520
FXCA62 TJSJ 241844
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
244 PM AST Sun Aug 24 2025

.KEY MESSAGES...

* Northerly swells and increasing winds across the Caribbean
  waters will promote choppy to hazardous seas, rough surf
  conditions, and life-threatening rip currents through early in
  the week.

* Hazy conditions and hot temperatures will continue through at
  least Tuesday across all islands.

* For the U.S. Virgin Islands, breezy conditions and increasing
  passing showers with isolated thunderstorms are expected on
  Monday as Invest AL99 moves south of the area.


&&

.SHORT TERM...Rest of today through Tuesday...

Mostly sunny skies and hazy conditions prevailed across the
islands today. However, during the early afternoon hours, an
isolated thunderstorm developed over Maricao and vicinity, leaving
mostly minor accumulations as of 2 PM AST. Another hot day was
observed across most areas with maximum temperatures ranging from
the upper 80s to low 90s across the lower elevations of the
islands with heat indices ranging between 109F-114F along most
southern and northern coastal sections of PR, and from 105F-110F
across the USVI. The wind was from the east between 14 to 18 mph
with sea breeze variations and higher gusts at times.

For the rest of this afternoon, shower and thunderstorm activity
will continue over western PR, while hazy conditions prevail
across the rest of the area with little to no rainfall expected.
The Saharan Air Layer will peak tonight into early Monday morning,
and diminishing by late Monday/early Tuesday. Therefore, hot
conditions are expected on Monday/Tuesday across all islands, and
heat products will likely be issued once again. Diurnally induced
thunderstorms are expected to develop once again over western PR
on each afternoon. Meanwhile, on Monday, Invest AL99 is expected
to move mainly south of the region, increasing winds and scattered
showers with isolated thunderstorms across portions of the
Caribbean waters and passages. Some of this activity will move
briefly over portions of St. Croix, and over portions of SE PR.


.LONG TERM...Wednesday through Sunday...

/FROM PREV DISC ISSUED AT 457 AM AST Sun Aug 24 2025/

A seasonal weather pattern is expected in the long-term forecast.
Low-level moisture content will fluctuate from below-normal to near-
normal levels, as patches of moisture embedded in the trades stream
across from time to time. Dynamics aloft will remain marginal for
the most part, with weak ridging alternating with periods of
troughiness throughout the forecast period. As a result, 500 mb
temperatures will remain near climatological normals, while 700500
mb lapse rates could be slightly steeper toward the end of the
period.

At the surface, a high-pressure system over the central Atlantic
will promote easterly winds during the first part of the long-term
period, gradually shifting east-southeasterly toward the weekend.
This overall setup will maintain a seasonal weather pattern, with
occasional passing showers moving across windward coastal areas
during the night and morning hours. In the afternoons, showers and
thunderstorms are expected to develop over interior and
western/northwestern Puerto Rico as sufficient instability and low-
level moisture combine with diurnal heating and orographic lift.
Meanwhile, the southern coastal hills of Puerto Rico will likely
observe limited shower activity. In contrast, interior and
western/northwestern Puerto Rico may experience localized to
elevated flooding threats each afternoon, mainly resulting in urban
and small stream flooding, particularly in flood-prone areas.

In addition, the southeasterly winds will promote warm air advection
across the region. Model guidance suggests 925 mb temperatures and
1000850 mb thickness values will remain well above normal through
the weekend. This pattern will support hot surface temperatures, and
when combined with sufficient low-level moisture, could result in
sweltering heat indices and an elevated heat threat for the period.
As a result, the issuance of Extreme Heat Warnings or Heat
Advisories cannot be ruled out. Residents and visitors are advised
to stay hydrated, avoid prolonged exposure to the sun during peak
hours, take frequent breaks if working outdoors, and check on
vulnerable populations such as the elderly, children, and those with
chronic health conditions.


&&

.AVIATION...

(18z TAFs)

Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, brief MVFR cigs are
possible at TJBQ thru 24/22z, and VCTS expected at TISX by Monday
morning. HZ due to Saharan dust will peak overnight across the
local area and VSBY may drop to around 6SM. East winds will
continue at 12-16 kt with stronger gusts and sea breeze variations
thru 24/22z, bcmg 8-12 kt overnight, and increasing 15-20 kt aft
25/13z.


&&

.MARINE...

A long period northerly swell will continue to spread across the
islands through early this week, resulting in hazardous seas for the
Atlantic waters and local passages. Another tropical wave will move
into the Caribbean by late tonight, moving mainly to the south of the
USVI and PR through Tuesday. This will result in moderate to fresh
easterly winds and choppy to rough seas, particularly across the
Caribbean waters. Small Craft Advisories are in effect for all
waters, except the southern and southwestern coastal waters of PR.
Seas are expected to build up to 8 feet across the Atlantic waters
and passages later tonight through Tuesday, and fresh to strong
winds between 20 and 25 kt with gusts up to 35 kt are expected
across the offshore Caribbean waters on Monday.


&&

.BEACH FORECAST...

Seas will continue to build between 6 and 8 feet across portions
of the Atlantic waters and Caribbean Passages tonight. Offshore
buoy 41043 indicated the swell peaking at 9 feet and 13 seconds
early this morning, and the Rincon and San Juan buoys were at 5
feet and 14 seconds. Swell decay from the offshore buoy suggest
that seas could build up to 8 feet across the nearshore waters by
late this afternoon. Therefore, the High Surf Advisory was
extended through at least Monday, and the Small Craft Advisory
(SCA) for the eastern and coastal waters of PR and the USVI is now
in effect. Also, the offshore Caribbean waters (AMZ733) were
added to the SCA, starting on Monday morning as seas and winds are
expected to reach SCA criteria due to the passage of Invest AL99
over the Caribbean Sea, well south of the local area. SCA
conditions are now expected to continue through at least Tuesday.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Tuesday afternoon for PRZ001-002-
     005-008-010-012-013.

     High Surf Advisory until 6 PM AST Monday for PRZ001-002-005-008-
     010-012.

     Extreme Heat Warning until 5 PM AST this afternoon for
     PRZ001>005-007-008-010-011.

     Heat Advisory until 5 PM AST this afternoon for PRZ012-013.

VI...High Rip Current Risk through Tuesday afternoon for VIZ001-002.

     High Surf Advisory until 6 PM AST Monday for VIZ001.

     Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...Small Craft Advisory until 6 PM AST Tuesday for AMZ711-712-716-
     723-741-742.

     Small Craft Advisory from 6 PM this evening to 6 PM AST Tuesday
     for AMZ726.

     Small Craft Advisory from 6 AM Monday to 6 PM AST Tuesday for
     AMZ733.

&&

$$

SHORT TERM...DSR
LONG TERM....CVB
AVIATION...DSR