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829
FXCA62 TJSJ 060914 CCA
AFDSJU

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
514 AM AST Fri Nov 6 2026

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

.KEY MESSAGES...
Issued at 232 AM AST Fri Nov 6 2026

- A persistent west-southwest to southwesterly steering flow will
  focus afternoon thunderstorm activity across the interior and
  steer it toward the north-central, northeastern, and eastern
  municipalities, including the San Juan metropolitan area.

- An unseasonably moist and unstable airmass will maintain
  elevated risks for urban and small-stream flooding, rapid river
  rises, and localized flash flooding across the islands through
  Sunday.

- Showery conditions will prevail across the USVI through the
  weekend.

- A northeasterly swell is expected this weekend, increasing the rip
  current risk to high for northern and eastern beaches of Puerto
  Rico, Culebra, and the U.S. Virgin Islands.

&&

.Short Term(Today through Sunday)...
Issued at 232 AM AST Fri Nov 6 2026

A broad mid-to-upper-level trough north of Hispaniola, alongside
a surface low to the north, will be the primary weather features
for the next few days as they move towards the central Atlantic.
This pattern has disrupted the typical easterly trade winds,
establishing a low-to mid-level west-southwesterly flow that
continually pools deep tropical moisture across the northeastern
Caribbean. Precipitable water values will remain anomalously high
between 2.00 and 2.30 inches, approaching the 90th climatological
percentile, within a deeply saturated column extending through 500
mb. Recent atmospheric soundings show surface-based CAPE
exceeding 2300 J/kg, weak capping, and a deep warm cloud layer,
while aerosol models show little to no Saharan dust, creating an
environment that favors strong convective development.

The west-southwesterly steering flow will shift the usual
precipitation patterns and storm trajectories across Puerto Rico
and the U.S. Virgin Islands. After morning showers pass over the
southern and western portions of the islands, daytime heating and
local sea breeze convergence will trigger shower and thunderstorm
development along the Cordillera Central each afternoon. Steering
winds of 5 to 15 knots will carry these showers and thunderstorms
downstream toward the north-central, northeastern, and eastern
portions of the islands, including the San Juan metro area. High
precipitation efficiency in slow-moving cells will produce intense
localized rainfall, resulting in ponding of water, urban and
small-stream flooding, and quick river rises. Cumulative
rainfall over saturated soils will progressively increase the
threat of localized flash flooding and mudslides in areas of steep
terrain. Additionally these thunderstorms could produce
waterspouts across the coastal waters of the islands.

&&

.Long Term(Monday through Friday)...
Issued at 232 AM AST Fri Nov 6 2026

To start the next workweek, a plume of tropical moisture will linger
near the region under a light southwesterly steering flow as a
frontal low continues to move away from the region. Both the GFS and
the ECMWF are in general agreement with regards to available
moisture towards midweek. Precipitable water (PWAT) values should
stay generally above normal values (2.0 inches) through midweek. 850-
870 mb relative humidity (RH) is forecast to range between high-end
normal values to above normal values through Tuesday, before
trending towards more normal values. 700-500 mb should stay above
normal through most of the period. 925 mb wind speeds will be on
a decreasing trend through Tuesday (being light and variable)
before gradually increasing once again towards Wednesday and
through the end of the forecast period.

A surface high and then another frontal low will move over the
western Atlantic towards the end of the period. The steering flow
is forecast to be southwesterly on Monday before becoming more
southerly Tuesday onwards, with more moderate E to SE surface flow
to end the period. Diurnal heating and local effects are forecast
to result in afternoon showers and t-storms, guided by the above
mentioned flow. This will sustain a flooding risk, especially each
afternoon. Overnight and morning showers will also affect
windward sectors. Although the moisture plume will linger towards
early Thursday, the southerly steering flow will quickly result in
additional moisture over the islands towards the end of the
period as the above mentioned frontal low moves northward towards
the Western Atlantic, possibly sustaining the flooding risk. The
model guidance diverges more through this period, with the GFS
trending towards above normal PWAT and 700-500 mb RH while the
ECMWF trends towards more normal values. Above normal 925 mb
temperatures are forecast for most of the period, prompting at
least a limited heat risk and possibly reaching two standard
deviations by the second half of the workweek.

&&

.AVIATION...
(06Z TAFS)
Issued at 232 AM AST Fri Nov 6 2026

Mainly VFR conditions are expected to prevail across TJSJ/TIST/TJBQ
thru the morning hours, while intermittent periods of -SHRA/VCTS
prevails at TJPS and TISX. Between 06/16-22z, tempo MVFR to brief
IFR conds are possible at TJSJ/TIST/TISX due to +TSRA/SHRA with
mtn tops obscd along the Cordillera and eastern mountain ranges.
Mostly VCSH expected across the rest of the PR and USVI terminals.
By 06/13Z, surface winds will shift from light and variable to a
south-southwesterly to west-southwesterly flow at 5 to 13 knots,
accompanied by local sea breeze variations.

&&

.MARINE...
Issued at 232 AM AST Fri Nov 6 2026

Light southwesterly winds will gradually become more westerly
through Saturday as a low pressure strengthens north of the region.
Increasing showers and thunderstorms will result in deteriorating
weather conditions across most regional waters and local passages
today and into the weekend, particularly across the Atlantic waters.
Gusty winds, reduced visibility, and frequent lightning are possible
with the strongest thunderstorms. Meanwhile, a northerly swell will
begin arriving today, with most of the swell energy expected by
Saturday evening and persisting through early next week. This may
result in hazardous marine conditions, particularly across the
Atlantic waters and northern passages. However, uncertainty remains
regarding the strength of the incoming swell and the extent of the
resulting marine hazards.

&&

.BEACH FORECAST...
Issued at 232 AM AST Fri Nov 6 2026

A moderate risk of rip currents will prevail across most northern,
northwestern, and eastern-exposed beaches of the islands today, with
a low risk elsewhere. However, beach conditions are expected to
gradually deteriorate as a northerly swell begins to reach the local
Atlantic waters. Model guidance continues to suggest that most of
the swell energy will arrive by Saturday evening, with additional
pulses maintaining hazardous beach conditions through early next
week. Although uncertainty remains regarding the strength of the
incoming swell and the extent of its coastal impacts, a high risk of
rip currents remains possible along the northern, northwestern and
eastern-exposed beaches of Puerto Rico and the U.S. Virgin Islands
during the weekend and into early next week. Beachgoers should
closely monitor forecast updates and follow the advice of local
beach patrols and flag warning systems.

In addition, showers and thunderstorms may affect coastal areas of
the islands today and through the weekend, particularly along
northern Puerto Rico. Beachgoers should remain weather alert, as
gusty winds and dangerous lightning may occur even when
thunderstorms remain offshore. Seek shelter immediately whenever
thunder is heard.

&&

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

$$

AVIATION/SHORT TERM...DSR
LONG TERM....MRR
BEACH/MARINE...CVB

NWS SJU Office Area Forecast Discussion