487
FXCA62 TJSJ 051852
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
252 PM AST Sat Jul 5 2025

.KEY MESSAGES...

 * Saharan dust particles will remain across the region resulting
   in hazy skies at least until Monday.

 * Hot and breezy conditions will continue on Sunday across
   coastal areas.

 * A moderate risk of rip currents will return next week across
   most east, northern, and southern beaches of the islands.

 * A Heat Advisory is in effect through 4 PM AST this afternoon
   for the lower elevations and urban areas of Puerto Rico.


&&

.SHORT TERM...This afternoon through Monday...

Sunny to partly cloudy and hazy skies prevailed across Puerto
Rico and the U.S. Virgin Islands today. Diurnally induced
afternoon showers and isolated thunderstorms developed over the
northwest quadrant of PR, while streamers were observed downwind
of the USVI. Maximum temperatures were from the mid-80s to the
low 90s across the lower elevations of the islands, and from the
upper-70s to mid-80s across the higher elevations of Puerto Rico.
The wind was from the east to southeast between 15 and 20 mph
with sea breeze variations and higher gusts across coastal areas.

For the rest of this afternoon, the diurnally induced showers and
isolated thunderstorms will continue mainly over the west coast
and western waters of PR. Gusty winds and occasional lightning
strikes are expected with this activity. Across the USVI and
eastern PR, breezy conditions and shallow cloudiness with limited
shower activity is expected. For the rest of the weekend, a dense
Saharan Air Layer(SAL) with suspended Saharan dust will persist,
resulting in hazy skies, poor air quality, and reduced
visibilities. A weak low-to mid-level ridge over the region will
promote a trade wind cap inversion. This in addition to the SAL
will limit moisture content across the islands. In general, shower
activity will develop mainly due to local and diurnal effects over
western PR. Winds will acquire a more easterly component on
Sunday, and ENE on Monday.

By Monday, a weak trade wind perturbation will move into the
region, bringing passing showers into the area, and aiding in the
development of showers and thunderstorms across the interior and
western PR. Across the USVI, mostly scattered showers are
expected from time to time. Although no widespread significant
rain is anticipated, some minor urban and small stream flooding is
possible with the thunderstorms. Temperatures will be just a tad
lower, but still with a limited heat risk anticipated for Puerto
Rico.

.LONG TERM...Tuesday trough Sunday...

On Tuesday, a tropical wave is expected to pass well south of the
region, but a patch of shallow moisture content should arrive by
Tuesday evening from the east/northeast. Increasing passing
showers once again through the night across the USVI and eastern
PR.

/From Prev Discussion issued at 441 AM AST Sat Jul 5 2025/

A broad surface high pressure anchored across the central
Atlantic will dominate the weather pattern across Puerto Rico and
the U.S. Virgin Islands from Wednesday through Sunday. This
feature will promote southeasterly winds through Saturday,
gradually shifting to an easterly flow late Saturday into Sunday
as the high extends westward into the western Atlantic. At mid to
upper levels, a ridge pattern will establish over the region,
promoting increasingly stable conditions and suppressing vertical
cloud development. As a result, significant convection is not
expected during the period, with only brief and isolated showers
possible across eastern areas during the overnight and early
morning hours.

A surge of Saharan dust will affect the islands from late
Wednesday through Sunday, leading to hazy skies and further
reducing shower activity. The latest guidance from the NASA
Goddard Earth Observing System Model V5 suggests that the highest
concentration of Saharan dust is expected on Friday and Sunday,
with aerosol optical depth values ranging between 0.20 and 0.30.
This will result in the driest and haziest conditions during those
days, maintaining an overall pattern of warm, stable, and mostly
dry weather through the weekend.


&&

.AVIATION...

(18Z TAFs)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, SHRA/TSRA in and around TJBQ
may cause tempo MVFR conds thru 05/22z. HZ due to Saharan dust
expected to cause VSBY to drop to near 6SM thru Sunday evening.
The 05/12z TJSJ sounding indicated ESE winds up to 18 kt blo
FL050.


&&

.MARINE...

A broad surface high pressure over the central Atlantic will
continue to result in moderate to fresh easterly winds across the
region. Therefore, wind-driven seas will result in choppy marine
conditions across the Atlantic waters and the Caribbean Waters for
the following days. Saharan dust particles will be in place at
least until Monday, resulting in hazy skies and limited shower
activity.


&&

.BEACH FORECAST...

There is a low risk of rip currents for all islands through the
rest of the weekend. However, life-threatening rip currents often
occur in the vicinity of groins, jetties, reefs, and piers.

For the upcoming workweek the risk of rip current will become
moderate across the northern coastal areas of Puerto Rico on
Monday, and extending into the east and southeast coasts and
across St. Croix from Tuesday onward.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 4 PM AST this afternoon for PRZ001>005-007-
     008-010-011.

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

$$

DSR/GRS