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079
FXCA62 TJSJ 221829
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
229 PM AST Sat Aug 22 2026

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

.KEY MESSAGES...
Issued at 204 PM AST Sat Aug 22 2026

 * Variable weather conditions are expected through this evening,
   with periods of passing showers and daytime heating effects.

 * Hot and humid conditions will maintain an elevated heat threat
   across coastal and urban areas, with heat indices potentially
   reaching around 110F. A Heat Advisory is in effect for areas
   where the highest heat indices are expected from 10 AM to 5 PM
   AST today.

 * A weak tropical wave will approach and move across the region
   on Monday, increasing moisture and the frequency of showers, although
   the deepest moisture is expected to remain mainly south over
   the Caribbean waters.

 * A low risk of rip currents will continue across all beaches
   for the upcoming days.

&&

.Short Term(This evening through Monday)...
Issued at 204 PM AST Sat Aug 22 2026

Generally calm weather conditions with only a few showers
developed across Puerto Rico and the U.S. Virgin Islands
during the morning hours. Despite the limited shower activity,
the combination of available low- level moisture and high
temperatures has allowed heat indices to climb into the 100 to 108
degree Fahrenheit range. Heat will therefore remain an important
consideration for those spending extended periods outdoors through
the remainder of the afternoon. Afternoon convection is starting
to develop across western PR and the Culebra and Saint
Thomas streamer also began to develop possibly affecting the
metro area.

Tonight, precipitable water decreases and relatively dry air
persists through the mid-levels. This will favor mostly dry and
stable conditions overnight across Puerto Rico and the U.S. Virgin
Islands.

On Sunday, warm conditions will continue as 925 mb temperatures
rise into the two standard deviation criteria. Also, the weak
700 and 500 mb lapse rates around 5 degrees C/km and limited mid-
level moisture should restrict instability and the coverage of
showers and thunderstorms. Most areas should remain dry, although
an isolated afternoon shower and thunderstorm cannot be ruled out.
Regardless, heat will remain the more widespread concern during
the daytime, and appropriate precautions should be taken during
prolonged outdoor activities. Sunday night into Monday, models
continue to suggest a slight increase in moisture across the
islands as a weak tropical wave approaches the region. The
flooding and lighting threat for that period remains limited.

&&

.Long Term(Tuesday through next Friday)...
Issued at 204 PM AST Sat Aug 22 2026

The main long-term forecast concerns are persistent excessive heat
and the evolution of the mid-level ridge as a couple of weak
tropical disturbances move through the Caribbean. Confidence remains
moderate through Tuesday, then decreases somewhat for the latter
half of the week as model differences become more pronounced.

On Monday, the deterministic GFS suggests the mid-level ridge will
erode by the afternoon. If this occurs, reduced mid-level inhibition
combined with daytime heating and local effects should support a
better opportunity for afternoon convection across the interior and
western portions of Puerto Rico. Farther east, the U.S. Virgin
Islands and windward portions of Puerto Rico should experience
mainly isolated, fast-moving showers. Limited to elevated excessive
heat conditions will remain a concern, particularly across coastal
and urban areas.

By Tuesday, a weak tropical wave is forecast to approach the region.
However, the deterministic GFS and ECMWF differ on the strength of
the mid-level ridge and associated moisture. Nevertheless,
increasing moisture should support showers and isolated
thunderstorms across the U.S. Virgin Islands and eastern Puerto Rico
as early as Tuesday morning, followed by additional convection over
the interior and western portions of Puerto Rico during the
afternoon. Confidence in rainfall coverage and amounts remains
limited, however. The GFS is more aggressive in weakening the mid-
level ridge, while guidance also suggests increasing trade winds. A
faster low-level flow could limit rainfall duration and reduce the
potential for significant accumulations.

Any rainfall would be beneficial given the ongoing drought
conditions across portions of Puerto Rico and the U.S. Virgin
Islands, particularly if precipitation occurs within reservoir
watersheds. However, given the expected progressive nature of the
showers and current model uncertainty, confidence remains low that
this wave will provide meaningful drought relief.

Guidance generally favors the mid-level ridge rebuilding over the
region Wednesday, which should once again suppress widespread
convection while maintaining hot conditions. Another disturbance is
being monitored for Thursday, although current GFS guidance keeps
the bulk of its moisture and associated activity south of the local
islands over the Caribbean Sea. Another possible tropical wave may
approach Friday, but current guidance suggests limited organization
and moisture. Given the lead time and model variability, confidence
in the Thursday-Friday evolution remains low.

Overall, periods of excessive heat will remain one of the primary
hazards during the long-term period, particularly Monday and Tuesday
and potentially into Wednesday. Rainfall opportunities will increase
at times with passing disturbances, but confidence in significant or
widespread accumulations remains low.&&

&&

.AVIATION...
(18Z TAFS)
Issued at 204 PM AST Sat Aug 22 2026

Mainly VFR conds expected across all terminals thru the period.
SHRA/TSRA development over W PR may result in brief MVFR conds
at/near TJBQ aft 23/17Z. VCSH near TJSJ after 23/17Z. E winds
10-15 kt with higher gusts, becoming lighter overnight.

&&

.MARINE...
Issued at 204 PM AST Sat Aug 22 2026

Showers and isolated thunderstorms moved across regional waters and
local passages during the morning hours, though they have
diminished. The latest scatterometer data shows mainly moderate
winds across local Atlantic and Caribbean waters, while altimeter
data reported seas between 3 and 5 feet. A surface high pressure
over the Western Atlantic, combined with a low pressure across the
central Atlantic, will continue to promote moderate E-ESE winds
across the region for the rest of the weekend and early next week.
As a surface high pressure strengthens, the local pressure
gradient will likely increase, leading to moderate to locally
fresh trades and choppy conditions; small craft must exercise
caution. A weak tropical wave is expected to approach the local
area by late Sunday into Monday, increasing frequency of showers
across regional waters and passages.

&&

.BEACH FORECAST...
Issued at 204 PM AST Sat Aug 22 2026

The beach forecast remains on track. The latest nearshore buoys
reported seas between 2 and 3 feet during the morning hours, and
based on local bathymetry, breaking waves should lead to a low rip
current risk. Nevertheless, beachgoers should pay attention to beach
conditions, as life-threatening rip currents can often occur near
reefs, jetties, groins, and piers. The low risk is expected to
continue for the rest of the weekend and early next week. As a
surface high pressure builds in the western Atlantic and local
pressure gradient increases, the risk will likely upgrade to
moderate, particularly over northern and eastern-exposed beaches of
Puerto Rico and the U.S. Virgin Islands. Residents and visitors are
encouraged to opt for beaches with lifeguards, as life-threatening
rip currents are possible along the surf zone. Besides rip currents,
beachgoers should monitor the weather conditions, as showers and
isolated thunderstorms are likely each afternoon, particularly near
coastal areas of western Puerto Rico. Periods of heavy showers,
gusty winds, and isolated lightning are likely, beachgoers must seek
shelter whenever they hear thunder.

&&

.FIRE WEATHER...
Issued at 204 PM AST Sat Aug 22 2026

Critical fuels continue across the islands, with moderate to extreme
drought conditions. During the morning hours, moisture content
gradually dropped, though they were brief and did not reach fire
weather criteria. Additionally, winds picked up, between 10 and 15
mph, with gusts up to 20 and 23 mph. Due to abundant moisture
lingering across the area, the risk for fire danger should remain
low today; however, conditions may deteriorate tomorrow as a drier
air mass filters into the region, becoming favorable for fire
spread. Residents and visitors are urged to avoid outdoor burning,
as conditions will enhance wildfire ignition and rapid spread.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007-
     008-010>013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...None.
&&

$$

SHORT TERM/AVIATION...MMC
LONG TERM...CAM
MARINE/BEACH FORECAST/FIRE WEATHER...MNG

NWS SJU Office Area Forecast Discussion