112
FXCA62 TJSJ 120641
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
241 AM AST Sun Apr 12 2026

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

.KEY MESSAGES...
Updated at 240 AM AST Sun Apr 12 2026

* Locally induced showers and thunderstorms are expected to
  develop once again over the interior and western portions of
  Puerto Rico this afternoon, where the flood threat is elevated.

* Across the US Virgin Islands, showers are expected to increase
  from late tonight into Monday morning.

* There is a Flood Watch for Puerto Rico and the US Virgin
  Islands, and will be in effect from 10 AM Monday through 8 AM
  Wednesday.

* A High Risk of Rip Currents remains in effect for the western,
  northern, and eastern coast of Puerto Rico and Culebra through
  Monday afternoon.

&&

.Short Term(Today through Tuesday)...
Issued at 240 AM AST Sun Apr 12 2026

Clear to partly cloudy skies were observed overnight across the
islands. Passing showers were noted mainly across the Anegada
Passage and Caribbean waters. As of 2 AM, minimum temperatures
were from the low 60s across the higher elevations of Puerto Rico
to the mid 70s across the lower elevations of the islands. The
wind was from the east at 10 mph or less. For the rest of the
morning hours, low-level clouds with scattered showers currently
over the Leeward Islands, are expected to move across portions of
the USVI and eastern PR. This surge in moisture will combine with
daytime heating and the sea breeze convergence to trigger the
development of showers and thunderstorms along the mountain ranges
of PR during the afternoon hours. Urban and small stream flooding
is likely with this activity.

For Monday and Tuesday, the combination of an approaching front,
a developing pre-frontal trough, and a mid-to upper-level trough
will promote a moist and unstable weather pattern across the
region. Satellite derived Total Precipitable Water (TPW) imagery
indicates a deep moisture plume from the NW Atlantic and another
developing over the eastern Caribbean. Global model guidance
indicates the Precipitable Water Content (PWAT) increasing from
1.70 inches today to near 2.00 inches through Tuesday, which is
above the 75th percentile for the season. Colder than normal 500
mb temperatures of -10C and -11C are also expected in response to
the deep layer upper level trough. Winds will generally be light
from the east to southeast over land areas, as the surface trough
develops over the region. However, a northeasterly component is
expected between Monday afternoon and early Tuesday morning as the
front sinks further southward across the islands. This period is
expected to be the most active in terms of the heaviest showers.
Daily rainfall accumulations are expected to range between 1 and
3 inches with locally higher amounts. This rainfall over saturated
soils will maintain an elevated threat for urban and river
flooding as well as potential mudslides in areas of steep terrain.
Therefore, a Flood Watch is in effect for all of PR and the USVI
during this time frame.

&&

.Long Term(Wednesday through Sunday)...
Issued at 240 AM AST Sun Apr 12 2026

The wet and unsettled weather pattern may extend into the long-term
forecast. A surface high pressure is expected to build over the
Western Atlantic, gradually increasing the pressure gradient,
resulting in strengthening southeasterly to easterly winds. These
conditions will bring back breezy to locally windy conditions across
the coastal areas of the islands. Nevertheless, the influence of the
deep-layered trough and abundant moisture content across the CWA
will maintain a limited to elevated risk of flooding.  From the
latest model guidance, at least through Saturday, PWAT values should
increase and remain above normal for this time of the year (between
1.6 and 1.8 inches, low chance for 2.0 inches). Additionally,
moisture content in the low and mid levels should remain high
through most of the period, with relative humidity above 60 - 70 %,
and steep lapse rates in the 850 - 700 mb levels. Due to the
proximity of the trough, mid level temperatures will likely remain
cooler than normal (around - 8 degrees Celsius), while a jet streak
in the high levels will maintain strong winds (70 - 80 kt) through
Saturday, allowing ventilation and cloud growth. Additionally,  the
Galvez-Davison Index (GDI) suggests deep convection activity across
the CWA, with isolated to scattered thunderstorms in the afternoons
and the night hours. The most likely scenario, from Wednesday
through Saturday, is moderate to locally heavy showers and isolated
thunderstorms moving over windward sections of Puerto Rico and the
U.S. Virgin Islands throughout the day, with afternoon convection
over the interior into northwestern/western sections of Puerto Rico.
Due to the expected weather event in the short term, saturated soils
and above-normal river levels are very likely and may enhance
flooding potential. Hence, the limited to elevated flooding threat
remains, with a limited lightning potential. Impacts may include
urban and small stream flooding, with localized flash flood,
landslides, and rapid river rises. By Sunday into Monday, weather
conditions should gradually improve, but there are discrepancies
between global solutions for early next week as members of the GEFS
are tending to wetter conditions, while ENS members are tending to a
seasonal pattern.

&&

.AVIATION...
(06Z TAFS)
Issued at 240 AM AST Sun Apr 12 2026

Mainly VFR conditions are expected to prevail through the morning
hours across all terminals. However, passing -SHRA en route fm the
Leeward terminals may reach the USVI and eastern PR terminals.
From 16z-22z, +SHRA/TSRA are expected to develop over the
interior of PR, causing mostly VCTS across the PR terminals, with
possible tempo MVFR conds at TJBQ/TJSJ. East winds between 8-14 kt
with sea breeze variations expected aft 12/14z. An approaching
front from the NW Atlantic waters could lead to +TSRA across the
offshore Atlantic waters and Mona Passage from late tonight into
Monday morning.

&&

.MARINE...
Issued at 240 AM AST Sun Apr 12 2026

A broad surface high pressure across the central Atlantic and a
front over the western Atlantic will promote moderate trades
through the rest of the weekend. Pulses of northerly swell will
continue to move through the Atlantic waters and passages,
where small craft should continue to exercise caution for the next
several days. Between Monday through Wednesday, the combination of
the front and associated pre-frontal trough will increase showers
and thunderstorms across the local waters, creating locally
hazardous marine conditions. Small Craft Advisory conditions are
expected across the Atlantic waters due to seas building up to 7
feet through midweek.

&&

.BEACH FORECAST...
Issued at 240 AM AST Sun Apr 12 2026

A life-threatening risk of rip currents will persist through at
least Monday afternoon as a pulse of northerly swell maintains a
High Rip Current Risk across the north-facing beaches of Puerto
Rico from the northwest through the northeast, as well as Culebra,
and this risk may be extended. Across Vieques and the U.S. Virgin
Islands, a moderate risk of rip currents will continue, while a
low risk persists along the southern and more protected beaches of
Puerto Rico. Increasing winds early to midweek could expand areas
of High Rip Current Risk. Avoid the water at high-risk beaches;
rip currents are likely and can be life-threatening. Sharing is
saving.

&&

.HYDROLOGY...
Issued at 240 AM AST Sun Apr 12 2026

As a mid-to upper-level trough approaches from the northwest, the
likelihood of flooding is increasing from late tonight until at
least midweek. An elevated flooding risk is forecast through this
period. Showers and thunderstorms will 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 continues
to increase. Residents and visitors are urged to remain alert to
changing weather conditions and to avoid flooded roadways. A Flood
Watch (FFASJU) and an Hydrologic Outlook (ESFSJU) are currently
in effect to highlight this flooding potential.

&&

.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/MARINE...DSR
LONG TERM/BEACH...MNG
MARINE/AVIATION...DSR

NWS SJU Office Area Forecast Discussion