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949
FXCA62 TJSJ 111802
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
202 PM AST Sat Apr 11 2026

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

.KEY MESSAGES...
Updated at 157 PM AST Sat Apr 11 2026

* A Flood Watch was issued for Puerto Rico and the US Virgin Islands
  and will be in effect from 10 AM Monday throught8 AM Wednesday as
  an increase in rainfall and flooding risk is anticipated due to
  the approaching mid to upper level trough.

* A High Risk of Rip Currents remains in effect for the western,
  northern, and eastern coast of Puerto Rico and Culebra through
  early next workweek due to a long-period NNW swell.

&&

.Short Term(This evening through Monday)...
Issued at 157 PM AST Sat Apr 11 2026

The short-term forecast remains on track for this afternoon and
Sunday, with a more unsettled and wetter pattern expected to develop
from Sunday night onward. For the rest of this afternoon, available
moisture will remain near to slightly above normal, while east to
east-southeast steering flow will support convective development
across the interior and western to northwestern portions of Puerto
Rico due to diurnal heating, local orographic effects, and sea
breeze convergence. A limited to locally elevated flooding risk will
persist where stronger showers develop, mainly in urban areas,
roads, and poor drainage locations. Warm to hot conditions will
continue across coastal and urban areas.

Tonight into Sunday, conditions will gradually become more favorable
for shower and thunderstorm development as a mid to upper-level
trough approaches from the northwest and columnar moisture
increases. Overnight and morning showers will continue across
eastern Puerto Rico and the local islands, followed by more active
afternoon convection over the interior and western sections of
Puerto Rico. Although Sunday is not expected to be the most active
day of the event, broader shower coverage and isolated thunderstorms
should result in an increasing flooding risk by late in the day,
particularly where repeated rainfall activity occurs.

Further deteriorating weather conditions are then expected Sunday
night through Monday as the trough interacts with above-normal
tropical moisture over the area. Recent model guidance now places
the bulk of rainfall activity somewhat farther east than previous
cycles, favoring the U.S. Virgin Islands, Vieques, Culebra, and
eastern to northern Puerto Rico. However, uncertainty remains in
place, as the exact positioning and evolution of the upper-level
trough will determine where the heaviest and most persistent
rainfall ultimately develops.

Given wet antecedent conditions in portions of the area and the
potential for repeated heavy rainfall, the likelihood of urban and
small stream flooding, isolated flash flooding, landslides, and
rapid river rises will increase early this week. Therefore, a Flood
Watch is now in effect for the entire forecast area from Monday 14Z
through Wednesday. The highest impacts during the short-term period
are still expected late Monday into Monday night, with hazardous
conditions likely to continue beyond this forecast period.

&&

.Long Term(Tuesday through next Friday)...
Issued at 459 AM AST Sat Apr 11 2026

A wetter and unstable pattern will continue from Monday night into
Tuesday as a deep-layered trough and upper-level low remain
northwest of the region, supporting favorable conditions aloft. Deep
tropical moisture will remain in place through midweek, with
precipitable water values at times exceeding climatological maxima.
Although some drying is possible late Wednesday into early Thursday,
moisture is expected to increase again late week, maintaining a very
moist pattern through at least Saturday.

The primary concern is an elevated to locally significant flooding
risk, with the highest impacts expected Monday evening through
Tuesday. Periods of heavy and repeated rainfall may result in urban
and small stream flooding, isolated flash flooding, and localized
landslides. A Hydrologic Outlook (ESFSJU) is currently in effect to
highlight this potential. Rainfall amounts will be refined in later
forecasts as confidence increases. While it is still too early for
more specific flood headlines, a Flood Watch may be needed if
conditions warrant.

Although activity may become somewhat less organized at times late
week, sufficient moisture and instability will persist to support
continued showers and thunderstorms with localized flooding impacts,
especially over areas that become saturated earlier in the period.
Confidence is moderate overall.
&&

.AVIATION...
(18Z TAFS)
Issued at 157 PM AST Sat Apr 11 2026

Mainly VFR conds expected through the pd. E to ESE winds 10-15 kt
with sea breeze variations and higher gusts, becoming lighter/vrb
aft 11/22Z. Winds will remain ESE Sun and increase to 15-20 kt
with higher gusts by aftn. VCSH to continue at times across
TJSJ/TIST/TISX and other windward terminals. Best potential for
tempo MVFR/brief IFR conds due to SHRA/TSRA and lower cigs/vsbys
will be this afternoon and aft 12/16Z.

&&

.MARINE...
Issued at 157 PM AST Sat Apr 11 2026

Moderate trades will prevail through the weekend as a broad surface
high pressure builds from the Central Atlantic. A 4 to 5 feet
northwest to north swell will continue to spread across the Atlantic
waters and passages, building seas up to 6 feet for the next few
days. Therefore, small craft should continue to exercise caution,
mainly across the Atlantic waters. Another pulse of the 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. Increasing winds and seas building up to
7 feet are also expected, and Small Craft Advisories could be issued
for the Atlantic waters during this period.

&&

.BEACH FORECAST...
Issued at 157 PM AST Sat Apr 11 2026

Another pulse will arrive on Sunday, maintaining the High Rip
Current Risk in effect for the northwest to northeast beaches of
Puerto Rico and Culebra through at least Monday. 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 of Puerto Rico. More information
is available at weather.gov/beach.sju.

&&

.HYDROLOGY...
Issued at 459 AM AST Sat Apr 11 2026

As a mid to upper level trough approaches from the northwest, the
likelihood of flooding is increasing for late Sunday into the next
workweek. An elevated flooding risk is forecast through at least
midweek. The first round of showers are expected to reach the region
Sunday night into early Monday. Showers and thunderstorms will then
increase in frequency on Monday, but the heaviest activity is
anticipated for Monday night into Tuesday. Although a level of
uncertainty is still present, the days with the highest potential
for flooding are Monday and Tuesday. However, above normal
moisture will persist through late in the week. The likelihood of
urban and small stream flooding, isolated flash flooding,
landslides and rapid river rises is increasing. Residents and
visitors are urged to remain alert to changing weather conditions
and to avoid flooded roadways. A Hydrologic Outlook (ESFSJU) is
currently in effect to highlight this potential. A Flood Watch
(FFASJU) will also likely be issued later today.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Monday afternoon for PRZ001-002-
     005-008-010-012.

     Flood Watch from Monday morning through Wednesday morning for
     PRZ001>013.

VI...Flood Watch from Monday morning through Wednesday morning for
     VIZ001-002.

AM...None.
&&

$$

SHORT TERM/AVIATION...CVB
HYDROLOGY...MRR
LONG TERM...ICP
MARINE/BEACH...MMC

NWS SJU Office Area Forecast Discussion