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437
FXCA62 TJSJ 090842
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
442 AM AST Fri Jan 9 2026

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

.KEY MESSAGES...
Issued at 418 AM AST Fri Jan 9 2026

* Showers and localized flooding risk this afternoon: Afternoon
  showers are expected across western Puerto Rico, with brief,
  heavy rainfall that may cause ponding in poorly drained and
  urban areas.

* Pleasant overnight temperatures: Below-normal to seasonably
  cool minimum temperatures are expected across Puerto Rico and
  the US Virgin Islands overnight and early morning.

* Moderate rip current risk: Rip currents are possible along the
  Atlantic-facing beaches of Puerto Rico, Culebra, St Thomas, St
  John, and the north and east-facing beaches in St Croix.
  Hazardous swimming conditions are possible at exposed beaches.

&&

.Short Term(Today through Sunday)...
Issued at 418 AM AST Fri Jan 9 2026

Overnight, Puerto Rico and the U.S. Virgin Islands experienced calm
weather under clear to partly cloudy skies. While passing showers
were observed across the region, most remained over the Atlantic and
Caribbean waters. A few reached portions of St. Croix, resulting in
minimal rainfall accumulation. Overnight lows ranged from the upper
60s to low 70s across lower elevations, while higher elevations in
Puerto Rico observed temperatures in the upper 50s and low 60s.
Winds remained light and variable throughout the night.

A weak surface trough lingering northeast of the region will
continue to bring trade wind showers into the islands. Recent
precipitable water (PWAT) suggests moisture levels remaining near or
slightly below seasonal levels (1.20 to 1.45 inches) through early
next week.

Today, passing trade wind showers will continue to affect windward
sections of the islands. During the afternoon, limited moisture
combined with daytime heating and sea breeze convergence will likely
trigger showers across the interior and western to southwestern
Puerto Rico. This weather pattern is expected to persist through
Saturday.

By Sunday, a mid-to-upper-level ridge will build over the
southwestern Atlantic, while a Tropical Upper Tropospheric Trough
(TUTT) begins to develop over the central Atlantic, northeast of the
Lesser Antilles. Consequently, patches of low-level moisture will
continue to drift over the islands, bringing morning showers and
potential afternoon convection over interior and southwestern Puerto
Rico. As temperatures at the 500 mb level drop to approximately -
10C, isolated thunderstorms cannot be ruled out during the
afternoon hours.

Temperatures at the 925 mb level are expected to remain near
climatological normals. Daytime highs will reach the low to mid-80s
across lower elevations and the mid to upper 70s across the higher
elevations of Puerto Rico.

&&

.Long Term(Monday through Friday)...
Issued at 418 AM AST Fri Jan 9 2026

Looking ahead into early next week, a deep-layer mid-to-upper-
level trough is forecast to amplify over the Atlantic Ocean east
of the northeast Caribbean on Monday. This feature will migrate
further into the Central Atlantic by Tuesday or Wednesday. As it
moves, it will generate surface disturbances that the prevailing
trade winds will advect into Puerto Rico and the US Virgin
Islands, resulting in periods of shower activity. Simultaneously,
a mid-to-upper-level ridge will build over the Northeast
Caribbean. This feature is expected to limit the vertical
development of showers and promote subsidence aloft (sinking air)
due to the presence of a dry air mass.

Model discrepancies exist around Thursday, January 15, regarding
the strength of the ridge versus the influence of a secondary
trough. ECMWF 09/00z suggests a mid-to-upper-level ridge holding
firm over the region, maintaining suppressed convective activity.
GFS 09/00z proposes a mid-to-upper-level trough swinging by the
area, which would displace the ridge and provide more favorable
upper-level dynamics for precipitation. However, the GFS also
indicates an increase in mid-to-upper-level cloud cover, which
may inhibit widespread vertical development despite the favorable
dynamics.

Given the aforementioned weather pattern, residents and visitors
in PR and the USVI can anticipate brief periods of passing
showers, especially in the evening and early morning hours in
windward locations and in the afternoon in leeward locations
(western and interior PR).

&&

.AVIATION...
(06Z TAFS)
Issued at 418 AM AST Fri Jan 9 2026

Mainly VFR conds are expected to prevail across all terminals during
the forecast period. Brief VCSH/SHRA are expected this morning at
TJSJ/TIST/TISX aft 09/13Z-14Z. Locally induced SHRA over central and
southwestern PR, may cause brief tempo MVFR cigs at TJPS btw 09/17Z-
21Z. E-ENE winds btw 08 to 14 kt with sea breeze variations and
higher gusts expected aft 09/13z.

&&

.MARINE...
Issued at 418 AM AST Fri Jan 9 2026

A long-period northeasterly swell continues to spread across the
Atlantic waters and local Caribbean passages, gradually subsiding
today. A surface high pressure over the western Atlantic, along with
weak induced surface troughs northeast of the region, will promote
moderate east to northeast trade winds today through the the rest of
the week.

&&

.BEACH FORECAST...
Issued at 418 AM AST Fri Jan 9 2026

A moderate risk of rip currents is in place along the Atlantic-
facing beaches of Puerto Rico, St. Thomas, and St. John, as well
as the north- and east-facing beaches of St. Croix. Under these
conditions, rip currents are possible, particularly at exposed
beaches, and can pose a hazard to swimmers. Beachgoers are urged
to exercise caution, remain near lifeguarded areas when available,
and avoid entering the water if conditions appear unsafe.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...GRS
KEY MESSAGES/LONG TERM/MARINE/BEACH FORECAST....CAM

NWS SJU Office Area Forecast Discussion