447
FXCA62 TJSJ 100810
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
410 AM AST Thu Jul 10 2025

.KEY MESSAGES...

* Showers will continue to move across the Atlantic and Caribbean
  waters, as well as southern PR through the morning hours. Like
  previous days, diurnally induced afternoon showers and isolated
  thunderstorms are expected over portions of the Cordillera
  Central and western PR today.

* Moderate to high concentrations of Saharan dust are expected to
  return late tonight through at least Sunday, resulting in hazy
  skies, reduced visibility, and poor air quality.

* Breezy to locally windy conditions will promote choppy seas and
  a moderate risk of rip currents over the next few days.

&&

.SHORT TERM...Today through Saturday...

Moisture from a passing tropical wave generated scattered showers
and a few isolated thunderstorms across the region overnight. Driven
by a strong steering low, some showers moved over eastern, southern,
and northern Puerto Rico as well as St. Croix in the U.S. Virgin
Islands, with a few reaching further inland onto the central
interior since 8 PM AST. Radar-estimated rainfall accumulations
generally remained below a quarter of an inch across most areas,
expect in parts of southern Puerto Rico, particularly the coastal
areas of Guayama, where totals exceeded one inch. Surface observing
stations reported a persistent gentle to moderate breeze along the
coast and in some elevated windward areas, with sustained winds
around 10-15 mph and gusts up to 25 mph. Low temperatures remained
warm, in the low 80s across most of northeastern and southern Puerto
RIco, including the San Juan metro area, Culebra, and the U.,S.
Virgin Islands.

A tropical wave will continue moving away from the area today,
steered by a broad surface high over the western Atlantic. In its
wake, stronger east-southeasterly winds will bring breezy to windy
conditions and user in much drier air (with  precipitable water
dropping to around 1.30 inches, well below typical levels), along
with moderate to high concentrations of Saharan dust. This marks the
start of a hazier, warmer, and more stable weather pattern across
Puerto Rico and the U.S. Virgin Islands, expected to persist
through the weekend. Meanwhile, a mid- to upper-level trough to the
northeast will gradually desplace a mid-level ridge and settle
northwest of the area by Saturday. However, its influence will
likely remain limited due to the dry and stable environment.

Today will be a transition day. Morning showers associated with the
departing tropical wave may linger, followed by isolated to
scattered afternoon showers and isolated thunderstorms over western
Puerto Rico driven by lingering moisture, diurnal heating and local
effects. Increasing dust and dry air will suppress most convection
later in the day, reducing visibility and affecting air quality,
conditions that may impact sensitive groups, while drier and fair
weather spreads across the U.S. Virgin Islands and eastern Puerto
Rico. Highs will reach the upper 80s to low 90s, with heat indices
elevated to levels warranting a Heat Advisory, mainly for lower
elevations and urban areas of Puerto Rico

From tonight through Saturday, expect persistently hazy, dry, and
warm conditions with minimal chances for rainfall. Winds will be
strongest Friday, reaching 25-30 knots before gradually easing to 10-
15 knots by Saturday. Friday is likely to be the haziest and hottest
day, with abundant sunshine and limited relief from the breeze.
However, warm conditions will potentially prompt the issuance of
Heat Advisories every day. Residents and visitors are advised to
take appropriate precautions during this period, especially those
sensitive to reduced air quality and heat.

.LONG TERM...Sunday through Thursday...

On Sunday, Saharan Dust concentrations will begin to diminish.
However, we still anticipate hazy skies across the U.S. Virgin
Islands and Puerto Rico. The latest model guidance continues to
indicate a Tropical Upper-Tropospheric Trough (TUTT) shifting
westward towards Hispanola and lingering there through the
beginning of the workweek weakening the high pressure system at
the surface and forcing the breezy to locally windy conditions to
diminish. On Monday and Tuesday, the approach of easterly trade
wind perturbations will gradually enhance moisture levels across
the region. As atmospheric moisture increases, so will the
potential for shower and thunderstorm activity, particularly
during the afternoon hours over western and southwestern Puerto
Rico, with pockets of showers over eastern Puerto Rico in the
morning hours. Additionally, model guidance indicate that moisture
will extend from the surface through the mid and upper levels of
the atmosphere, supporting increased atmospheric instability and
enhancing the potential for convective development during this
period. By midweek, a tropical wave is expected to approach the
forecast area, bringing increased tropical moisture. However, the
most intense part of the wave is expected to pass south of Puerto
Rico and the U.S. Virgin Islands. Nevertheless, scattered showers
and thunderstorms are anticipated each afternoon, especially
across interior and western areas. We will continue to monitor
conditions closely for any significant changes.

&&

.AVIATION...
(06Z TAF)

SHRA/TSRA will likely affect TJSJ, TJPS, and USVI terminals
through 10/13Z, with afternoon SHRA/TSRA expected near TJBQ
between 10/17-23Z, possibly causing brief MVFR conditions. VCSH
are also possible around TJSJ and USVI terminals throughout the
period, especially after 10/23Z. Moderate to high concentrations
of Saharan dust will generate hazy skies, with visibilities
reduced to 5-6 SM after 10/13Z. Breezy to locally windy winds of
16-22 knots between 10/13- 23Z, diminishing to 10-15 knots after
10/23Z.

&&

.MARINE...

An easterly perturbation will continue to reach the Lesser Antilles
and move near the US Virgin Islands and Puerto Rico by late today
and early Friday morning. Another pulse of suspended Saharan dust
particles will arrive as early as late tonight and persist through
the weekend.

&&

.BEACH FORECAST...

Breezy to locally windy conditions over the next several days
will promote a persistent moderate risk of rip currents across
most local beaches of Puerto Rico and the US Virgin Islands.
Beachgoers are encouraged to exercise caution as life-threatening
rip currents are possible in the surf zone.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST Friday for
     PRZ001>005-007-008-010-011.

VI...None.
AM...Small Craft Advisory until noon AST today for AMZ711.

&&

$$

SHORT TERM/AVIATION...ICP
LONG TERM/MARINE/BEACH FORECAST...MMC