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107
FXCA62 TJSJ 200907
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
507 AM AST Tue Jan 20 2026

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

.KEY MESSAGES...
Issued at 507 AM AST Tue Jan 20 2026

 * Several small craft advisories remain in effect at least until
   Thursday night, mostly due to an increase in the surface winds.

 * Hazardous coastal conditions persist today, with a high risk of
   rip currents across all north-exposed beaches in Puerto Rico,
   including Culebra, Vieques, and the U.S. Virgin Islands.

 * Variable weather conditions will persist today, with periods of
   sun and passing showers across eastern sections of Puerto Rico
   and the U.S. Virgin Islands.

 * A surface disturbance moving westward across the area from
   Wednesday into Friday will result in deteriorating weather conditions,
   increasing the potential for showers and isolated
   thunderstorms.

&&

.Short Term(Today through Thursday)...
Issued at 507 AM AST Tue Jan 20 2026

Variable to showery weather persists over the waters and windward
areas as breezy easterly winds continue to steer showers into the
region. Since midnight, radar estimated rainfall accumulations
indicate that at least minimal accumulations fell over northern PR
(up to 0.20 in), eastern (up to 0.60 in) PR, Vieques (up to 0.42
in), St. Thomas (0.01 in), St. John (0.01 in) and St. Croix (0.01
in). Similar to yesterday, stations over interior PR reported
minimum temperatures in the low to mid 60s. Stations over western
and eastern PR have reported lows in the upper 60s while other
lower elevation and coastal stations over the islands reported
minimum temperatures in the 70s. Patchy fog was also detected over
some areas of PR.

A surface high over the central to eastern Atlantic, interacting
with a frontal boundary over the western Atlantic, will promote
breezy to windy easterly flow for most of the period, with more ENE
winds by Wednesday and ENE to ESE winds on Thursday. 925 mb winds
are expected to remain above normal through at least Wednesday,
supporting windy and gusty surface flow. Wednesday is forecast to be
the windiest day, with sustained winds in the low to mid 20s
possible with higher gusts and sea breeze variations, particularly
over windward coastal areas of the islands. Unsecured outdoor items
could blow around or be damaged. As a surface trough veers and backs
surface flow on Thursday, conditions should be more breezy with 925
mb wind speeds at high end normal values. Unsecured items could
still blow around.

Current satellite derived precipitable water (PWAT) values indicate
a plume with high end normal values (around 1.45 in) moving over the
region. With ridging over the area already eroding, instability
aloft will gradually increase during the period, evidenced by cooler
500 mb temperatures and steeper lapse rates. The frequency of
showers will also gradually increase as an upper-level trough (TUTT)
is east of the region. Current model guidance indicates PWAT
possibly at around 1.7 in over western Puerto Rico this afternoon
due to convective showers and then more seasonal PWAT values on
Wednesday, with Wednesday afternoon convection over W-SW PR under
the more ENE winds. The fast moving nature of these showers will
serve to limit rainfall accumulations, these showers can still
promote localized ponding of water over roadways, urban, and poorly
drained areas. PWAT values however sharply increase to above normal
values late Wednesday and Thursday with model guidance suggesting up
to 1.9 inches as a surface trough/disturbance moves over the region,
with available moisture reaching the mid levels resulting in above
normal 850 to 500 mb relative humidity. This will all further
increase shower frequency, aid in afternoon convective formation and
sustain a limited flooding risk. Isolated t-storms are possible late
Wednesday to Thursday, particularly over the waters during the
overnight to morning hours and with stronger afternoon convection
over interior to western PR. 925 mb temperatures will be normal to
slightly above normal values for this time of the year.

&&

.Long Term(Friday through Tuesday)...
Issued at 507 AM AST Tue Jan 20 2026

Some changes were introduced to the long-term forecast. For
Friday, surface conditions will remain unsettled as a surface
disturbance moves across the area, inducing instability and plenty
of moisture. Therefore, the forecast calls for a pattern with an
increase in the frequency of isolated to scattered showers,
especially in the morning and evening hours across eastern
sections of Puerto Rico, followed by afternoon showers along the
western interior. Model guidance suggests precipitable water
values fluctuating between 1.6 and 1.9 inches, slightly above
climatological normals. When combined with colder temperatures at
500 mb, these conditions may support the development of one or two
isolated thunderstorms with the strongest shower activity.
Although showers might result in some hazardous conditions, no
rainfall threat is forecast due to the breezy conditions resulting
in fast-moving showers across the area. Some moisture will remain
across the area from early Saturday and spread during the day;
therefore, in contrast to yesterday, Saturday looks more showery
with isolated to scattered showers.

Weather conditions will improve by late Saturday into Sunday as
the disturbance moves out of the region and a drier air mass
filters into the local islands. At the surface, a broad high-
pressure system extending across the Atlantic basin will promote
mostly easterly winds across the area. At the mid to upper levels,
subsidence will inhibit widespread shower development; however,
local effects may still support brief isolated to moderate
showers, with no flooding threat expected each day. On late Monday
into Tuesday, surface conditions will change as winds begin to
veer in response to a pre-frontal trough moving southward near
northern Hispaniola. Winds will turn more northeasterly, resulting
in a more advective pattern and slightly cooler temperatures,
particularly during the morning and nighttime hours.

&&

.AVIATION...
(06Z TAFS)
Issued at 507 AM AST Tue Jan 20 2026

Mainly VFR conditions will prevail. Winds at the terminals will
continue to 12 knots with higher gusts through 20/13Z. After 20/13Z
E winds at up to 15 to 20 knots with gusts up to around 23 to 30
kts, as well as sea breeze variations and local effects. Winds
decreasing to up to around 13 kts with higher gusts after 20/23Z.
SHRA/VCSH will continue at the terminals, briefly reducing VIS and
CIGS.

&&

.MARINE...
Issued at 507 AM AST Tue Jan 20 2026

A broad surface high pressure extending from the Central Atlantic
into the Caribbean will continue to maintain a tight pressure
gradient, producing moderate to locally fresh east winds.
Therefore, wind-driven seas are forecast for the rest of the
workweek, resulting in choppy to hazardous marine conditions for
small craft operators. Therefore, several Small Craft Advisories
remain in effect for most of the local exposed and offshore waters
for the Atlantic and Caribbean, including the local passages.
Improving marine conditions are forecast for the upcoming weekend.
Mariners should exercise caution, particularly across the Atlantic
waters and passages.

&&

.BEACH FORECAST...
Issued at 507 AM AST Tue Jan 20 2026

A high risk of rip currents remains in effect across the
northern, exposed coastal areas of Puerto Rico, including Culebra,
Vieques, and the U.S. Virgin Islands, due to hazardous conditions
with breaking waves up to 7 feet. On Wednesday and into the rest
of the week, coastal conditions might improve in some areas;
however, an increase in surface winds from the east will induce
choppy seas, resulting in localized hazards. Residents and
visitors are urged to continue following the warning flag system
and to favor beaches with lower rip current risk, such as those
along Puerto Rico`s western and southern coasts.

For the western and southern coastal areas, where the risk
remains moderate, beachgoers can expect breezy to locally windy
conditions to continue, which may still result in unsecured
objects being blown around, particularly in the most exposed
locations. Beachgoers should remain cautious both in and near the
water until conditions improve further. For localized, up-to-date
risk levels, visit weather.gov/beach/sju.

&&

.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 Wednesday night for
     AMZ711-712-716-723-726-733.

     Small Craft Advisory from 6 PM this evening to midnight AST
     Wednesday night for AMZ741.

&&

$$

SHORT TERM & AVIATION...MRR
LONG TERM, MARINE, BEACH FORECAST & KEY MESSAGES....LIS

NWS SJU Office Area Forecast Discussion