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345
FXCA62 TJSJ 231859
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
259 PM AST Sun Aug 23 2026

...New SHORT TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER...

.KEY MESSAGES...
Issued at 259 PM AST Sun Aug 23 2026

- A weak tropical wave moving across the islands will bring
  periods of shower activity this afternoon across W PR and
  tonight across USVI and E PR.

- A Heat Advisory remains in effect until 4 PM AST. An elevated
  heat threat is expected to prevail on Monday, increasing to
  significant around midweek.

- A wetter and more unstable pattern is expected Tuesday into
  Wednesday, with a better chance of showers and thunderstorms
  across the islands due a tropical wave.

- A low risk of rip currents is expected along local beaches
  through at least Tuesday, increasing to a moderate risk along
  north and eastern exposed beaches by mid ween onward.

&&

.Short Term(This evening through Tuesday)...
Issued at 259 PM AST Sun Aug 23 2026

During the morning hours, overall quiet conditions prevailed,
with only minimal showers across the windward areas of Puerto
Rico. Around midday, cloudiness increased, with USVI streamers
reaching portions of eastern Puerto Rico, while showers across
interior Puerto Rico began to develop. Daytime maximum
temperatures ranged from the upper 80s to low 90s across coastal
and urban areas and from the low 80s across higher-elevation
areas. A Heat Advisory remains in effect until 4 PM AST. Residents
are encouraged to stay well hydrated, wear lightweight and loose-
fitting clothing, take frequent breaks from the sun, and follow
other heat-safety precautions.

The overall wind flow will remain moderate easterly across the
region, associated with a surface high pressure system over the
Atlantic. For the rest of the afternoon, convection and isolated
thunderstorms across western sections, driven by local effects,
are ongoing and are expected to continue through sunset. This
activity is associated with a weak tropical wave moving across the
islands, which is causing precipitable water values to increase
toward seasonal averages of around 1.75 to 1.9 inches. During the
overnight period, wind-driven showers are forecast across the USVI
and the windward sectors of Puerto Rico. By Monday, a seasonal
pattern is expected as the tropical wave moves away. Nevertheless,
limited afternoon convection and an elevated heat threat will
remain.

Global model guidance continues to suggest an increase in the
frequency of showers and afternoon convection as another tropical
wave arrives in the region, with precipitable water values
reaching up to 2 inches based on guidance. As a result, a more
active shower and thunderstorm pattern is expected throughout
Tuesday, particularly where local and diurnal effects enhance
convection.

For the remainder of the short-term period, an elevated to
significant heat threat is forecast to prevail, particularly
across coastal and urban areas of the islands. Additional heat
product alerts will likely be needed in the coming days.

&&

.Long Term(Wednesday through Sunday)...
Issued at 335 AM AST Sun Aug 23 2026

During the long-term period, the weather pattern will be mainly
dominated by high pressure across the central Atlantic and the
passage of tropical waves, primarily from the east to southeast.
Aloft, a mid-level ridge will dominate for most of the period.

By Wednesday, remnant moisture associated with a tropical wave will
remain across the region. Current guidance indicates that
precipitable water values will remain near seasonal levels; however,
moderate to locally high concentrations of Saharan dust will persist
across the region before decreasing Wednesday night into Thursday.
As a result, mainly fair weather, hazy skies, and hot temperatures
are expected across the U.S. Virgin Islands. Across Puerto Rico,
expect passing morning showers over windward areas, with limited
afternoon convection across western municipalities.

By Thursday, overall drier air will dominate, with PWAT values
falling below seasonal averages. However, intermittent patches of
moisture will continue to move across the region. An upper-level
trough will linger, resulting in cooler 500-mb temperatures, while
the mid-level ridge will still provide some stability. Despite this,
diurnal heating and local effects will support the development of
afternoon convection, including isolated thunderstorms across
western Puerto Rico, which could result in a limited flood threat.

From Friday into Saturday, current model guidance suggests the
arrival of a tropical wave, increasing tropical moisture up to 2.25
inches. Uncertainty remains in the forecast during this period, so
residents and interests across the region are encouraged to continue
monitoring the latest forecasts and the evolution of the tropical
wave. By Sunday, precipitable water values are expected to decrease
to seasonal or below-normal levels, limiting rainfall chances.

One persistent hazard throughout the period will be excessive heat,
with an elevated heat threat expected on most days. Wednesday could
pose a particularly significant heat threat due to above-normal 925-
mb temperatures, southeasterly winds, the presence of Saharan dust,
and seasonal moisture levels. Residents are encouraged to stay well
hydrated, wear lightweight and loose-fitting clothing, take frequent
breaks from the sun, and follow other heat-safety precautions.

&&

.AVIATION...
(18Z TAFS)
Issued at 259 PM AST Sun Aug 23 2026

Mainly VFR conds expected across all terminals thru the forecast
period. SHRA/TSRA development over W PR may result in brief MVFR
conds at/near TJBQ aft 23/18Z-22Z. VCSH expected at TJSJ, TJPS
and USVI terminals overnight into Monday morning. E-ESE winds
12-16 kts with slightly higher gusts, becoming lighter overnight,
increasing again aft 23/13Z around 23/13Z.

&&

.MARINE...
Issued at 259 PM AST Sun Aug 23 2026

No changes were introduced to the marine forecast. Recent
scatterometer data shows moderate trade winds across the regional
waters and passages, while the latest altimeter scan reported seas
between 2 and 4 feet, with isolated areas at 5 feet. This pattern
should continue through midweek as the surface high pressure
builds over the central Atlantic. A weak tropical wave approaching
the Caribbean basin should increase the frequency of showers
across the local Caribbean waters and passages this afternoon into
the evening. Afterward, another tropical wave is forecast to
approach the eastern Caribbean around Tuesday, bringing enhanced
shower and thunderstorm activity once again. As winds gradually
increase by midweek and become moderate to locally fresh, seas
should build to 3-5 feet, occasionally 6 feet, across offshore
waters and passages; small craft must exercise caution.

&&

.BEACH FORECAST...
Issued at 259 PM AST Sun Aug 23 2026

Beach conditions remain tranquil for beachgoers, as the low risk
of rip currents continues across the islands. The nearshore buoys
show seas between 1 and 3 feet, with winds between 10 and 15 kt,
occasionally up to 20 kt. These conditions should continue for the
first part of the week, though beachgoers must exercise caution,
as life-threatening rip currents can often occur in the vicinity
of jetties, reefs, groins, and piers. By Wednesday into Thursday,
a gradual increase in winds and seas will likely upgrade the risk
to moderate, particularly across northern and eastern-exposed
beaches of the islands, increasing the likelihood of rip currents
along the surf zone. The moderate risk should continue throughout
the end of the week. As mentioned in the previous discussion,
showers and isolated thunderstorms can be expected each afternoon,
moving across western coastal areas of Puerto Rico. Beachgoers
should remain weather alert, as isolated thunderstorms could
produce gusty winds and lightning.

&&

.FIRE WEATHER...
Issued at 259 PM AST Sun Aug 23 2026

During the morning hours, moisture content is associated with a
tropical wave approaching the region. RAWs/AWOS stations across
the southern coastal plains of Puerto Rico and St. Croix in the
U.S. Virgin Islands reported winds between 20 - 23 mph, with gusts
up to 31 mph. Although stations reported a gradual decrease in RH
values and the Guanica station reached threshold values, it was
brief. Given the current conditions and the forecast, the risk
will remain low for the rest of today, though residents and
visitors are encouraged to avoid outdoor burning, as critical dry
fuels and drought conditions continue and could increase the
likelihood of wildfire ignition and rapid spread.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 4 PM AST this afternoon for PRZ001>003-005-
     007-008-010>013.

VI...Heat Advisory until 4 PM AST this afternoon for VIZ001-002.

AM...None.
&&

$$

SHORT & LONG TERM/AVIATION...YZR
MARINE/BEACH/FIRE...MNG

NWS SJU Office Area Forecast Discussion