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861
FXCA62 TJSJ 050630
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
230 AM AST Thu Nov 5 2026

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

.KEY MESSAGES...
Issued at 142 AM AST Thu Nov 5 2026

 - Light southwesterly winds will favor the development of showers
   and thunderstorms across the interior and northeastern portions
   of Puerto Rico this afternoon, with activity potentially
   extending into St.Thomas and St.John.

 - Urban and small stream flooding is anticipated, and isolated
   flash flooding cannot be ruled out, as well as rapid river
   rises and landslides, particularly in areas with persistent
   rainfall.

 - A gradual improvement in weather conditions is expected by the upcoming
   workweek, with a decreasing trend in shower and thunderstorm
   activity.

 - Another northerly swell is expected this weekend, increasing
   the rip current risk to high for northern Puerto Rico, Culebra,
   and St. Thomas.

&&

.Short Term(Today through Saturday)...
Issued at 142 AM AST Thu Nov 5 2026

Mostly clear skies prevailed overnight across Puerto Rico and the
US Virgin Islands, allowing temperatures to fall into the 70s
across coastal areas and into the 60s to lower 70s across the
mountainous regions. Similar to previous nights, winds remained
light and variable across the islands.

A moist and unstable weather pattern will persist through Saturday
as a low-pressure system and its associated frontal boundary
north of the islands continues to bring additional tropical
moisture into the region. Precipitable water values are expected
to range between 2.0 and 2.4 inches, while winds gradually shift
from southerly to southwesterly today, becoming more westerly
Friday into Saturday. Despite this shift, winds will remain
relatively light, allowing daytime heating and local effects to
play a significant role in shower and thunderstorm development.
This afternoon, convection is expected to develop across the
interior of Puerto Rico before spreading toward the northeastern
sections, with some activity potentially reaching the US Virgin
Islands. As winds become more westerly Friday into Saturday, the
focus of afternoon convection will shift toward the interior and
eastern portions of Puerto Rico, as well as the US Virgin Islands.
Although these areas are favored for the highest rainfall
accumulations, most of the islands could experience some rainfall
due to the light winds and the influence of local effects. The
short-term will mostly focus on the periods of rainfall and
thunderstorm activities each day.

The main concern throughout the period will be the potential for
excessive rainfall, as weak steering winds could allow showers and
thunderstorms to linger or repeatedly develop over the same
areas. With soils already saturated from previous rainfall,
additional heavy rainfall could quickly lead to urban and flash
flooding, rapid rises along rivers and streams, and landslides in
steep terrain. These hazards will be particularly concerning
during the afternoon hours across areas experiencing persistent
activity, although localized flooding cannot be ruled out
elsewhere. Residents and visitors are urged to remain weather-
aware, monitor forecast updates, and avoid crossing flooded roads
or waterways. Those in flood-prone areas or near steep slopes
should be aware of their vulnerably.

Temperatures will remain above normal for November, with daytime
highs reaching the upper 80s to lower 90s in some urban and
coastal areas. During sunnier periods, heat indices could reach
the upper 90s to lower 100s in isolated locations, rather than the
more widespread elevated values observed over the past couple of
days. Those spending time outdoors, especially during the hot peak
hours, should follow heat safety recommendations, including
staying hydrated, taking frequent breaks, and seeking shade to
reduce the risk of heat exhaustion.

&&

.Long Term(Sunday through Thursday)...
Issued at 142 AM AST Thu Nov 5 2026

The upper trough and frontal low will continue moving away from the
islands to start the long term period. However, a plume of tropical
moisture will linger through at least late Tuesday night under a
general southwesterly steering flow. Model guidance have somewhat
diverged once again in terms of available precipitable water (PWAT)
values, however they should range from high-end normal values to
above normal (2.0 inches) values. Available moisture is forecast to
reach the mid-levels through at least Tuesday, before mid-level
drier air intrudes. 925 mb wind speeds will be on a decreasing trend
through Tuesday before gradually increasing once again towards
Wednesday and Thursday as a surface high and then another frontal
low move over the western Atlantic. In summary, the steering flow is
forecast to be southwesterly through at least Monday, under more
light and variable surface winds, before backing to become more
southerly Tuesday onwards, under gradually increasing E to SE
surface flow. Diurnal heating and local effects will still result in
afternoon showers and t-storms, and with the southwesterly flow,
they are forecast to be steered towards east-interior PR, the metro
area and northeastern PR. This will sustain a flooding risk,
especially each afternoon through Tuesday. PWAT values are forecast
decrease towards more normal values on Wednesday, which should be
the driest day of the period. Current model guidance suggests an
upper trough developing above the region midweek onwards.
Additionally, as a frontal low moves northward over the western
Atlantic, another above normal moisture plume could reach the
islands on Thursday and increase the flooding risk. Above normal 925
mb temperatures are still forecast for most of the period, prompting
at least a limited heat risk.

&&

.AVIATION...
(06Z TAFS)
Issued at 142 AM AST Thu Nov 5 2026

Mainly VFR conds expected across all TAF sites. However, SHRA/TSRA
expected aft 05/17Z, with stronger impacts at TJSJ btwn
05/17Z-21Z. PROB30 groups at TJSJ and TIST account for heavier
SHRA/TSRA and psbl MVFR CIGS/VIS. VCSH/VCTS expected at TJPS and
TJBQ, with brief MVFR conds psbl at TJPS. Heavy SHRA/TSRA and
lightning may impact arrival/departure routes, especially at TJSJ.
SW winds at 5-10 kt becoming lighter/VRB by 05/23Z. Moderate to
high forecast confidence.

&&

.MARINE...
Issued at 142 AM AST Thu Nov 5 2026

A weak local pressure gradient will continue to favor generally
light southwesterly winds today, becoming variable at times while
gradually turning more westerly. Shower and thunderstorm activity is
expected to increase across the regional waters today and Friday,
particularly over the Atlantic waters and northern portions of the
local passages. Stronger thunderstorms may produce locally gusty
winds, reduced visibility, and frequent lightning. Seas will remain
relatively subdued through today before a long-period north-
northwesterly swell begins to arrive on Friday. Additional swell
energy is expected through the weekend, potentially resulting in
hazardous conditions for small craft, particularly across the
Atlantic waters and exposed passages. However, uncertainty remains
regarding the strength of the incoming swell and the extent of
marine impacts. Additional pulses of northeasterly swell may arrive
early next week.

&&

.BEACH FORECAST...
Issued at 142 AM AST Thu Nov 5 2026

A moderate risk of rip currents continues along portions of the
northern and eastern-exposed beaches of the islands early today,
with a low risk elsewhere. As wind-driven seas continue to diminish,
the moderate risk should decrease across additional beaches later
today. However, life-threatening rip currents remain possible near
jetties, groins, piers, and reefs, even where a low risk is forecast.

Beach conditions are expected to deteriorate again beginning Friday
as a long-period north-northwesterly swell reaches the local waters.
An increasing risk of rip currents is anticipated along northern-
exposed beaches of Puerto Rico and the U.S. Virgin Islands during
the weekend, with a high risk possible. However, uncertainty remains
regarding the strength of the incoming swell and the extent of its
coastal impacts. Additional pulses of northerly swell may prolong
hazardous beach conditions into early next week.

In addition, showers and thunderstorms may affect coastal areas of
northern and eastern Puerto Rico, including the San Juan
Metropolitan Area, today and Friday. Periods of heavy rainfall,
gusty winds, and frequent lightning will be possible. Beachgoers
should remain alert to changing weather conditions and seek shelter
whenever thunder is heard.

&&

.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