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520
FXCA62 TJSJ 221758
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
158 PM AST Thu Oct 22 2026

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

.KEY MESSAGES...
Issued at 158 PM AST Thu Oct 22 2026

- Seasonal to above-normal tropical moisture, combined with a
  southeasterly flow, will maintain a wetter pattern from this
  afternoon through Saturday. Heavy downpours may cause urban and
  small-stream flooding, rapid rises in river levels, and isolated
  flash flooding.

- This afternoon, the interior, north-central, and northwestern
  portions of Puerto Rico have the greatest potential for
  rainfall. Tonight, showers and thunderstorms are likely across
  the Caribbean waters and Mona Passage, with some activity
  potentially moving into southern and western Puerto Rico
  overnight.

- A northerly swell is expected to arrive late tonight into
  Friday, resulting in a high risk of rip currents along north-
  facing beaches beginning tomorrow and potentially continuing
  into early next week.

- Warm and humid conditions will persist, particularly during
  periods of sunshine. Heat impacts may become more pronounced
  early next week, especially along the coasts, in low-lying
  areas, interior valleys, and urban areas.

&&

.Short Term(This evening through Saturday)...
Issued at 158 PM AST Thu Oct 22 2026

Relatively calm weather conditions prevailed today across Puerto
Rico and the U.S. Virgin Islands under partly to mostly cloudy
skies. During the early morning hours, a strong cluster of
thunderstorms developed over the Mona Passage; however, only a few
light showers reached the western coast of Puerto Rico, leaving
minimal rainfall accumulation. Maximum temperatures remained in
the upper 80s to low 90s across lower elevations and in the upper
70s to low 80s across the higher mountains.

A wetter weather pattern is expected to prevail over the next few
days as abundant tropical moisture, with precipitable water (PWAT)
values reaching 2.10 to 2.20 inches, continues moving northward into
the local area. This moisture, combined with a southerly flow driven
by surface high pressure over the central Atlantic and a broad
trough to the northwest, will support shower and thunderstorm
development. For the rest of today, showers are expected to develop
along the interior toward the northern portions of Puerto Rico,
though widespread cloudiness may keep this activity localized. Late
tonight into Friday morning, a shortwave trough moving across the
region will promote showers and isolated thunderstorms over the
Caribbean waters, moving into southern and southwestern coastal
Puerto Rico.

From Friday into Saturday, abundant moisture will persist as winds
slightly increase and shift from the east-southeast. Passing showers
will continue to favor portions of eastern Puerto Rico and the U.S.
Virgin Islands during the overnight and morning hours, followed by
afternoon convection across interior, northern, and western Puerto
Rico. Increasing winds will maintain showers moving relatively
quick, though some of these showers could linger, promoting
additional rainfall accumulations, particularly over western and
northern portions of Puerto Rico. Given the expected rainfall, urban
and small-stream flooding, rapid river rises, localized flash
flooding, and landslides remain possible, especially where soils are
already saturated. Warm and humid conditions will persist daily,
with localized heat impacts possible around peak heating hours.
Please continue to monitor weather updates closely.

&&

.Long Term(Sunday through Thursday)...
Issued at 200 AM AST Thu Oct 22 2026

Wet and unsettled conditions will continue into Sunday before
gradually improving early next week as drier and more stable air
spreads across the region. Surface high pressure over the central
Atlantic and lower pressure to the northwest will maintain a
southeasterly flow, keeping tropical moisture over Puerto Rico and the
U.S. Virgin Islands. Precipitable water values near 2.0 to 2.2
inches and sufficient mid-level moisture will support passing
showers and isolated thunderstorms across windward sectors during
the overnight and morning hours. During the afternoon, daytime
heating, sea-breeze convergence, and local terrain effects will
favor additional showers and thunderstorms across interior,
northern, and western Puerto Rico. Although the overall rainfall
threat should be lower than during the preceding days, locally
heavy downpours may still cause urban and small-stream flooding
where showers repeatedly affect the same areas. Rainfall
accumulated during the short-term period may also leave vulnerable
slopes more susceptible to landslides.

A more noticeable drying trend is expected Monday as drier air
filters into the mid-levels and available moisture becomes
increasingly confined to the lower portion of the atmosphere.
Precipitable water values should decrease toward seasonal levels,
although residual moisture and local effects will continue to
support afternoon showers and isolated thunderstorms, mainly
across interior and western Puerto Rico. Lighter steering winds
could allow localized rainfall accumulations, maintaining some
flooding potential despite decreasing overall shower coverage.
Warm and humid conditions will also remain a concern, particularly
Sunday and Monday, when periods of sunshine may increase heat
impacts across coastal and urban areas and among heat-sensitive
individuals.

From Tuesday through Thursday, a building mid-level ridge and
increasingly limited moisture should favor a drier and more stable
weather pattern. Subsidence and warming aloft will suppress
widespread convective development as precipitable water values
trend below normal. Brief passing showers and isolated afternoon
convection will remain possible, but the potential for widespread
heavy rainfall and flooding should diminish as the week
progresses.

&&

.AVIATION...
(18Z TAFS)
Issued at 158 PM AST Thu Oct 22 2026

Mainly VFR conds expected across PR and USVI terminals thru the
evening, with ISOLD SHRA, resulting in VCSH mainly at TJBQ/TJSJ.
Increasing moisture will favor more frequent SHRA/TSRA mainly
across TJPS aft 23/03Z, with PROB30 TSRA and MVFR/IFR conds thru
23/14Z. Sfc winds mainly S-SE at 5-10 kt, bcmg L/V overnight, then
10-12 kt with higher gusts and sea-breeze variations.

&&

.MARINE...
Issued at 158 PM AST Thu Oct 22 2026

Light to gentle southeasterly winds will become east to southeast
and increase from gentle to locally fresh Friday into the weekend
as the pressure gradient tightens. A north-northwesterly swell is
expected to arrive late tonight into early Friday, followed by
additional pulses through the weekend. Seas will build to 5 to 6
feet across portions of the Atlantic waters and Mona Passage.
Small craft operators should exercise caution. More frequent
showers and thunderstorms, including nighttime activity, will
bring lightning, gusty winds, reduced visibility, and locally
higher seas.

&&

.BEACH FORECAST...
Issued at 158 PM AST Thu Oct 22 2026

A northwesterly swell is expected to arrive late tonight into
Friday, bringing back a high risk of rip currents along north-
facing beaches of Puerto Rico, Culebra, and northern U.S. Virgin
Islands. Hazardous swimming and beach conditions with breaking
waves of around 6 to 7 feet are forecast. Additional swell pulses
will likely maintain the high risk through the weekend and into
early next week. Beachgoers are strongly urged to avoid entering
the water at beaches under a high rip current risk. Heed all beach
signs and instructions from lifeguards and local authorities.
Also, shower and thunderstorm activity will bring lightning and
gusty winds to coastal areas. If thunderstorms approach, leave the
beach immediately and seek shelter.

&&

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

$$

SHORT TERM/AVIATION...GRS
LONG TERM...MRR
MARINE/BEACH...YZR

NWS SJU Office Area Forecast Discussion