685
FXCA62 TJSJ 050841
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Sat Jul 5 2025

.KEY MESSAGES...

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

 * Warmer conditions are forecasted for today with heat indices
   that would rank between 100 to 111 Fahrenheit degrees from 10
   AM to 2 PM. As a result a heat advisory is in effect for all
   the coastal areas of Puerto Rico, including the vicinity of
   Caguas.

 * There is a low risk of rip current for all the coastal along
   Puerto Rico, Culebra, Vieques and St. Thomas and a moderate
   risk of rip current across St. Croix.

&&

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

Fair weather was observed across the islands during the night hours.
Very brief showers were observed across the local waters, but
without impact to land areas. A surface high pressure will maintain
the wind flow from the southeast during the weekend, and out of the
east by Monday, at speeds of 14-19 kts, with stronger gusts. In the
flow, a dense Saharan Air Layer will persist, resulting in hazy
skies and reduced visibilities. A trade wind cap inversion will be
present at 850 mb too, with any little available moisture trapped in
the lowest level of the atmosphere. This moisture may result in a
couple of brief and weak showers across eastern Puerto Rico and the
Virgin Islands. Even if conditions are not favorable for strong
convection, an isolated, but strong, storm may develop in the
afternoon along the northwest due to strong diurnal heating.
Temperatures will remain above normal, with an elevated risk of heat
for Puerto Rico and a limited heat risk for the Virgin Islands
today. Everyone should stay hydrated, look for shaded areas and
avoid strenuous activities in the exterior.

Not many changes are expected for Sunday, but by Monday, the higher
concentration of Saharan dust will depart. A weak disturbance will
move into the region, bringing passing showers into the area, and
aiding in the development of showers and thunderstorms across the
interior and west. Although no widespread significant rain is
anticipated, some minor urban and small stream flooding could be
reported. Temperatures will be just a tad lower, but still with a
limited heat risk anticipated for Puerto Rico.

.LONG TERM...Wednesday trough Sunday...

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...

(06Z TAFS) VFR conditions expected to prevail through the forecast
period. HZ due to Saharan dust will persist, but VIS remaining at
P6SM. TSRA expected after 17z for TJBQ, with periods of reduced VIS
and low ceilings. Winds will be from the SE at 14-17 kts, and
stronger gusts.

&&

.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. Variable weather conditions will persist for the rest of
the weekend into the upcoming workweek.

&&

.BEACH FORECAST...

There is a low risk of rip current across all the coastal areas of
Puerto Rico including Culebra and Vieques and St. Thomas.
However, for St. Croix the risk will go up to moderate across the
exposed beaches. For the upcoming workweek the risk of rip
current will become moderate again across the northern coastal
areas of Puerto Rico and extending into the east and southeast on
Tuesday.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon
     for PRZ001>005-007-008-010-011.

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

$$

SHORT TERM & AVIATION...ERG
LONG TERM & MARINE....LIS