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817
FXCA62 TJSJ 021830
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
230 PM AST Fri Oct 2 2026

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

.KEY MESSAGES...
Issued at 230 PM AST Fri Oct 2 2026

- Showers and thunderstorms will continue to develop this
  afternoon across interior, western, and northwestern Puerto
  Rico. Streamer activity will also bring scattered showers and
  isolated thunderstorms to the San Juan metro area and eastern
  sections.

- Locally heavy rainfall may lead to urban and small-stream
  flooding, as well as rapid river rises, especially in areas with
  already saturated soils.

- Strong showers and thunderstorms remain possible through the
  weekend. Remember: seek shelter immediately whenever you hear
  thunder or see frequent lightning.

- High temperatures and humid conditions will persist over the
  next few days, with elevated heat risk from Sunday into early
  next week across the islands.

- A moderate risk of rip currents continues along the northern
  and eastern beaches of Puerto Rico, as well as portions of the
  U.S. Virgin Islands.

&&

.Short Term(This evening through Sunday)...
Issued at 230 PM AST Fri Oct 2 2026

The short term period will be characterized by a seasonal weather
pattern with advective showers and streamers developing from the
morning into the afternoon across the US Virgin Islands and eastern
Puerto Rico, and in the afternoons across the interior and western
Puerto Rico. Nonetheless, a couple of synoptic features will be
enhancing the observed shower activity. The upper-level low pressure
system currently positioned to the northeast of the US Virgin
Islands that had been promoting upper-level convergence in the
vicinity of the islands will depart the region by Saturday
afternoon. From Saturday into Sunday a low pressure system currently
located over the west Atlantic Ocean will move southward and
position itself over La Hispanola. While the enhanced weather from
this system will likely remain to the west of Puerto Rico, it will
continue to promote cooling of the mid-tropospheric temperatures
further steepening the lapse rates at those levels. This will
increase the potential for the development of deep convective cells.

While a surface-induced perturbation is currently over La Hispanola,
the associated precipitable water (PWAT) will serve as one of the
main drivers for shower and thunderstorm activity today.
Furthermore, the atmospheric column will moisten towards the
afternoon, especially over the western sector of Puerto Rico. The
mid-tropospheric temperatures will also undergo cooling into the
afternoon hours further steepening the lapse rates. Breezy ESE
conditions will prevail, aiding in the development of streamers from
El Yunque and the smaller islands. These features combined with
local effects, and the ESE wind flow will also lead to showers and
thunderstorms across the interior, western and northwestern Puerto
Rico during the afternoon. Given the rainfall received since
yesterday and the current streamflows, where frequent downpours
occur there is a chance for flooding along urban areas, roads, small
streams, and washes along with a small chance for flash floods.

For Saturday, there will be slightly above seasonal PWAT values
across western Puerto Rico. There is some disagreement between the
models with some showing a deep moisture profile while others show
drier low-levels (around 700 mb). Nonetheless, there is higher
agreement in the column moistening during the afternoon hours. The
upper-level level low pressure system will begin approaching La
Hispanola continuing to promote cooling at the mid-levels and steep
lapse rates. The steering flow will remain locally breezy and form
the ESE. This will continue to promote streamers from el Yunque and
the smaller islands during the morning and afternoons with impacts
to the US Virgin Islands and eastern Puerto Rico. Combined with
local effects, these conditions will also lead to the development of
showers and thunderstorms across the interior, western and
northwestern sectors of Puerto Rico during the afternoon. Similar
flooding risks to those seen for today will persist on Saturday.

Model guidance suggest that drier low-levels (around 700 mb) will
prevail on Sunday. Nonetheless, there will be similar favorable
conditions to those seen on Saturday making the development of
convection possible, especially over western Puerto Rico. The upper-
level low will finally settle over La Hispanola further promoting
cooler mid-levels and steep lapse rates. Thus, associated to
advective showers may be expected over eastern Puerto Rico during
the night and early morning, while rainfall from streamers can be
expected over the region during the afternoon. Similarly, local
effects coupled with favorable conditions will lead to showers and
thunderstorms across the interior and western Puerto Rico during the
afternoon. Similar flooding risks to those seen for today will
persist on Sunday.

With seasonal PWAT and low-level temperature values from normal-to-
above normal levels for the season the heat risk is expected to be
limited for today and Saturday, with an elevated risk expected by
Sunday. These levels of heat may affect individuals sensitive to
heat, without effective cooling and adequate hydration. Citizens and
visitors are invited to remain alert of the changing weather
conditions.

&&

.Long Term(Monday through Friday)...
Issued at 440 AM AST Fri Oct 2 2026

Generally, the long-term period will be characterized by a seasonal
weather pattern. A building high-pressure system over the central
Atlantic  will be the main weather feature for the long term period,
enhancing an easterly wind flow from Monday through Tuesday. Under
this pattern, the latest model guidance suggests seasonal
precipitable water (PWAT). Despite the moisture lingering at the low
levels, a mid-level ridge established over the region will promote
stable conditions with warmer temperatures at 500 MB rounding
between -6 and -4 degrees. That stability combined with some
slightly drier mid-levels will inhibit some of the shower
development during these days. Under these conditions, low-level
lingering moisture, daytime heating, and local effects will be the
primary drivers for shower and thunderstorm activity through Tuesday.

A more southeasterly wind flow is forecast from Tuesday evening into
Wednesday, as the broad building high pressure over the Central
Atlantic deep into the area. An upcoming tropical wave and the
associated moisture field will move south of the CWA, enhancing
convection from late evening Tuesday into Wednesday. Although the
bulk of the moisture associated with this wave is expected to remain
over Caribbean waters, local effects, diurnal heating, and the
available moisture will enhance strong convection along the islands.
Due to the shift of winds to an east-southeasterly flow, the
activity will shift more toward the interior and northwestern
portions. Given the expected conditions, there is a chance to
observe a limited to elevated flooding threat with the heaviest
shower activity, especially on Tuesday and Wednesday.  As a result,
urban and small-stream flooding is possible over roadways and poorly
drained areas, and flash flooding cannot be ruled out.

In addition, an elevated heat risk from Monday is expected due to
more stability anticipated and seasonal moisture levels. For those
sensitive to the heat, staying hydrated and avoiding outdoor
activities during peak heating hours is highly recommended.

&&

.AVIATION...
(18Z TAFS)
Issued at 230 PM AST Fri Oct 2 2026

Mainly VFR conditions are expected to prevail across all
terminals during the fcst period. SHRA/TSRA will continue to
develop across the interior and western PR, resulting in VCTS at
TJBQ/TJPS thru 02/22-23Z. Brief MVFR/IFR conds are possible in
heavier SHRA/TSRA, along with mtn obsc across the interior.
Additional SHRA developing across the northeastern quadrant of PR
will result in VCSH/SHRA at TJSJ/TIST/TISX thru 02/22Z. E-ESE
winds btw 10-15 kt, with higher gusts and sea breeze variations
thru 02/22Z. Winds are expected to diminish aft 02/23Z, to 10 kt
or less with land breeze variations thru 03/13-14Z.

&&

.MARINE...
Issued at 230 PM AST Fri Oct 2 2026

Surface high pressure north of the region will maintain moderate to
locally fresh easterly trade winds through at least early tonight,
producing up to choppy conditions. The pressure gradient will then
relax over the weekend, promoting more moderate winds. This will in
turn result in a more moderate chop through early next week.
Lingering moisture behind yesterday`s disturbance and a trough that
will move to the west and northwest of the local area will support
showers and thunderstorms into the weekend. Thunderstorms may
produce locally hazardous conditions for small craft, including
gusty winds, higher seas, lightning, and reduced visibility.

&&

.BEACH FORECAST...
Issued at 230 PM AST Fri Oct 2 2026

A moderate rip current risk (rip currents are possible in the surf
zone) will continue across most exposed north- and east-facing
beaches of Puerto Rico and the U.S. Virgin Islands through the
weekend and at least through midweek. Even in areas where the risk
of rip currents is low, life-threatening rip currents can often
occur in the vicinity of groins, jetties, reefs, and piers. Always
swim near a lifeguard and follow beach patrol guidance and posted
warning flags. Afternoon thunderstorms are more likely to develop
across western Puerto Rico this weekend. If you hear thunder, leave
the water immediately and seek shelter inside a substantial building
or enclosed vehicle.

&&

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

$$

SHORT TERM...RVM
LONG TERM...JCP/LIS
KEY MESSAGES/AVIATION...GRS
MARINE/BEACH FORECAST...MRR

NWS SJU Office Area Forecast Discussion