478
FXCA62 TJSJ 021840
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
240 PM AST Tue Dec 2 2025

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

.KEY MESSAGES...
Issued at 235 PM AST Tue Dec 2 2025

* A surface trough will continue to produce showers and isolated
  thunderstorms across portions of Puerto Rico this afternoon. A
  limited to localized elevated flooding threat can be expected.

* Daily passing showers and a few afternoon thunderstorms will
  continue through the period in a typical seasonal pattern.

* U.S. Virgin Islands may experience brief periods of moderate to
  heavy showers over or near the islands, but impacts should be
  limited to ponding on roadways and in areas with poor drainage.

* Moderate rip currents will persist through most of the week along
  the north and east coasts of Puerto Rico and the USVI. Small craft
  should exercise caution from Wednesday onward as a weak
  northeasterly swell and increasing winds return.

&&

.Short Term(This evening through Thursday)...
Issued at 235 PM AST Tue Dec 2 2025

The frequency of showers increased during the morning hours, with
some moving over northern and eastern portions of Puerto Rico and
the U.S. Virgin Islands. Based on WSR-88D rainfall estimates,
localized areas in St. Croix reached 0.35 inches, but did not
present a flood threat.  The 12z sounding showed an increase in
moisture content compared to the 02/00z sounding (PWAT values from
1.35 to 1.67 inches). As the surface trough slowly approaches the
local area, winds now from the NE-ENE continue to weaken with 0-1 km
mean below 10 kt, meaning that showers may move slower.  The mid-
level temperatures slightly increased this morning, as the RAOB
reported a 500 mb temperature of -7.7 degrees Fahrenheit, cooler
than normal. Nevertheless, it is still an indicator of potential
deep convection this afternoon. Due to mostly clear skies over the
mountain ranges of Puerto Rico, convection activity started by
midday, with some showers and isolated thunderstorms developing over
those areas. So far, radar rainfall estimates ranged between 1.3 -
1.5 inches at Yabucoa and San Lorenzo, while Vieques and Guayama
reached 1.70 - 1.90 inches.

Variable conditions will persist through the forecast period.
Although the surface trough is expected to cross the region tonight
and retire by tomorrow, low to mid level relative humidity will keep
increasing as winds shift from the east and pool seasonal to above-
normal moisture content. From the probabilistic guidance of the GFS
and ECMWF, theres a higher chance of observing seasonal to above
climatological normal Precipitable Water (PWAT) values (1.6 - 1.8
inches). The most likely scenario could be showers moving across the
waters into windward sections tonight into tomorrow, with afternoon
convection over the interior and western portions of Puerto Rico.
Nevertheless, based on the latest guidance, the upper-level trough
is expected to move over the Leeward Islands, with the subsidence
area over the CWA limiting deeper convection activity. Guidance also
suggests warmer than normal 500 mb temperatures (up to
-5 degrees Fahrenheit), inhibiting cloud growth. Additionally, winds
will gradually increase tomorrow, with showers becoming more
progressive and less stationary. Rainfall accumulations will likely
promote ponding of water over roadways, poorly drained and urban
areas. Given the expected weather conditions, the flood and
lightning threat should remain limited.

Seasonal temperatures are expected across the CWA, as the latest
model guidance keeps suggesting seasonal 925 mb temperatures, with
slightly warmer temperatures on Wednesday. Nevertheless, heat
indexes should remain below thresholds, posing no heat threat.

&&

.Long Term(Friday through next Monday)...
Issued at 438 AM AST Tue Dec 2 2025

A mid- to upper-level ridge building from the west over the
northeast Caribbean will likely displace a trough aloft eastward
and away from the region by Friday, promoting a more stable
atmosphere. This ridge aloft is expected to build and persist
throughout the forecast period, supporting subsidence and dry air
aloft, and reinforcing the trade-wind inversion.

With this pattern in place, an advective trade-wind regime will
prevail. As a result, there is a low (10-20%) to moderate (30-50%)
chance of occasional passing showers across the windward areas of
Puerto Rico and the US Virgin Islands each day. Afternoon
convection across the interior and western Puerto Rico also
carries a low to moderate chance of developing daily, but current
guidance does not indicate a flooding threat at this time.

Overall, expect a mix of sunshine and clear skies with periods of
passing clouds. Windward locations can anticipate occasional brief
showers carried by the prevailing trades.

&&

.AVIATION...
(18Z TAFS)
Issued at 235 PM AST Tue Dec 2 2025

VRB WX conds expcd across the CWA, with VCTS over JSJ, JPS, and IST
this aftn. TEMPO conds are likely over JPS btwn 03/18-22z due -TSRA
over the mountain ranges of PR, which may reduce CIGs/VIS and
promote MVFR conds. VCSH are likely by 03/22-23z, with winds
weakening and becoming VRB for most TAF sites. Easterly winds are
expcd to return around 03/13-14z, btw 8 - 11 kt.

&&

.MARINE...
Issued at 235 PM AST Tue Dec 2 2025

A surface trough located just northeast of the islands will continue
to promote light northeasterly winds across the regional waters this
afternoon. As the trough progresses westward through tonight and
into Wednesday, winds will gradually shift from the east southeast,
briefly easing before increasing again later in the week. Afternoon
thunderstorms remain possible over the coastal waters through
midweek due to the proximity of the trough, with locally higher
winds and seas near any storms.

A weak easterly to northeasterly swell will persist across the local
waters through Thursday, maintaining moderate seas, especially
across the Atlantic waters and the Anegada Passage. Additionally,
high pressure building over the central Atlantic will support the
return of moderate to locally fresh east to northeast winds, leading
to choppier conditions and an increase in short-period wind waves.

Seas will generally range from moderate to locally rough at times
across the offshore Atlantic zones, with more tranquil but still
occasionally choppy conditions in the Caribbean passages. Mariners
should remain aware of shifting winds as the trough moves west and
prepare for deteriorating marine conditions toward the second half
of the week.

&&

.BEACH FORECAST...
Issued at 235 PM AST Tue Dec 2 2025

A moderate risk of rip currents will continue this afternoon along
the north and east-facing beaches of Puerto Rico, including Vieques
and Culebra, and across the U.S. Virgin Islands. A weak easterly to
northeasterly swell, combined with locally increasing winds, could
maintain hazardous surf conditions. Life-threatening rip currents
remain possible and can quickly pull swimmers away from shore,
mostly across northern and eastern exposed beaches through the
period.

Even where the risk is lower, rip currents may still form near
groins, jetties, reefs, and piers. Beachgoers are strongly
encouraged to swim near a lifeguard and stay alert to changing surf
conditions.

Passing showers and a few isolated thunderstorms may move over the
waters and coastal areas through the afternoon and early evening.
Brief downpours could reduce visibility and create choppy seas for
small craft near the shore.

For localized and updated risk levels, visit
weather.gov/beach/sju.|

&&

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

$$

SHORT TERM/AVIATION...MNG
KEY MESSAGES/MARINE/BEACH FORECAST...CVB
LONG TERM...CAM

NWS SJU Office Area Forecast Discussion