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643
FXCA62 TJSJ 080545
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
145 AM AST Wed Jul 8 2026

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

.KEY MESSAGES...
Issued at 145 AM AST Wed Jul 8 2026

* The greatest potential for showers and isolated thunderstorms
  will occur today, mainly across western Puerto Rico. Localized
  flooding, dangerous lightning, and brief thunderstorm wind gusts
  will be possible. The next increase in tropical moisture and
  shower activity is expected early next week with another
  tropical wave.

* Breezy to windy easterly trade winds will persist through much of
  the forecast period. Hazardous conditions for small craft will
  continue across portions of the local waters, while a moderate
  risk of rip currents persists along many local beaches.

* Warm to hot conditions will persist through the forecast period.
  Heat concerns will increase late this week into early next week,
  while drier conditions will also increase the risk of fire
  spread.

* Moderate to high concentrations of Saharan dust will overspread
  the region through much of the forecast period, resulting in
  hazy skies, reduced visibility, and degraded air quality.


&&

.Short Term(Today through Friday)...
Issued at 145 AM AST Wed Jul 8 2026

Passing trade-wind showers moved across the local islands and
windward areas overnight. Temperatures remained around 80 degrees
across exposed coastal areas of eastern Puerto Rico and the U.S.
Virgin Islands, while the higher elevations cooled into the
mid-60s. The deepest tropical moisture associated with a departing
tropical wave will shift west of the area this morning; however,
sufficient low-level moisture, cooler-than-normal temperatures
aloft, and daytime heating will support scattered showers and
isolated thunderstorms this afternoon, mainly across the interior
and western Puerto Rico. Persistent mid-level dry air will limit
the overall coverage and organization of convection before
activity gradually diminishes this evening as drier-than-normal
air and moderate to high concentrations of Saharan dust overspread
the region.

Thursday through Friday, below-normal moisture, moderate to high
concentrations of Saharan dust, and persistent mid-level dry air
maintained by nearby ridging will promote a drier and more stable
weather pattern. Although another tropical wave will move across
the eastern Caribbean, the bulk of its tropical moisture is
expected to remain over the open Caribbean waters, resulting in
little local impact beyond maintaining breezy to windy easterly
trade winds. Expect mainly isolated passing showers, with
localized afternoon convection across western Puerto Rico, hazy
skies, and little to no thunderstorm activity.

Today`s primary hazards include localized urban and small-stream
flooding, frequent lightning, brief thunderstorm wind gusts,
breezy to windy trade winds, and increasing heat indices across
the lower elevations, coastal areas, and urban locations. By
Thursday and Friday, flooding and thunderstorm threats will
diminish considerably, while heat, fire danger, breezy to windy
trade winds, and periods of moderate to high concentrations of
Saharan dust reducing visibility and air quality become the
primary weather concerns.


&&

.Long Term(Saturday through Wednesday)...
Issued at 145 AM AST Wed Jul 8 2026

Saharan Dust and stable conditions will likely persist this upcoming
weekend, though moisture content should increase early next week. As
mentioned in the previous discussion, the wind pattern will likely
be dominated by a series of surface high pressures, with winds
veering from the E-ESE for most of the period. Although the local
pressure gradient may weaken by Sunday, winds should remain
seasonal, with breezy to locally windy conditions throughout the
forecast period. Shower activity should remain limited on Saturday
and Sunday, as model guidance continues to suggest drier-than-normal
conditions (PWAT values between 1.2 and 1.4 inches), with dry slots
in the low and mid levels. Additionally, a dense, broad plume of SAL
will continue to filter into the region, with moderate and high
concentrations across the CWA. These conditions will likely result
in hazy skies, reduced visibility, and deteriorated air quality.
Although daytime heating, local effects, and sea breeze convergence
may induce convection, any shower development should remain fast-
moving and short-lived, with low rainfall accumulations. A weak
tropical wave should approach the Caribbean Basin, pooling tropical
moisture into the region, through global model solutions disagree in
the time of arrival of the system. The ECMWF shows abundant moisture
content approaching late Sunday night into early Monday, while the
GFS continues to suggest more shower activity by Monday afternoon
into the evening. Although the long-term forecast is tending more to
the latest GFS solutions and NBM suggestions, theres uncertainty
regarding the TOA and any shower activity related to the tropical
wave. Variability remains high as Saharan Dust concentrations
persist across both the Atlantic and Caribbean Basin, according to
the latest NASA GEOS Dust AOT, which may weaken the tropical wave.
The weather pattern on Tuesday and Wednesday will be similar to
Saturday and Sunday, with drier and more stable conditions across
the islands.

In terms of heat, seasonal temperatures combined with available
moisture will lead to heat indices reaching and exceeding 100
degrees Fahrenheit, particularly over urban and low-lying areas of
the islands. As mentioned in previous discussions, the presence of
Saharan Dust will likely continue to inhibit nighttime cooling, with
warmer minimum temperatures. Therefore, the heat threat will likely
remain elevated throughout the forecast period.

&&

.AVIATION...
(06Z TAFS)
Issued at 145 AM AST Wed Jul 8 2026

VCSH/SHRA will continue across TJSJ/TIST/TISX through 08/10-14Z.
SHRA/isol TSRA will develop near TJSJ/TJBQ between 08/16-22Z,
producing brief MVFR/IFR VIS/CIGS and gusty winds. SHRA will
diminish from E-W late today as drier air and increasing HZ spread
across the area. Moderate to high concentrations of Saharan dust
will produce HZ and occasional VIS reductions at all TAF sites.
E-ESE sfc winds increase to 20-25 kt with G30-35 kt through
08/22Z, diminishing thereafter.

&&

.MARINE...
Issued at 145 AM AST Wed Jul 8 2026

A broad surface high pressure over the central Atlantic will
maintain moderate to fresh east to east-southeast winds and choppy
to hazardous seas through the end of the workweek. A fast-moving
tropical wave will briefly increase showers and isolated
thunderstorms this morning before drier, dustier conditions return
by later this evening. Moderate to high concentrations of Saharan
dust will continue to produce hazy skies and occasional
visibility reductions. Small craft advisories will be in effect
from noon today through late Friday night, due to a combination of
7 ft seas and 20- 25 kt easterlies across both Atlantic and
Caribbean waters, including the Mona Passage.

&&

.BEACH FORECAST...
Issued at 145 AM AST Wed Jul 8 2026

Wind driven waves will maintain a moderate risk of rip currents
across most beaches of Puerto Rico and the US Virgin Islands through
the next several days. Breezy conditions and periods of passing
showers with possible isolated thunderstorm development will
continue today with the passage of a tropical wave. An elevated heat
threat will prevail most days, with heat indices ranging between 100-
110F across most coastal areas, particularly along the north, west,
and southern coastlines of Puerto Rico. Beach goers are encouraged
to stay hydrated, seek shade frequently, avoid prolonged sun
exposure during the hottest part of the day, and move indoors
immediately if thunderstorms develop.

&&

.FIRE WEATHER...
Issued at 145 AM AST Wed Jul 8 2026

The departure of a tropical wave will maintain slightly higher
low-level moisture today, limiting fire weather concerns despite
breezy to locally windy easterly trade winds. However, critically
dry vegetation and persistent soil moisture deficits will continue
to support wildfire development, and any ignition could still
spread through the available fine fuels. By Thursday, below-normal
moisture, moderate to high concentrations of Saharan dust, and
increasingly dry conditions will overspread the region, while
breezy to windy trade winds persist. This combination will become
more favorable for wildfire growth through the end of the workweek
and into the weekend. Residents and visitors should avoid outdoor
burning and exercise extreme caution with any activity capable of
producing sparks or open flames.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory from noon today to midnight AST Friday
     night for AMZ711-733-741.

     Small Craft Advisory from noon today to midnight AST tonight for
     AMZ712-735.

&&

$$

EVE...DSR/MNG
MID...ICP

NWS SJU Office Area Forecast Discussion