932
FXCA62 TJSJ 110749
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
349 AM AST Fri Jul 11 2025

.KEY MESSAGES...

* High concentrations of Saharan dust will continue to promote
  hazy skies, reduced visibilities and poor air quality through
  the weekend, especially impacting sensitive groups.

* Hot temperatures will continue, with heat indices reaching
  levels that affect most individuals sensitive to heat.

* A Heat Advisory is in effect today for all the coastal and urban
  areas of Puerto Rico, including the Caguas Valley area.

* Breezy to locally windy conditions will promote choppy seas and
  a moderate risk of rip currents across the region.

&&

.SHORT TERM...Today through Sunday...

Partly cloudy and hazy skies prevailed during the overnight hours
across Puerto Rico and the U.S. Virgin Islands. Light passing trade
wind showers moved briefly over land areas leaving minor rainfall
accumulations, mainly across the USVI and eastern PR. By midnight,
minimum temperatures were still in the low-80s across most coastal
and lower elevations of the islands. Meanwhile, across the higher
elevations of PR, temperatures were from the mid-60s to low-70s. The
wind was from the east to northeast between 6 and 12 mph with gusts
near 20 mph.

A Saharan air layer (SAL) with moderate to high concentrations of
Saharan dust will linger over the islands through the rest of the
short-term period. Therefore, expect hazy skies along with reduced
visibilities and poor air quality to persist through at least early
Sunday. A 700mb ridge moving north of the area from the tropical
Atlantic and a broad surface high pressure over the western Atlantic
will continue to promote breezy (15-20 mph) east to east-southeast
winds today. This surface high will weaken by this evening, while
another broad surface high builds from the central Atlantic during
the weekend. As the 700mb ridge shifts further into the southwestern
Atlantic, winds will acquire a northeasterly component from tonight
into the weekend. These changes in the wind direction will mainly
cause afternoon showers to develop each day further south than
previous days, and a slight improvement in heat indices,
particularly on Sunday.

For today and Saturday, a similar weather pattern is expected with
breezy and hazy conditions prevailing. Also, warmer minimum
temperatures at night due to the SAL preventing efficient cooling at
the surface will cause that days begin warmer than normal.
Therefore, hot temperatures are expected mainly across most coastal
and urban areas of Puerto Rico. Heat advisory conditions will likely
continue each day. Residents and visitors, are advised to take
appropriate precautions during this period, particularly those who
are sensitive to heat and poor air quality conditions.

.LONG TERM...Monday through Friday...

A enhancement in moisture levels is expected by the beginning of
the workweek with the arrival of several trade wind perturbations
into the islands. The latest precipitable water content shows
values between 1.60 to 2.00 inches from early Monday through late
Tuesday. Therefore, there is an increase in the potential for
shower activity across the area, in particular over eastern Puerto
Rico and the U.S. Virgin Islands during the morning hours.

As the week progresses, a tropical wave is expected to approach the
islands from the east by early evening on Wednesday and lasting
through at least Friday. The latest model guidances has the bulk of
the wave arriving into the area by Thursday morning, increasing the
chance for showers and thunderstorms across the region with PWAT
values up to 2.20 inches. Despite of the wave passage, moderate to
heavy showers and thunderstorms are anticipated each afternoon,
particularly across the central and western municipalities of Puerto
Rico. We will continue to monitor the weather conditions closely for
any significant changes in the forecast.

Saharan dust concentrations will begin to decrease on Monday.
Nonetheless, minor concetrations of these particles will continue to
linger across the region through Thursday. Another pulse of
Saharan dust will arrive by late Thursday/ early Friday following
the wave passage. This event will promote, once again, hazy skies,
reduced visibilities and deteriorated air quality throughout the
area until the weekend.

&&

.AVIATION...

(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, VCSH cannot be ruled out across
all sites. Higher concentrations of Saharan dust are expected fm
11/14z-12/22z, this could lead to lower VSBY btw 5-6 SM. This may
cause false BKN/OVC cigs at times. Winds will continue E-ESE at 15-
20 kt with sea breeze variations and higher gusts aft 11/13z.

&&

.MARINE...

A surface high pressure across the central Atlantic will continue to
result in moderate southeasterly winds across the region. Therefore,
mariners can expect moderate to fresh easterly winds and choppy seas
across the islands through the weekend. An extensive Saharan Air
Layer will move across the Northeastern Caribbean lingering through
the weekend, and leaving hazy skies, reduced visibilities a
deteriorated air quality.

&&

.BEACH FORECAST...

A moderate rip current risk continues along the northern and
eastern facing beaches of Puerto Rico , Culebra, Vieques and St.
Croix. Always swim near lifeguards and obey posted warnings.
Conditions may be dangerous for inexperienced swimmers.

Expect hot and hazy conditions through the weekend, with
excessive heat posing a risk, especially in urban and coastal
areas. Heat indices may exceed 108F, so stay hydrated, seek
shade, and avoid peak sun hours.


&&

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

VI...None.
AM...None.
&&

$$

SHORT TERM...DSR
LONG TERM....GRS