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043
FXCA62 TJSJ 180644
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
244 AM AST Sat Apr 18 2026

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

.KEY MESSAGES...
Updated at 232 AM AST Sat Apr 18 2026

* A wet pattern will persist through much of the forecast period,
  which, combined with local effects, will promote showers and
  thunderstorms producing flooding rains across portions of PR
  each day.

* Periods of showers also anticipated over the US Virgin Islands.

* Beachgoers can expect a moderate risk of rip currents along
  north and east-facing beaches, Vieques, Culebra and the US
  Virgin Islands.

* An improvement  in the weather condtions is anticipated from
  Tuesday onwards.

&&

.Short Term(Today through Monday)...
Issued at 232 AM AST Sat Apr 18 2026

A mid- to upper-level trough will persist across the region through
Monday, maintaining an unstable and wet pattern. Precipitable
water values remain near to above normal, generally between the
50th and 75th percentile, while sufficient mid-level moisture and
500 mb temperatures near or below -8 C will support convective
development and periods of locally heavy rainfall. The primary
concern continues to be flooding, lightning and rapid river rises.
Soils are saturated and rivers remain elevated; therefore, any
additional rainfall may quickly lead to urban and small stream
flooding, river rises, and isolated flash flooding, particularly
in areas that receive repeated rounds of rainfall.

This afternoon, convection is expected to develop across the interior
and western Puerto Rico. The Metropolitan area should see some
rainfall activity during the morning and afternoon hours from time
to time. On Sunday, a similar diurnal pattern is expected, with
afternoon convection across interior and western Puerto Rico
followed by additional showers overnight. By Monday, lingering
moisture and instability will continue to support shower activity,
although gradual improvement cannot be ruled out. Across the
USVI, rainfall coverage and intensity will remain more variable,
with lower confidence compared to Puerto Rico.

Residents and visitors should continue to monitor forecasts, as
flooding impacts may develop quickly where heavier showers
persist.

&&

.Long Term(Tuesday through Saturday)...
Issued at 232 AM AST Sat Apr 18 2026

The current forecast remains consistent with the previous
discussion, showing no significant changes. Drier and more stable
conditions are anticipated to return as the influence of the short
term periods upper-level trough weakens and moves away from the
region. A stable air mass will be present aloft due to a building
mid-level ridge over the area. At the surface, a dominant high-
pressure system over the central Atlantic will maintain light to
moderate easterly winds through the middle of the week then becoming
northeasterly and southeasterly at the second half of the week.
Precipitable water (PWAT) values are expected to drop to normal
values with high end normal to above normal values at times.

Local weather will be seasonal with passing showers over windward
sectors during the morning and afternoon hours. This will be
followed by afternoon convective activity across the interior and W
PR on Tuesday with steering wind variations prompting afternoon
convection over SW PR on Wednesday and W-NW PR on Thursday and N PR
on Friday and Saturday. The combination of available moisture,
daytime heating, and local effects could lead to moderate to heavy
rainfall and isolated thunderstorms during these afternoons.
Temperatures at 500 mb are forecast to remain seasonal (-6 C to -
8 C), isolated thunderstorms are still possible, particularly to
end the period due to a nearby mid to upper trough. Given previous
rainfall, saturated soil, and elevated river levels, the
potential for flooding remains. Temperatures at 925 mb will also
stay seasonal throughout most of the period.

&&

.AVIATION...
(06Z TAFS)
Issued at 232 AM AST Sat Apr 18 2026

Mainly VFR conditions prevail across all TAF sites. Period of
VCTS/SHRA possible after 18/14Z across TJSJ, TJBQ, and TJPS.
Therefore brief periods of MVFR are possible across those
terminals. Prevailing winds should remain from east around 10 to
15 kts gusts around 22 knots after 18/14Z near SHRA/TSRA and with
sea breeze variations.

&&

.MARINE...
Issued at 232 AM AST Sat Apr 18 2026

An unstable weather pattern across the regional waters will persist
through the weekend, resulting in periods of strong thunderstorms,
with the strongest activity expected offshore across the western
regional waters, including the Mona Passage and Atlantic waters,
each afternoon. Thunderstorms will produce locally higher winds,
frequent lightning, and reduced visibility. A surface high over the
Atlantic will promote mainly moderate easterly winds, occasionally
fresh at times, resulting in moderate to locally choppy seas through
the weekend. A small northeasterly swell will also continue to
propagate across the Atlantic waters and Caribbean passages through
early next week.

&&

.BEACH FORECAST...
Issued at 232 AM AST Sat Apr 18 2026

A moderate risk of rip currents is expected to persist throughout
the weekend across northern exposed beaches. This may result in life-
threatening rip currents. Heed the advice of lifeguards, beach
patrol flags, and posted signs.

Visitors should also remain mindful of the weather in addition to
surf hazards. An unsettled weather pattern will continue, with the
potential for heavy showers and thunderstorms producing locally
gusty winds and brief heavy rainfall, mainly during the afternoon
hours. If thunder is heard, seek shelter indoors immediately.

For additional information and location-specific rip current
details, please visit: weather.gov/beach/sju.

&&

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

$$

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

NWS SJU Office Area Forecast Discussion