455
FXCA62 TJSJ 140737
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
337 AM AST Sun Sep 14 2025

.KEY MESSAGES...

* A couple of tropical waves will increase the frequency of
  showers and thunderstorms through much of the workweek. This
  will the risk of flooding elevated. Additional threats include
  rapid river rises, landslides, and frequent lightning.

* The Virgin Islands will also see an increase in showers and
  thunderstorms, with water surges along the drainage guts,
  ponding of water on roadways, and occasional lightning and
  landslides.

* Weather will likely improve later in the week and into next
  weekend, but it will be very hot again for Puerto Rico and the
  Virgin Islands. These heat indices will be affecting anyone
  without effective cooling or adequate hydration.

* The risk of rip currents will be moderate for most of the
  workweek. Also, there is a risk of lightning strikes each
  afternoon across most of the local beaches in Puerto Rico and
  the Virgin Islands.


&&

.SHORT TERM...Today through Tuesday...

Overnight, relatively calm weather conditions prevailed, with
isolated showers moving across local waters and passages. Some of
these showers reached parts of the U.S. Virgin Islands and eastern
Puerto Rico, resulting in minimal accumulations. Low temperatures
were in the upper 70s to low 80s in coastal and urban areas, and
from the upper 60s to low 70s in the mountains.

A tropical wave east of the U.S. Virgin Islands is forecast to move
over the local islands today. The associated moisture field will
begin to enter the area this morning, with precipitable water values
exceeding 1.90 inches and potentially reaching 2.30 inches later in
the afternoon. For the U.S. Virgin Islands, Vieques, and Culebra,
showers will gradually increase during the morning, with isolated
thunderstorms developing in the afternoon. In Puerto Rico, afternoon
convective activity is expected to produce heavy rainfall and
thunderstorms across central and western municipalities, spreading
toward the northwestern and northern parts of the island. Streamer
activity from "El Yunque" will also impact the San Juan metro area
and adjacent municipalities this afternoon. This activity could lead
to urban and small stream flooding, rapid river rises, water surges,
and landslides. The strongest thunderstorms are expected to bring
frequent lightning and gusty winds. With soils already saturated
from previous rainfall, the risk of flooding will remain from
limited to elevated across the area for the next few days. Residents
and visitors are advised to continue monitoring weather conditions
throughout the weekend and plan accordingly, especially in flood-
prone areas.

By Monday, an atmospheric disturbance will arrive, promoting another
round of unstable weather. This disturbance has precipitable water
values up to 2.35 inches, which will support another day of strong
showers and thunderstorms. Areas previously affected by heavy rain
may experience additional flooding and rapid river rises. The 925 mb
temperatures are expected to remain at or above-normal for the
period. Highs will be in the mid to upper 80s along coastal and
urban areas, and in the upper 70s to mid 80s in higher elevations.

.LONG TERM...Wednesday through Sunday...

A tropical wave crossing Puerto Rico and the Virgin Islands, along
with an upper level trough will maintain unsettled weather
conditions through Thursday. Precipitable water values are
expected to be at 2.0 to 2.25 inches, which is about one standard
deviation above normal for mid-September. These features will
maintain the probability of precipitation on the high side. Since
afternoons have been so active, soils are already saturated and
rivers are running high, especially along the interior and western
Puerto Rico. Therefore, it is very likely that urban and small
stream flooding will continue, each day. Also, rivers may reach
flood stage too, while landslides, lightning strikes and gusty
winds could also develop. Showers will also reach eastern Puerto
Rico at times, and although soils are not as saturated, impacts
should be similar. Across the Virgin Islands, periods of showers
and thunderstorms will cause water surge along guts and drainage
channels, with ponding of water on roadways and isolated urban
flood.

Moving into Friday and the weekend, the attention shifts toward
the system being monitored by the National Hurricane Center. So
far, the guidance shows this tropical wave developing and moving
toward the northwest before reaching the northeastern Caribbean.
As the system moves, it will push some drier air into the islands,
so weather conditions should improve, at least in terms of rain.
The thing is that although it will not be as wet, winds should
shift from the southeast, and 925 mb temperature values will soar,
going nearly two standard deviation above normal. As a result,
very hot temperatures will come back, with the likelihood of
experiencing Heat Advisory or Extreme Heat Warning conditions.
This level of heat will impact anyone without effective cooling or
adequate hydration.


&&

.AVIATION...
(06z)

Mainly VFR to brief MVFR conds across all terminals during the fcst
period. A tropical wave is expected to move into the area today
promoting VCSH/VCTS over TIST/TISX/TJSJ thru 14/23Z. SHRA/TSRA will
gradually increase over TJBQ/TJPS aft 14/17Z. Reduced VIS, mountain
obsc and low cigs expected thru 14/23Z. Sfc winds from the ESE at 10-
14 kts, with higher gusts and sea breeze variations aft 14/14Z.

&&

.MARINE...
A surface high-pressure located over the central and eastern Atlantic
is interacting with a frontal boundary in the Western Atlantic,
resulting in light to moderate east-southeasterly winds through
tomorrow. An approaching tropical wave will move over the U.S.
Virgin Islands and Puerto Rico today, increasing the likelihood of
showers and thunderstorms. After the tropical wave passes, local
winds will shift to moderate and occasionally fresh as the high-
pressure tightens the local pressure gradient. Another tropical wave
is expected to move through the area around Tuesday.

&&

.BEACH FORECAST...
The risk of life-threatening rip currents will increase to moderate
beginning Sunday and persist through most of the workweek, particularly
for northern and eastern exposed beaches of Puerto Rico and Saint
Croix in the U.S. Virgin Islands.

Even with a low risk, life-threatening rip currents can still occur
near groins, jetties, reefs, and piers, so beachgoers are advised to
exercise caution at all times.

Additionally, thunderstorms are likely during the afternoon hours,
producing dangerous lightning strikes; be prepared to seek shelter
if thunder is heard.

&&

.HYDROLOGY...

Active afternoons have maintain the soils saturated across most of
the interior and western half of Puerto Rico. These periods of
heavy rain has also maintain the rivers at above normal to much
above normal levels. These unsettled weather pattern is expected
to persist through much of the workweek, as moisture remains above
normal due to a couple of approaching tropical waves.

Since soils are saturated, much of the precipitation will quickly
become excessive runoff, causing urban or flash flooding, water
surges along rivers, rivers going above flood stage, and
landslides too.

The rivers across the eastern third of Puerto Rico are not as
full, but these rivers usually react much faster than the river in
the west, hence, periods of heavy rain will likely result in rapid
river rises as well.

For the Virgin Islands, periods of heavy rain will cause water
surges along drainage guts, and ponding of water on roadways.
Urban flooding could develop too, while landslides in areas of
steep terrain cannot be ruled out.


&&

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

$$

SHORT TERM/AVIATION...GRS
LONG TERM/MARINE/BEACH/HYDROLOGY....ERG