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694
FXCA62 TJSJ 211710
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
110 PM AST Sun Jun 21 2026

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

.KEY MESSAGES...
Issued at 1256 PM AST Sun Jun 21 2026

* Father`s Day is expected to bring the most active weather of the
  forecast period as a tropical wave moves across the region.
  Periods of heavy rainfall, thunderstorms, and urban and small-
  stream flooding are possible across portions of Puerto Rico.
  Mainly fair weather conditions will continue across the U.S.
  Virgin Islands.

* Moderate concentrations of Saharan dust will continue to affect
  the region early this week and possibly the second part of the
  week, resulting in hazy skies, reduced visibility, and degraded
  air quality, particularly for sensitive groups.

* Another tropical wave may approach the region by the middle of
  the week, bringing an additional chance for showers and
  thunderstorms. Forecast details will continue to be refined as
  confidence increases.

&&

.Short Term(This evening through Tuesday)...
Issued at 1256 PM AST Sun Jun 21 2026

A passing tropical wave promoted shower activity during the morning
hours across portions of eastern and northeastern Puerto Rico. As
the day progressed, these showers spread along the northern coast,
while convective activity intensified across western Puerto Rico.
Doppler radar estimated rainfall accumulations between 1.0 and 2.0
inches by early afternoon. Meanwhile, mainly fair weather prevailed
across the U.S. Virgin Islands, which saw few clouds and no
significant rainfall. Maximum temperatures reached the upper 80s to
low 90s across lower elevations, and the low-to-mid 80s in the
higher mountains. Winds blew from the east at 15 to 20 mph, with
local sea breeze variations and higher gusts reaching around 30 mph,
particularly along coastal areas.

Showers and a few isolated thunderstorms will continue to develop
through the afternoon hours across central and western Puerto Rico,
bringing additional accumulations of 1 to 2 inches. However, by
later this afternoon, the tropical wave is expected to move
westward, eventually exiting the region tonight into early Monday.
By Monday, a drier airmass will filter into the area alongside
moderate concentrations of Saharan dust. This will result in hazy
skies, reduced visibility, and poor air quality. Sensitive groups,
particularly individuals with respiratory conditions, should take
the necessary precautions to limit outdoor exposure and follow
medical guidance.

By Tuesday, similar conditions will prevail as a mid-level ridge
strengthens over the region, promoting drier and more stable
conditions aloft. At the upper levels, a low-pressure system located
north of the northeast Caribbean will continue migrating northward,
losing its influence over the local area. While another low-pressure
system is forecast to build over the Caribbean Sea, it will have
little impact on local weather. Overall, passing trade-wind showers
will continue to affect windward and eastern areas of Puerto Rico
and the U.S. Virgin Islands during the morning hours, while the rest
of the region remains on the drier side. Afternoon convection
remains possible across western and central Puerto Rico, driven by
daytime heating and local effects. Seasonably warm temperatures will
persist, with highs reaching the upper 80s to low 90s across coastal
and urban locations, and from the low to mid 80s in the mountains.


&&

.Long Term(Wednesday through next Saturday)...
Issued at 1256 PM AST Sun Jun 21 2026

A tropical wave is forecast to move across the region on Wednesday
and Thursday. While the wave will bring an increase in low-level
moisture and result in a higher frequency of passing showers, model
guidance suggests precipitable water values will remain near
seasonal levels. In addition, mid-level relative humidity is
expected to remain relatively low, while temperatures near 500 mb
stay close to normal, limiting the potential for widespread deep
convection. As a result, periods of passing showers are expected,
particularly across windward and eastern sections during the morning
hours and across western Puerto Rico during the afternoon due to
local effects. However, significant rainfall accumulations are not
anticipated at this time.

Dust aerosol model guidance suggests that low to moderate
concentrations of Saharan dust may reach the local islands by
Thursday. The arrival of this dust could promote hazy skies and
occasionally reduced visibility while also contributing to a more
stable atmosphere. Although the tropical wave is expected to enhance
shower activity, the extent to which rainfall associated with the
wave offsets the effects of the dust remains somewhat uncertain.
Therefore, residents and visitors are encouraged to continue
monitoring the latest forecasts for updates regarding both rainfall
potential and air quality conditions. At this time, the highest
concentrations of Saharan dust will Friday. Therfore, those with
respiratory conditions are urged to follow the health experts
recommendations and avoid outdoor activities.

By Friday and continuing through Saturday, moisture levels are
expected to remain near to slightly below seasonal normals while
relatively dry mid-level air persists across the region. This should
support a decrease in shower coverage and a return to a more typical
trade-wind weather pattern. Nevertheless, patches of shallow
moisture embedded within the trades may still result in brief
passing showers across windward areas from time to time.
Temperatures will continue near seasonal normals. While no
significant weather impacts are anticipated through the end of the
forecast period, those planning outdoor activities should remain
aware of passing showers and any lingering hazy conditions that
could produce localized visibility reductions.

&&

.AVIATION...
(18Z TAFS)
Issued at 1256 PM AST Sun Jun 21 2026

A tropical wave will bring SHRA/-TSRA, particularly at TJBQ/TJSJ
thru 21/23z. Winds will be from the E-ESE at 15 to 20 kt through
21/23z, with gusts up to 30 kt, especially around SHRA/TSRA and
and sea breeze variations. Winds will be calm to light and
variable overnight thru 22/14Z.

&&

.MARINE...
Issued at 1256 PM AST Sun Jun 21 2026

A tropical wave moving across the Caribbean will continue to support
showers and isolated thunderstorms over the local waters through
late tonight. Meanwhile, a broad surface high pressure system over
the central Atlantic will maintain moderate to locally fresh
easterly to east-southeasterly winds through the next several days,
resulting in choppy seas across the local waters and Caribbean
passages. Small craft should exercise caution. In addition, moderate
to occasionally high concentrations of Saharan dust will persist
into early next week, producing hazy skies, reduced visibility, and
poor air quality.

&&

.BEACH FORECAST...
Issued at 1256 PM AST Sun Jun 21 2026

A moderate risk of rip currents remains in effect for most local
beaches, including northern and eastern Puerto Rico, Vieques,
Culebra, and portions of the U.S. Virgin Islands, while a low risk
persists for the south-central and western coasts of Puerto Rico and
the northern U.S. Virgin Islands. Life-threatening rip currents
remain possible. Scattered showers and isolated thunderstorms
associated with a tropical wave will continue across portions of the
local waters and islands tonight before gradually diminishing on
Monday. Meanwhile, moderate to high concentrations of Saharan dust
will persist across the region through early next week, resulting in
hazy skies, reduced visibility, and poor air quality.

&&

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

$$

DAY...GRS/CAM
EVE...ICP/MMC

NWS SJU Office Area Forecast Discussion