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365
FXCA62 TJSJ 281826
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
226 PM AST Fri Aug 28 2026

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

.KEY MESSAGES...
Issued at 226 PM AST Fri Aug 28 2026

* Extreme heat remains the primary hazard through Saturday, with
  some relief expected Sunday into Monday before hazardous heat
  returns around midweek.

* Wetter and windier conditions are expected Sunday into Monday
  as moisture associated with Dollys remnants moves across the
  region. Lingering moisture may continue into Tuesday.

* Flooding, lightning, and gusty winds will become the main hazards
  Sunday into Monday. Urban flooding is likely with the heaviest
  rainfall, with isolated flash flooding possible. Rainfall
  amounts and the location of the highest totals remain uncertain.

* Marine and coastal hazards will increase late this weekend into
  early next week as winds and seas build, increasing risks for
  small craft, rip currents, and breaking waves.

&&

.Short Term(This evening through Sunday)...
Issued at 226 PM AST Fri Aug 28 2026

Tonight into Saturday, intermittent pockets of wetter and drier
air will continue streaming across the region within the easterly
flow. Passing showers will affect the USVI and windward portions
of Puerto Rico tonight, and while thunderstorms are not explicitly
expected, one or two isolated thunderstorms cannot be ruled out. A
drier air mass will follow during the day Saturday, with heat
remaining the primary hazard. Only minimal localized shower and
thunderstorm development is expected during the afternoon.

Sunday will mark a transition toward increasingly unsettled and
windy conditions. Winds will gradually strengthen through the day
as deeper tropical moisture associated with the remnants of Dolly
approaches the region, with showers and thunderstorms becoming
progressively more frequent. Activity should first increase across
the USVI Sunday morning, spread into Vieques, Culebra, and
eastern Puerto Rico by late morning into early afternoon, and
expand across Puerto Rico later in the day. With winds initially
becoming northeasterly ahead of the approaching wave, afternoon
shower and thunderstorm development should favor the southwestern
quadrant of Puerto Rico. Locally heavy rainfall may produce urban
and poor-drainage flooding, with isolated flash flooding possible
where the heaviest rainfall persists. Lightning and gusty winds
will also become increasingly important hazards.

Conditions will deteriorate further Sunday night as the wave and
deepest tropical moisture move across the islands. Numerous
showers and thunderstorms are expected, with the most persistent
activity favoring the USVI, Vieques, Culebra, and eastern Puerto
Rico. Periods of heavy rainfall will support an elevated excessive
rainfall risk, with urban and poor-drainage flooding becoming
increasingly likely and isolated flash flooding remaining
possible. Lightning and gusty winds will remain additional
hazards.

&&

.Long Term(Monday through next Thursday)...
Issued at 226 PM AST Fri Aug 28 2026

Higher-than-normal forecast uncertainty persists into the
beginning of the long-term period, primarily due to the evolution
of Tropical Storm Dolly and its associated moisture field. The
latest National Hurricane Center forecast indicates that Dolly
should continue moving quickly westward while weakening,
potentially degenerating into a remnant low before reaching the
local islands as it encounters increasingly unfavorable
environmental conditions. Nevertheless, Dolly and its associated
moisture will continue to be closely monitored for potential
impacts across the region.

A wetter pattern is favored Monday and possibly Tuesday as
moisture associated with Dolly`s remnants moves across or near the
local area. This should support increased shower and thunderstorm
activity, with a more widespread risk of limited flooding.
Steering flow should favor passing showers across windward areas,
followed by afternoon convection mainly across the interior and
western to northwestern portions of Puerto Rico. Locally heavier
rainfall will ultimately depend on Dolly`s track and structure.

Forecast confidence decreases regarding the timing and magnitude
of the moisture increase. Both the GFS and ECMWF generally
indicate above-normal precipitable water values from the beginning
of the workweek through at least Tuesday. However, the GFS
remains wetter and more aggressive in its moisture field, while
the ECMWF shows stronger ridging near the region that could
disrupt the system and limit the northward extent of deeper
moisture. Therefore, rainfall forecasts remain subject to change
as Dolly`s evolution becomes better defined.

Moisture should gradually decrease by late Tuesday as guidance
indicates low to moderate concentrations of Saharan dust reaching
the local islands. Nevertheless, precipitable water values are
forecast to remain above normal through midweek before becoming
more seasonable thereafter. Lingering moisture associated with
Dolly`s remnants should then be followed by another tropical wave
passing mainly south of the region Wednesday night into Thursday.
Additional moisture is expected on Friday. These features should
maintain periods of passing showers across windward areas, with
afternoon convection developing over Puerto Rico under a generally
east-southeast steering flow.

The increased cloud cover and rainfall expected Monday should
help limit the heat threat, with a more limited risk of excessive
heat currently anticipated. However, elevated to potentially
significant heat risks may return during much of the remainder of
the long-term period, particularly during intervals of reduced
cloud cover and rainfall.

Given the higher-than-normal uncertainty surrounding Dolly`s
evolution, continue to monitor the latest advisories from the
National Hurricane Center and subsequent local forecasts for
updates.

&&

.AVIATION...
(18Z TAFS)
Issued at 226 PM AST Fri Aug 28 2026

VFR conds are expected to prevail across most terminals thru the
fcst period. VCSH will remain psbl at TJPS this aftn, while
SHRA/iso TSRA across interior and W PR may briefly affect TJBQ and
vicinity with MVFR or lower cigs/vsbys. A weak disturbance will
bring passing SHRA overnight, mainly across TJSJ/TIST/TISX, with
brief MVFR conds psbl. Conds should improve and become mostly
VFR/drier after 29/13Z. E-ESE winds will peak at 15-20 kt thru
around 28/23Z, diminish to 5-10 kt overnight, then increase again
to 15-20 kt after 29/13Z.

&&

.MARINE...
Issued at 226 PM AST Fri Aug 28 2026

A weak tropical wave will bring a gradual increase in showers and
isolated thunderstorms by early Saturday. What used to be Tropical
Storm Dolly is now a broad tropical wave, moving westerly across the
central Tropical Atlantic, and reaching the islands from Sunday into
Monday. This will result in squally weather, strong gusts, and
higher seas across most local waters. Small craft advisories may be
issued as early as Saturday into Sunday for the Atlantic offshore
waters and the Anegada Passage.

&&

.BEACH FORECAST...
Issued at 226 PM AST Fri Aug 28 2026

The moderate risk of rip currents should continue along the east and
north facing beaches of Puerto Rico and the U.S. Virgin Islands
through Saturday. Beachgoers must exercise caution, as life-
threatening rip currents are possible along the surf zone. What used
to be Tropical Storm Dolly is now a broad tropical wave and will
deteriorate Sunday and Monday, swells from the system will increase
the risk to high, inexperienced surfers and beachgoers are urged to
remain out of the water. In addition, thunderstorms with cloud to
ground lightning and gusty winds are expected during this period.
Therefore, avoid unnecessary trips to the beach, particularly those
along the east and northern coast of Puerto Rico and the US Virgin
Islands.

&&

.HYDROLOGY...
Issued at 226 PM AST Fri Aug 28 2026

The remnants of Tropical Storm Dolly will arrive into the area late
on Sunday and Monday as a strong tropical wave. A widespread and
long-lasting rainfall event is not anticipated at this time.
Instead, areas of squally weather will bring periods of moderate to
locally heavy rainfall. These rains are expected to be mostly
beneficial due to the ongoing drought, but are not expected to be
enough to end the severe to extreme drought conditions. While the
risk of flooding will be low to locally moderate, some areas may
experience flooding if the drainage system is clogged with dead
vegetation debris or if it is in an area with poor drainage. Please
refer to the latest Hydrologic Outlook, ESFSJU, for more details.

&&

.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.
&&

$$

EVE...CAM
DAY...ICP/MMC

NWS SJU Office Area Forecast Discussion