875
FXCA62 TJSJ 291748
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
148 PM AST Wed Apr 29 2026

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

.KEY MESSAGES...
Updated at 145 PM AST Wed Apr 29 2026


* An elevated flooding risk is expected this afternoon across
  interior, western, and northern Puerto Rico as afternoon showers
  and thunderstorms develop. Saturated soils and elevated river
  levels may worsen impacts in vulnerable areas.

* Wet and unstable conditions will persist through Thursday,
  bringing another round of showers and isolated thunderstorms with
  a limited to elevated flooding threat, mainly across interior and
  western Puerto Rico.

* Warmer-than-normal temperatures will continue through the short
  term, with heat indices near 100F across urban and coastal areas.
  Those sensitive to heat should stay hydrated and limit prolonged
  sun exposure.

* A moderate rip current risk will continue for north- and east-
  facing beaches of the islands. Beachgoers should exercise caution
  along exposed beaches.

&&

.Short Term(This evening through Friday)...
Issued at 145 PM AST Wed Apr 29 2026

Mostly tranquil conditions persisted through mid-morning, with few
showers moving across local waters. Satellite-derived products show
abundant tropical moisture across the CWA, with PWAT values between
1.8 and 2.0 inches. This was also seen in the 12z RAOB, with PWAT
values reaching 2.0 inches, above the 75th percentile .
Additionally, the sounding had a skinny profile and showed abundant
low and mid moisture content (between 70 and 80%), and steep lapse
rates (up to 6 inches per km), which may suggest a favorable
environment for flooding. Based on the latest HIRES models, the
highest potential for flooding is expected in the afternoon, with
showers and thunderstorms developing over the mountain ranges of
Puerto Rico and moving over the western and northern areas. Due to
previous rainfall activity, some areas may be vulnerable due to
saturated soil and elevated river levels, and the flooding risk may
be higher. Hence, the flooding threat will remain elevated over the
aforementioned areas. Other areas, such as eastern Puerto Rico,
including the San Juan Metropolitan Area, Vieques, Culebra, and
portions of the U.S. Virgin Islands, can expect ponding of water
over roadways and poorly drained areas.

Wet and unstable conditions will persist tonight and Thursday,
transitioning to a seasonal pattern on Friday. Theres a col region
just north of the region that will linger through late tomorrow,
with winds weakening and becoming light from the east. As a surface
high pressure exiting southeast CONUS moves north of the region, the
pressure gradient will increase, and seasonal trade winds will
return. In the upper levels, a trough will linger through late
Thursday, with the favorable side for convection near the CWA. From
the latest model guidance, PWAT will remain well above normal,
between 2.0 and 2.2 inches. The proximity of the trough will
maintain cool mid-level temperatures (500 mb temperatures around 7
degrees Celsius), and a jet streak in the upper levels will allow
ventilation (250 mb winds between 60 and 70 kt). Additionally, the
Galvez-Davison Index (GDI) suggests the potential for isolated to
scattered thunderstorms as well. Tonight, showers are expected
across local waters, some moving over windward sections of the
islands into the morning hours. Afternoon convection is anticipated,
with showers and thunderstorms developing once again over interior
Puerto Rico, some moving over the western side, with a limited to
elevated flood threat. As the upper-level trough departs and a drier
airmass gradually filters into the region, a transition to stable
conditions is expected on Friday. Although diurnal heating combined
with local effects will result in showers and isolated thunderstorms
in the afternoon, the flooding potential will likely remain limited.

The latest guidance suggests warmer than normal conditions
throughout the short term (925 mb temperatures well above normal).
Combined with the available moisture content,  heat indices will
likely reach 100 degrees Fahrenheit, particularly over urban and
coastal areas of the islands. Although the conditions wont reach
Heat Advisory criteria, people sensitive to heat should exercise
caution by staying hydrated and avoiding long exposure to the sun.

&&

.Long Term(Saturday through next Tuesday)...
Issued at 304 AM AST Wed Apr 29 2026

To start the weekend, current guidance has been variable and still
indicates above-normal precipitable water content, around 1.8 to 2
inches, and 500 mb temperatures near -7 degrees C. A high-pressure
system will be positioned over the central Atlantic, leading to a
northeasterly flow at around 10 to 15 mph. The trough pattern aloft
will be exiting the area, allowing for more stability and higher
heights; however, expect wind-driven showers early across eastern
Puerto Rico, followed by afternoon convection across the
northwestern quadrant of Puerto Rico, with the possibility of a few
lightning strikes. Accordingly, a limited flood threat will persist
on Saturday over northwestern Puerto Rico due to the high potential
for ponding of water on roads and in poorly drained areas. By
Sunday, expect a similar pattern with localized showers during the
afternoon, particularly over northwestern Puerto Rico.

Transitioning into early next week, a gradual drying trend is
anticipated, leading to improving weather conditions. The driest
period currently looks to be Monday through Wednesday. Precipitable
water values will decrease to near-normal levels or even below
normal, while 250 mb heights will further increase and 500 mb
temperatures will warm as ridging builds aloft, bringing greater
atmospheric stability. Although afternoon showers may still develop
due to local effects, their coverage and intensity will be reduced.
Any shower activity during this period should be brief and limited.

Even though there will likely be a break from the rain, the main
concern during this period will be persistent warm conditions, as
indicated by temperature guidance at 925 mb and a prevailing east to
southeasterly wind flow, suggesting values will remain above normal
through the forecast period. Maximum surface temperatures will range
from the upper 80s to the low 90s across coastal and urban areas,
and from the low to mid-80s in higher elevations. Heat indices will
likely reach the upper 90s to the low 100s degrees F each day. As a
result, a limited heat threat will remain in place for urban,
coastal, and low-elevation areas. Residents and visitors are
encouraged to stay hydrated and avoid prolonged sun exposure during
peak heat hours.

&&

.AVIATION...
(18Z TAFS)
Issued at 145 PM AST Wed Apr 29 2026

Mainly FR conds will likely continue across most TAF sites. Aftn -
TSRA/+TSRA will continue across interior PR, with VCTS for PR sites
through 29/23z. TSRA may reduce CIGs/VIS, that may lead to MVFR
conds over JSJ from 29/18-29/19z. AMDs will be issue if TSRA
extends. PROB30s were included for JSJ and IST btwn 30/06 - 30/12z,
as -SHRA/+SHRA may move over the terminals and lead to brf MVFR
conds. Winds from the E-SE will weaken and become light and VRB aft
29/23z, strengthening back by 30/12-30/14z btwn 8 - 12 kt.

&&

.MARINE...
Issued at 145 PM AST Wed Apr 29 2026


Light to gentle easterly to east-southeasterly winds will prevail
through Thursday as a weak pressure gradient remains over the
region. Winds will strengthen slightly by late Thursday into Friday
as high pressure builds north of the area and seasonal trade winds
return. Moist and unstable conditions will promote scattered showers
and isolated thunderstorms across the local waters and nearshore
zones through Thursday, which may produce locally higher winds and
seas. Small northeasterly swells will continue to move across the
regional waters during the next few days. Seas are expected to
remain between 2 and 4 feet, occasionally higher near showers and
thunderstorms.

&&

.BEACH FORECAST...
Issued at 145 PM AST Wed Apr 29 2026

A moderate risk of rip currents will continue for north- and east-
facing beaches of the islands due to pulses of a small, long-period
northeasterly swell. Life-threatening rip currents remain possible
in the surf zone. A low risk of rip currents will persist elsewhere,
though isolated stronger currents may develop near piers, jetties,
reefs, and channels. Beachgoers should exercise caution and monitor
the weather, as showers and thunderstorms may affect coastal areas
at times through Thursday.

For additional information and location-specific rip current
details, please visit weather.gov/beach/sju.

&&

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

$$

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

NWS SJU Office Area Forecast Discussion