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479
FXCA62 TJSJ 041822
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
222 PM AST Tue Aug 4 2026

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

.KEY MESSAGES...
Issued at 218 PM AST Tue Aug 4 2026

- Showers and isolated thunderstorms will continue this
  afternoon, leading to ponding of water on roadways and in poorly
  drained areas across southwestern Puerto Rico.

- Warm-to-hot conditions will continue this workweek,
  particularly across urban and low-lying areas of the islands.
  The Heat Advisory continues in effect through 4 PM AST.

- Increasing easterly winds will lead to choppy seas and a moderate
  risk of rip currents across north and east-facing beaches of
  the islands.

- A more stable weather pattern is forecast for the next few
  days, with limited shower activity and an increase of Saharan
  Dust concentrations late this weekend.

&&

.Short Term(This evening through Thursday)...
Issued at 218 PM AST Tue Aug 4 2026

Moderate concentrations of Saharan dust resulted in hazy skies
across the islands this morning, while only a few passing showers
moved across the local waters. Dust concentrations diminished
significantly through the morning hours, allowing for improved
visibility and a more favorable environment for convective
development. At the same time, a larger portion of the urban and
coastal areas experienced elevated heat risk compared to previous
days as temperatures rose quickly, aided by above-normal moisture.

By late morning into the early afternoon, showers and isolated
thunderstorms developed as a weak surface perturbation moved across
the area from the northeast, inducing a more east-northeasterly low-
level flow. This activity will continue through the remainder of the
afternoon, mainly across the interior and southern to southwestern
portions of Puerto Rico, while streamers downwind of the local
islands persist. Some thunderstorms may become strong, producing
frequent lightning, locally heavy rainfall, gusty winds, and small
hail. A Special Weather Statement was issued earlier for portions of
Ponce and Juana Diaz after Doppler radar indicated strong wind
signatures and the potential for pea-sized hail. Although locally
heavy rainfall will provide beneficial moisture across drought-
affected areas, amounts will remain localized and insufficient to
significantly improve ongoing drought conditions.

For Wednesday and Thursday, winds will remain from the east-
southeast while a drier and more stable air mass gradually filters
into the region. Precipitable water values will decrease to near or
below seasonal normals, accompanied by drier mid-level air and
warming aloft, limiting the coverage and intensity of afternoon
convection. Still, local effects and daytime heating will support
isolated to scattered afternoon showers across the interior and
western to northwestern sections of Puerto Rico each day.

The main concern through the remainder of the forecast period will
be the increasing heat risk. Above-normal low-level temperatures,
decreasing cloud cover, and limited rainfall will promote dangerous
heat across the urban and coastal areas of Puerto Rico and the U.S.
Virgin Islands. Heat Advisories will likely be needed on both
Wednesday and Thursday, and if current trends continue, an Extreme
Heat Warning cannot be ruled out across coastal and urban locations.

&&

.Long Term(Friday through next Monday)...
Issued at 329 AM AST Tue Aug 4 2026

The long-term forecast remains on track, with variable weather
conditions dominating the overall outlook. Surface high pressure
extending across the western and central Atlantic will promote an
easterly wind flow on Friday, and is expected to shift out of the
southeast from Saturday onward as the high pressure migrates
eastward. Upper-level low pressure moving across the region from
Saturday into Monday will provide instability aloft, reflected in
cooler 500 mb temperatures dropping to between -6C and -7C,
particularly Saturday through Sunday.

Generally drier conditions are expected overall, though patches
of low-level moisture carried by the trade winds will move across
the region from time to time. The next tropical wave will pass
from Saturday afternoon into Sunday morning, slightly increasing
moisture content across the local islands. The latest model
guidance continues to suggest precipitable water (PWAT) values of
1.75 to 2.00 inches on Saturday. However, because this wave is
embedded in drier air and Saharan dust, it will move through
relatively quickly, and PWAT values will drop rapidly by Sunday
morning to below-normal levels around 1.25 inches. Consequently,
overall rainfall with this wave will not be significant, though a
few passing showers are likely over windward sections of the
islands. During the afternoon hours, available moisture combined
with diurnal heating and local sea-breeze effects could trigger
localized convective activity across central and western Puerto
Rico. Warmer-than-normal temperatures will persist throughout the
forecast period. Model guidance indicates 925 mb temperatures near
two standard deviations for this time of the year, which combined
with lingering moisture could result in Heat Advisories or
Extreme Heat Warnings, particularly over the weekend.
&&

.AVIATION...
(18Z TAFS)
Issued at 218 PM AST Tue Aug 4 2026

Mainly VFR expected brief MVFR/IFR psbl in +SHRA/TSRA ovr interior
and SW PR thru 04/22Z. VCTS at TJPS, with TEMPO TSRA producing brief
reductions in CIGs/VIS, mtn obsc, and sfc gusts/vrb winds. VCSH
expected at TJSJ/TIST/TISX. ENE sfc winds 12-18 kt with gusts up to
25 kt and sea breeze variations thru the aftn, bcmg lgt/vrb aft
04/23Z. Isold SHRA ovr lcl waters may affect ern terminals ovrnght,
but VFR conds should prevail. ESE winds 10-15 kt with sea breeze
variations aft 05/13Z. Isold to sct SHRA/TSRA dvlpg aft 05/16Z ovr
the interior and W-NW PR may briefly affect TJPS/TJBQ with brief
MVFR conds.

&&

.MARINE...
Issued at 218 PM AST Tue Aug 4 2026

A surface high pressure building over the western Atlantic will
maintain easterly moderate winds tonight and early Wednesday,
becoming moderate to locally fresh on Wednesday afternoon as the
local pressure gradient increases. As winds strengthen, building
seas up to 6 feet may lead to choppy seas, particularly across local
offshore Atlantic waters and Caribbean Passages. Isolated afternoon
thunderstorms may generate locally hazardous marine conditions,
mainly across the coastal waters of western Puerto Rico. Another
tropical wave is forecast to approach and move across the local
waters during the upcoming weekend.

&&

.BEACH FORECAST...
Issued at 218 PM AST Tue Aug 4 2026

No changes were introduced to the beach forecast. The latest
nearshore buoys reported seas between 1 and 2 feet, with the Ponce
buoy reaching 3 feet, which should lead to breaking waves between 2
and 3 feet. Hence, the risk of rip currents remains low for the rest
of today and is likely to persist tomorrow, Wednesday. Although the
risk is low, beachgoers should be aware of life-threatening rip
currents in the vicinity of jetties, reefs, piers, and groins. As
winds gradually strengthen Wednesday onward, the risk of rip
currents should become moderate, particularly across northern and
eastern-facing beaches of Puerto Rico and the U.S. Virgin Islands.
At this point, life-threatening rip currents are possible along the
surf zone; beachgoers must exercise caution. The moderate risk will
likely prevail for the rest of the forecast period. Aside from rip
currents, beachgoers should stay weather alert, particularly this
afternoon and Wednesday, due to showers and isolated thunderstorms
moving near coastal areas of Puerto Rico, with gusty winds and
lightning.

&&

.FIRE WEATHER...
Issued at 218 PM AST Tue Aug 4 2026

As mentioned in the previous discussions, critically fuels continue
across the islands, particularly across the southern portions of
Puerto Rico and St. Croix in the U.S. Virgin Islands. In the morning
hours, stations across southern Puerto Rico reported winds between
10 and 13 mph, with gusty winds up to 20 mph. Additionally, relative
humidity gradually decreased across the area (down to 60%), though
it remained above fire weather criteria. As Saharan dust
concentrations continue to diminish, the trade wind perturbation
combined with daytime and local effects resulted in showers and
isolated thunderstorms across the mountain ranges into southern
portions of Puerto Rico, lowering the risk for fire weather for the
rest of today. However, a more stable weather pattern and
strengthening winds are likely in the next few days, and combined
with  very dry fuels, the fire danger will likely increase.
Residents and visitors are encouraged to continue to monitor the
fire weather conditions and avoid outdoor burning.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 4 PM AST this afternoon for PRZ001>005-007-
     008-010>013.

VI...Heat Advisory until 4 PM AST this afternoon for VIZ001-002.

AM...None.
&&

$$

SHORT TERM/AVIATION...CVB
LONG TERM...GRS
MARINE/BEACH/FIRE...MNG

NWS SJU Office Area Forecast Discussion