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811
FXCA62 TJSJ 291825
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
225 PM AST Thu Oct 29 2026

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

.KEY MESSAGES...
Issued at 221 PM AST Thu Oct 29 2026

- Strong thunderstorms and heavy showers will continue to affect
  portions of interior, northwestern, and north central Puerto
  Rico, including parts of the San Juan metro area, through the
  rest of the afternoon. Urban and small stream flooding, frequent
  lightning, and gusty winds are possible.

- Hot and humid conditions will continue across Puerto Rico and the
  U.S. Virgin Islands, particularly during the late morning and
  afternoon hours. Those sensitive to heat should take
  precautions.

- Exceptionally high tides will persist through at least Friday, with
  the highest tide expected late Friday morning. Localized
  coastal flooding remains possible along vulnerable, low-lying
  shorelines, even as northerly swell energy subsides.

- Unsettled weather conditions are expected this weekend, with an
  increasing potential for showers and thunderstorms. Locally
  heavy rainfall could lead to flooding, particularly in areas
  with poor drainage and locations that have already received
  significant rainfall.

&&

.Short Term(This evening through Saturday)...
Issued at 221 PM AST Thu Oct 29 2026

Today, generally quiet weather conditions prevailed across
Puerto Rico and the US Virgin Islands during the morning hours. By
early afternoon, showers developed across the San Juan metropolitan
area and southeastern Puerto Rico, supported by daytime heating,
available moisture, and southeasterly winds. The main concerns with
any heavier showers are ponding of water on roads and localized
urban flooding, particularly in areas with poor drainage.

Tonight into Friday, a drier air mass moving into the region from
the east will gradually limit shower activity. However, passing
showers may still affect eastern Puerto Rico and the U.S. Virgin
Islands overnight, followed by isolated to scattered afternoon
showers across western and northwestern Puerto Rico on Friday due to
daytime heating and local effects. Overall, the flooding threat
should remain limited, with most areas experiencing relatively quiet
weather conditions.

By Saturday, a gradual increase in moisture is expected as a
deepening trough over the western Caribbean influences the region.
Although some afternoon showers and isolated thunderstorms may
develop across interior and western Puerto Rico, the better
potential for increased shower coverage appears to be by late
Saturday, potentially increasing into Sunday. This trend is
supported by both the GFS and ECMWF, which indicate precipitable
water values approaching or exceeding 2.0 inches, along with
increasing mid level moisture by late Saturday. These conditions
could lead to periods of moderate to locally heavy rainfall,
increasing the potential for urban and small stream flooding in
areas receiving persistent showers. Lightning will also be a concern
with any thunderstorm development. Confidence is moderate in the
increasing moisture trend, but uncertainty remains regarding the
location and intensity of the heaviest rainfall.

Overall, the best day for outdoor activities will be Friday into the
first half of Saturday. Above-normal temperatures will persist, so
adequate hydration and precautions against heat exposure are
recommended. The most active day of the short term period will be
late Saturday.

&&

.Long Term(Sunday through Thursday)...
Issued at 227 AM AST Thu Oct 29 2026

Current model guidance suggests a humid pattern throughout the long
term period, favoring unsettled weather conditions and an increased
potential for rainfall. Precipitable water (PWAT) values are
expected to remain at or above 2 inches beginning Sunday, above
normal values based on November climatology (75th percentile).
Meanwhile, relative humidity in the 850 to 700 mb layer is expected
to remain near seasonal levels, while relative humidity in the 700
to 500 mb layer is forecast to remain above normal.

At the surface, high pressure over the Atlantic will promote
easterly to northeasterly winds at the start of the period,
gradually becoming southeasterly to southerly early next week.
Aloft, an upper level trough is expected to remain primarily west of
the region through the beginning of the period. However, some
uncertainty remains, as current model guidance suggests that the
trough will gradually move away from the region early next week. The
upper-level trough, along with embedded shortwave troughs, will
support mid-level temperatures near -6C through at least Monday,
potentially favoring cloud development and deeper convection
across the region. From Tuesday onward, guidance indicates a
gradual warming of mid-level temperatures, which could become
less favorable for deeper convection. By midweek, winds are
expected to become very light, potentially resulting in slow
moving showers and increasing the risk of localized flooding.
However, confidence in the overall rainfall coverage and intensity
remains limited, as upper level dynamics may become less
favorable. Afternoon convection will also depend on cloud cover
and the amount of daytime heating.

Overall, showers are expected during the overnight and morning hours
each day, particularly across the U.S. Virgin Islands and eastern to
southeastern Puerto Rico. During the afternoon, convection is
expected to develop across the interior, western, and northwestern
portions of Puerto Rico, with localized showers and streamers also
developing downwind of El Yunque and across the local islands on
most days. Periods of heavy rainfall could lead to urban and small
stream flooding. In addition, thunderstorms may produce frequent
lightning and gusty winds. Continue to monitor the forecast for
updates as model guidance becomes more consistent.

At this time, upper level dynamics appear more favorable for
enhanced convection on Sunday, at the beginning of the period. Later
in the week a mid-level ridge could help inhibit development. But
lighter winds could favor localized rainfall accumulation due to the
slow movement of showers. Nevertheless, cloud cover will remain an
important factor in determining the extent and intensity of
afternoon convection. Forecast uncertainty remains, as global models
continue to show some disagreement regarding the evolution of the
upper level pattern.
&&

.AVIATION...
(18Z TAFS)
Issued at 221 PM AST Thu Oct 29 2026

VFR conds across all terminals. SHRA/TSRA across interior and NW PR
thru 22Z may cause mtn obscurations and brief MVFR conds. SE at 8-16
kts and higher gust near the heaviest thunderstorm activity, bcmg
lgt/VRB overnight. SE winds becoming E by 30/12Z.
&&

.MARINE...
Issued at 221 PM AST Thu Oct 29 2026

A surface high-pressure system over the central Atlantic will
maintain moderate east to southeasterly winds across the regional
waters through the next few days. The long-period northerly swell
affecting the local waters will continue to gradually subside
through tonight into Friday. Nevertheless, choppy conditions may
persist across portions of the offshore waters and local passages.
Scattered showers and isolated thunderstorms will remain possible,
particularly over the waters north and west of Puerto Rico,
resulting in locally gusty winds and brief periods of reduced
visibility.

&&

.BEACH FORECAST...
Issued at 221 PM AST Thu Oct 29 2026

The High Rip Current Risk has expired as the northerly swell
continues to gradually subside. However, a moderate risk of rip
currents will persist along portions of the north-facing beaches of
Puerto Rico and Culebra, as well as across the U.S. Virgin Islands.

Additionally, the ongoing period of exceptionally high tides will
continue through at least Friday. Localized coastal flooding will
remain possible around the time of high tide, particularly along
susceptible low-lying shorelines, with the highest tide expected
late Friday morning. Although northerly swell energy continues to
diminish, these exceptionally high tides may still exacerbate
coastal impacts, including localized water intrusion and minor
coastal flooding.

&&

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

$$

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

NWS SJU Office Area Forecast Discussion