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217
FXCA62 TJSJ 101800
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
200 PM AST Sat Oct 10 2026

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

.KEY MESSAGES...
Issued at 157 PM AST Sat Oct 10 2026

- A surface induced trough will continue to promote the
  development of fast moving showers and isolated thunderstorms
  this afternoon.

- An upper-level low will move across the region tonight into Sunday,
  enhancing the instability and the potential for additional
  showers and thunderstorms through early next week.

- A low rip current risk will persist through late Tuesday.
  However, life-threatening rip currents often occur in the
  vicinity of groins, jetties, reefs, and piers.

&&

.Short Term(This evening through Monday)...
Issued at 157 PM AST Sat Oct 10 2026

Satellite and radar imagery continue to show fast-moving showers
moving across the U.S. Virgin Islands, eastern and northern Puerto
Rico since the early morning hours, driven by a passing induced
surface trough and its associated moisture field. Despite the
frequency of this activity, rainfall accumulations have remained
between 0.50 and just under 1.00 inch. Maximum temperatures have
reached the mid-to-upper 80s across coastal and urban areas, and the
mid-70s to low 80s along the central mountain range of Puerto Rico.
Winds have prevailed from the east-northeast at 15 to 20 mph, with
higher gusts and sea breeze variations.

For the rest of the day, as the surface-induced trough moves over
the region, steering winds will shift slightly from the east. By the
afternoon, showers will continue to develop along the interior,
western and southwest Puerto Rico. While these showers will be fast-
moving, an isolated thunderstorm or two cannot be ruled out.

A mid-to-upper-level low will gradually approach the region from the
east alongside an upper-level jet, which will enhance divergence and
ventilationparticularly later this afternoon and tonight. Satellite
imagery shows a broad area of moisture and cloudiness east of the
U.S. Virgin Islands, expected to reach the islands by this afternoon
as the upper-level low migrates westward. Instability will also
increase as 500 mb temperatures drop to -7 to -8 C. Under this
pattern, fast-moving passing showers and isolated thunderstorms will
continue across windward sectors of the islands, followed by
afternoon convection over the interior and mainly the northwestern
quadrant of Puerto Rico on Sunday. A similar pattern is expected
Monday, with passing showers and isolated thunderstorms impacting
windward sectors primarily during the morning hours. Although the
overall heat risk will remain limited over the next few days, warm
temperatures will persist, and residents and visitors are encouraged
to stay hydrated and seek shade during peak afternoon heat.

&&

.Long Term(Tuesday through next Friday)...
Issued at 157 PM AST Sat Oct 10 2026

A strong upper-level low will be the dominant feature for most of
the long term period. The upper-level low will meander south of the
islands, with associated instability aloft dropping 500 mb
temperatures below -7 degrees Celsius on Tuesday and Wednesday,
causing steep mid-level lapse rates. Furthermore, associated to the
upper-level low, a surface-induced trough will favor low-level
convergence and seasonal to above normal PWAT values around 1.85 to
2.20 inches, which, combined with daytime heating and local effects,
could support deep, organized convection each day. Although the
upper-level low is forecast to exit the area from Thursday onwards,
lingering moisture could still promote shower and thunderstorm
activity.

On Tuesday and Wednesday, a gentle-to-moderate east-southeasterly
flow will steer slow-moving showers and thunderstorms, primarily
focusing activity over the interior to northwestern sections of
Puerto Rico. For the remainder of the period, model guidance
suggests a frontal boundary exiting the eastern CONUS, inducing a
pre-frontal trough north of the CWA. This interaction will result in
winds shifting to a more east-northeasterly flow, focusing the
convection onto the interior and southwestern Puerto Rico.
Regardless, passing shower and thunderstorm activity cannot be ruled
out across eastern Puerto Rico and the USVI each day.

These conditions will maintain a limited to elevated risk of
flooding each day, with urban and small stream flooding and flash
flooding possible particularly on Tuesday and Wednesday, when
lighter winds will favor slow-moving showers with higher rainfall
accumulations. In addition, localized strong wind gusts and frequent
lightning are expected with the strongest thunderstorms.

&&

.AVIATION...
(18Z TAFS)
Issued at 157 PM AST Sat Oct 10 2026

SHRA/TSRA will continue to result in reduced VIS and lower CIGS at
TJPS through at least 10/21Z. An induced sfc trough will enhance
SHRA/TSRA activity across the local flying area. Periods of
MVFR/IFR conds are possible, particularly under heavier SHRA/TSRA.
The highest SHRA/TSRA frequency is expected across the eastern TAF
sites. Brief reductions in VIS and CIGS are possible with passing
SHRA/TSRA. Sfc winds will prevail from the ENE at 15 kt with
occasional higher gusts. Winds will gradually veer toward the E
tonight. A further wind shift toward the SE is expected around
11/15Z.

&&

.MARINE...
Issued at 157 PM AST Sat Oct 10 2026

Moderate to fresh easterly trade winds will continue to prevail
across the local waters through the remainder of the weekend as a
surface high-pressure system builds over the western Atlantic.
These winds will maintain generally tranquil marine conditions,
with seas up to 5 feet across the Atlantic and Caribbean waters,
as well as the local passages. However, locally choppy conditions
are expected across portions of the offshore waters, where small
craft operators should exercise caution. Meanwhile, for tonight
into Sunday an induced surface trough moving across the region
will continue to enhance shower and thunderstorm activity across
the local waters. This activity may result in periods of reduced
visibility, gusty winds, and locally higher seas, particularly
near stronger showers and thunderstorms. Mariners are urged to
remain alert to rapidly changing weather conditions, especially
when navigating areas affected by thunderstorm activity.

&&

.BEACH FORECAST...
Issued at 157 PM AST Sat Oct 10 2026

A low risk of rip currents will continue across the beaches of
Puerto Rico and the U.S. Virgin Islands through at least Monday,
with generally favorable coastal conditions expected. However,
beachgoers should remain alert to other coastal hazards,
particularly the potential for showers and thunderstorms
associated with an induced surface trough moving across the
region. Thunderstorm activity may result in frequent lightning,
gusty winds, and brief periods of heavy rainfall, especially
during the afternoon hours along coastal areas. Although the risk
of rip currents will remain low, beachgoers are urged to exercise
caution and seek shelter immediately if thunderstorms develop
nearby. A moderate risk of rip current is forecast from Tuesday
across the northern coastal areas of Puerto Rico.

&&

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

$$

SHORT TERM & KEY MESSAGES...GRS
LONG TERM....JCP
AVIATION, MARINE & BEACH FORECAST...LIS

NWS SJU Office Area Forecast Discussion