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303
FXCA62 TJSJ 110754
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
354 AM AST Sat Jul 11 2026

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

.KEY MESSAGES...
Issued at 350 AM AST Sat Jul 11 2026

* Above-normal temperatures will persist today with maximum
  temperature in +2 or +3 degrees from normals, enhancing warm
  conditions across urban sections and some western coastal areas.

* Moderate to fresh easterly winds, occasionally strong, will
  persist through early next week, especially across coastal waters
  and exposed areas.

* For most of the short term period, moderate to high
  concentrations of Saharan dust will result  in hazy skies and
  reduced air quality and limited shower activity.

* From Sunday into Monday, a tropical wave is expected to increase
  moisture across the region, increasing to a higher potential
  for showers and isolated thunderstorms.

* For today, elevated to critical fire weather conditions will
  continue through the weekend due to dry soils, low relative
  humidity, and breezy conditions.

&&

.Short Term(Today through Monday)...
Issued at 350 AM AST Sat Jul 11 2026

Fair and tranquil weather conditions prevailed across the County
Warning Area (CWA) throughout the overnight hours. Satellite
imagery indicated minimal cloud coverage, with expansive areas of
mostly clear skies dominating the region. Additionally, local
radar observed a dry and stable environment, with no significant
shower activity detected across the islands or the surrounding
coastal waters. Overnight low temperatures remained warm, hovering
in the upper 70s across the western plains and most coastal
areas, while the San Juan metropolitan area experienced lows in
the lower 80s. Meanwhile, much cooler conditions were observed
across the higher elevations of the central interior, where
minimum temperatures comfortably dropped into the low to mid-70s.

Precipitable water (PWAT) derived from satellite imagery shows a
drier air mass dominating the local region today, with PWAT
values around 1.30 inches. At the surface, a broad high-pressure
system over the central Atlantic extending into the Caribbean,
coupled with strong high pressure at the 700 mb level located over
the western Atlantic, will maintain a steady easterly wind flow.
Within the lowest 3 kilometers (1000-700 mb layer), sustained
winds will range from 12 to 16 mph, with gusty conditions
occasionally reaching up to 30 mph. Given the suppressed moisture
profile and widespread subsidence, conditions call for a mostly
dry day with limited cloudiness. There is only a very low chance
of localized, short-lived afternoon showers along the western
interior sections, and no flooding impacts are expected across the
islands.

Regarding the HEAT THREAT today, impacts will be heavily driven by
daily temperatures rather than deep available moisture. Due to the
aforementioned lack of cloud cover allowing for maximum solar
insolation, daytime high temperatures are forecast to rapidly
climb 2 to 3 degrees above climatological normals, reaching the
lower 90s across the southwestern and south-central plains, as
well as the San Juan metropolitan area. Furthermore, model
guidance at the 925 mb level indicates temperatures staying around
the 50th percentile, which supports this significant diurnal
warming trend. The breezy easterly winds in the lower levels will
allow drier air to mix down to the surface, which typically limits
widespread excessive humidity. However, particularly between 12 PM
and 2 PM, localized heat indices are expected to briefly peak
between 106 and 108 F, specifically across the San Juan metro
area and the western coastal municipalities between Anasco and
Aguada. Because these peak heat values of 106 to 108 F will be
highly localized, a Heat Advisory will not be issued for today.
However, residents are urged to stay hydrated, avoid strenuous
outdoor activities, and take breaks in the shade when working
outdoors.

Conditions for Sunday and Monday will change as the moisture field
from a distant tropical wave moving well south of the islands
increases the frequency of cloudiness and occasional passing
showers across the area. Accompanying this moisture, which is
forecast to remain on the lower side of climatological normals,
another pulse of Saharan dust will move in. These moderate dust
concentrations will result in hazy skies across the region.
Therefore, the forecast for these days includes morning passing
showers across eastern sections, followed by localized afternoon
convection across the western interior sections. In terms of the
heat threat, conditions will become more favorable for widespread
heat indices between 104 and 108 F. The influx of low-level
moisture will increase dewpoint temperatures, and when combined
with good periods of daytime solar radiation, there is a medium to
high probability that Heat Advisories will be required if these
conditions materialize. Residents and visitors are urged to stay
tuned for further weather updates and to remain hydrated
throughout the day.

&&

.Long Term(Tuesday through Saturday)...
Issued at 350 AM AST Sat Jul 11 2026

The overall weather pattern during the first half of the long-term
period will remain influenced by a weak upper-level trough/nearby
upper-level low. This feature will help maintain instability despite
a gradual drying trend. Model guidance continues to indicate mid-
level relative humidity values ranging between the the and 75th
percentiles through Wednesday, while 500-mb temperatures remain
relatively cool, around -8 to -9 degrees Celsius. These conditions
will support the potential for locally enhanced convection,
especially where sea breeze convergence and daytime heating are
maximized. The best chance for showers and thunderstorms will be
from Tuesday into Wednesday, with passing showers favoring the
U.S. Virgin Islands and eastern Puerto Rico during the morning
hours, followed by scattered afternoon convection across the
interior and western sections of Puerto Rico. Although locally
heavy rainfall and isolated ponding of water remain possible,
widespread flooding is not anticipated. At the same time, Saharan
Air Layer (SAL) intrusion is forecast to affect the region from
Tuesday through Thursday. The latest model guidance continues to
indicate moderate to locally high concentrations of Saharan dust
at times, resulting in hazy skies, reduced visibility, and
deteriorating air quality, particularly for sensitive groups.
While the upper-level pattern remains somewhat favorable for
instability, the presence of the SAL may suppress convective
coverage and intensity by introducing drier air aloft and limiting
deep cloud development.

From Thursday through Saturday, precipitable water values are
forecast to decrease to near or below normals as mid-level
temperatures gradually warm and relative humidity decreases. This
evolution should promote a more stable environment, limiting shower
activity primarily to brief trade-wind showers during the overnight
and morning hours, followed by isolated afternoon convection over
portions of the western interior of Puerto Rico. Any rainfall should
generally remain localized, with a low flooding threat through the
latter half of the workweek.

Seasonal to slightly above-normal temperatures are expected
throughout the period. Combined with sufficient low-level moisture,
afternoon heat indices will likely exceed 100 degrees Fahrenheit
across urban and coastal areas, particularly along the northern and
southern coastal plains of Puerto Rico and portions of the U.S.
Virgin Islands. In addition, the presence of Saharan dust may reduce
overnight radiational cooling, leading to warmer-than-normal minimum
temperatures and maintaining an elevated heat risk through much of
the workweek despite the gradual drying trend.&&

.AVIATION...
(06Z TAFS)
Issued at 350 AM AST Sat Jul 11 2026

VFR conditions are expected to prevail across all terminals during
the next 24 hours. A very dry air mass will maintain mostly clear
skies, limiting cloudiness to only a FEW high-level clouds. Hazy
skies due to suspended Saharan dust particles could slightly
reduce surface visibility at times.. Mainly easterly surface
winds at around 10 to 13 kts will persist through the early
morning, increasing to around 15 to 18 kts with higher gusts by
11/15Z.

&&

.MARINE...
Issued at 350 AM AST Sat Jul 11 2026

A broad surface high pressure centered over the central Atlantic,
combined with a low pressure over northern South America, will
maintain a tight pressure gradient across the northeastern Caribbean
through at least this evening. This pattern will support moderate to
fresh easterly winds with occasional strong gusts, particularly
across the offshore Caribbean waters. These conditions will maintain
choppy to hazardous seas, especially across the offshore Caribbean
waters and the Mona Passage. Moderate to high concentrations of
Saharan dust will persist through the weekend, producing hazy skies
and reduced visibility. A weak tropical wave is expected to move
across the local waters around Sunday, increasing the risk of
showers and thunderstorms, along with locally higher winds and seas
near the strongest activity.

&&

.BEACH FORECAST...
Issued at 350 AM AST Sat Jul 11 2026

Increasing trade winds will elevate the risk of life-threatening rip
currents along many beaches across Puerto Rico and the U.S. Virgin
Islands through the weekend. Beachgoers should swim near lifeguards
whenever possible, heed beach warning flags, and never swim alone.

In addition, a limited risk of excessive heat is expected along many
local beaches each afternoon. Stay well hydrated, seek shade when
possible, and use sunscreen to reduce the risk of heat-related
illnesses.&&

.FIRE WEATHER...
Issued at 350 AM AST Sat Jul 11 2026

Conditions are highly favorable for rapid fire dispersion across
the region today. Surface observations have been indicating
relative humidity values dropping into the lower 50s, generally
ranging between 50 and 60 percent, particularly across the
southern coastal plains of Puerto Rico. This significantly dry air
mass is being accompanied by breezy conditions, with sustained
easterly winds between 15 and 18 mph and frequent wind gusts
between 25 and 30 mph. Given these breezy and dry conditions,
coupled with persistent rainfall deficits, critically dry fuels
continue across much of Puerto Rico, Vieques, Culebra, and St.
Croix. Therefore, a Fire Danger Statement remains in effect today.
Additional fire weather products may be needed through the
weekend, particularly tomorrow, Saturday; please stay tuned to the
forecast.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until midnight AST tonight for AMZ711-733-
     741.

&&

$$

LIS/MMC/CAM

NWS SJU Office Area Forecast Discussion