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467
FXCA62 TJSJ 010608
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
208 AM AST Fri May 1 2026

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

.KEY MESSAGES...
Updated at 159 AM AST Fri May 1 2026

* Another day with showers and thunderstorms across the interior
  and northwestern Puerto Rico is expected, particularly during
  the afternoon hours. An elevated flooding risk is expected for
  these areas as these conditions may cause urban and small stream
  flooding. Saturated soils and elevated river levels may worsen
  impacts on vulnerable areas.

* Across the U.S. Virgin Islands, mainly fair weather conditions
  will prevail with a few passing showers moving into the area from
  time to time.

* Drier and stable conditions are expected to begin to filter into
  the region later tonight into the weekend, with limited shower
  activity.

* Warmer-than-normal temperatures will continue through the
  weekend, with heat indices reaching or exceeding 100F across
  urban and coastal areas.

&&

.Short Term(Today through Sunday)...
Issued at 159 AM AST Fri May 1 2026

Overall, weather conditions remained calm during the overnight
hours, with a few showers moving into the southern coast of Puerto
Rico, Vieques, Culebra, and the northern U.S. Virgin Islands.
Elsewhere, fair weather prevailed under mostly cloudy skies. Doppler
radar and satellite imagery detected isolated to scattered showers
across regional waters with no significant impacts. Overnight
minimum temperatures ranged from the mid-70s in coastal and urban
areas to the low-to-mid 60s across the mountains, with light and
variable winds at 5 knots or less.

Abundant moisture persists across the region today, with
precipitable water (PWAT) values around 2.00 inches. Combined with
daytime heating and local effects, afternoon convective activity is
likely once again. This could produce showers and isolated
thunderstorms, particularly across the interior and northwestern
portions of Puerto Rico. Because winds remain light, slow-moving
showers may enhance the flooding potential; therefore, the risk of
flooding remains elevated for localized portions of northwestern
Puerto Rico. Given that soils are already saturated from previous
rainfall, rapid river rises and isolated landslides cannot be ruled
out. Across the U.S. Virgin Islands, conditions will stay relatively
stable, with only passing morning showers and minimal impacts
throughout the day.

A gradual decrease in moisture is expected to begin tonight and
continue into the weekend, with PWAT values dropping to between 1.30
and 1.60 inches. This drying trend will be supported by the arrival
of a drier air mass and a surface high-pressure system strengthening
over the central Atlantic. This setup will promote light to moderate
southeasterly winds through early next week, while a mid-level ridge
provides stability aloft. Although drier and stable conditions are
anticipated this weekend, daytime heating and local effects could
still trigger a few localized showers across northwestern Puerto
Rico.

As the weekend approaches and drier air filters in, temperatures are
expected to rise. Warm to hot conditions will persist, especially
across coastal and urban areas, where daily maximums will reach the
upper 80s to low 90s. In higher elevations, temperatures will range
from the upper 70s to mid-80s. Heat indices are forecast to reach or
exceed 100F each day. Residents and visitors are urged to stay
hydrated and take frequent breaks in shaded or air-conditioned areas
to mitigate the risk of heat-related illness.

&&

.Long Term(Monday through Friday)...
Issued at 159 AM AST Fri May 1 2026

The long-term period will be mainly dominated by generally tranquil,
near-seasonal conditions across both Puerto Rico and the U.S. Virgin
Islands. Surface high pressure over the central Atlantic will
promote east to southeast winds at 8 to 15 mph throughout the
period. Aloft, a ridging pattern will persist through Wednesday,
supporting stable conditions. As mentioned in previous discussions,
the driest period is expected from Monday through Wednesday. A
drying trend will lead to improving conditions. Model guidance has
been somewhat variable over the past few days, previously indicating
below-normal moisture content and now suggesting near-normal values.
Nevertheless, PWAT values are expected to remain lower, around 1.5
inches or less. Combined with a mid to upper-level ridge, this will
enhance atmospheric stability. Afternoon showers may still develop
due to local effects and diurnal heating; however, coverage will be
limited and activity brief. Rain chances will range from 10 to 40
percent each afternoon across northwestern Puerto Rico.

By Thursday, moisture will increase back to near-normal levels as
patches of moisture move into the region. At the same time, an upper-
level trough will begin to amplify, briefly increasing instability
and the potential for shower development. However, the latest GFS
and ECMWF runs indicate that the trough will quickly move away,
allowing ridging to reestablish itself in the mid to upper levels as
early as Friday.

At 925 mb, temperature guidance continues to indicate above-normal
values (around the 75th percentile) for this time of year. Combined
with a prevailing east to southeasterly wind flow, warm conditions
will persist throughout the forecast period. Daytime highs will
range from the upper 80s to low 90s in coastal and urban areas, and
from the upper 70s to mid-80s in higher elevations. Heat indices
will reach the upper 90s to low 100s degrees F each day. A limited
heat threat will persist across urban, coastal, and low-elevation
areas. Residents and visitors should stay hydrated and limit
prolonged sun exposure during peak heating hours.

As a result, generally sunny and warm days will prevail, with some
light, wind-driven showers overnight and during the early morning
hours in windward areas, along with limited afternoon convection
across northwestern Puerto Rico. Thursday will have the best chances
for rainfall, but overall, minimal impacts are expected.

&&

.AVIATION...
(06Z TAFS)
Issued at 159 AM AST Fri May 1 2026

Mainly VFR conditions will likely continue across most TAF sites.
However, SHRA/TSRA expected to develop over the interior and northwestern
Puerto Rico in the afternoon hours. This activity will result in
brief MVFR/IFR conditions with VCTS for TJPS and TJBQ through
01/22-23Z. Winds will be light and variable early this morning,
becoming SE between 8-12 kt after 01/14Z. Winds will return to
light and variable by 01/23Z through 02/14Z.

&&

.MARINE...
Issued at 159 AM AST Fri May 1 2026

A broad surface high over the central Atlantic interacting with
lower pressure and a weak trough near the region will maintain an
east to east-southeasterly flow across the local waters through the
weekend. Winds will increase from 515 knots today to 1020 knots
with higher gusts through Saturday night and Sunday. Seas will
generally range from 3 to 5 feet, occasionally up to 6 feet, driven
by a combination of local wind waves and a small, long-period
northerly swell moving through the Atlantic waters and passages.
Scattered showers and isolated thunderstorms associated with the
nearby trough and moisture will continue at times, producing locally
higher winds and seas. Conditions will gradually improve early next
week as the pressure gradient relaxes and seas subside.

&&

.BEACH FORECAST...
Issued at 159 AM AST Fri May 1 2026

A moderate risk of rip currents will persist across north- and east-
facing beaches of Puerto Rico, including Culebra, and across all of
the U.S. Virgin Islands. A small, long-period northeasterly swell
continues to move through the local waters, supporting breaking
waves around 3 to 5 feet along exposed beaches. Another weak
northerly swell arriving by Saturday will maintain this pattern. No
significant changes are expected in the beach forecast, but life-
threatening rip currents remain possible and beachgoers should
exercise caution.

For additional information, visit weather.gov/beach/sju.

&&

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

$$

SHORT TERM...GRS
LONG TERM....YZR
MARINE/BEACH...ICP

NWS SJU Office Area Forecast Discussion