National Weather Service Today's Weather Impact Levels

768
FXCA62 TJSJ 180835
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
435 AM AST Sun Jan 18 2026

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

.KEY MESSAGES...
Issued at 413 AM AST Sun Jan 18 2026

* Trade wind passing showers will affect the windward sections
  from time to time, resulting in slippery roads and ponding of
  water in low- lying and poor drainage areas.

* Deteriorated marine and beach conditions resulting in hazardous
  seas and a high risk of rip currents. Small Craft and
  beachgoers are encouraged to exercise caution and follow the
  flag warning system respectively.

* Breezy to windy conditions could lead for unsecured items to be
  blown around, with outdoor objects potentially displaced in the
  most exposed locations.

&&

.Short Term(Today through Tuesday)...
Issued at 413 AM AST Sun Jan 18 2026

Stable weather conditions prevailed across the local islands, with a
few clouds and passing showers affecting some land areas. Shower
activity was quite minimal, resulting in limited rainfall
accumulations. According to satellite imagery, residents and
visitors enjoyed periods of clear skies, including across parts of
western and interior Puerto Rico. Overnight temperatures remained
slightly warmer than seasonal values, with upper 70s across coastal
areas and low to mid 60s across the mountain sections.

For today, low-level conditions remain seasonable, and a broad
surface high pressure over the central Atlantic will continue to
produce a moderate easterly flow of 15 to 20 knots. These surface
conditions, along with some shallow moisture intrusions, will
support brief passing showers, mainly across windward areas due to
the east-southeasterly wind flow. In the mid levels, a mid-level
ridge will persist through the day, keeping moisture near to
slightly below climatological values. The established stable
conditions aloft will maintain warmer temperatures at 500 mb and
drier air, limiting shower development to short-lived activity.
Therefore, residents and visitors can generally expect fair weather
today, with only brief passing showers and no flood threat
associated with afternoon activities. In addition, since strong
showers are not forecast, a lightning threat is not anticipated.

From Monday through Tuesday, low-level moisture increases under
persistent easterly trade winds of 15 to 25 knots, driven by an
induced surface perturbation associated with an upper-level trough
located well east of the region. Although similar mid- to upper-
level conditions persist from the previous day, the forecast calls
for more frequent passing showers, particularly during the morning
hours, and locally enhanced rainfall during the afternoon across
interior and western sections. At the surface, there are some
changes as a broad high-pressure system interacts with a frontal
boundary moving eastward into the Atlantic. As a result, surface
winds will return from the east, drifting showers across the western
interior and portions of the central interior during the afternoon
hours. By Tuesday, weather conditions slightly deteriorate as low-
to mid-level relative humidity increases toward and above the 75th
percentile, driven by an upper-level trough reflected at the surface
and embedded within the 03 km flow. As a result, an increase in
shower frequency is forecast. At this time, Tuesday appears to be
the wettest day of the short-term period, supporting deeper cloud
development and a greater potential for shower activity.

&&

.Long Term(Wednesday through Sunday)...
Issued at 413 AM AST Sun Jan 18 2026

As noted in previous discussions, model guidance continues to
indicate a humid and unsettled pattern throughout the long-term
period across Puerto Rico and the U.S. Virgin Islands. The most
unstable conditions are expected on Thursday, with unsettled weather
persisting through Saturday. Precipitable water values rising
above 1.75 inches after Wednesday reflect above-normal moisture
associated with a deep tropical plume, enhancing overall shower
coverage.

This pattern will support thunderstorms and periods of moderate to
locally heavy rainfall, increasing the potential for localized
flooding, particularly in urban, poor drainage, and low-lying
areas. Repeated showers over the same locations could worsen
runoff issues, while frequent lightning may pose hazards to
outdoor activities. Although east to northeast winds of 17 to 20
mph should help limit widespread flooding, locally enhanced
rainfall will remain possible, especially in terrain-favored
areas.

Temperatures are expected to trend back toward seasonal norms by
Thursday, but persistent high moisture and cloud cover will
maintain humid conditions through the remainder of the period.

&&

.AVIATION...
(06Z TAFS)
Issued at 413 AM AST Sun Jan 18 2026

VFR conditions will prevail across all TAF sites. Winds will remain
VRB to light at up to 10 knots, increasing to around 15 knots after
18/14Z. Some VCSH will continue across the eastern TAF sites;
however, no significant impacts to visibility or ceilings are
expected.

&&

.MARINE...
Issued at 413 AM AST Sun Jan 18 2026

The broad surface high pressure will continue to strengthen over the
central Atlantic during the next few days. Fresh to locally strong
east to northeast winds, and the arrival of a long-period
northwesterly swell will result in choppy to rough seas, leading to
hazardous marine conditions the rest of the weekend.

&&

.BEACH FORECAST...
Issued at 413 AM AST Sun Jan 18 2026

A High Rip Current Statement remains in effect for the north and
east- facing beaches of Puerto Rico, including Culebra, and the
U.S. Virgin Islands through 6 AM AST on Monday. Residents and
visitors are urged to follow the warning flag system and to opt
for beaches with lower risk such as the western and southern
beaches of Puerto Rico.

Besides rip currents, beachgoers should exercise caution due
breezy to windy conditions across the coastal areas of the
islands. Unsecured objects may blown around, with outdoor objects
potentially displaced in the most exposed locations.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for PRZ001-002-005-
     008-012.

VI...High Rip Current Risk through late tonight for VIZ001-002.

AM...Small Craft Advisory until midnight AST Monday night for AMZ711-
     723.

     Small Craft Advisory until 6 PM AST this evening for AMZ712-716-
     726-733-741.

&&

$$

SHORT TERM/AVIATION...LIS
LONG TERM/MARINE/BEACH FORECAST...MMC

NWS SJU Office Area Forecast Discussion