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499
FXCA62 TJSJ 101822
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
222 PM AST Fri Apr 10 2026

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

.KEY MESSAGES...
Updated at 221 PM AST Fri Apr 10 2026

* A High Risk of Rip Currents is in effect for the northern coast
  of Puerto Rico and Culebra through late Sunday due to a long-
  period, northwest to northerly swell.

* Mainly fair weather conditions will prevail today through at
  least Saturday, with isolated showers over eastern Puerto Rico
  and the U.S. Virgin Islands and afternoon convective activity
  over central and western Puerto Rico.

* An approaching mid to upper level trough will result in a wetter
  and more unstable pattern with an increased flooding risk as it
  reaches the islands late Sunday into the next workweek.

&&

.Short Term(This evening through Sunday)...
Issued at 222 PM AST Fri Apr 10 2026

Very calm weather conditions prevailed today under mostly clear to
partly cloudy skies. Satellite and radar observations showed a few
showers moving into the eastern portions of Puerto Rico and the
northern U.S. Virgin Islands during the morning hours; however,
rainfall accumulations were minimal. It was another warm day across
the region, with highs reaching the upper 80s to lower 90s along
coastal and urban areas, while temperatures stayed in the low to mid-
80s in the higher mountains. The Luis Munoz Marin International
Airport in San Juan observed a high of 88F, which is 2F above the
average temperature for April 10th. Heat indices climbed above
100F, particularly over the north-central region of Puerto Rico.

For the rest of the day, calm conditions are expected to continue
across the region. Nonetheless, a few showers may develop across
western Puerto Rico due to daytime heating and local effects.
Similar conditions should prevail on Saturday as a mass of drier air
filters into the area. East-southeast winds will persist, driven by
a broad surface high dominating the central Atlantic, with
precipitable water values remaining around 1.50 inches.

From Sunday afternoon onward, an increase in moisture is
anticipated, with precipitable water values exceeding 2.00 inches as
a mid-to-upper level trough approaches the northeastern Caribbean.
Consequently, the end of the weekend will serve as a transition from
a relatively dry pattern to a wetter, more unstable forecast. This
shift will likely bring an increase in shower frequency to eastern
Puerto Rico and the U.S. Virgin Islands during the morning, followed
by enhanced afternoon showers and thunderstorms.

These conditions will enhance the potential for flooding across the
area. The mid-to-upper level trough is expected to move over Puerto
Rico and the U.S. Virgin Islands by early Monday, elevating the risk
of urban and small stream flooding, as well as rapid river rises.
While a brief break in rainfall this weekend may allow for some
drying, soils remain saturated across eastern and southern Puerto
Rico. Currently, most streams are running at normal to high levels
across the region. Residents and visitors are encouraged to monitor
weather updates throughout the weekend as conditions evolve. Please
refer to the latest Hydrologic Outlook (ESFSJU) for additional
details.

&&

.Long Term(Monday through Friday)...
Issued at 457 AM AST Fri Apr 10 2026

A wetter and more unstable pattern will develop Monday and persist
through midweek as a deep-layered trough and developing upper-level
low remain northwest of the region, supporting favorable divergence
aloft through at least Tuesday night. Deep moisture will surge into
the area from the east on Monday, with precipitable water values
exceeding climatological maxima before organizing into a moisture
band that lingers over the region Tuesday into Wednesday, then
gradually shifts southwestward into the Caribbean by Thursday. Low-
level winds will veer from EENE Monday to ESE by midweek,
supporting a transition from a more typical diurnal pattern early
Monday to increasingly widespread and organized convection Monday
afternoon through at least Tuesday, and possibly into Wednesday.
Cooler temperatures aloft through Tuesday night will enhance
instability, followed by gradual warming by Wednesday into Thursday,
leading to a slow decrease in convective intensity, although a moist
column will persist.

The primary concern is an elevated to locally significant flooding
risk, increasing Monday afternoon and peaking Tuesday into
Wednesday. Periods of heavy and repeated rainfall may result in
urban and small stream flooding, isolated flash flooding, and
localized landslides or rapid river rises. Slower storm motion,
particularly on Tuesday, could enhance rainfall totals in affected
areas. Model guidance has been consistent in highlighting this
event, including the ECMWF Extreme Forecast Index, which indicates
anomalously high rainfall potential building Monday, peaking Tuesday
into Wednesday, and diminishing by Thursday. Although activity
should become less organized late in the period, above-normal
moisture will continue to support scattered showers with localized
impacts. Confidence is moderate to locally high in the overall
pattern, though some uncertainty remains in the exact placement of
the heaviest rainfall.

For additional details, including rainfall expectations and
hydrologic conditions, refer to the Hydrologic Outlook (ESFSJU).

&&

.AVIATION...
(18Z TAFS)
Issued at 222 PM AST Fri Apr 10 2026

Mainly VFR conds are expected across TAF sites this forecast
period. The site with the greater chance to observe SHRA & VCSH is
TJBQ from 11/18Z thru 11/22Z. This could result in intermittent
periods of MVFR conds due to lower cigs and reduced vis. Winds
will continue mainly from the ESE at around 10 to 15 kts and gusts
around 20 to 23 mph and sea breeze variations. Lighter winds
returning aft 11/23Z with increasing potential of VCSH across
eastern TAF sites.

&&

.MARINE...
Issued at 222 PM AST Fri Apr 10 2026

As a broad surface high pressure system builds over the central
Atlantic, winds have become more easterly and will persist from
that direction through the weekend. A 4- to 5-foot northwest to
northerly swell will spread across the Atlantic waters and local
passages, building seas up to around 6 feet over the next few
days. Therefore, small craft should continue to exercise caution,
especially over the Atlantic waters.

Another pulse of northerly swell is expected on Sunday. By early
next week, a frontal boundary and a pre-frontal trough will
increase showers and thunderstorms across the regional waters.
Winds will also strengthen from moderate to locally fresh, with
seas building up to around 7 feet. As a result, Small Craft
Advisories may be issued for the Atlantic waters during this
upcoming period.

&&

.BEACH FORECAST...
Issued at 222 PM AST Fri Apr 10 2026

A 4 to 5 foot long-period northwest to northerly swell will
gradually spread across the Atlantic waters and local Caribbean
passages today. The latest San Juan buoy observations show seas of
around 5 feet with periods of 11 to 12 seconds, which should
result in breaking waves of approximately 6 to 7 feet. This will
maintain a high risk of life-threatening rip currents along the
north-facing beaches of Puerto Rico and Culebra, where a High Rip
Current Risk remains in effect through the weekend. By early
Sunday, another pulse of northerly swell is expected to reach the
northern exposed coastal waters.

Across the USVI and Vieques, a moderate risk of rip currents is
expected to persist over the next several days, while a low risk
will continue along the southern and more protected beaches. More
information is available at weather.gov/beach.sju.


&&

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

     High Rip Current Risk through Saturday afternoon for PRZ012.

VI...None.
AM...None.
&&

$$

SHORT TERM...GRS
LONG TERM...ICP
AVIATION/MARINE/BEACH...YZR

NWS SJU Office Area Forecast Discussion