250
FXCA62 TJSJ 061900
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
300 PM AST Mon Apr 6 2026

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

.KEY MESSAGES...
Updated at 300 PM AST Mon Apr 6 2026

* Flooding risk will remain elevated through midweek. Afternoon and
  nighttime showers and isolated thunderstorms may lead to urban and
  small stream flooding, with isolated flash flooding possible
  across Puerto Rico and the US Virgin Islands.

* Hazardous marine and coastal conditions will continue this
  evening, resulting in choppy to rough seas and life-threatening
  rip currents. The Rip Current Statement remains in effect through
  this evening, while the Small Craft Advisory was extended through
  late tonight.

* Breezy to locally windy conditions will persist through midweek,
  unsecured items may blow around.

* Warmer conditions are expected from Tuesday through Thursday,
  increasing heat risk and resulting in heat-related impacts,
  especially for sensitive individuals outdoors without adequate
  hydration or cooling.&&

.Short Term(This evening through Wednesday)...
Issued at 300 PM AST Mon Apr 6 2026

A strong surface high over the central Atlantic will gradually
move westward during the period as lows move enter the western
Atlantic and another strong high moves over the western Atlantic
by around midweek. This will result in breezy ESE flow throughout
most of the period as 925 mb wind speeds stays at mainly high end
normal values. Precipitable water (PWAT) values will be at high-
end normal to above normal (above 1.75 in) values for this time of
the year throughout most of the period as moisture from the
Caribbean continues to be steered over the region. The mid-level
relative humidity is forecast to persist at normal to above-normal
levels. Atmospheric instability will be present due to mid- to
upper-level short wave troughs and a jet streak near the region.
Galvez-Davison Index (GDI) values are forecast at 30 to 40
tomorrow and Wednesday, also suggesting the potential for t-storm
development. Despite expectations of periods with minimal or no
rainfall, portions of the islands will experience daily rounds of
moderate to locally heavy showers due to available moisture,
diurnal heating, local sea breeze convergence, and orographic
effects all playing a role. These heavier showers are most likely
during the overnight and morning hours across windward sectors
and, shifting to the western and northern portions of PR, as well
as downwind of El Yunque, the USVI, Vieques, and Culebra each
afternoon along with possible isolated t-storms. This will result
in a limited to elevated risk of flooding each day. Forecast
impacts include reduced visibility, ponding of water on roads and
in poorly drained areas, and flooding in urban areas, roads, small
streams, and washes. Tonight, afternoon convection will gradually
dissipate or move offshore, while high res model guidance
suggests that trade wind showers will be steered toward windward
sectors (east/south) of the islands. Showers and t-storms can also
linger over the offshore waters as isolated systems or as MCSs.
Under the ESE flow, 925 mb temperatures are forecast to be near to
above normal. This pattern suggests a limited heat risk is
possible, Tuesday and Wednesday.

&&

.Long Term(Thursday through next Sunday)...
Issued at 300 AM AST Mon Apr 6 2026

A gradual transition toward a slightly more stable pattern is now
expected to begin earlier than indicated in previous model cycles,
particularly starting Thursday. Mid-level moisture is forecast to
decrease, with 700500 mb relative humidity values dropping closer
to near-normal levels. While the overall pattern will remain
somewhat moist, this trend suggests a modest reduction in the depth
of available moisture compared to earlier in the week.

Despite this drying trend, a generally unsettled pattern will
persist. Residual troughing aloft and lingering moisture will
continue to support periods of cloudiness and shower activity,
especially during the afternoon hours due to diurnal heating and
local effects. However, coverage and intensity of convection should
be somewhat lower than in previous days. Winds will remain from the
east-southeast, continuing to advect moisture into the region,
although not as efficiently as earlier in the week. Saturated soils
and elevated streamflows from rainfall earlier in the week will
continue to support an elevated flooding risk, although more
localized in nature, particularly across interior and western Puerto
Rico during the afternoon hours.

By Friday into Saturday, conditions are expected to become
relatively more stable, with mid-level drying limiting vertical
development of convection. This should result in more isolated to
scattered shower activity, primarily over western and interior
Puerto Rico during the afternoon, with more limited impacts
elsewhere.

By the end of the forecast period and beyond, model guidance
suggests a return to a wetter and more unstable pattern as another
deep-layered trough approaches the region and combines with well-
above-normal moisture. However, this portion of the forecast remains
in the longer range and carries higher uncertainty. Stay tuned for
further updates as confidence improves.

&&

.AVIATION...
(18Z TAFS)
Issued at 300 PM AST Mon Apr 6 2026

Mainly VFR conditions with brief MVFR conditions possible. ESE
winds at 10 to 20 kts will continue with higher gusts and sea
breeze variations, especially near SHRA. -SHRA/VCTS can continue
to develop over the interior and over the waters and steered
northward. Winds decreasing after 06/23Z, with land breeze
variations and locally higher near -SHRA/possible VCTS that will
be steered towards E and S sites. Winds increasing again from the
ESE at 10 to 20 kts with higher gusts after 07/13Z.

&&

.MARINE...
Issued at 300 PM AST Mon Apr 6 2026

Hazardous marine conditions will persist through at least early
tomorrow as a strong high-pressure system over the Atlantic
maintains moderate to fresh southeasterly winds. The latest
altimeter scans show seas between 6 and 8 feet across local Atlantic
waters, while scatterometers show winds between 15 and 20 knots and
localized areas between 20 and 25 knots. Therefore, expect confused
seas, particularly across Atlantic waters and local passages
throughout the day. Small Craft Advisories were extended for the
Atlantic offshore waters and the Anegada Passage through midnight
and late tonight, respectively. Conditions are expected to gradually
improve tomorrow, Tuesday , with seas subsiding to around 5 feet in
the Atlantic and up to 4 feet in the Caribbean. While trade wind
showers continue to move across the region, isolated to scattered
thunderstorms are likely this afternoon, especially over coastal
waters near western, northern, and northwestern Puerto Rico. Shower
and thunderstorm coverage may increase later this week due to a
series of troughs approaching the region.

Based on the latest guidance, marine conditions will deteriorate by
Friday as a series of swells spread across the local Atlantic waters
and passages, bringing back choppy to rough seas that may persist
over the next weekend. Small craft operators are encouraged to stay
informed of the latest updates regarding the marine forecast.

&&

.BEACH FORECAST...
Issued at 300 PM AST Mon Apr 6 2026

The beach forecast remains on track. The latest nearshore buoys
reported seas between 3 and 5 feet, with the Arecibo buoy detecting
a swell period of around 10 seconds. Adding the bathymetry
component, breaking waves should range between 7 and 9 feet.
Therefore, theres a high chance of life-threatening rip currents
still present along the northern and eastern beaches of Puerto Rico,
Culebra, and St. Croix in the U.S. Virgin Islands. Hence, the Rip
Current Statement continues over the aforementioned beaches through
this evening. Beachgoers are urged to avoid going into the water,
walking over rocks or jetties, as life-threatening rip currents are
very likely. Heed the advice of lifeguards, beach patrol flags, and
signs. For the rest of the beaches, the risk should remain low to
moderate, but beachgoers should exercise caution when visiting a
beach under moderate risk, as life-threatening rip currents are
possible. Although conditions should gradually improve tonight, they
may deteriorate by the end of the week due to a series of swells
arriving and spreading across local Atlantic waters and passages.
Residents and visitors are encouraged to check the latest beach
conditions before heading to the beach at weather.gov/sju and
https://www.weather.gov/beach/forecast?site=sju&action=.

In addition to the life-threatening rip currents, beachgoers
visiting beaches over western and northwestern Puerto Rico in the
afternoons should remain weather alert due to the development of
isolated thunderstorms. Hazards include gusty winds, reduced
visibility due to heavy rainfall, and lightning. Seek shelter inside
a building whenever you hear lightning.
&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 PM AST this evening for PRZ001-002-
     005-008-012.

VI...High Rip Current Risk until 6 PM AST this evening for VIZ002.

AM...Small Craft Advisory until 6 AM AST Tuesday for AMZ711.

     Small Craft Advisory until midnight AST tonight for AMZ723.

&&

$$

SHORT TERM/AVIATION...MRR
LONG TERM...CVB
MARINE/BEACH FORECAST...MNG

NWS SJU Office Area Forecast Discussion