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178
FXCA62 TJSJ 200635
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
235 AM AST Sat Jun 20 2026

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

.KEY MESSAGES...
Issued at 235 AM AST Sat Jun 20 2026

* A Heat Advisory remains in effect today for coastal and urban
  areas of Puerto Rico and the U.S. Virgin Islands. Sensitive
  individuals may experience heat-related illnesses without
  adequate hydration, cooling, and frequent breaks from the heat.

* Moderate to high concentrations of Saharan dust will continue
  through at least late tonight, reducing air quality and
  visibility while increasing the risk of respiratory issues for
  sensitive groups. Dust concentrations may briefly decrease on
  Sunday as a tropical wave moves through the region, but are
  expected to increase again behind the wave and persist into
  early next week.

* A tropical wave moving through the region on Sunday will
  increase the potential for heavy rainfall, thunderstorms, urban
  and small-stream flooding, and isolated flash flooding across
  portions of Puerto Rico and the U.S. Virgin Islands.

* Dangerous heat index values will continue each afternoon
  through much of the forecast period, increasing the risk of heat
  exhaustion and heat stroke, especially in coastal and urban
  areas, poorly ventilated locations, and among vulnerable
  populations.

* Life-threatening rip currents remain possible at some exposed
  beaches across Puerto Rico and the U.S. Virgin Islands.
  Beachgoers should swim near lifeguards and follow local beach
  safety guidance.

&&

.Short Term(Today through Monday)...
Issued at 235 AM AST Sat Jun 20 2026

Overnight, we had little or no rain as a drier air mass with
moderate to high concentrations of Saharan Air Layer (SAL)
remained over the Northeast Caribbean. The SAL limited nocturnal
radiational cooling, leaving overnight temperatures in the upper
70s to the lower 80s across coastal and urban areas, and in the
mid to upper 60s along the mountains. Most wind stations reported
east to east-southeast winds of 5 to 15 mph, with fluctuations due
to land breezes. However, some stations in the Northern US Virgin
Islands reported northeast winds of 15 to 20 mph, with higher
gusts.

Another day under hazy skies due to moderate to locally high
concentrations of Saharan Dust Particles is expected across the US
Virgin Islands and Puerto Rico today. This air mass will degrade
air quality and visibility, possibly worsening respiratory
symptoms in sensitive individuals. Additionally, the combination
of warmer-than-normal maximum temperatures and available moisture
will lead to dangerous heat indices, especially between 10 and 4
PM AST. This intense heat will affect many individuals sensitive
to high temperatures, particularly those without effective cooling
methods or sufficient hydration. Therefore, a Heat Advisory is in
effect for coastal and urban areas in the USVI and PR.

Still, the strong surface high-pressure system across the
Atlantic Ocean will tighten the local pressure gradient, resulting
in breezy east-to-east-southeast winds across much of the region.
This wind flow will transport occasional pockets of moisture,
clouds, and showers across the USVI and PR`s windward sectors. At
the same time, daytime heating and local effects may trigger
isolated to scattered afternoon convection across the interior and
western portions of Puerto Rico, as well as downwind from the
USVI. At this moment, looks like this weather pattern will repeat
on Monday as a dry, dusty air mass filters in behind Father`s
Day`s trailing tropical wave.

The NASA Dust Aerosol Optical Thickness guidance continues to
indicate low to moderate concentrations of Saharan dust
surrounding the Father`s Day tropical wave. However, model
guidance still suggests the best rain day for the region, although
weather guidance has been overestimating rainfall over the past
few days. That being said, this feature will increase moisture
availability and enhance the potential for showers and
thunderstorms, raising the risk of heavy rainfall, urban and
small-stream flooding, and isolated flash flooding across portions
of Puerto Rico and the U.S. Virgin Islands. Forecast confidence in
the amount and intensity of rainfall remains somewhat uncertain.
This uncertainty arises from the interaction between the moist air
mass associated with the tropical wave and the drier, more stable
air mass of the SAL surrounding the wave. We will continue to
monitor the situation closely and update the forecast as our
confidence grows.

&&

.Long Term(Tuesday through Saturday)...
Issued at 235 AM AST Sat Jun 20 2026

The long-term pattern aligns towards a typical June weather
conditions. Moisture content, relative humidity values, and mid-
level temperatures are forecast to remain near normal values for
this time of the year, supporting a fairly typical trade-wind
pattern across the islands.

On Tuesday, a relatively stable air mass will prevail across the
region. Passing trade-wind showers will continue to affect windward
and eastern sections of the islands, while leeward areas experience
mostly fair weather. Temperatures will remain seasonably warm, with
highs in the upper 80s to low 90s across coastal and urban areas.

A tropical wave is forecast to move across the region on Wednesday
and Thursday. While the wave will bring an increase in low-level
moisture and result in a higher frequency of passing showers, model
guidance suggests precipitable water values will remain near
seasonal values. In addition, mid-level relative humidity values
remain relatively low and temperatures near 500 mb stay close to
normals, limiting the potential for widespread deep convection. As a
result, periods of passing showers are expected, particularly across
windward and eastern sections in the morning as well as the
afternoon convection across western PR, but significant rainfall
accumulations are not anticipated at this time.

By late Thursday and continuing through Saturday, a slightly drier
air mass will filter into the region. This will promote a decrease
in shower coverage and support a return to a more typical trade-wind
weather pattern. Although isolated showers will remain possible
across windward areas, mostly fair weather conditions are expected
elsewhere. Temperatures will continue near seasonal normals, and no
significant weather impacts are anticipated through the end of the
forecast period.

&&

.AVIATION...
(06Z TAFS)
Issued at 235 AM AST Sat Jun 20 2026

A dense SAL will continue to lower visibilities across portions of
the local flying area. Thus, expect HZ with VSBY dropping to near
6 SM, limited SHRA/-SHRA activity, without ruling them out. SHRA
will form along the Cordillera and W-PR by this afternoon. Winds
will be calm to light and variable overnight, and after 20/13z,
expect E-ESE winds at 10-20 kt, with gusts up to 30 kt. A tropical
wave will begin to reach the region, increasing the chance for
SHRA/TSRA after 20/2350z.

&&

.MARINE...
Issued at 235 AM AST Sat Jun 20 2026

A broad surface high pressure building over the Central Atlantic
will continue to promote moderate to locally fresh easterly to east-
southeasterly winds over the next several days. These conditions
will create choppy seas across local waters and Caribbean passages;
small craft should exercise caution. Meanwhile up to moderate and
high concentrations of Saharan Dust will persist throughout the
weekend and into the workweek, resulting in hazy skies, reduced
visibility, and poor air quality. A tropical wave is expected to
move across the Caribbean Sea Sunday into Monday, increasing the
likelihood of showers and isolated t-storms across the regional
waters.

&&

.BEACH FORECAST...
Issued at 235 AM AST Sat Jun 20 2026

Breezy to locally windy conditions will maintain up to a moderate
risk of rip currents during the next few days. Areas under a
moderate risk of rip currents today and tonight include: northern,
southeastern and southwester PR, as well as St. Croix, Vieques and
Culebra. Life-threatening rip currents are possible in the surf zone
at areas with a moderate risk. Even in areas with a low risk, life-
threatening rip currents often occur in the vicinity of groins,
jetties, reefs, and piers. The moderate risk is forecast to spread
across most of the local beaches, with most of them being under a
moderate risk late tomorrow and into the workweek.

Concentrations of Saharan Dust will continue to move over the
islands during the next several days, resulting in hazy skies,
reduced visibility, and poor air quality. High heat indices will
also persist during the period, sensitive groups should take
necessary precautions. Residents and visitors are encouraged to
follow the latest weather forecast, as afternoon showers and
isolated thunderstorms can be expected this weekend and early next
week, particularly near coastal areas of western/northwestern Puerto
Rico.

&&

.FIRE WEATHER...
Issued at 235 AM AST Sat Jun 20 2026

A Fire Danger Statement has been issued for today across portions
of the coastal plains and hills of southern and western Puerto
Rico, Vieques and St. Croix due to the combination of critically
dry fuels, sustained winds of 15 to 20 mph with gusts up to 25
mph, and minimum relative humidity values in the low 50s or even
in the 40s. These conditions will favor rapid wildfire ignition
and extreme fire behavior, meaning any fires that develop will
likely spread quickly and become difficult to contain. Outdoor
burning is highly discouraged.

Fire and emergency officials should be aware that weather
conditions are becoming more conducive for the ignition and spread
of wildfires.

&&

.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.
&&

$$

KEY MESSAGE/SHORT TERM/AVIATION/FIRE WEATHER...CAM
LONG TERM....MMC
MARINE/BEACH FORECAST...MRR

NWS SJU Office Area Forecast Discussion