639
FXCA62 TJSJ 241625
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1225 PM AST Sun May 24 2026

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

.KEY MESSAGES...
Issued at 1214 PM AST Sun May 24 2026

* Morning showers across windward areas of Puerto Rico and the U.S.
  Virgin Islands will be followed by afternoon showers and isolated
  thunderstorms across central and western Puerto Rico each day.

* Moisture content will increase from Tuesday into midweek,
  elevating rain chances and the flooding risk.

* Breezy to locally windy conditions will continue through at least
  midweek. Secure loose outdoor objects.

* Fresh to locally strong easterly winds are resulting in choppy to
  rough seas. A Small Craft Advisory remains in effect for the
  offshore Atlantic waters and a high risk of rip currents will
  return Monday across most beaches.

* A Saharan Air Layer is anticipated to move in late Wednesday and
  persist through the end of the week, along with warmer
  temperatures.

&&

.Short Term(This evening through Tuesday)...
Issued at 1214 PM AST Sun May 24 2026

For the rest of today, daytime heating combined with sea-breeze
convergence will interact with higher than normal moisture content
(1.89 inches from the TJSJ upper-air sounding) to trigger another
round of heavy afternoon showers and isolated thunderstorms. This
activity will primarily develop over central and western Puerto
Rico, and rainfall accumulations of 0.75 to 2.00 inches are
expected, leading to localized urban and small-stream flooding.
Meanwhile, the USVI will experience generally fair weather
conditions with passing showers.

Going into Monday, global models indicate a brief, temporary
drying trend as PWAT values drop toward 1.301.60 inches, and the
mid-levels dry out. While passing windward showers will remain
possible across the islands, afternoon convective coverage over
western PR should be more isolated compared to the weekend. Windy
conditions are expected to prevail generally, with 925 mb winds
peaking near 25 kt.

From late Monday night through Tuesday, a significant resurgence
of tropical moisture and atmospheric instability is forecast, as
an easterly perturbation arrives behind the wind surge. Models
agree that low-to mid-level relative humidity will surge back up
to near 80%, while 800-700 mb lapse rates steepen. PWAT content is
expected to peak just above 2.00 inches. Dynamic cooling aloft
with 500 mb temperatures near -7C to -8C will combine with this
deep tropical moisture to yield more widespread shower coverage
and stronger thunderstorm development. This will significantly
increase the risk of urban and small-stream flooding, rapid river
rises, and localized mudslides in steep terrain.

&&

.Long Term(Wednesday through next Saturday)...
Issued at 411 AM AST Sun May 24 2026

A wet and slightly unstable weather pattern is expected to
develop across Puerto Rico and the U.S. Virgin Islands on
Wednesday as tropical moisture moves across the region as
suggested by the GFS and the ECMWF global model guidances. PWAT
values from the moisture arriving in the islands are forecast to
range between 2.00 and 2.16 inches, which is above the normal
climatological range for the season. At the surface, a broad high
pressure over the central Atlantic will promote east-southeasterly
winds, favoring warm conditions across northern and western
Puerto Rico, resulting in heat indices in the low 100s. Aloft,
some instability will be present due to a low-pressure system near
250 mb reflecting into the mid-levels around 500 mb, enhancing
upper-level support for shower and thunderstorm development.
Under this pattern, periods of showers and isolated thunderstorms
are expected across the local waters and windward sectors during
the morning hours, followed by stronger convection across the
interior and northwestern Puerto Rico during the afternoon. Urban
and small-stream flooding, ponding of water on roads, remain
possible due to slow-moving showers. Frequent lightning and gusty
winds will also pose hazards near the strongest thunderstorms.
Across the U.S. Virgin Islands, shower activity will be more
limited and fast-moving, although isolated ponding of water cannot
be ruled out. Additionally, by late Wednesday into Thursday, the
NASA Goddard Earth Observing system model V5 suggest an increase
of the particles of Saharan dust across the islands.

From Thursday through Saturday, improving conditions aloft near 250
mb will gradually promote a more stable weather pattern across the
forecast area. At the surface, strengthening high pressure spreading
into the eastern Atlantic will tighten the pressure gradient and
shift winds more from the southeast, resulting in breezy to locally
windy conditions. This wind flow will support a warming trend across
the islands, as forecast 925 mb temperatures show. Heat indices are
expected to reach elevated levels each afternoon, especially across
northern, western, and urban sections of Puerto Rico, increasing the
risk of heat-related illnesses for sensitive populations. Although a
more stable pattern is forecast overall, local effects and daytime
heating will still support afternoon convection each day,
particularly along the northwestern quadrant and portions of the San
Juan metropolitan area. Brief periods of heavy rainfall, lightning,
and gusty winds will remain possible, with the strongest activity
occurring. By Sunday, a surface trough developing over the western
Atlantic will promote a more southerly wind flow across the region
while PWAT values decrease closer to around 1.60 inches. This
pattern may continue the warm conditions across the islands while
maintaining isolated to scattered afternoon convection, mainly over
western and northwestern Puerto Rico.

&&

.AVIATION...
(18Z TAFS)
Issued at 1214 PM AST Sun May 24 2026

Tempo MVFR conds possible at TJBQ btw 24/18-22z due to locally
induced SHRA/TSRA. Elsewhere, mostly VCSH and VFR conds expected
to prevail through late Monday. The 24/12z TJSJ sounding indicated
ESE winds up to 25 kt blo FL060. At the sfc, mainly E winds with
sea breeze variations expected to continue btw 17-22 kt with gusts
near 30 kt through late this afternoon.

&&

.MARINE...
Issued at 1214 PM AST Sun May 24 2026

Moderate to locally strong easterly winds will persist across the
regional waters through at least midweek, with the strongest winds
expected on Monday (20 to 25 knots with gusts up to 30 knots), as
strong high pressure over the central Atlantic continues to support
a strong pressure gradient across the northeastern Caribbean. This
pattern will continue to produce choppy to rough seas of up to 7
feet across the offshore Atlantic. Consequently, a Small Craft
Advisory remains in effect there through at least Tuesday morning,
while small craft operators should continue to exercise caution
elsewhere. Mariners should also be aware of afternoon thunderstorms
near the western coastal waters of Puerto Rico each day, producing
locally higher winds and seas.

&&

.BEACH FORECAST...
Issued at 1214 PM AST Sun May 24 2026

Tonight, a moderate risk of rip currents persists across most
beaches of Puerto Rico and the U.S. Virgin Islands. This means life-
threatening rip currents are possible in the surf zone. Winds are
expected to strengthen further by tomorrow, Monday, increasing the
risk to high across many exposed beaches. A high risk of rip
currents means life-threatening rip currents are likely in the surf
zone. Beachgoers are urged to exercise caution and heed the advice
of local officials and beach safety personnel. Another beach hazard
will be quick weather changes and afternoon thunderstorms each day
across western Puerto Rico. If thunder is heard, seek shelter
immediately inside a building. For additional information and
location-specific rip current forecasts, visit weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until 6 AM AST Tuesday for AMZ711.

&&

$$

AVIATION/SHORT TERM...DSR
BEACH/MARINE/KEY MESSAGES...YZR
LONG TERM...LIS

NWS SJU Office Area Forecast Discussion