621
FXCA62 TJSJ 230737
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
337 AM AST Sat May 23 2026

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

.KEY MESSAGES...
Issued at 326 AM AST Sat May 23 2026

* At least through the Holiday weekend: morning passing showers
  are expected across the windward areas of Puerto Rico and the
  U.S. Virgin Islands, followed by afternoon thunderstorms across
  central and western Puerto Rico.

* Breezy conditions to locally windy conditions will continue
  across the regional waters through early next week, resulting
  in choppy seas.

* A moderate risk of rip currents will continue through the
  weekend for most north-and east-facing beaches of Puerto Rico,
  Culebra, Vieques, and St. Croix.

&&

.Short Term(Today through Monday)...
Issued at 326 AM AST Sat May 23 2026

Variable weather conditions prevailed overnight under clear to
partly cloudy skies. Scattered showers affected portions of eastern
and northeastern Puerto Rico, as well as the San Juan metropolitan
area, by the early morning hours. Doppler radar estimated rainfall
accumulations between 0.10 and 0.30 inches across these areas, as
the showers were moving relatively fast, steered by the trade winds.
Similar to yesterday, a few showers brushed the southern coast of
Puerto Rico, Vieques, and the northern U.S. Virgin Islands.
Overnight lows ranged from the low to mid-70s across coastal and
urban areas, and from the low to mid-60s in higher elevations.
Easterly winds prevailed at 5 to 10 mph with occasional higher gusts
and land breeze variations, particularly across coastal regions.

Today, an extensive plume of tropical moisture will continue to move
into the area, bringing precipitable water (PWAT) values between
1.75 and 2.00 inches. By Sunday, PWAT values will spike slightly
above normal, reaching 2.15 to 2.20 inches. Under this pattern,
daily showers will likely continue across the islands, along with
afternoon convection across the interior and western Puerto Rico
enhanced by daytime heating and local effects. Mid-level
temperatures (at the 500 mb level) will gradually cool over the next
few days to between -6C to -8C, supporting the potential for a few
isolated thunderstorms. At the surface, a strong high pressure
system over the central Atlantic will promote moderate to fresh
easterly winds through next week.

Expect showers and isolated thunderstorms to affect the region
daily, with the strongest activity occurring during the afternoon
hours across the interior and western Puerto Rico, fueled by
abundant incoming moisture. The latest model guidance continues to
suggest rainfall accumulations of 1 to 2 inches each day, with
localized maximums potentially exceeding 3 inches along the eastern
half and western portions of Puerto Rico. Given the expected
saturated soil profile, increasing rainfall rates, and consecutive
days of precipitation, the threat of urban, small stream, and
localized flash flooding will be elevated through Sunday afternoon.

Similar weather conditions are anticipated on Monday; however, brief
patches of drier air filtering in from time to time may somewhat
limit shower development, particularly across the windward areas of
the islands. Warm, seasonal temperatures will persist through early
next week, especially across coastal and urban areas. Maximum
temperatures are expected to range from the upper 80s to low 90s
along the coasts, and from the low to mid-80s in higher elevations.
Heat indices will rise to between 100 and 105 degrees Fahrenheit.
Residents and visitors are urged to stay hydrated, seek shade, and
monitor local conditions to ensure safety during peak heating hours.

&&

.Long Term(Tuesday through Saturday)...
Issued at 326 AM AST Sat May 23 2026

Variable conditions are likely in the long term, with wet and
slightly unstable conditions near the next midweek, transitioning to
seasonal conditions by the upcoming weekend. As mentioned in
previous discussions, a surface high pressure is expected to extend
into the central Atlantic, promoting east-southeasterly winds,
remaining breezy across coastal areas. In the mid to upper levels,
theres a lingering upper-level trough extending into the region
while a ridge tries to build over the western Atlantic. From the
latest deterministic guidance, PWAT values are still anticipated to
increase (most likely between 1.8 and 2.0 inches) from early Tuesday
to Wednesday as tropical moisture pools into the region and the
influence of the trough. Additionally, the latest ensemble member
agrees to above normal moisture content across the CWA, with 25th
and 75th percentiles close (mean around 1.9 inches). The influence
of the trough should maintain cool mid-level temperatures (500 mb
temperatures between -7 and -8 degrees Celsius), with divergence
aloft that should allow cloud growth. Additionally, the latest model
solutions keep suggesting areas of enhanced vorticity, near eastern
areas of the CWA, that should increase instability as well. Given
the expected conditions and considering local effects and diurnal
heating, the most likely scenario could be isolated to scattered
showers moving over the U.S. Virgin Islands and eastern portions of
Puerto Rico, including Vieques and Culebra, with afternoon
convection over interior and northwestern Puerto Rico. In addition,
island streamers could also develop and likely move over the waters
into portions of eastern Puerto Rico. Rainfall accumulations could
lead to urban and small stream flooding, with localized flash
flooding over the aforementioned areas. In addition to flooding,
some other hazards may include gusty winds and lightning. From
Wednesday onwards, uncertainty increases as concentrations of SAL
may approach and gradually filter into the region. Nevertheless,
considering that the latest model guidance is now suggesting warmer-
than-normal temperatures, daytime heating, and available moisture
may break and result in shallow convection over interior and
northwestern Puerto Rico. Although showers are expected, the
flooding threat should remain low.

As temperatures may increase and remain warmer than normal, with the
available moisture, the heat threat will likely remain limited,
affecting mostly individuals sensitive to heat, who must take
necessary precautions. Additionally, with concentrations of SAL that
may filter into the region, people sensitive to these particles
should exercise caution as well and stay up to further updates.

&&

.AVIATION...
(06Z TAFS)
Issued at 326 AM AST Sat May 23 2026

Mainly VFR conds expected across all TAF sites. Passing SHRA will
result in -SHRA/VCSH across the TJSJ/TIST/TISX thru 23/14Z. Aftn
SHRA/TSRA will develop across central, western PR, and downwind
from El Yunque possibly resulting in brief MVFR/IFR conds over
TJBQ/TJSJ btwn 23/17-21Z. E winds up to 15-20 kts after 23/14Z,
with higher gusts and sea breeze variations, decreasing to less
than 5 kts aft 23/22-23Z.

&&

.MARINE...
Issued at 326 AM AST Sat May 23 2026

Moderate to fresh easterly winds will persist across the regional
waters through next week due to strong high pressure over the
central Atlantic. Choppy seas up to 6 feet will continue across the
offshore waters and passages, where small craft should exercise
caution. Marine conditions will likely deteriorate Monday into
Tuesday as winds strengthen and seas build, with Small Craft
Advisory conditions possible across portions of the offshore
Atlantic waters. Isolated afternoon thunderstorms may produce
locally higher winds and seas near the western coastal waters of
Puerto Rico.

&&

.BEACH FORECAST...
Issued at 326 AM AST Sat May 23 2026

A moderate risk of rip currents will continue through the weekend
for most north- and east-facing beaches of Puerto Rico, Culebra,
Vieques, and St. Croix. Increasing winds and building seas early
next week will likely result in a high risk of rip currents across
many exposed beaches Monday into Tuesday.

&&

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

$$

SHORT TERM...GRS
LONG TERM...MNG
MARINE/BEACH FORECAST...ICP

NWS SJU Office Area Forecast Discussion