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410
FXCA62 TJSJ 121302 CCA
AFDSJU

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
902 AM AST Sun Jul 12 2026

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

.KEY MESSAGES...
Issued at 340 AM AST Sun Jul 12 2026

 * Moisture from a tropical wave passing south of the region will
  increase today and Monday, leading to a higher potential for
  showers across portions of western and interior Puerto Rico. The
  additional moisture will also contribute to heat indices
  ranging from 100 to 111F.

 * A Heat Advisory is in effect today from 10 AM to 5 PM. Heat
   indices are expected to reach dangerous levels, ranging between
   100 and 111F in some areas.

 * Moderate concentrations of Saharan dust will persist across the
   islands today, resulting in hazy skies and reduced visibility
   at times.

 * Breezy conditions will persist today, with moderate to fresh easterly
   winds expected across the region. These winds may result in
   choppy marine conditions and create difficult conditions for
   some outdoor and marine activities.

 * A moderate risk of rip currents continues across several local
   beaches. Life-threatening rip currents are possible, especially
   near piers, jetties, and sandbars.

&&

.Short Term(Today through Tuesday)...
Issued at 340 AM AST Sun Jul 12 2026

Fair weather conditions prevailed across the County Warning Area
(CWA) throughout the overnight hours. Satellite imagery indicated
minimal cloud coverage, with expansive areas of clear skies
dominating the region. Additionally, local radar observed a dry
and stable environment, with no shower activity detected across
the islands or the surrounding coastal waters. Overnight low
temperatures remained warm, in the upper 70s to lower 80s across
the coastal and metropolitan areas, while temperatures across the
higher elevations of the central interior dropped into the low to
mid-70s. As the morning progresses, a light haze will begin to
overspread the region due to an incoming pulse of Saharan dust.

A broad surface high pressure over the central Atlantic extending
into the Caribbean will hold an easterly wind flow with sustained
winds between 12-15 mph and some gusty winds. The presence of
Saharan dust particles will remain in place across the region
during the day, resulting in hazy skies and warm temperatures
throughout the day. As the day progresses, the moisture field from
a distant tropical wave moving well south over the Caribbean Sea
will gradually move low-level moisture into the region. The
moisture available will enhance a variable pattern across the area
with an increase in the showers` development as well as high
chances of observed heat indices that could reach 108 and 110
degrees. Having said that, for today, the heat threat will remain
elevated, and a heat Advisory is in effect from 10 AM to 5 PM AST
across all coastal areas and the vicinity of Caguas in Puerto Rico
and the U.S. Virgin Islands. In terms of showers, Hi-Resolution
models and the NBM model suggest rainfall activity along western
interior areas. Although showers will remain quite limited in coverage
due to the presence of the Saharan Dust particles, the heaviest
showers can result in some low-lying water accumulations.

By Monday, the surface high pressure will maintain steady easterly
winds below 3 kilometers, pushing a moisture field trailing over
the islands. This will increase precipitable water (PWAT) values
by 1.7 to 1.8 inches, making Monday the day with the highest
probability of shower activity. In fact, the GFS-based Galvez-
Davison Index (GDI) shows enhanced afternoon showers across the
western interior and western Puerto Rico, with a low probability
for one or two isolated thunderstorms embedded within the heaviest
downpours. On Tuesday, dry weather will quickly return as the
moisture leaves the area and strong stability takes over under the
upper-level ridge. A dense layer of Saharan dust will cover the
region, causing hazy conditions and suppressing most daytime rain
development. Along with the dry air, a limited to elevated heat
threat will develop due to maximum solar radiation and easterly
winds. This will increase daytime temperatures, pushing heat
indices between 100 and 108 F across coastal and urban areas.
Furthermore, the combination of these hot temperatures, low
relative humidity values, and breezy easterly winds will maintain
critically dry fuels and a high fire danger risk, especially along
the southern plains of Puerto Rico. For beachgoers and mariners,
the breezy conditions will also maintain choppy seas and a
moderate risk of rip currents across most local beaches.

&&

.Long Term(Wednesday through Sunday)...
Issued at 340 AM AST Sun Jul 12 2026

From Wednesday through Saturday, the primary impacts will
be periods of hazy skies, reduced visibility, poor air quality, and
hot daytime conditions as a Saharan Air Layer (SAL) affects the
region. Moderate to locally high concentrations of Saharan dust are
expected Wednesday through Thursday, resulting in the greatest
impacts during this long term period, particularly for sensitive
individuals in areas of thicker dust concentrations. Dust
concentrations should gradually decrease toward the weekend,
although some haze may linger through Saturday.

Shower activity will generally remain limited throughout the period.
On Wednesday, passing trade-wind showers will favor the U.S. Virgin
Islands and eastern Puerto Rico during the morning, followed by
isolated to scattered afternoon showers across the interior and
western sections of Puerto Rico. An increase in low and mid-level
moisture on Thursday may result in slightly greater shower coverage.
However, warm mid-level temperatures, modest lapse rates, and the
lingering influence of the SAL will maintain a relatively stable
atmosphere, preventing widespread deep convection. By Friday and
Saturday, moisture decreases to near or below normals while stable
mid-level conditions persist, limiting rainfall mainly to brief
trade-wind showers and isolated afternoon convection over western
Puerto Rico. No flooding concerns are anticipated through the period.

Seasonal to slightly above-normal temperatures are expected
throughout the period. Combined with abundant sunshine and
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. The presence of
Saharan dust through Thursday may also limit overnight radiational
cooling, resulting in warmer-than-normal minimum temperatures and
prolonging heat stress despite the gradual drying trend.

&&

.AVIATION...
(06Z TAFS)
Issued at 340 AM AST Sun Jul 12 2026

VFR conditions will prevail for the forecast period along the TAF
sites. Saharan dust will continue to affect the region, resulting
in HZ. E winds will persist between 12 and 18 knots, with higher
gusts between 20 and 25 knots possible. Showers will mainly
affect the western interior of PR resulting in brief periods of
lower ceilings and reduced visibility, especially near TJBQ from
12/19Z to 12/21Z. Winds will gradually diminish during the
overnight hours, with VFR conditions expected to continue.

&&

.MARINE...
Issued at 340 AM AST Sun Jul 12 2026

A weak tropical wave will move well south of the local islands
across the Caribbean Sea today. Meanwhile, strong Atlantic high
pressure will maintain moderate to locally fresh easterly to east-
northeasterly winds, resulting in choppy seas across the regional
waters. The high pressure will strengthen through early next week,
tightening the local pressure gradient and sustaining moderate to
fresh east to east-southeast winds and hazardous marine conditions.

&&

.BEACH FORECAST...
Issued at 340 AM AST Sun Jul 12 2026

Breezy trade winds will continue to create a moderate risk of life-
threatening rip currents along many beaches across Puerto Rico and
the U.S. Virgin Islands today. Through the middle of the week, the
rip current risk will remain elevated, particularly along north- and
east-facing beaches. Beachgoers should swim near lifeguards whenever
possible, heed beach warning flags, and never swim alone. An
elevated extreme heat risk is also expected along many beaches
today and through the first half of the week. Stay well hydrated,
seek shade whenever possible, and apply sunscreen to help reduce
the risk of heat-related illnesses.

This afternoon, isolated thunderstorms may develop over western
Puerto Rico. If you are at the beach or participating in outdoor
activities, remain alert for lightning. Remember: When thunder
roars, go indoors. Move to a substantial building or a hard-top
vehicle immediately.

&&

.FIRE WEATHER...
Issued at 340 AM AST Sun Jul 12 2026

Although a relatively drier airmass remains in place across the
local area this morning, moisture associated with a tropical wave
will gradually increase through the day. As a result, RH values may
briefly fall to near critical levels during the late morning,
particularly across the southern coastal plains, before recovering
into the low to mid 50s this afternoon as deeper moisture
overspreads the region. Easterly to east-northeasterly winds will
become easterly by around 10 AM, increasing to 10 to 15 mph with
locally higher speeds along the coast. The increasing moisture will
also support the development of showers across the western interior
during the afternoon.

While humidity values will improve later in the day, the
combination of briefly low RH values and breezy easterly winds
during the first half of the day will result in a moderate fire
danger, particularly across the southern coastal plains.
Therefore, a Fire Danger Statement has been issued for those
areas.

&&

.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.
&&

$$

LIS/CAM/MMC

NWS SJU Office Area Forecast Discussion