887
FXCA62 TJSJ 050209 CCA
AFDSJU

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
1009 PM AST Sat Oct 4 2025

.UPDATE...

Recent buoy data continue to show strong wave activity across the
local waters. The San Juan buoy reports a wave height of 9 feet
with a 13-second period, resulting in breaking waves between 12
and 14 feet. Therefore, a Coastal Flood Warning remains in effect
along the northern coast of Puerto Rico. The Atlantic buoy
(41043) continues to show energy of 9 feet at 13 seconds, which is
expected to keep reaching the northern coastal areas; as a
result, the advisory remains in effect until 12 PM AST and may be
extended if conditions persist. For the western coastal zone of
Puerto Rico, Culebra, and St. Thomas, a High Surf Advisory remains
in effect until 6 AM Monday.

In terms of weather conditions, a more variable day is expected
with increased moisture across the region and a cut-off low
pressure system at upper levels, resulting in enhanced instability
over the island.

&&

.PREV DISCUSSION... /issued 250 PM AST Sat Oct 4 2025/

KEY MESSAGES...

* A strong, long-period northerly swell will continue to produce
  hazardous beach and marine conditions through at least early
  next week. A Coastal Flood Warning, High Surf Warning, Rip
  Current Statements, and Small Craft Advisories remain in effect.

* Showers and thunderstorms this afternoon will enhance the
  flooding and lightning threat across from el Yunque to the
  metropolitan area and from the interior to western sectors of
  Puerto Rico. If thunder roars, stay indoors.

* Across the U.S. Virgin Islands, brief passing showers and a few
  thunderstorms throughout the period.

SHORT TERM...Tonight through Monday...

The day began calm, clear, and pleasant across most of the area,
with isolated to locally scattered showers occasionally affecting
eastern Puerto Rico, the U.S. Virgin Islands, and the local islands.
As this activity dissipated, nearly stationary showers developed
downstream from the U.S. Virgin Islands by late morning and later
over the southern hills of Puerto Rico and downstream from the
Sierra de Luquillo during the early afternoon. Radar estimates
indicate rainfall totals peaking near 1.0 to 1.5 inches over
portions of Salinas and close to 2 inches across western St. Thomas,
though no flooding has been reported. Afternoon highs reached the
low to mid-90s across coastal and urban areas, while heat indices
rose into the mid to upper 100s in isolated locations of western and
northern Puerto Rico. Winds remained generally light and variable,
occasionally peaking near 10 to 15 mph along a few coastal spots,
with conditions primarily driven by sea breeze circulations during
the afternoon pea

A weak upper-level trough will continue meandering just to the west-
southwest of the islands, while a mid-level ridge to the north
gradually weakens. This setup, combined with near-normal
precipitable water values around 1.8 inches and cooler mid-level
temperatures near -7C, will favor lingering scattered evening
showers and thunderstorms. Some of this activity may persist through
the early evening hours before gradually tapering off overnight.
Gentle east to east-southeast winds of 812 mph during the day will
give way to light to calm and variable winds overnight, maintaining
warm and humid conditions. Brief passing showers and a few isolated
thunderstorms are still possible across eastern Puerto Rico, the
U.S. Virgin Islands, and nearby waters. Widespread hazards are not
expected, but occasional gusts, localized rainfall totals exceeding
half an inch, and very isolated ponding of water remain possible.

On Sunday, deeper moisture will lift into the region, raising
precipitable water values above normal and supporting more frequent
afternoon showers and thunderstorms, with the most active areas
expected across the north and northwest quadrants of Puerto Rico. By
Monday, an approaching tropical wave crossing the eastern Caribbean
will add further moisture and instability, with its axis forecast to
reach the local area late Monday night. This will favor increased
showers and thunderstorms, shifting the focus toward the interior
and south-southwest due to stronger east-northeast winds. Main
concerns both days will include localized ponding on roadways,
isolated small-stream flooding, and frequent lightning, along with
elevated heat stress during the late morning and early afternoon
hours. While heat stress may ease slightly with the wind shift on
Monday, warm and muggy nights will persist, with passing showers and
a few isolated thunderstorms favoring eastern Puerto Rico and the
U.S. Virgin Islands.

LONG TERM...Tuesday through Saturday...
PREV DISCUSSION... /issued 306 AM AST Sat Oct 4 2025/

The forecast period starts with a wet and unstable pattern due to
the influence of an upper-level low over the region. By Tuesday, the
convergence of this low with an approaching weak tropical wave is
expected to enhance the potential of convective activity,
specifically showers and thunderstorms, across the U.S. Virgin
Islands and Puerto Rico. High atmospheric moisture will sustain the
showers and thunderstorm activity through Tuesday evening, with
PWAT content near-to-above-normal (2.00 to 2.25 inches). A
noticeable change is anticipated for Wednesday, as a depRecent
buoy data continue to show strong wave activity across the local
waters. The San Juan buoy reports a wave height of 9 feet with a
13-second period, resulting in breaking waves between 12 and 14
feet. Therefore, a Coastal Flood Advisory remains in effect along
the northern coast of Puerto Rico. The Atlantic buoy (41043)
continues to show energy of 9 feet at 13 seconds, which is
expected to keep reaching the northern coastal areas; as a result,
the advisory remains in effect until 12 PM AST and may be extended
if conditions persist. For the western coastal zone of Puerto
Rico, Culebra, and St. Thomas, a High Surf Advisory remains in
effect until 6 AM Monday. In terms of weather conditions, a more
variable day is expected with increased moisture across the region
and a cut-off low pressure system at upper levels, resulting in
enhanced instability over the island.arting upper-level low
allows drier air to move in, causing PWAT values to fall to the
1.50 to 1.75 inch range. Looking ahead to Thursday, local
conditions will become dependent on the evolution of a tropical
wave currently near the coast of Africa.

Regarding the potential system, the National Hurricane Center (NHC)
has given this wave a medium formation chance (50%) over the next 7
days. Although the latest model guidance indicate increasing
moisture by the weekend, the system`s eventual trajectory and
intensity remain highly uncertain. All residents and visitors must
continue to track the progress of this system as it moves westwards
over the Atlantic Ocean.

AVIATION...
(18Z TAFs)

Mainly VFR conditions are expected to prevail. However, SHRA/TSRA
development will continue through 04/23Z, resulting in mountain
obscuration and occasional brief MVFR conditions at all PR
terminals, with periods of reduced visibility and low ceilings.
Across the USVI, SHRA activity will remain mostly in the vicinity
during the period, with little to no operational impact. Winds will
remain gentle to moderate from the east-southeast at 814 knots,
with sea-breeze variations, becoming light to calm after 04/23Z,
except for gusty and variable conditions near SHRA/TSRA.

MARINE...

A col near the region will promote a light to gentle variable wind
flow across the islands for the next few days. A long-period north
to northwesterly swell across the local Atlantic waters and passages
will continue to create hazardous marine conditions through early
next week. Small Craft Advisories remain in effect through at
least 6 PM AST Monday. Inexperienced mariners, especially those
operating smaller vessels, should avoid navigating in hazardous
conditions. Additionally, a tropical wave will approach the region
by Monday, increasing the frequency of showers.

BEACH FORECAST...

A strong, long-period northerly swell will continue to produce
hazardous beach conditions through at least Monday night along the
Atlantic exposed beaches, including from western to northeastern
Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands. As a
result, the high risk of life-threatening rip currents continues
in the aforementioned areas.

The Coastal Flood Advisory and High Surf Advisory were both
upgraded to Warnings due to recent buoy observations with the
combination of the next expected high tides. The Coastal Flood
Warning will be in effect at least until 6 AM AST Sunday for the
northern and eastern coast of Puerto Rico, and the High Surf
Warning until 6 AM AST Monday, for the same areas and also
including Culebra and St. Thomas. Potential impacts include: Large
breaking waves up to 14 to 18 feet and occasionally higher in
some isolated areas. Widespread coastal flooding, highest risk at
high tide. Additionally, significant beach erosion, dangerous
surf, and life-threatening rip currents. Please refer to our
Coastal Hazard Message (CFWSJU) for additional details. Residents
and visitors are urged to monitor the beach forecast and follow
the beach flag warning system. Beachgoers, do not risk your life,
it`s better to stay out of the water throughout the weekend!

[Next high tides: La Puntilla, San Juan at 6:52 PM AST (1.68 ft),
Arecibo at 6:19 PM AST (1.81 ft), Crash Boat, Aguadilla at 6:11 PM
AST (1.61 ft)]

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Coastal Flood Warning until noon AST Sunday for PRZ001-002-005-
     008.

     High Rip Current Risk through Tuesday afternoon for PRZ001-002-
     005-008-010-012-013.

     High Surf Warning until 6 AM AST Monday for PRZ001-002-005-008.

     High Surf Advisory until 6 AM AST Monday for PRZ010-012.

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

     High Surf Advisory until 6 AM AST Monday for VIZ001.

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

     Small Craft Advisory until midnight AST tonight for AMZ745.

&&

$$

LIS/RVT