National Weather Service Today's Weather Impact Levels

297
FXCA62 TJSJ 120750
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
350 AM AST Tue May 12 2026

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

.KEY MESSAGES...
Issued at 350 AM AST Tue May 12 2026

* Breezy to locally windy conditions will continue through at
  least the weekend as surface high pressure maintains a tight
  pressure gradient. Frequent passing showers will affect windward
  areas overnight and in the morning.

* Limited excessive rainfall impacts are expected Tuesday through
  Thursday, mainly across western Puerto Rico during the
  afternoon and eastern Puerto Rico/U.S. Virgin Islands overnight
  into the morning hours. Localized flooding and water ponding in
  poor drainage areas will remain possible.

* Heat risk will increase through the week and into the weekend
  as warmer-than- normal temperatures persist. Heat indices above
  100F are likely across urban and coastal areas, with Heat
  Advisory conditions possible Thursday through the weekend.

* A generally stable pattern will limit widespread thunderstorm
  activity through most of the period, although we cannot rule out
  isolated thunderstorms each afternoon across interior and
  western Puerto Rico. A slightly wetter and more unstable
  pattern may develop by late weekend into early next week.

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

&&

.Short Term(Today through Thursday)...
Issued at 350 AM AST Tue May 12 2026

In general, tranquil weather conditions prevailed overnight.
However, another wind surge brought a patch of moisture, promoting
passing showers across the local waters, the US Virgin Islands,
and Puerto Rico`s windward locations. Low temperatures ranged from
the mid-70s to the low-80s at urban and coastal sites, to the
mid- and upper-60s at mountain sites. The winds were mainly from
the east to east-southeast at 10 to 15 mph, with higher gusts
across windward locations, and 5 to 10 across leeward sites, where
land breeze fluctuations were also noted.

A surface high pressure will continue tightening the local
pressure gradient, creating breezy to locally windy conditions
across the region through at least the middle of the week. Under
this wind pattern, pockets of low-level moisture embedded within
the winds will be advected across the region, resulting in periods
of showery weather, particularly during the overnight and early
morning hours across windward areas.

A somewhat stable atmosphere is expected to continue due to a
mid- to upper-level ridge, which is promoting subsidence aloft,
limiting significant vertical development, and reducing the
potential for widespread thunderstorm activity through the period.
Nevertheless, local effects, strong diurnal heating, and sea
breeze convergence will support afternoon convection each day
across portions of eastern and interior Puerto Rico, as well as
western Puerto Rico and parts of the U.S. Virgin Islands. Although
we did not include thunderstorms in the forecast, we cannot rule
out isolated thunderstorms, particularly given the excessive
heating expected each afternoon.

We kept the limited flooding risk through the short term,
especially across western Puerto Rico during the afternoon hours
and across eastern Puerto Rico and the U.S. Virgin Islands during
the evening and early morning hours.

Model guidance has been consistently indicating the potential for
warm-to-hot heat indices each day. But even hotter around the
middle of the week, when we continue evaluating the necessity of
issuing a Heat Advisory, as above-normal temperatures continue to
present. This trend will increase the risk of heat-related
effects, primarily for individuals highly sensitive to heat,
especially those outdoors without effective cooling and/or
adequate hydration.

&&

.Long Term(Friday through Tuesday)...
Issued at 350 AM 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...
(06Z TAFS)
Issued at 350 AM AST Tue May 12 2026

Mainly VFR conditions will prevail with fast-moving SHRA/-SHRA
arriving due to the breezy E-ESE winds. SHRA/+SHRA will form
across the interior and northwest PR between 12/17-23z, probably
affecting JBQ, which could promote brief MVFR or brief IFR conds.
Winds will prevail from the E-ESE at 5-15 kt with higher gusts,
then after 12/13z winds will range between 15-20kt with higher
gusts and sea breeze variations.
&&

.MARINE...
Issued at 350 AM AST Tue May 12 2026

The surface high pressure over the western Atlantic will be replaced
by a low pressure system over the central Atlantic. Expect the
moderate to locally fresh east to southeast winds to prevail across
the regional waters, before gradually weakening after midweek. Seas
are expected to range between 3 to 5 feet with occasional wave
heights reaching up to 6 feet. Choppy seas are expected to prevail
across the local waters.

&&

.BEACH FORECAST...
Issued at 350 AM AST Tue May 12 2026

Breezy to locally windy conditions will continue across the region
through at least midweek, maintaining a moderate risk of rip
currents along most local beaches, particularly along north- and
east-facing coastlines.

A weak long-period northeasterly swell is also expected to arrive
across the Atlantic beaches by midweek, which could further
increase the risk of dangerous rip currents. 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.
&&

$$

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

NWS SJU Office Area Forecast Discussion