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926
FXCA62 TJSJ 251817
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
217 PM AST Sun Oct 25 2026

...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST...

.KEY MESSAGES...
Issued at 155 PM AST Sun Oct 25 2026

- A Heat Advisory remains in effect until 5 PM AST this afternoon
  for Puerto Rico and the U.S. Virgin Islands. Hot and humid
  conditions will increase the risk of heat-related illnesses,
  especially across urban and low-lying areas or with prolonged
  outdoor activity.

- Life-threatening rip currents will impact exposed northern,
  northwestern, and eastern beaches of Puerto Rico and Culebra,
  where a High Rip Current Risk remains in effect through Tuesday
  afternoon. A moderate rip current risk persists for Vieques and
  the U.S. Virgin Islands.

- Relatively drier conditions will persist across Puerto Rico and
  the U.S. Virgin Islands over the next few days. However,
  pockets of low- level moisture will produce passing showers,
  primarily over southern and southeastern Puerto Rico during the
  afternoon and overnight hours.

&&

.Short Term(This evening through Tuesday)...
Issued at 155 PM AST Sun Oct 25 2026

The morning was tranquil across Puerto Rico and the U.S. Virgin
Islands, with little to no rainfall reported. Satellite imagery
showed mostly clear to partly cloudy skies across the region, with
high clouds streaming from west to east. The 12Z TJSJ sounding
indicated a precipitable water (PWAT) value of 1.72 inches, lower
than yesterday, with mean low-level winds from the southeast at 10
to 13 kt. Plenty of drier air was observed between 850 and 200 mb,
limiting shower activity. The main hazard today has been the heat.
Under southeasterly flow, maximum temperatures reached the upper 80s
to lower 90s across the lowlands, urban areas, and coastal sections
of Puerto Rico and the U.S. Virgin Islands, with elevated heat
indices mainly across coastal and urban areas. A Heat Advisory
remains in effect until 5 PM AST for all of Puerto Rico and the U.S.
Virgin Islands. Residents and visitors are advised to stay hydrated
and avoid prolonged exposure to the sun. Additionally, continue to
monitor forecasts and alerts, as additional heat-related products
may be issued over the coming days. Temperatures at 925 mb are
expected to remain above normal, combined with sufficient moisture
at the surface and southeasterly wind flow.

The overall pattern remains on track, with a mid to upper-level
trough over the western Caribbean and a ridge aloft over the eastern
Caribbean, along with southeasterly surface flow. Based on the
latest model guidance, the remainder of the afternoon will feature
warm to hot conditions and a few shallow passing showers driven by
local effects across northwestern Puerto Rico. No significant
flooding concerns are expected, as any showers should move quickly.
From tonight into Monday, guidance suggests that an area of
increased moisture, with PWAT values near 2 inches, will move into
the Caribbean waters and could bring periods of persistent passing
showers. The highest chance of observing this activity will be
across southeastern and southern Puerto Rico during the overnight
hours, where ponding of water on roads and in poorly drained areas
will be possible.

Both GFS and ECMWF guidance indicate decreasing moisture levels and
warming temperatures aloft. Despite these trends, moisture in the
low levels may support passing showers and isolated afternoon
thunderstorms. Forecast confidence decreases on Tuesday, as the GFS
indicates a return to PWAT values near 2.0 inches, while the ECMWF
maintains a drier environment, with values decreasing into the 25th
percentile. Continue to monitor the forecast as adjustments and
updates become available.

&&

.Long Term(Wednesday through next Saturday)...
Issued at 421 AM AST Sun Oct 25 2026

Fair weather conditions should continue over the second part of
the workweek, becoming wetter and unstable by the weekend. A
surface high pressure over the central Atlantic should continue to
maintain a SE-S wind flow through most of the forecast period.
However, the steering flow should remain weak as the surface high
interacts with a deep-layered trough deepening into the tropics,
weakening the local pressure gradient.

Aloft, global model solutions continue to suggest a ridge in the
central Atlantic interacting with the trough, though the ridge
should continue to dominate the weather pattern on Wednesday and
Thursday. During this period, guidance suggests a drop in moisture
content across the CWA, with PWAT values below climatological
normal (below 1.75 inches), as a dry slot filter in the low and
mid levels. Additionally, the vicinity of the ridge will likely
maintain warmer-than-normal mid level temperatures (above 6 C),
leading to subsidence and stability aloft.

According to the latest CFS forecast, the CWA may be under a
suppressing area, disfavoring deep convection. Although daytime
heating and local effects will drive the afternoon convection,
showers and isolated thunderstorms over the mountain ranges of
Puerto Rico may not produce significant rainfall, lowering the
flood chance. Friday onwards, the weather conditions may become
wetter and unstable as the deep- layered trough and a TUTT
approaches the local area, cooling mid level temperatures (between
-6 and -8 C), with steeper mid-level lapse rates, increasing
instability aloft. Additionally, CFS forecasts the MJO across the
local area, enhancing upward motion and favoring deeper
convection. Additionally, PWAT values should reach above-normal
values (up to 2.25 inches), reflected in both low and mid levels,
reflected in the latest deterministic guidance of the GFS and
ECMWF.

Additional to afternoon convection across Puerto Rico, showers
and isolated thunderstorms may move across windward sections of
Puerto Rico and the U.S. Virgin Islands during the night and
morning hours, followed by afternoon convection across the
mountain ranges of Puerto Rico. Due to low steering winds, showers
and thunderstorms may linger longer than usual, increasing
rainfall accumulations over the aforementioned areas. Therefore,
the flood threat will remain elevated on Friday and Saturday, with
mainly urban and small stream flooding, along with rapid river
rises. Thunderstorms may produce gusty winds and frequent
lightning.

&&

.AVIATION...
(18Z TAFS)
Issued at 155 PM AST Sun Oct 25 2026

Mainly VFR conditions thru the forecast period.  Afternoon shallow
convection may produce brief MVFR conditions and mountain obs across
TJBQ. Additional VCSH & SHRA will affect southern and eastern
terminals tonight into early Monday. SE winds around 10 to 15 kt
will prevail, with sea breeze variations and gusts up to 20 kt,
becoming 10 kt or less overnight.

&&

.MARINE...
Issued at 155 PM AST Sun Oct 25 2026

Surface high pressure across the central Atlantic will maintain
moderate to locally fresh southeasterly winds across the region
through at least Tuesday. Choppy seas will persist across the
Atlantic waters and the Mona Passage through the next few days. A
long-period northerly swell will spread across the Atlantic
waters and local passages by Monday, building seas up to around 7
feet and maintaining hazardous marine conditions through at least
Tuesday.

&&

.BEACH FORECAST...
Issued at 155 PM AST Sun Oct 25 2026

A combination of a subsiding northerly swell and additional
long-period northerly swell pulses will generate life-threatening
rip currents along north-facing beaches of Puerto Rico and
Culebra through mid-week. Consequently, a High Rip Current Risk
remains in effect for the northern, western, and eastern beaches
of Puerto Rico and Culebra through at least Tuesday night.
Beachgoers are strongly urged to stay out of the water in these
areas. Always heed posted alerts, flags, and instructions from
lifeguards and local officials.

&&

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

     Heat Advisory until 5 PM AST this afternoon for PRZ001>013.

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

AM...None.
&&

$$

SHORT TERM/AVIATION...YZR
LONG TERM...MNG
MARINE/BEACH FORECAST...GRS

NWS SJU Office Area Forecast Discussion