845
FXCA62 TJSJ 050708
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
308 AM AST Sun Oct 5 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.

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

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

&&

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

The most recent satellite derived precipitable water imagery shows
that moisture has rise into the islands, with values closer to 1.9
inches over the Virgin Islands and the local waters. This moisture
is mostly focused near the surface and in the upper levels, but the
mid levels remains drier than normal. The moisture in the upper
levels is due to an upper level low centered just west of Puerto
Rico. The low induced some showers and thunderstorms near St. Thomas
and St. Croix, but rainfall accumulations were not too significant.

For today, a long wave trough well north of the region maintain the
trade winds very week, out of the east-southeast, and below 8 knots.
The upper level low will increase instability aloft a little, and
will allow for a modest increase in moisture in the mid-levels. As a
result, another active afternoon is anticipated for the interior and
western Puerto Rico, with some showers and thunderstorms also
reaching portions of the San Juan metro area. These rains will
increase the risk of urban and small stream flooding, as well as
lightning strikes in the vicinity of the thunderstorms. The Virgin
Islands and eastern Puerto Rico will also observe passing showers
and thunderstorms. Even though flooding is not anticipated here,
ponding of water and wet roads can be expected, as well as
occasional lightning strikes.

For Monday and Tuesday, the islands will remain under the influence
of the upper level low. Winds will remain very light, out of the
northeast on Monday and out of the southeast on Tuesday. Moisture
will also increase as a tropical wave approaches the region. Again,
the pattern will favor increasing showers over portions of the
Virgin Islands and eastern Puerto Rico throughout the day, but the
strongest activity will be focused for the interior and western
Puerto Rico. Some of these storms will also stream from El Yunque
toward the San Juan metro area. The risk of flooding will remain on
the medium side, meaning that it should be mostly urban and small
stream flooding, although isolated flash flooding cannot be ruled
out.

Temperatures will be on the increase too. Urban and coastal areas,
as well as valleys in the mountain will experience heat indices
above 102 degrees, and locally reaching levels where those sensitive
to heat and without adequate cooling or hydration may be affected.


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

An upper-level low northeast of the region will begin to move away
from the area by Wednesday. Subsequently, a mid-to-upper level ridge
will take place across the area, promoting drier air intrusion and
stable conditions aloft from Wednesday into Thursday. The latest
precipitable water (PWAT) analysis indicates normal climatological
values throughout much of the period. Additionally, the 500mb
temperatures will also remain within normal values (between 6 to 7
 degrees Celsius) during the period.

By Thursday, moisture will slightly increase with the arrival of an
atmospheric disturbance, promoting showers and isolated
thunderstorms across the area. Under this moist pattern and with
southeasterly winds, the shower activity will be expected toward the
central and northwestern municipalities of Puerto Rico. For the U.S.
Virgin Islands, showery weather is anticipated each morning across
the islands. Winds will prevail mostly from the southeast in
response to a surface high pressure in the central Atlantic.
However, by the end of the period, the steering winds will depend on
the potential development of a tropical wave near the islands.

The second half of the forecast will depend on the development of a
broad tropical wave located south of the Cabo Verde Islands. The
National Hurricane Center (NHC) is monitoring the aforementioned
wave with a low formation chance (30%) in the next 48 hours, and a
medium formation chance (60%) in the next 7 days. The latest model
guidance continues to suggest an increase in moisture content
associated with this system from Friday onwards. At this time, there
is high uncertainty in terms of the trajectory and intensity of this
wave. Residents and visitors are urged to continue monitoring the
progress of this system as it moves over the Atlantic Ocean.

&&

.AVIATION...
(06Z TAF)

Mainly VFR conditions are expected to prevail through the forecast
period. SHRA and TSRA are expected to reach the USVI and TJSJ
terminals through the day, with brief periods of reduced VIS and low
ceilings. After 17Z, widespread SHRA and TSRA are anticipated for
the Cordillera Central and western PR. Impacts are expected to be
more significant for the TJBQ terminal, until around 22Z. Winds will
be from the ESE below at 6-11 kts.

&&

.MARINE...

A col near the region will promote a light to gentle variable wind
flow across the islands today. A long-period north to northwesterly
swell will spread across the local Atlantic waters and passages
through early next week, deteriorating marine and coastal conditions
through the upcoming workweek. 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 Warning and High Surf Warning continues in
effect due to the latest buoy observations with the combination
of the next expected high tides. The Coastal Flood Warning will be
in effect at least until 6 PM AST Sunday for the northern and
eastern coast of Puerto Rico, and the High Surf Warning until 6 PM
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 7:03 AM AST (1.5 ft);
Arecibo at 6:38 AM AST (1.7 ft), and Crash Boat, Aguadilla at 6:30
AM AST (1.5 ft).

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Coastal Flood Warning until 6 PM AST this evening for Prz005-002-
005-008.

 High Rip Current Risk through Tuesday afternoon for Prz005-002-
005-008-010-012-013.

 High Surf Warning until 6 AM AST Monday for Prz005-002-005-008.

 High Surf Advisory until 6 AM AST Tuesday for Pros-012.

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

     High Surf Advisory until 6 AM AST Tuesday for VIZ001.

     High Surf Advisory from 6 PM this evening to 6 AM AST Tuesday
     for VIZ002.

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

&&

$$

ERG/GRS