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964
FXCA62 TJSJ 121602
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1202 PM AST Wed Aug 12 2026

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

.KEY MESSAGES...
Issued at 1202 PM AST Wed Aug 12 2026

- Showers and thunderstorms will continue across the region as
  lingering moisture from a previous tropical wave moves across
  the islands.

- Saharan dust particles will return by Thursday, with a much
  drier air mass dominating the region.

- The heat threat will remain in place for the rest of the week,
  with hot temperatures and heat indices that could increase to
  around 108F, and up to 112F in isolated areas.

- Deteriorating marine and coastal conditions are forecast from
  Friday into the weekend. For more detailed information, read the
  Marine and Beach sections.

- Forecast uncertainty increases late this weekend into early
  next week as AL92 could approach the northeastern Caribbean,
  bringing increasing rain and thunderstorm potential. It remains
  too early to determine what impacts, if any, may occur.

&&

.Short Term(This afternoon through Friday)...
Issued at 1202 PM AST Wed Aug 12 2026

Abundant tropical moisture currently lingers over the region,
driving precipitable water values above 2.00 inches, well above
climatological normals. Atmospheric soundings indicate strong
convective instability paired with light-to-moderate low-level
steering flow. Daytime heating combined with local sea breeze
convergence and terrain interaction will trigger strong shower and
thunderstorm development this afternoon, particularly across the
interior, northern, and western portions of Puerto Rico, while
scattered passing showers impact the U.S. Virgin Islands and
eastern sections of PR. Strong gusty winds and urban and small
stream flooding remain the main weather hazard through late this
evening.

Quick drying will take place rapidly overnight into Thursday as a
robust Saharan Air Layer (SAL) with moderate concentrations of
dust spreads across the northeastern Caribbean. Latest model
guidance shows precipitable water values collapsing to between
1.10 and 1.40 inches, nearly two standard deviations below
seasonal levels, while mid-level relative humidity drops below 20
percent. This stable, dusty air mass will cap deep atmospheric
convection through Friday. Consequently, shower activity will be
suppressed across all the islands, limited only to shallow, brief
trade wind showers across windward areas during the overnight and
early morning hours, with a low probability of afternoon
thunderstorms or heavy showers as on previous days over western
PR. Hazy skies and poor air quality will prevail, posing potential
respiratory impacts for sensitive populations.

In addition to the SAL, strengthening of the Azores High will
promote a wind surge across the northeastern Caribbean by the end
of the workweek. Breezy trade winds averaging 15 to 25 mph with
stronger gusts are expected across the islands. These winds will
also promote elevated surf action and dangerous rip currents for
swimmers along the northern, eastern, and southern beaches of all
the islands. Furthermore, intense solar radiation combined with
the dry, dusty air layer on Thursday and Friday will push maximum
temperatures into the upper 80s and low 90s. When combined with
residual low-level moisture, peak afternoon heat indices will
likely reach heat advisory thresholds along coastal and urban
areas.

&&

.Long Term(Saturday through next Wednesday)...
Issued at 205 AM AST Wed Aug 12 2026

No major changes to the long-term forecast or the uncertainty
regarding AL92. Breezy to locally windy east to east-northeast winds
will continue into the weekend, with gusts potentially affecting
unsecured outdoor items across exposed coastal and higher-elevation
areas. Winds could approach advisory levels at times. A relatively
dry air mass and lower concentrations of Saharan dust will also
persist, with only brief passing showers expected. Heat and fire
weather concerns may continue under the dry and breezy pattern.

Forecast uncertainty increases considerably late this weekend into
early next week as AL92 moves westward to west-northwestward across
the tropical Atlantic. A wetter pattern with increasing showers and
thunderstorms, along with greater lightning and flooding risks, is
possible. However, considerable uncertainty remains regarding the
system`s track, intensity, timing, and any direct or indirect impacts
to Puerto Rico and the U.S. Virgin Islands. Continue to monitor NHC
and local forecasts.

&&

.AVIATION...
(18Z TAFS)
Issued at 1202 PM AST Wed Aug 12 2026

Locally induced SHRA/TSRA will continue to increase across the
local terminals through at least early this evening. Tempo MVFR
to brief IFR conds are possible at TJSJ/TJBQ fm 12/17-23. Across
the USVI terminals brief MVFR cigs possible at times. Mtn top
obscd across eastern PR. Also, HZ may reduce VIS to around 6SM at
times. The 12/12z TJSJ sounding indicated ESE winds up to 16 kt
blo FL050.

&&

.MARINE...
Issued at 1202 PM AST Wed Aug 12 2026

A broad surface high pressure and the influence of the previous
tropical wave will continue to result in moderate southeasterly
winds across the region for the rest of the day. Under this pattern,
the moisture field associated with the tropical wave will promote
thunderstorm activity that could trigger localized hazardous marine
conditions, with gusty winds and frequent lightning. As the surface
high pressure develops over the central Atlantic, a tightening
pressure gradient will enhance moderate to locally fresh easterly
winds across the region. This will result in choppy to hazardous
seas, building up to 7 feet across the exposed waters and 5 to 6
feet across the coastal waters. Given the expected conditions, Small
Craft Advisories may be in effect from Thursday night through the
weekend.

&&

.BEACH FORECAST...
Issued at 1202 PM AST Wed Aug 12 2026

A moderate risk of rip currents will continue through Thursday
for all northern and eastern exposed beaches of Puerto Rico, while
southern and western coastal areas will maintain a generally low
risk. Visitors and residents should remain alert this afternoon
into the evening, as developing coastal thunderstorms may
introduce localized hazards; immediate shelter should be taken if
lightning or heavy rain occurs near the shore. Looking ahead from
Friday through Monday, building trade winds will bring breezy
conditions and deteriorating surf across local waters, pushing the
rip current risk to HIGH for exposed coastlines. Formal High Rip
Current Statements will likely be issued tomorrow, and all
beachgoers are strongly urged to exercise extreme caution, swim
near lifeguards, and avoid entering hazardous surf conditions over
the coming days.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 4 PM AST this afternoon for PRZ001>005-007-
     008-010-011.

VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...DSR
KEY/MARINE/BEACH...LIS
LONG TERM....MRR

NWS SJU Office Area Forecast Discussion