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565
FXCA62 TJSJ 021655
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1255 PM AST Mon Nov 2 2026

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

.KEY MESSAGES...
Issued at 1245 PM AST Mon Nov 2 2026

- A seasonal weather pattern will continue through midweek, with
  passing showers across eastern Puerto Rico and the U.S. Virgin
  Islands, followed by afternoon showers and thunderstorms mainly
  over western and northwestern Puerto Rico.

- Afternoon thunderstorms may produce locally heavy rainfall,
  frequent lightning, ponding of water on roads, and minor rises
  along small streams. Most activity should diminish during the
  evening hours.

- Warmer conditions are expected through midweek as winds become
  more southerly. Heat indices could reach Heat Advisory criteria
  across urban, coastal, and lower-elevation areas, so continue
  to follow heat safety recommendations.

- A wetter pattern is expected from Thursday through Saturday.
  Increasing moisture and slow-moving showers and thunderstorms
  could raise the flooding threat, including urban and small-
  stream flooding, with isolated flash flooding possible.

- Choppy marine conditions will gradually improve through midweek
  as winds and seas diminish. The risk of rip currents will also
  decrease across many beaches. However, another swell arriving
  late in the week could bring hazardous surf and rip current
  conditions during the weekend, particularly along the northern
  coast of Puerto Rico and the northern U.S. Virgin Islands. Refer
  to the Beach Forecast section for additional details.

&&

.Short Term(This evening through Wednesday)...
Issued at 1245 PM AST Mon Nov 2 2026

Latest upper-air soundings and recent satellite-derived moisture
imagery indicate a seasonal trade wind pattern across the local
area, with precipitable water values lingering near 2.00 inches. A
persistent east-to-southeast steering flow will continue to
transport patches of shallow moisture, along with pockets of dry air
and minor accumulations of Saharan dust across the U.S. Virgin
Islands and Puerto Rico through midweek. While large-scale dynamic
forcing remains largely absent due to an upper-level ridge,
sufficient low-level moisture and daytime heating will combine with
the sea breeze convergence and orographic lift to support daily
convection, mainly over northwestern PR and from streamers
developing downwind of the islands.

The primary threat from these afternoon thunderstorms will be
localized heavy rainfall, capable of producing rapid accumulations
that may lead to ponding on roadways and minor rises in small
streams. Activity is expected to diminish rapidly as daytime heating
wanes each evening, leaving most overnight and early morning hours
relatively quiet aside from brief passing trade wind showers across
windward areas. Meanwhile, winds are expected to gradually shift
more southerly through midweek, in response to a developing surface
low pressure from a frontal boundary well north of the region and
weakening of the surface high over the western Atlantic. This light
to moderate deep-layer southerly flow, combined with seasonal
moisture and daytime heating, could drive afternoon heat indices
into heat advisory criteria, particularly along urban and lower-
elevation areas. Residents and visitors are encouraged to follow
heat safety recommendations, particularly those working or spending
extended periods outdoors.

&&

.Long Term(Thursday through Monday)...
Issued at 310 AM AST Mon Nov 2 2026

A more unstable pattern could unfold or continue during the long
term period, particularly from Thursday through Saturday. A moist
environment will be present, with precipitable water around 2.0 to
2.3 inches, which is considered above normal values based on
November climatology (75th percentile). The 850 to 700 mb relative
humidity remains high, generally between 75 to 90%, while the 700 to
500 mb layer also shows an increase in moisture, reaching around 70
to 80% by Friday into Saturday. Overall, the moisture profile
suggests a deep and relatively moist atmospheric column through this
period, supporting favorable conditions for precipitation.

At the synoptic level, an upper-level low, along with its associated
surface low and frontal boundary, will move northward across the
Atlantic waters during the period (the most unstable part will
remain north of the eastern Caribbean). However, this evolution will
favor southerly to southwesterly low-level winds, allowing tropical
moisture to be transported to our region, as the features move
farther north. Light winds will generally prevail across the local
area, contributing to weak steering flow and potentially slow moving
showers, allowing showers to move slowly and increasing rainfall
accumulations, mainly across southern, interior, and northern
portions of Puerto Rico, as well as the U.S. Virgin Islands. As a
result, flooding will remain one of the main concerns (Level 2 of
4), indicating the potential for flooding in urban areas, along
roads, and near small streams and washes. Additionally, isolated
flash flooding cannot be ruled out. Other factors to consider are
the NCICS forecasts, including the 200-hPa Velocity Potential and
Outgoing Longwave Radiation (OLR), which suggest upper-level
divergence. There are also signals of equatorial Rossby and Kelvin
waves across the Caribbean during this period, which could enhance
rainfall activity. Continue to monitor the forecast as confidence
increases and updated model guidance becomes available.

By Sunday and Monday, global models agree that a mid to upper level
ridge will build bringing a more stable pattern. In terms of
moisture content, model differences become more apparent. The GFS
maintains higher moisture, particularly in precipitable water and
the 850 to 700 mb relative humidity, suggesting that a greater
amount of moisture remains available in the atmospheric column. In
contrast, the ECMWF indicates more reduction in moisture, with lower
precipitable water values and a drier low to mid-level profile. This
disagreement introduces some uncertainty regarding the extent of
moisture available during this period. Isolated to scattered
afternoon showers may still develop across portions of the islands
due to daytime heating and local effects, but rainfall coverage and
intensity should decrease those days, reducing the flood concerns.

&&

.AVIATION...
(18Z TAFS)
Issued at 1245 PM AST Mon Nov 2 2026

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, SHRA/TSRA development over the
interior of PR may cause tempo MVFR conds at TJSJ and TJBQ through
02/21Z. Mostly VCSH expected across the rest of the PR and USVI
terminals til around 02/22z. The 02/12z TJSJ sounding indicated SE
winds up to 22 kt blo FL100. Weak sea breeze variations developing
along the northern coast of PR should diminish by 02/21z. Light
winds with a southeast component will prevail overnight.

&&

.MARINE...
Issued at 1245 PM AST Mon Nov 2 2026

Moderate to locally fresh easterly winds will maintain choppy marine
conditions across the regional waters through Tuesday, with seas
generally between 3 and 5 feet, occasionally up to 6 feet. However,
a gradual improvement in wind-driven marine conditions is expected
by midweek as a broad area of low pressure develops north of the
region, weakening the local pressure gradient. As a result, winds
will gradually diminish and shift from the east to southeast,
becoming more southerly by midweek. Although winds and seas should
gradually subside during the latter part of the week, increasing
moisture and instability will favor more frequent showers and
thunderstorms, particularly from Thursday into the weekend. Locally
higher winds and seas will remain possible near thunderstorms.

&&

.BEACH FORECAST...
Issued at 1245 PM AST Mon Nov 2 2026

A moderate risk of rip currents will persist along the northern and
eastern-exposed beaches of Puerto Rico, including Culebra and
Vieques, and the U.S. Virgin Islands through at least tonight, while
a low risk will prevail elsewhere. However, as wind-driven seas
gradually diminish, the areas under a moderate risk are expected to
become more limited through Thursday, with improving beach
conditions across much of the region. Nevertheless, even where a low
risk prevails, life-threatening rip currents can still occur near
jetties, groins, piers, and reefs.

By the end of the workweek and into the weekend, a north-
northwesterly swell is expected to reach the northern exposed
waters. Although current model guidance suggests that this swell may
not be strong enough to increase the rip current risk beyond
moderate, uncertainty remains regarding its intensity. A stronger
swell than currently forecast could result in more hazardous surf
and rip current conditions during the weekend. Therefore, beachgoers
should continue to monitor the forecast for potential changes.
Additionally, showers and isolated thunderstorms will remain
possible near coastal areas, with increasing activity expected from
Thursday into the weekend as a wetter and more unstable weather
pattern develops.

&&

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

$$

SHORT TERM/AVIATION...DS
LONG TERM...YZR
MARINE/BEACH FORECAST...CVB

NWS SJU Office Area Forecast Discussion