533
FXCA62 TJSJ 060900
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sun Jul 6 2025

.KEY MESSAGES...

* High-level clouds may slightly reduce daytime heating, but a
  limited risk of excessive heat remains, especially affecting
  sensitive groups.

* Fire danger is elevated today across southern Puerto Rico due to
  very dry soils and fuels, low humidity, and breezy conditions,
  increasing potential for rapid fire spread after ignition.

* Persistent Saharan dust will maintain hazy skies and reduced
  visibility today, which may impact outdoor activities.

* Rip current risk is low today but will rise to moderate tonight
  and in the coming days. Exercise caution, especially on exposed
  beaches.


&&

.SHORT TERM...Today through Tuesday...

Mostly stable weather conditions prevailed during the night hours
across all the local islands. Late in the night and into the early
morning hours, a few isolated thunderstorms were detected by Doppler
radar over the Mona Passage. These thunderstorms remained over the
waters and did not affect land areas. Around 2 AM, some isolated
showers were observed across the eastern side. Shower activity was
relatively insignificant, and rainfall accumulations were minimal.
Overnight temperatures ranged in the 80s across the coastal areas
and the U.S. Virgin Islands, and in the lower 70s across most of the
mountain areas, with some locations reporting temperatures in the
upper 60s. Winds remained from the east at up to 10 mph, with land
breeze variations.

The forecast remains on track. Today, the islands will be under a
breezy pattern with easterly winds as a broad surface high-pressure
system remains in place across the central Atlantic, tightening the
pressure gradient. Under this pattern, Saharan dust particles will
persist across the region. According to the NASA Goddard Earth
Observing System Model V5, values of aerosol optical depth thickness
[550 nm] will stay between 0.20 and 0.30. This pattern will favor
mostly hazy skies with some cloudiness throughout the day.
Widespread shower activity is not expected; however, afternoon
convection is possible across the western interior due to local and
diurnal effects, with a limited flooding threat for the day.
Additionally, there will be a limited heat threat across the coastal
and urban areas with heat indices that could reach 105 to 108
degrees.

For the rest of the short-term period, stability will persist as a
mid-level ridge remains in place, providing drier air aloft and a
strong trade wind cap over the islands. Although stable weather
conditions will continue, trapped moisture at the 850 mb level will
favor some diurnal convection, mostly between 12 PM and 5 PM across
the western interior. For Tuesday, despite previous discussions
mentioning a tropical wave moving near the area, increasing the
potential for showers, global models now indicate that the bulk of
the moisture associated with this disturbance will remain well south
of the islands. Therefore, while some moisture is still expected,
widespread shower activity is not forecast at this time.

.LONG TERM...Wednesday through Sunday...

A trade wind perturbation will affect the region Wednesday,
bringing brief periods of enhanced moisture and localized showers.
Following this, a weak tropical wave will cross the area Thursday
into Friday, steered westward by a strong Bermuda-Azores High. A
wind surge will then bring breezy to windy conditions Friday into
the weekend, with 700 mb winds peaking near 3540 knots. This
pattern will support enhanced low-level moisture transport, though
mid- to upper-level dryness and a strong trade wind cap inversion
will limit deeper moisture availability and convection. Dry air
above 850 mb will persist due to subsidence from mid-level ridging
and later reinforced by a Tropical Upper-Tropospheric Trough
(TUTT) expected to cross the region Saturday. The most significant
drying will occur into early Sunday, with precipitable water
(PWAT) falling well below climatological norms.

Limited phasing of moisture and instability will restrict
widespread or organized convection; however, some afternoon
convection remains likely each day following the general wind flow
and driven by diurnal heating and local effects. Activity may
increase late Sunday as the TUTT shifts west and PWAT returns to
typical levels. A moderate to high Saharan Air Layer (SAL) event
is anticipated from Thursday onward, coinciding with the drying
trend and strengthening winds. This will contribute to hazy skies,
reduced visibility, and overall atmospheric stability.

Winds will generally flow from east to east-southeast, shifting
briefly to east-northeast Saturday night into Sunday as the
surface high repositions over the western Atlantic. Temperatures
will remain near seasonal norms, with Friday likely the warmest
day due to the strongest southeasterly flow component. Except for
excessive rainfall hazards, all other weather hazardsincluding
periods of excessive heat, gusty winds, and isolated afternoon
lightningare possible through the long-term period.


&&

.AVIATION...
(06Z TAF)

VFR conditions will persist along all the TAF sites during the
period. HZ and a diminution of VIS are still forecast until 07/23Z.
VCSH to SHRA is possible across TJBQ at around 07/19Z if a shower
develops along the western interior, diminishing the visibility
and lowering the ceilings. Winds will peak at 07/15Z from the E up
to 15 knots with gusty winds.


&&

.MARINE...

Moderate easterly winds will prevail today, but local effects will
lead to choppy seas near coastal areas, prompting small craft
operators to exercise caution. Moderate to locally fresh winds
will return tonight and persist over the next few days, expanding
the area where caution is advised. Saharan dust will keep skies
hazy through tonight, with another event expected later in the
workweek. Afternoon thunderstorms may affect coastal waters and
local passages, particularly near western Puerto Rico, each day.
In addition, tropical waves approaching Tuesday and Thursday will
likely increase the chances for showers, thunderstorms, gusty
winds, and locally higher seas.


&&

.BEACH FORECAST...

Moderate winds and improved marine conditions will result in a low
rip current risk across all beaches today. However, as winds
increase tonight and persist through the upcoming days, the rip
current risk is expected to gradually rise to moderate in select
areasbeginning along northwestern Puerto Rico tonight, then
extending to the north-central coast, Culebra, and Saint Croix on
Monday, and reaching Vieques and southeastern Puerto Rico by
Monday night. Beachgoers are advised to exercise caution,
particularly at exposed northern and eastern shorelines. For the
latest and most detailed updates on rip current risks, please
consult the Surf Zone Forecast (SRFSJU).


&&

.FIRE WEATHER...

The fire danger risk is elevated today as winds back from the east
and a drier air mass moves into the area. Persistent high-level
clouds may slightly reduce daytime heating, though they are
unlikely to significantly increase humidity or produce rainfall,
thus having minimal impact on lowering fire danger. Breezy
conditions combined with lower relative humidities, and very dry
and deteriorated soils and fuelsespecially in the driest
southern plains and hills of Puerto Ricowill support an increased
potential for fire spread. Refer to the latest Fire Danger
Statement (RFDSJU) for additional guidance.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...LIS
LONG TERM....ICP
AVIATION...LIS
PUBLIC...ICP/LIS