468
FXCA62 TJSJ 260750
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
350 AM AST Sat Jul 26 2025

.KEY MESSAGES...

* An increased risk of urban and small stream flooding is
  expected across the local islands on Sunday and Monday as
  tropical waves move through the area.

* Heat indices exceeding 100 degrees will continue to prevail
  across the forecast area during the next several days.

* There is a moderate risk of rip currents along the northwest
  coast of Puerto Rico and Saint Croix.

&&

.SHORT TERM...Today through Monday...

A few high clouds were observed in the sky during the night hours.
Some showers managed to move across the local waters, but impacts to
land were minimal. Temperatures remained a little warm in coastal
areas, in the mid-70s, but managed to cool down to the 60s in the
mountain. In the big picture, there is a high pressure driving the
trade winds from the east, and breezy too, with speeds of 15 to 20
mph. In the flow, some Saharan dust is embedded, so hazy skies are
expected again today. With strong heating, showers and thunderstorms
are expected to fire up in the interior and west, where the risk of
urban and small stream flooding is elevated. Streamers are also
expected to develop from the Virgin Islands, Vieques and Culebra.
These lines of showers will reach eastern Puerto Rico too, but
accumulations are not expected to be too significant.

The pattern will shift for Sunday, as a tropical wave reaches the
region. The envelope of moisture  observed in satellite-derived
product show precipitable water values around 2.2 inches, and some
intermittent thunderstorms are also observed by GOES-19 Flash Extent
Density products. As the wave progresses, periods of showers are
expected to first increase in the vicinity of the Virgin Islands in
the overnight hours, gradually moving into Puerto Rico in the
morning and afternoon hours. Rainfall accumulations are expected to
range from 1 to 3 inches, so some localized urban and small stream
flooding can be anticipated, as well as gusty winds within the
thunderstorms. The areas with the highest risk of flooding are the
east-southeat, and the west-northwest.

On Monday, yet another waves will move in. This one does not look as
concentrate as the one for Sunday, but still, showers will manage to
reach portions of eastern Puerto Rico and the Virgin Islands through
the day. Also, with enough sunshine, stronger showers and
thunderstorms are anticipated in the afternoon along the Cordillera
Central, eastern and western Puerto Rico.

The temperature forecast is a little trickier, since it will depend
on how dense the cloud deck of the tropical waves will be. Since the
lowest chances of rain are today, then temperatures should warm up
more, with heat indices surpassing 100 degrees in urban and low-
elevated areas. This level of heat affects primarily those
individuals extremely sensitive to heat, especially when outdoors
without effective cooling or adequate hydration.

.LONG TERM...Tuesday through Saturday...

A mid-level ridge pattern is expected to prevail across the local
islands throughout the forecast period, with some weakening
anticipated on Wednesday and Thursday. At lower levels, a surface
high-pressure northeast of the region will continue to yield
easterly winds for much of the cycle, with a tropical wave moving
across the eastern Caribbean during the weekend. In terms of
precipitable water, lingering moisture is expected on Tuesday,
with a sharp decrease on Wednesday. Although the trades will
continue to bring patches of moisture from time to time on
Thursday and Friday, deep tropical moisture advection is expected
from Saturday night into Sunday, associated with the passage of
the aforementioned tropical wave. Overall, Monday through at least
Friday, moisture will be confined below 850 mb. As a result,
Tuesday is expected to be a transitional day with afternoon
showers and thunderstorms developing across much of central and
western Puerto Rico. Once a drier airmass encompasses the area,
expect a seasonal weather pattern with afternoon showers and
isolated thunderstorms, mainly focused across west Puerto Rico on
Wednesday and Thursday. The intensity and areal coverage of
showers and thunderstorms are expected to increase once again over
the upcoming weekend, associated with the passage of the tropical
wave.

Having said this, the risk for urban and small stream flooding
is expected to increase by the end of the forecast cycle. Warm to
hot temperatures will continue to prevail with heat indices
exceeding 100 degrees each day. The hottest days are likely to be
Wednesday and Thursday. Some haziness is anticipated on Tuesday.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions expected to prevail through the forecast
period. VCSH are expected in the Caribbean Sea and Atlantic
waters, but with no impacts to operations. SHRA and TSRA are
expected for the western Cordillera Central from 17-22Z, with
mountain obscuration expected. After 27/05Z, a tropical wave will
reach TISX terminal, with periods of reduced VIS and low ceilings.
Winds will be from the E at 15-20 kts, with stronger gusts and
sea breeze variations.

&&

.MARINE...

A moderate to locally fresh easterly wind flow will continue to
prevail across the local waters during the weekend into early next
week. A tropical wave will reach the area late tonight into
Sunday, increasing the chance for showers and thunderstorms,
particularly across the Caribbean waters and local passages. A
second tropical wave is forecast to arrive early next week.

&&

.BEACH FORECAST...

Beachgoers can expect a moderate risk of observing life-threatening
rip currents along the exposed beaches in the northwest coast of
Puerto Rico and Saint Croix. In contrast, elsewhere, can expect a
low risk of rip currents. Regardless of the low risk, isolated
stronger rip currents may occur, especially near piers, jetties,
and channels. A tropical wave will reach the area late tonight into
Sunday, increasing the chance for showers and thunderstorms,

&&

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

$$

SHORT TERM...ERG
LONG TERM....OMS
AVIATION...ERG