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521
FXCA62 TJSJ 270533
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
133 AM AST Fri Mar 27 2026

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

.KEY MESSAGES...
Issued at 129 AM AST Fri Mar 27 2026

* An unsettled and wet weather pattern driven by a trough will
  continue across the region, with the most active period expected
  today and tonight. Scattered to numerous showers and thunderstorms
  are likely, especially during the afternoon and evening hours.

* This may lead to urban and small stream flooding, along with quick
  river rises and streams in areas receiving repeated rainfall.
  Landslides and rockfall are also possible with this setup. Some
  thunderstorms may reach near-severe strength, producing frequent
  lightning, gusty winds, and pea-sized hail.

* For the U.S. Virgin Islands, passing showers and isolated
  thunderstorms may result in ponding of water on roads and in low-
  lying areas.

* Marine and coastal conditions are expected to deteriorate early
  next week as a northerly swell arrives. This will likely result in
  Small Craft Advisories and Rip Current Statements, with hazardous
  breaking waves and dangerous surf conditions possible. High Surf
  Advisories cannot be ruled out.

&&

.Short Term(Today through Sunday)...
Issued at 129 AM AST Fri Mar 27 2026

Early in the night, the most active portion of the trough was
located north of Puerto Rico, accompanied by a line of strong
thunderstorms. These thunderstorms were evident in GOES-19 infrared
imagery and the Geostationary Lightning Mapper (GLM) data. Most of
the activity remained over Atlantic waters, although some brushed
the northern narrow strip of Puerto Rico. Expect this pattern to
persist for the rest of the night into the morning hours.

As previously discussed, a wet and unsettled weather pattern is
expected today though at least Saturday, with today and tonight
being the most active period as the trough deepens into a cutoff low
at upper levels. The most active portion of the trough is still
expected to remain to the north. However, the subtropical jet will
intensify into a 90-100-knot jet streak near or over the forecast
area, enhancing divergence and ventilation aloft. Cold air advection
at mid-levels will result in 500 mb temperatures dropping to
between -8 to -10 Celsius, prompting steeper lapse rates across
the area.

These favorable dynamics will combine with well above-normal column
moisture. Therfore, expect another active day, particularly in the
afternoon, as favorable dynamics and above-normal moisture interacts
with diurnal heating and local effects. Elevated streamflows and
saturated soils from previous rainfall will increase the risk of
flooding. According to model guidance, largest rainfall
accumulations are expected over interior and western/northwestern
Puerto Rico this afternoon under a southeasterly wind flow. At
coastal areas, particularly along rivers such as Rio Culebrina,
Guanajibo, Anasco, Manati and others, overflow is possible due to
excess runoff from earlier rainfall. This could impact roads and low-
water crossings may become impassable, especially at night when
flood hazards are more difficult to recognize. Landslides and
rockfall are also possible with this setup. Given the favorable
upper-level dynamics, some thunderstorms may reach near-severe
strength, producing frequent lightning, gusty winds, and pea-sized
hail, particularly in the mountains.

By tonight, shower and thunderstorm activity will depend on the
position of the trough relative to the overall wind pattern. Model
guidance suggest winds will back from east-southeast to east -
northeast during the night. This could result in more erratic shower
and thunderstorm movement and may also lead to the development of
convergence zones across the area. Most of the activity is still
expected to remain over Atlantic waters. However, special attention
should be given this evening as conditions evolve, particularly
across the northeastern portion of the CWA.

Saturday looked to be transitioning day in previous model cycles.
However, the latest model guidance indicates drier air filtering
in later than previously suggested, arriving during the evening
and nighttime hours.As a result, another active afternoon is
expected with activity focused more over interior and southwestern
Puerto RIco. From Saturday through Sunday, drier air will
gradually move in, leading to a reduction in rainfall activity and
improved weather conditions, along with a lower flooding
potential across the islands. However, lingering moisture and
local effects could still support isolated showers and
thunderstorms over the area.

&&

.Long Term(Monday through Friday)...
Issued at 129 AM AST Fri Mar 27 2026

A persistent subtropical jet will remain over the region, supporting
period of favorable conditions as embedded disturbances pass nearby.
At the surface, a strengthening high over the western-central North
Atlantic will promote breeze to windy northeast flow early in the
week, briefly shifting more east to east-northeast before a surface
trough develops to the northeast. Moisture will increase rapidly
after early Monday, with precipitable water values rising to well
above normal and remaining elevated through the period. Despite some
lingering mid-level dryness early on, conditions will support daily
shower and thunderstorm development, along with increasing trade wind
shower activity.

Hazard risks will increase through the period as a wetter and more
unstable pattern becomes established. Flooding impacts will become
more likely from Monday onward, particularly in urban and poorly-
drained areas, and may be exacerbated over saturated soils. Breezy
to windy conditions will persist, and thunderstorms may produce
lightning and locally erratic winds. Confidence is medium in an
active pattern, and uncertainty remains in the timing and intensity
of embedded features that may enhance rainfall.

&&

.AVIATION...
(06Z TAFS)
Issued at 129 AM AST Fri Mar 27 2026

A trough will promote SHRA/TSRA resulting in MVFR/IFR conds at times
due to reduced VIS/CIGs in SHRA/TSRA. Mostly VCSH/VCTS will affect
TIST/TISX, with VCTS/TSRA posbl across interior and W/NW PR, mainly
impacting TJBQ/TJSJ/TJPS. Afternoon SHRA/TSRA may result in mtn obsc
across interior PR. Winds may become light/vrb overnight with higher
gusts near SHRA/TSRA, then increase after 27/14Z. Sfc winds will be
ESE-SE at 8-15 kt with higher gust near SHRA/TSRA.

&&

.MARINE...
Issued at 129 AM AST Fri Mar 27 2026

A surface high pressure will develop over the north central Atlantic
during the next few days, and settle over the Azores late in the
weekend. Meanwhile, a series of weak surface troughs are expected to
linger over the northeastern Caribbean through the end of the week,
before another front approaches the  region early next week. This
weather pattern will promote mostly light to moderate east to
southeast trades through early tomorrow, before turning more east to
northeast for the rest of the period. Stronger winds are expected
with the approaching front, becoming moderate to locally fresh. Seas
will remain between 3 and 5 feet through the weekend.

Marine conditions will gradually deteriorate by Monday, as a large
swell is forecast to build seas up to 10 feet and spread across the
local Atlantic waters and passages for most of the workweek.

&&

.BEACH FORECAST...
Issued at 129 AM AST Fri Mar 27 2026

A low to moderate risk of rip currents continues across the beaches
of Puerto Rico and the U.S. Virgin Islands, expected to persist this
weekend. Although there isn`t a high risk, beachgoers must exercise
caution, as life-threatening rip currents are still possible along
beaches under a moderate risk. The beach forecast remains on track
for the first part of the week. A large swell is expected to arrive
and spread across the local Atlantic waters and Caribbean passages
by Monday night into early Tuesday. From the latest model guidance,
seas up to 10 feet and periods between 11 and 12 seconds are likely
to produce large breaking waves along north-facing beaches of Puerto
Rico and the U.S. Virgin Islands. These breaking waves could result
in life-threatening rip currents and high surf conditions, while
coastal flood conditions cannot be ruled out. Residents and visitors
are encouraged to continue to stay informed and updated with the
latest beach forecast.

Besides rip currents, beachgoers are encouraged to stay weather
alert for the rest of the afternoon and tomorrow Friday due to
showers and isolated thunderstorms moving over coastal areas of
northwestern Puerto Rico likely to produce lightning.

&&

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

$$

SHORT TERM & AVIATION...CVB
LONG TERM...ICP
MARINE & BEACH FORECAST...DSR

NWS SJU Office Area Forecast Discussion