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809
FXCA62 TJSJ 121736
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
136 PM AST Tue May 12 2026

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

.KEY MESSAGES...
Issued at 136 PM AST Tue May 12 2026

 * A limited heat risk will persist through midweek, increasing to
   elevated levels from Thursday through Saturday, particularly
   across urban and coastal areas of Puerto Rico where heat
   indices could range between 105 and 110 degrees.

 * Breezy to locally windy conditions will continue through at
   least the weekend as surface high pressure across the central
   Atlantic tightens the local pressure gradient across the
   northeastern Caribbean.

 * Moderate to fresh easterly winds combined with a weak northeasterly
   swell will maintain choppy marine conditions and a moderate
   risk of rip currents through the period. Small craft should
   exercise caution, while life-threatening rip currents will
   remain possible along most north- and east-facing beaches of
   Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands.

 * Stable weather conditions are expected across the U.S. Virgin
   Islands through the period, with mainly fair weather prevailing
   with some brief passing showers embedded within the trade
   winds.

&&

.Short Term(This evening through Thursday)...
Issued at 136 PM AST Tue May 12 2026

A stable weather conditions are expected across the U.S. Virgin
Islands through the period, with mainly fair weather prevailing
aside from brief passing showers embedded within the trade winds.
Rico. Rainfall accumulations from the morning into the afternoon
generally remained below one inch. Surface winds persisted from
the east-southeast at up to 15 mph, with higher gusts near coastal
areas and in stronger showers. As of 1 PM, daytime temperatures
ranged from the mid to upper 80s across coastal areas, mainly due
to persistent cloud cover throughout the day, while slightly fresh
conditions prevailed across the interior and mountainous
sections.

For tonight into Tuesday, a surface high pressure system and an
induced surface trough associated with a distant mid-level
perturbation will continue to promote east-southeast to southeast
low-level flow across the local islands. This pattern will
maintain a limited heat threat, particularly across northern and
western Puerto Rico, where heat indices will likely remain
elevated during the afternoon hours. Under this pattern, patches
of shallow moisture with cloudiness embedded within the trade
winds, and precipitable water values near normal levels, will
continue moving across the area overnight and during the early
morning hours. On the other hand, a broad mid-level ridge between
700 and 500 mb will gradually strengthen and expand across the
northeastern Caribbean, favoring increased subsidence and a more
stable air mass. Meanwhile, northwesterly flow aloft near 250 mb
at around 15 to 20 kt will persist through the period. Limited
vertical development is expected under the strengthening ridge
aloft; however, local effects and afternoon heating may still
support isolated to scattered showers across portions of the
western interior each afternoon.

By Wednesday into Thursday, surface high pressure across the
central Atlantic and a developing low pressure system over the
northwestern Atlantic will tighten the local pressure gradient,
resulting in breezy southeast winds across the region. The
persistent southeast flow will continue transporting warm
Caribbean air across the islands, supporting above-normal
temperatures and increasing heat concerns at lower elevations and
urban areas, where heat indices could range between 105 and 110
degrees during the afternoon hours. Mid-level ridging will remain
the dominant feature, maintaining relatively stable conditions and
suppressing widespread convective activity. In addition, a plume
of Saharan dust is expected to gradually spread across the
northeastern Caribbean from Wednesday onward, promoting hazy
skies, reduced visibility at times, and drier air conditions.
While the overall pattern will favor mainly fair weather, passing
trade wind showers will remain possible across windward sectors
during the nighttime and morning hours, followed by isolated
afternoon convection mainly across the western interior of Puerto
Rico each day.

&&

.Long Term(Friday through next Monday)...
Issued at 136 PM AST Tue May 12 2026

Weather conditions over the upcoming weekend will remain mostly
stable, becoming slightly unstable on Monday. A broad surface high
pressure should linger over the Central Atlantic, promoting mainly
southeasterly winds that will likely result in breezy to locally
windy conditions across the islands. The high will drag and move
patches of moisture into the region, with isolated showers moving
over windward sections from time to time.  Another surface high
should build over the Western Atlantic, though the latest model
guidance suggests that it should linger there through the long-term
forecast instead of migrating eastward. The col region mentioned in
the previous discussions should remain far north of the region, with
winds remaining strong. In the mid to upper levels, the ridge will
continue to dominate the weather pattern throughout the weekend,
with warmer-than-normal 500 mb temperatures (between -5 and -6
degrees Celsius), with low potential of deep convection. Although
afternoon convection is expected on Friday and Saturday afternoon,
it should remain shallow, with limited shower activity across
western/northwestern Puerto Rico. Puddles over the road, reduced
visibility, can be expected, though no significant flooding
potential is expected. The latest model guidance continues to
suggest an upper-level trough that will deepen into the tropics,
which may become a cut-off low near the Bahamas by late Sunday, with
the CWA positioned under the favorable side of convection. Besides
cooling mid-level temperatures (around -7 degrees Celsius), the
proximity of the low should allow ventilation and cloud growth,
increasing the potential of deeper convection. With low to mid level
moisture content increasing, showers and isolated thunderstorms
likelihood is increasing. Hence, from Sunday onwards, frequent
passing showers are expected over windward sections of Puerto Rico
and the U.S. Virgin Islands, particularly overnight into the morning
hours, along with afternoon convection over interior and
western/northwestern Puerto Rico. Additionally, streamers may
develop over the waters and the San Juan Metropolitan Area. Taking
in consideration local effects, diurnal heating, and sea breeze
convergence, showers may persist and result in ponding of water over
roadways and poorly drained areas, along with minor flooding.

Minor concentrations of SAL may persist during the weekend, with the
highest concentrations remaining south of the CWA according to the
latest NASA DUex product. Nevertheless, residents and visitors
should take necessary precautions if sensitive to these particles.

As for temperatures, model guidance suggests warmer-to-hotter
conditions this weekend, with 925 mb temperatures well above normal.
If winds remain with a southerly component, with the available
moisture, urban and coastal areas will very likely experience heat
indices above 100 degrees Fahrenheit, localized areas reaching Heat
Advisory Criteria. Hence, the heat risk will remain elevated this
weekend,  stay hydrated and avoid long sun exposure.

&&

.AVIATION...
(18Z TAFS)
Issued at 136 PM AST Tue May 12 2026

Mainly VFR conditions will prevail across all TAF sites through
the forecast period. However, passing VCSH/SHRA embedded within
the trade winds, resulting in brief periods of MVFR conditions
due to reduced visibility and lower ceilings between FL020 and
FL030. Between 12/19Z and 12/21Z,-SHRA with isolated VCTS may
develop in the vicinity of TJBQ & TJSJ. Surface winds will remain
from the east- southeast at around 10 to 15 knots,Winds are
expected to gradually diminish after 13/06Z.

&&

.MARINE...
Issued at 136 PM AST Tue May 12 2026

No significant changes were made to the previous forecast. A broad
surface high pressure system over the central Atlantic, combined
with an induced surface trough that is expected to gradually
develop into a low pressure system as the week progresses, will
continue to promote moderate to locally fresh east to
southeasterly winds across the local waters. Under this pattern,
seas are expected to remain between 3 and 5 feet, with locally
higher seas across exposed offshore waters and in areas affected
by stronger winds. Therefore, mariners should continue to exercise
caution across portions of the local waters, especially in
offshore Atlantic waters and local passages where choppy
conditions are expected at times.

&&

.BEACH FORECAST...
Issued at 136 PM AST Tue May 12 2026

Surface high pressure across the central Atlantic will continue
to generate moderate to locally fresh east to southeasterly winds
across the region. These breezy conditions will persist through
tonight and Tuesday, maintaining a moderate risk of rip currents
along most local beaches, particularly across north- and east-
facing coastlines of Puerto Rico, Culebra, Vieques, and the U.S.
Virgin Islands. By midweek, a weak long-period northeasterly swell
is expected to reach the Atlantic waters and beaches, which could
further enhance the risk of dangerous rip currents across exposed
beaches. Beachgoers are urged to swim only at beaches with
lifeguards on duty, remain aware of changing surf conditions, and
avoid venturing too far from shore.

&&

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

$$

SHORT TERM...LIS
LONG TERM....MNG
AVIATION...LIS

NWS SJU Office Area Forecast Discussion