346
FXCA62 TJSJ 251839
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
239 PM AST Wed Jun 25 2025

.KEY MESSAGES...

* An area with slight drier air and suspended Saharan dust
  particles will promote hazy skies at least through Friday.

* Another tropical wave is expected to approach Puerto Rico and
  the U.S. Virgin Islands from the eastern Caribbean by late
  Saturday into Sunday.

* Wind-driven seas will continue to result in choppy marine
  conditions and moderate risk of rip current.

&&

.SHORT TERM...Tonight through Friday...

A generally stable weather pattern prevailed during the morning
hours across Puerto Rico and the U.S. Virgin Islands. Brief
passing showers affected the eastern sections of Puerto Rico
earlier in the day, while mostly clear skies were observed across
the western half of the island during the early morning. By around
11 AM, increased cloudiness was noted across most of the region,
with mid- to low-level clouds spreading inland from the east and
developing over interior areas. No significant rainfall activity
was observed across the region. Temperatures reached the low 90s
across coastal areas, while mountainous regions remained in the
low to mid-80s. Heat indices ranged from 100 to 108 degrees
Fahrenheit across coastal sectors of the island, and gusty winds
were reported across various locations.

Tonight, slightly breezy and hazy conditions are expected across
Puerto Rico and the U.S. Virgin Islands due to the ongoing
presence of Saharan dust particles. A surface high pressure over
the central Atlantic will continue to promote an easterly wind
flow between 15 to 20 knots during the daytime, helping to steer
patches of fragmented cloudiness and isolated showers across
eastern Puerto Rico and the U.S. Virgin Islands, especially near
St. Thomas. Overall, stable weather will prevail tonight,
supported by a mid-level ridge and limited moisture, with
precipitable water values ranging from 1.30 to 1.40 inches. By
Friday, a gradual change in the weather pattern is anticipated as
the larger Saharan dust particles shift westward and exit the
region. This will coincide with an increase in low-level moisture,
with precipitable water values forecast to rise to around 1.70
inches. Additionally, an upper-level feature may enhance
instability across the area, creating a more favorable environment
for convection. As a result, conditions could support the
development of more widespread showers and isolated thunderstorms,
particularly along the Cordillera Central and western sections of
Puerto Rico. This brief moist and unstable pattern is expected to
subside as drier air returns later in the weekend.


.LONG TERM...Saturday through Wednesday... from previous
discussion....

The latest model guidance suggests a surface trough lingering
across the region on Saturday, bringing east-southeast winds.
This shift in wind flow is expected to favor the development of
afternoon showers, particularly over the northwestern quadrant of
Puerto Rico.

A tropical wave is forecast to move in from the eastern
Caribbean between late Saturday and early Sunday. As it
approaches, increased moisture and instability will likely enhance
the coverage of showers and thunderstorms across portions of the
islands and adjacent waters. Forecast models indicate that the
moisture content will extend from the surface to mid- and upper
levels, potentially allowing convective activity to develop
vertically. This increases the risk of localized flooding,
especially during periods of heavier rainfall.

Despite this weekends unsettled/variable weather pattern,
conditions are expected to gradually improve starting by the
beginning of the workweek as a broad, drier air mass moves into
the region. Additionally, model guidance from the Dust Aerosol
Optical Thickness product suggests the arrival of Saharan dust,
potentially resulting in a moderate dust event. Aerosol optical
depth values are projected to range from 0.20 to 0.30, likely
persisting through the middle of the week.

We encourage the public to stay informed and monitor future
updates to the forecast as conditions evolve.


&&

.AVIATION...

VFR conditions will remain in place during the period across all
TAF sites. HZ will continue to result in lower VIS and hazy skies.
Winds will remain from the E up to 15 knots with gusty winds
until 25/23Z, increasing again around 26/13Z. VCSH are possible
around eastern TAF sites during the night.

&&

.MARINE...

A surface high pressure over the Atlantic will continue to
promote moderate to fresh easterly winds across the regional
waters, resulting in choppy seas over the local Atlantic and
Caribbean zones. Reduced visibility is expected to persist through
the end of the workweek due to suspended Saharan dust. By Friday,
a trade wind perturbation will increase the potential for showers
and isolated thunderstorms across the local waters, followed by
the arrival of another tropical wave during the weekend, which may
further deteriorate marine conditions. Mariners should exercise
caution and stay updated with the latest forecasts.

&&

.BEACH FORECAST...

Wind-driven seas will continue to result in moderate risk of rip
current along most of the coastal areas of the islands today into
tonight. The moderate risk of rip current will persist at leats
until Friday night.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 5 PM AST this afternoon for PRZ001-003-005-
     007-008-010-011.

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

$$

SHORT TERM & AVIATION...LIS
LONG TERM....CAM