591
FXCA62 TJSJ 110743
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
343 AM AST Mon May 11 2026

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

.KEY MESSAGES...
Issued at 343 AM AST Mon May 11 2026

* Breezy to locally windy conditions will persist through much of
  the week due to a tightened pressure gradient across the US
  Virgin Islands and Puerto Rico. Passing showers will continue to
  affect windward areas, especially during the overnight and
  morning hours.

* Afternoon convection will develop each day across portions of
  interior and western Puerto Rico, with the greatest potential
  for ponding of water on roads and reduced visibility. A limited
  flooding risk will persist during this period.

* Warm- to- hot conditions will continue through the week. Heat
  indices above 100 degrees Fahrenheit are expected across urban
  and coastal areas of Puerto Rico and the U.S. Virgin Islands,
  with a moderate to locally elevated risk of heat-related impacts
  by late week.

* Marine and beach conditions will remain hazardous at times due
  to breezy winds and persistent choppy seas. PR and the USVI have
  a moderate risk of rip currents along their north- and east-
  facing beaches through at least the upcoming weekend.

* Minor concentrations of Saharan dust are expected to arrive by
  Wednesday and linger into late week, resulting in hazy skies and
  possible reductions in air quality and visibility for sensitive
  groups.

&&

.Short Term(Today through Wednesday)...
Issued at 343 AM AST Mon May 11 2026

In general, tranquil weather conditions prevailed overnight.
However, a 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-northeast at 10 to 20 mph, with higher gusts
across windward locations, and 5 to 10 across leeward sites, where
land breeze fluctuations were also noted.

While surface high pressure strengthens across the western
Atlantic, the local pressure gradient will tighten, promoting
breezy to locally windy conditions across the islands. Pockets of
low-level moisture embedded within the trade wind flow will
continue to move across the region, resulting in periods of
showery weather, particularly during the overnight and early
morning hours across windward areas.

At the mid and upper levels, a persistent ridge pattern will
promote subsidence aloft and maintain generally stable atmospheric
conditions, 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.

As a result, a limited flooding risk will persist for 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 overnight hours.

In addition, model guidance suggests that warm-to-hot heat indices
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(Thursday through Monday)...
Issued at 343 AM AST Mon May 11 2026

A few changes were introduced to the long-term forecast, though no
significant flooding or lightning threats are expected. As mentioned
in the previous discussion, model guidance continues to suggest a
dry to typical weather pattern across the CWA, with a surface high
pressure over the Central Atlantic lingering and promoting SE winds
through most of the period. Additionally, another high pressure is
expected to move over the western Atlantic by Sunday, migrating
eastward and shifting winds from the E-ESE. In the mid to high
levels, a ridge will dominate most of the weather pattern through
Sunday, maintaining warmer mid-level temperatures (around -4 and -5
degrees Celsius) for this time of the year, resulting in stability
aloft and shallow convection. Nevertheless, an upper-level trough
may gradually deepen into the tropics by Sunday, weakening the ridge
and slightly introducing some instability. From the latest guidance,
PWAT values will remain seasonal (between 1.5 and 1.75 inches), with
mid-level moisture content increasing and lapse rates becoming
steeper. As a result, with breezy to locally windy conditions from
Thursday onward, passing showers will move from time to time across
windward sections of the islands, particularly during the night into
morning hours. As mentioned in the previous discussions, shallow
afternoon convection over interior and western/northwestern Puerto
Rico is expected in the long-term forecast, though the highest
potential of flooding may be seen later on Sunday into Monday,
resulting in a limited flooding and lightning risk. Nevertheless,
these areas can still expect moderate to locally strong showers,
resulting in puddles over the road, gusty winds, and reduced
visibility.

Warm-to-hot conditions will likely persist in the long-term
forecast, with winds from the southeast and available moisture
likely to result in heat indices surpassing 100 degrees Fahrenheit,
and even meet Heat Advisory Criteria, particularly over urban and
coastal areas of Puerto Rico and the U.S. Virgin Islands. Residents
and visitors should remain tuned to further updates, as these
conditions may affect most people sensitive to heat.

Based on the latest NASA DUex product, minor concentrations of SAL
are expected to arrive on Wednesday, likely to persist through the
end of the workweek. These conditions may slightly reduce visibility
and affect people sensitive to these particles.

&&

.AVIATION...
(06Z TAFS)
Issued at 343 AM AST Mon May 11 2026

Mainly VFR conditions are expected to prevail. Fast-moving SHRA
will be advected by breezy E-ESE winds across local terminals.
SHRA and possibly isolated TSRA will form across the interior and
northwest PR between 11/17-23z, affecting JBQ, this will promote
brief MVFR or IFR conds. Winds will prevail from the E-ESE at 5-15
kt with higher gusts, then after 11/13z winds will range between
15-20kt with gusts up to 30 kt, and sea breeze variations.

&&

.MARINE...
Issued at 343 AM AST Mon May 11 2026

A surface high pressure system over the central Atlantic will
continue to generate moderate to locally fresh east to southeast
winds across the regional waters through at least midweek, before
gradually weakening afterward. 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 as strong winds affect the
local waters.

In addition, a small long period northeasterly swell with a period
of around 13 seconds, is forecast to arrive by Thursday. Therefore
expect the combination of wind driven waves plus a small swell
affecting the local atlantic waters between late thursday and
Saturday.

&&

.BEACH FORECAST...
Issued at 343 AM AST Mon May 11 2026

Breezy conditions will continue to impact the region through at
least Tuesday. This will result in choppy seas across all local
waters. These conditions will also maintain a risk of rip currents
along many local beaches. We strongly urge the public to visit
only beaches designated as safe for swimming, remain alert near
the shoreline and never turn your back to the ocean.

This pattern is expected to continue into mid week as breezy
conditions persist.In a addition a small long period swell is
forecast to reach the Atlantic local waters on Thursday.

If you become caught in a rip current, remain calm and yell for
help. Avoid exhausting yourself and try to stay afloat while away
ting assistance. If possible, swim parallel to the shoreline until
you are out of the current, then make  your way back to the beach.
Do not attempt to swim direct;y against a rip current, as this can
quickly lead to exhaustion.

For additional information, visit weather.gov/beach/sju.

&&

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

$$

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

NWS SJU Office Area Forecast Discussion