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849
FXCA62 TJSJ 021908
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
308 PM AST Sun Aug 2 2026

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

.KEY MESSAGES...
Issued at 217 PM AST Sun Aug 2 2026

- Thunderstorms may affect St. Croix, and St. Thomas and western
  Puerto Rico during the afternoon hours.

- Moderate to high concentrations of Saharan Dust are forecast to
  arrive late tonight through Tuesday, resulting in deteriorated
  air quality and hazy skies.

- Significant to elevated heat risk will persist across lower
  elevations and urban areas of Puerto Rico and the U.S. Virgin
  Islands through most of the period, increasing the potential
  for heat- related illnesses, especially by the beginning of
  the workweek.

- Up to a moderate risk of rip currents will persist through
  Monday and low risk through Thursday.

&&

.Short Term(This evening through Tuesday)...
Issued at 217 PM AST Sun Aug 2 2026


Trailing moisture associated with the tropical wave, in combination
with lingering instability aloft, supported showers and isolated
thunderstorms across the Caribbean waters during the early morning
hours. Some of this activity moved over southwestern Puerto Rico,
producing beneficial rainfall across portions of the area. However,
rainfall accumulations remained generally light, with most locations
receiving around one-half inch or less.

Since late morning, skies have partially cleared across much of the
islands, with only isolated convection developing near Mayaguez and
a few thunderstorms remaining east of St. Croix. The intrusion of
drier air aloft has limited convective development so far despite
sufficient low-level moisture lingering across the region. For the
remainder of the afternoon, diurnal heating, sea breeze convergence,
and local effects will support isolated to locally scattered showers
and thunderstorms, mainly across the interior and western sections
of Puerto Rico. Although the flooding threat appears limited given
the expected localized nature of the convection.

The forecast remains on track through Tuesday. A gradual decrease in
moisture and an increase in Saharan dust concentrations will promote
a more stable pattern over the short term period. While afternoon
convection will continue each day due to local effects, activity
should remain isolated, favoring the interior and western sections
of Puerto Rico, with passing showers affecting the windward sectors
during the overnight and morning hours at times. Hazy skies and
deteriorating air quality are expected to become more noticeable
Monday and Tuesday as Saharan dust concentrations increase.

Cloud clearing today has allowed heat indices to reach advisory
criteria across localized areas, although most locations remained
below advisory thresholds. Above-normal low-level temperatures and
increasing Saharan dust concentrations are expected to limit
overnight cooling, resulting in warmer-than-normal minimum
temperatures and an elevated heat risk through Monday and Tuesday.
Therefore, Heat Advisories will likely be needed each day,
particularly across the urban and lower elevations of Puerto Rico.
Continue to monitor the forecast for updates regarding heat and air
quality products.

&&

.Long Term(Wednesday through next Saturday)...
Issued at 345 AM AST Sun Aug 2 2026

A tropical wave is expected to move across the region by Wednesday,
increasing the potential for showers and isolated thunderstorms. The
latest precipitable water (PWAT) analysis shows seasonal values
ranging from 1.75 to 2.00 inches from Wednesday through early
Thursday morning. Under this pattern, passing showers are
anticipated across the U.S. Virgin Islands and eastern Puerto Rico,
followed by afternoon convective activity over the interior and
western Puerto Rico. This daily activity will be driven by the
combination of available moisture, diurnal heating, and local
terrain effects.

Following the passage of the wave, a broad high-pressure system
extending across the western and central Atlantic will bring drier
air and more stable conditions to the area under an east-southeast
wind flow. While trade winds may occasionally drag small patches of
moisture across the region, no significant rainfall is expected
during this time frame. However, excessive heat will persist due
to above-normal temperatures at the 925 mb level, with daytime
highs reaching the upper 80s to low 90s across coastal and urban
areas each day. These temperatures, combined with the east-
southeasterly winds and the available moisture, could lead to high
heat indices throughout the period. Please continue to monitor
weather conditions as the week progresses.

&&

.AVIATION...
(18Z TAFS)
Issued at 217 PM AST Sun Aug 2 2026

Mainly VFR conds expected through the pd. Isold to sct SHRA/TSRA may
develop ovr the interior and W PR through 02/22Z, with brief MVFR
conds psbl at TJBQ/TJPS. VCSH/VCTS may also affect TISX through
early this evening. ESE winds 10-18 kt with higher gusts and sea
breeze variations, bcmg lgt/vrb aft 02/23Z. HZ will gradually
increase across the area through the pd, with more noticeable
impacts aft 03/12Z.

&&

.MARINE...
Issued at 217 PM AST Sun Aug 2 2026

A surface high pressure over the central Atlantic will continue to
promote moderate to locally fresh trades through the workweek.
Locally stronger winds due to the sea breeze are expected each
afternoon across the Atlantic and Caribbean coastal waters of Puerto
Rico through Thursday. Hazy conditions due to Saharan dust will return
by tomorrow.

&&

.BEACH FORECAST...
Issued at 217 PM AST Sun Aug 2 2026

Wind-driven waves will continue to support a moderate risk of rip
currents across the northwest to southeastern beaches of Puerto
Rico, Vieques, Culebra, and St. Croix. A low risk is expected by
Tuesday across the western to southern beaches of PR, and most
beaches of St. Thomas and St. John. Nevertheless, beachgoers
should be aware that life-threatening rip currents often occur in
the vicinity of jetties, reefs, and piers even when the risk is
low.

&&

.FIRE WEATHER...
Issued at 217 PM AST Sun Aug 2 2026

Critically dry fuels persist across southern Puerto Rico and St.
Croix, with Keetch-Byram Drought Index (KBDI) values remaining
well above the critical threshold. East to east- southeast winds
are expected to remain above or near the threshold values,
slightly which could promote the rapid spread of any fire that
develops. Residents and visitors should avoid outdoor burning and
exercise caution with activities that could generate sparks or
open flames, especially across areas with critically dry
vegetation.

&&

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

$$

SHORT TERM/AVIATION...CVB
LONG TERM...GRS
MARINE/BEACH FORECAST...MMC

NWS SJU Office Area Forecast Discussion