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172
FXCA62 TJSJ 171720
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
120 PM AST Wed Jun 17 2026

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

.KEY MESSAGES...
Issued at 115 PM AST Wed Jun 17 2026

* Periods of showers and isolated thunderstorms are expected on
  Thursday and Friday, and again late Fathers Day weekend into
  early next week, increasing the potential of urban and small
  stream flooding.

* Seasonal temperatures will continue for the rest of the workweek
  and Fathers Day weekend, with heat indices ranging from the mid
  90s and mid 100s across urban and low-lying areas of Puerto
  Rico and the U.S. Virgin Islands.

* Moderate concentrations of Saharan Dust are expected to arrive
  to the region by late Thursday, bringing hazy skies, reduced
  visibility, and deteriorated air quality.

&&

.Short Term(This evening through Friday)...
Issued at 115 PM AST Wed Jun 17 2026

A relatively dry and stable air mass will keep weather conditions
generally quiet across Puerto Rico and the U.S. Virgin Islands
through tonight. However, strong daytime heating, combined with
local effects, will still trigger scattered afternoon showers and
isolated thunderstorms, primarily over portions of the interior
and western Puerto Rico, where brief heavy rain could cause minor
ponding on roads. Additionally, breezy easterly winds and dry
conditions will maintain an elevated fire weather risk across the
southern coastal plains of Puerto Rico. As of 1 PM AST, daytime
highs were in the mid-80s to low 90s across all the islands, with
heat indices in the mid-to upper 90s.

Moisture will increase noticeably on Thursday as a weak tropical
wave moves into the region. Precipitable water values are forecast
to rise to around 1.75 inches, leading to greater coverage of
showers and thunderstorms. Passing showers will affect windward
coasts and the U.S. Virgin Islands during the morning, followed by
stronger convection over the interior and western PR in the
afternoon. The main impacts expected from this activity are
localized urban and small stream flooding, slippery roads, and gusty
winds.

A sharp drying trend takes hold on Friday as the tropical wave exits
and a dense layer of Saharan dust spreads across the region through
the morning hours. Precipitable water will drop significantly below
seasonal averages, to around 1.40 inches, and combined with the
Saharan Air Layer suppressing deep, organized convection and
limiting rainfall across the islands. The primary hazard will
transition to widespread hazy skies, reduced horizontal visibility,
and degraded air quality, which may affect individuals with
respiratory sensitivities. Breezy conditions will prevail through
the short-term period in response to a building surface high
pressure over the central Atlantic.

&&

.Long Term(Saturday through next Tuesday)...
Issued at 300 AM AST Wed Jun 17 2026

Over the weekend, a broad surface high-pressure system over the
central Atlantic will maintain a typical easterly trade wind
pattern across the northeastern Caribbean. A relatively dry air
mass and intermittent intrusions of Saharan dust will support
generally stable weather conditions, hazy skies at times, and warm
to locally hot daytime temperatures. Passing showers embedded
within the trade wind flow will continue, mainly across windward
areas, but rainfall accumulations are expected to remain light.

By early to mid next week, moisture associated with a tropical
wave will increase across the region, resulting in a more humid
and unsettled pattern. This will support periods of showers and
isolated thunderstorms, especially during the afternoon hours
across portions of western and interior Puerto Rico. While a few
locally heavy showers cannot be ruled out, widespread hazardous
weather is not expected.

Thereafter, a gradual return to a drier air mass is expected as
the Atlantic ridge reestablishes a typical trade wind pattern.
This will favor generally fair and warm conditions with passing
showers embedded in the easterly flow and limited afternoon
convection.

The primary hazards through the long-term period will include
periods of elevated heat, occasional Saharan dust intrusions,
strengthening trade winds at times, and localized impacts from
isolated showers and thunderstorms.

&&

.AVIATION...
(18Z TAFS)
Issued at 115 PM AST Wed Jun 17 2026

Mainly VFR conditions expected to prevail across all terminals
through the forecast period. However, SHRA and iso TSRA expected to
develop over western PR thru 17/22z, this may cause brief MVFR conds
at TJBQ. The 17/12z TJSJ sounding indicated ESE winds up to 22 kt
blo FL080. A tropical wave will increase SHRA with possible -TSRA
around 18/15z across the USVI terminals, with similar conditions
spreading gradually across the PR terminals through Thursday evening.

&&

.MARINE...
Issued at 115 PM AST Wed Jun 17 2026

A broad surface high pressure building over the Central Atlantic
will promote moderate to locally fresh E-ESE winds for the next
several days, resulting in choppy seas across local waters and
Caribbean passages that could lead to hazardous conditions for small
craft. Shower activity will gradually increase by Thursday morning
into Friday, as a tropical wave approaches the Caribbean Basin,
leading to localized heavy rainfall, gusty winds, and reduced
visibility. A dense layer of Saharan Dust will gradually filter into
the region by late Thursday, bringing hazy skies, reduced
visibility, and poor air quality through Saturday.

&&

.BEACH FORECAST...
Issued at 115 PM AST Wed Jun 17 2026

The low risk of rip currents continues tonight across the islands,
though beachgoers should stay aware of beach conditions as life-
threatening rip currents can occur in the vicinity of groins,
jetties, reefs, and piers. As winds gradually strengthen tonight,
the risk should become moderate and spread across most beaches of
the islands through Fathers Day weekend. Though the risk should
remain moderate, beachgoers must exercise caution as life-
threatening rip currents are possible along the surf zone. Residents
and visitors are encouraged to choose beaches with lifeguards and
follow the flag warning system.

Besides rip currents, beachgoers should stay weather alert, as
afternoon showers and isolated thunderstorms can be expected for the
rest of the workweek and possibly on Fathers Day weekend, which may
move over coastal areas of Puerto Rico and bring wind gusts and
lightning. Moderate concentrations of Saharan Dust will arrive by
Thursday, resulting in hazy skies, reduced visibility, and poor air
quality through Saturday.

&&

.FIRE WEATHER...
Issued at 115 PM AST Wed Jun 17 2026

Critically dry soils, hot daytime temperatures, and a
dry air mass will combine with sustained winds of 14 to 18 mph with
stronger gusts to maintain an elevated fire weather risk through
late this afternoon. The highest threat will remain concentrated
across the southern coastal plains of Puerto Rico, where a Fire
Danger Statement continues in effect through 4 PM AST. While a
passing tropical wave will briefly introduce higher moisture and a
chance for localized wetting rains on Thursday, any precipitation is
expected to be localized and insufficient to provide widespread or
lasting relief to the ongoing dry fuel conditions. Behind the wave
on Friday, a quick return to a very dry, stable air mass with
Saharan dust will cause relative humidity values to drop sharply
once again, allowing the critical fire weather danger to persist
through the end of the week. Outdoor burning and activities that
could generate sparks should be strongly discouraged.

&&

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

$$

SHORT TERM/AVIATION...DS
LONG TERM...LIS
MARINE/BEACH FORECAST...MNG

NWS SJU Office Area Forecast Discussion