak long-period swell with an
associated wave height of 3 ft will arrive in the local regions.
This weak swell is not expected to be significant for the local
and exposed waters. Therefore, seas will remain between 4 and 5
feet, occasionally up to 6 feet, at least until the upcoming
weekend.

&&

.BEACH FORECAST...
Issued at 259 PM AST Wed May 13 2026

A broad surface high pressure system over the Central Atlantic,
resulting in breezy to locally windy conditions, will continue
across the region through at least midweek. These conditions will
maintain a moderate risk of rip currents along most local beaches,
particularly along north- and east-facing coastlines. A long-
period northeasterly swell will arrive late tonight into tomorrow.
Combined with locally generated wind waves, this swell will
promote the development of life-threatening rip currents on
Thursday. As a result, beach conditions may become dangerous for
swimmers due to moderate to high rip current risk. Beach visitors
are urged to swim only at beaches with lifeguards on duty, remain
aware of surf conditions, and avoid venturing too far from shore.

&&

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

$$

SHORT TERM & AVIATION...GRS
LONG TERM....MNG
MARINE, BEACH FORECAST & KEY MESSAGES...LIS

NWS SJU Office Area Forecast Discussion