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444
FXCA62 TJSJ 060635
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
235 AM AST Mon Jul 6 2026

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

.KEY MESSAGES...
Issued at 235 AM AST Mon Jul 6 2026

* Dangerous heat will be the primary weather hazard today. A Heat
  Advisory is in effect today as hot temperatures combine with
  increasing humidity to produce dangerous heat indices. Similar
  conditions are expected Tuesday, with warm to hot conditions
  likely continuing through the remainder of the week.

* Moderate to locally high concentrations of Saharan dust will produce
  hazy skies, reduced visibility, and degraded air quality
  through Tuesday. A brief improvement is expected Wednesday
  before dusty conditions return late Wednesday into Thursday.

* A fast-moving tropical wave may bring a brief increase in
  showers and thunderstorms on Wednesday, with isolated
  lightning, locally heavy rainfall, and localized urban and
  small-stream flooding possible.

* Breezy easterly winds will continue each day, creating choppy
  marine conditions and maintaining a moderate risk of rip
  currents at most local beaches.


&&

.Short Term(Today through Wednesday)...
Issued at 235 AM AST Mon Jul 6 2026

Overnight, breezy easterly trade winds steered a few fast-moving
showers across the local waters and windward areas with little to
no impacts. More importantly, persistent high-level cloudiness,
warm surrounding waters, and continued onshore flow limited
nocturnal cooling, with many coastal locations only falling to
around 80 to 82 degrees. The lack of overnight relief, combined
with a shallow increase in low-level moisture confined below 850
mb, will result in higher humidity and dangerous heat indices
today despite having little impact on rainfall potential.
Afternoon temperatures will once again climb into the upper 80s
and lower 90s, while moderate to high concentrations of Saharan
dust and persistent dry mid-level air continue to promote hazy
skies, degraded air quality, and suppress widespread shower and
thunderstorm development. A Heat Advisory remains in effect for
portions of the islands today as dangerous heat becomes the
primary weather hazard. Similar conditions are anticipated again
on Tuesday. Breezy easterly trade winds will persist each day,
with the strongest gusts developing during the early afternoon due
to local sea-breeze influences.

A brief transition is expected on Wednesday as a fast-moving
tropical wave crosses the eastern Caribbean, bringing a temporary
increase in moisture and instability. This may result in increased
showers and isolated thunderstorms, with localized urban and
small-stream flooding and frequent lightning becoming the primary
weather hazards. Heat will remain a concern, especially across
coastal and urban areas, before another surge of drier air and
Saharan dust spreads across the region Wednesday night, quickly
restoring hazy skies, degraded air quality, and a hotter, more
stable weather pattern.


&&

.Long Term(Thursday through Monday)...
Issued at 235 AM AST Mon Jul 6 2026

The long-term forecast remains on track, with no significant changes
introduced since the previous discussion. A building surface high
pressure system north of the region will maintain a tight pressure
gradient, promoting breezy to windy conditions across the islands
through the first half of the long-term period. Winds are expected
to prevail from the east-east southeast through Saturday, before
veering from the east-northeast from Sunday into Monday morning.

On Thursday, moisture associated with the northern periphery of a
passing tropical wave will approach the region. Nonetheless, the
bulk of the moisture from this wave is expected to remain well south
of the area over the Caribbean Sea, keeping local impacts minimal.
The latest precipitable water analysis indicates below-normal
moisture for the period, with precipitable water (PWAT) values
dropping to 1.25 to 1.30 inches on Thursday. Therefore, no
significant flooding impacts are expected with this wave.

Following the passage of the wave, a mid-level ridge is expected to
strengthen, promoting drier and more stable conditions through the
remainder of the period. From Friday onward, a drier air mass will
begin to filter into the region alongside a dense plume of the
Saharan Air Layer (SAL). Moderate to high concentrations of dust
will reach the area throughout the weekend, promoting hazy skies,
reduced visibilities, and poor air quality. Sensitive groups,
particularly those with respiratory issues or allergies, should take
necessary precautions to limit outdoor exposure.

Conditions will remain very similar throughout the weekend, with a
slight increase in moisture expected by the beginning of next week
as another disturbance approaches the islands. Temperatures at 925
mb will remain within seasonal values during the period, with
maximum temperatures reaching the upper 80s and low 90s across
coastal and urban areas, and the low to mid-80s in the mountains.
However, heat indices are forecast to reach or exceed 100F each
afternoon. Residents and visitors are strongly urged to practice
heat safety by staying hydrated, limiting strenuous outdoor
activities, and taking frequent breaks in shaded or air-conditioned
areas.


&&

.AVIATION...
(06Z TAFS)
Issued at 235 AM AST Mon Jul 6 2026

VFR conditions will prevail at all TAF sites through the forecast
period. Moderate to high concentrations of SA dust will continue
to produce HZ and reduce VIS at times. Brief VCSH are possible in
the vicinity of TJSJ and TJBQ between 16-22Z. E-ESE winds of 10-18
kt will become locally gusty after 14Z due to sea-breeze
development, with the strongest gusts during the afternoon.


&&

.MARINE...
Issued at 235 AM AST Mon Jul 6 2026

A broad surface high pressure building over the central Atlantic
will promote a moderate to locally fresh east to east-southeast
winds, resulting in choppy seas for the next several days. By the
middle of the week, an approaching tropical wave will increase the
shower and thunderstorm activity across regional waters that may
lead to locally hazardous marine conditions. Meanwhile, moderate to
high concentrations of Saharan Dust will linger across the region
through mid week, bringing hazy skies, reduced visibility and poor
air quality.


&&

.BEACH FORECAST...
Issued at 235 AM AST Mon Jul 6 2026

The beach forecast continues on track. As winds continue to
strengthen, the moderate risk of rip currents will continue across
most beaches of Puerto Rico and the U.S. Virgin Islands. As
mentioned in previous discussions, beachgoers must exercised
caution, as life-threatening rip currents remain possible along the
surf zone. Based on the latest model guidance, winds will likely
remain strong, leading to breaking waves between 3 and 5 feet, for
the next few days. Besides rip currents, beachgoers should remain
weather alert, particularly for elevated heat risks today and the
arrival of a tropical wave that will increase shower and
thunderstorm activity and may move near coastal areas of the
islands on Wednesday. Additionally, moderate to high
concentrations of SAL will linger throughout the week, with the
lowest concentrations on Wednesday. Sensitive groups must continue
to follow medical recommendations.


&&

.FIRE WEATHER...
Issued at 235 AM AST Mon Jul 6 2026

Weather conditions will be less supportive of rapid wildfire
growth today and Tuesday as low-level moisture and relative
humidity increase. However, critically dry fuels and severe soil
moisture deficits persist across portions of southern Puerto Rico,
with Keetch-Byram Drought Index (KBDI) values remaining above 550
and locally exceeding 660. Any fire that develops may still spread
through the dry vegetation, particularly across the southern
coastal plains and adjacent lower elevations, although increased
humidity should limit fire growth compared to recent days.
Residents and visitors should continue to avoid outdoor burning
and exercise caution with any activity capable of producing sparks
or open flames.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for PRZ001>005-007-008-010>013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for VIZ001-002.

AM...None.
&&

$$

.EVE...GRS/MNG
.MID...ICP

NWS SJU Office Area Forecast Discussion