Buck Island Reef National Monument

Hydrologic Outlook issued April 9 at 11:19AM AST by NWS San Juan PR

Effective: Apr 9, 2026 11:19am
Expires: Apr 11, 2026 11:30am

ESFSJU

A mid to upper level trough is expected to move across Hispaniola
on Sunday, reaching Puerto Rico and the Virgin Islands late Sunday
into Monday. By Tuesday, the trough will be developing a closed
low pressure system in the mid and upper level of the atmosphere,
with a well defined trough (or possibly a low) developing at the
surface. As a result, favorable conditions for periods of
heavy rain are anticipated on Monday and Tuesday.

The first round of showers is expected to reach the region Sunday
night into early Monday. On Monday morning, showers and isolated
thunderstorms will stream across the Virgin Islands and portions
of eastern Puerto Rico. Then, in the afternoon, stronger activity
is expected to develop for the interior, moving into portions of
the south-central, west and southwest Puerto Rico.

By Tuesday, if a low pressure develops in the lower levels,
the steering winds will weaken significantly. As a result,
showers will move slow from the Atlantic Ocean into portions of
the east and north of Puerto Rico and the Virgin Islands.

At this time, soils continue to be saturated along the east and
south of Puerto Rico, but a break in recent rainfalls yesterday
and today will allow for the soil to dry a little. Streams are
mostly running near normal or high across the entire region.

Taking all these factors into consideration, the likelihood of
urban and small stream flooding, isolated flash flooding,
landslides and rapid river rises is increasing. While it is too
early to determine how much rainfall will fall, the most likely
scenario is for 1 to 3" each day, and very isolated higher
amounts. So far, the days with the highest potential for flooding
are Monday and Tuesday, but above normal moisture will persist
through late in the workweek.

At this time, confidence in the forecast is medium, since small
changes in timing of arrival and position of the feature could
affect the total precipitation received and the areas most
affected.

Usually, by mid-April, the Early Wet Season unfold in the
northeast Caribbean Islands. However, this year, the dry season
never arrived. In fact, the Last 60 Days Percent of Normal from
the National Water Prediction Service show 300 to 500% above
normal precipitation for southern Puerto Rico, from Salinas to
Lajas. Areas in the interior and north were also wetter than what
is expected for February and March, with nearly 100 to 200% above
normal.

Please, stay tuned for updates in the forecast this weekend. This
product will be updated as necessary to reflect updates in the
forecast. Additional information can be found in the Area Forecast
Discussion (AFDSJU).

Hydrologic Outlook issued April 10 at 11:19AM AST by NWS San Juan PR

Effective: Apr 10, 2026 11:19am
Expires: Apr 11, 2026 11:30pm

ESFSJU

A mid to upper level trough is expected to move across Hispaniola
on Sunday, reaching Puerto Rico and the Virgin Islands late Sunday
into Monday. The trough will also reflect at the surface, with the
axis reaching the islands Monday night into early Tuesday.

The first round of showers is expected to reach the region Sunday
night into early Monday. On Monday morning, showers and isolated
thunderstorms will stream across the Virgin Islands and portions
of eastern Puerto Rico. Then, in the afternoon, stronger activity
is expected to develop for the interior, moving into portions of
the south-central, west and southwest Puerto Rico. By late Monday
into Tuesday, conditions are expected to be even more favorable for
periods of heavy rain across the islands, but especially strong
along St. Thomas and St. John, Vieques, Culebra, eastern and
northern Puerto Rico.

Soils continue to be saturated along the east and south of Puerto
Rico, but a break in recent rainfalls will allow for the soil to dry
a little. Streams are mostly running near normal or high across the
entire region.

Taking all these factors into consideration, the likelihood of
urban and small stream flooding, isolated flash flooding,
landslides and rapid river rises is increasing. While it is too
early to determine how much rainfall will fall, the most likely
scenario is for 1 to 3" each day, and isolated higher
amounts. So far, the days with the highest potential for flooding
are Monday and Tuesday, but above normal moisture will persist
through late in the workweek.

At this time, the confidence in the forecast is medium, but
increasing, especially since there has been some consistency between
runs of the global guidance. However, some uncertainty still exist
in the exact amounts, timing and locations most affected. It is also
worth mentioning that cloud coverage could also impact the amounts
of rainfall expected, as cloudy skies tend to inhibit heavy rain
formation.

This product will be updated as necessary to reflect updates in the
forecast.