729
FXCA62 TJSJ 120838
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
438 AM AST Sat Jul 12 2025

.KEY MESSAGES...

* A lingering Saharan Air Layer (SAL) with moderate to high
  concentrations will continue to promote hazy skies, reduced
  visibilities and poor air quality across Puerto Rico and the
  U.S. Virgin Islands through at least early Sunday morning.

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

* A tropical wave will approach the islands by the middle of the
  week, increasing moisture and the potential for showers and
  thunderstorms.

&&

.SHORT TERM...Today through Monday...

Clear to partly cloudy and hazy skies prevailed during the early
morning hours across Puerto Rico and the U.S. Virgin Islands. Brief
passing showers were noted over land areas across eastern PR and the
USVI. However, no significant rainfall amounts were observed.
Minimum temperatures were from the upper-70s to low 80s across the
lower elevations to the mid-60s and upper 70s across the highest
elevations. The wind was light from the east to northeast.

A lingering Saharan Air Layer (SAL) with moderate to high
concentrations will continue to promote hazy skies and poor air
quality across the islands through at least early Sunday morning.
Hot temperatures are expected once again and a Heat Advisory will be
in effect from 10 AM to 5 PM today across the urban areas and lower
elevations of Puerto Rico. Residents and visitors, are advised to
take appropriate precautions during this period, particularly those
who are sensitive to heat and poor air quality conditions.

A TUTT-low north of the area today will gradually move west during
the rest of the period. This could enhance the diurnally induced
afternoon shower activity over western PR, with a slight increase in
the potential for isolated thunderstorm development. However, the
precipitable water content is expected to remain below normal levels
(~1.50 inches) until at least Sunday. On Monday, a trade wind
perturbation will move across the region, increasing shower activity
in general across the islands.

.LONG TERM...Tuesday through Saturday...

A trade wind perturbation is expected to arrive into the area on
Tuesday, increasing moisture into the area and the potential to
observe shower activity across the islands. The forecast have not
changed a lot with the previous model guidance, and continues to
suggest the arrival of a broad tropical wave by mid-week. The latest
precipitable water content analysis suggest values up to 2.10 inches
by Wednesday afternoon. Therefore, showers and thunderstorms are
likely over portions of central, western and eastern Puerto Rico,
and the U.S. Virgin Islands  from Wednesday morning through the
evening hours. This fast moving wave is expected to exit the region
by late Wednesday, followed by a atmospheric perturbation on
Thursday.

By the end of the workweek, a drier air mass accompanied by another
pulse of Saharan Air layer is anticipated to arrive into the area by
Thursday, following the atmospheric perturbation passage over the
region. This event will limit the shower activity across the
islands and will promote hazy skies, reduced visibilities and
deteriorated air quality throughout the area until the weekend.

Hot temperatures will continue across the region next week. Maximum
temperatures are expected to remain in the upper 80s to low 90s
along the coastal and urban areas, and around the mid 80s in the
higher elevations. Heat indices could reach values above 105 degrees
Fahrenheit each day, particularly over the northern, western and
southern municipalities of Puerto Rico. Residents and visitors,
please be aware of these conditions and plan accordingly if planning
to do outdoor activities under sun exposure.

&&

.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. HZ due to Saharan dust and reduced visibilities btw 6-8
miles expected. This may cause false BKN/OVC cigs at times across
the USVI terminals. Winds will increase from the E-ENE at 15-20 kt
with sea breeze variations and higher gusts aft 12/13z.

&&

.MARINE...

A surface high pressure across the central Atlantic will continue to
promote southeasterly winds across the region. Therefore, mariners
can expect moderate to fresh easterly winds and choppy seas across
the islands through the rest of the weekend. High Saharan dust
concentrations will continue to move across the northeastern
Caribbean through early next week, promoting hazy skies, reduced
visibilities and deteriorated air quality.

&&

.BEACH FORECAST...

Expect a moderate risk of rip currents along the northern and
eastern facing beaches of Puerto Rico, Culebra and St. Croix.

Precautions:

Swim only near lifeguards, heed posted warnings. Conditions may quickly
become dangerous, especially for less experienced swimmers.

Hot, hazy conditions are expected to persist through the weekend with
heat index values likely exceeding the 108F in urban and coastal
zones.

Safety Tips:

Stay well hydrated. Seek shade frequently. Avoid outdoor activity
during peak sun hours (typically 11AM2PM).

&&

.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
AVIATION...DSR