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199
FXCA62 TJSJ 171815
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
215 PM AST Fri Jul 17 2026

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

.KEY MESSAGES...
Issued at 207 PM AST Fri Jul 17 2026

* Mostly fair weather conditions will continue through the next
  few days with few passing morning showers and isolated
  afternoon showers are expected each day.

* Low concentrations of Saharan dust will continue through Sunday,
  increasing to moderate concentrations by late Sunday night,
  resulting in hazy skies and reduced air quality early next week.

* A low risk of rip currents will continue today across the
  beaches of Puerto Rico and the U.S. Virgin Islands, increasing
  to a moderate risk from tonight onward.

&&

.Short Term(This evening through Sunday)...
Issued at 207 PM AST Fri Jul 17 2026

Tranquil conditions prevailed during the morning hours across the
CWA, with few passing showers across the regional waters. Minimum
temperatures remained seasonal, between mid 70s and low 80s across
urban and coastal areas, and low 60s to low 70s across higher
elevations. As of 1:30 PM AST, temperatures increased and reached
the low 90s across the urban and coastal areas of the islands (92
degrees at the Luis Munoz Marin Airport in Carolina), with heat
indices between mid 90s and mid 100s. Winds have picked up, with
ASOS/WOS/CWOP stations reporting gusty winds between 20 and 25 mph,
with isolated areas reaching 30-35 mph (as recorded by AWOS at
Mercedita Airport in Ponce). From the latest 12z RAOB, PWAT values
remain below normal (1.37 in), with very dry mid levels (around
33%). Additionally, CIN, CAPE, LI have lowered compared to soundings
from the past few days, while mid-level temperatures have warmed
significantly (500 mb temperatures around -5 degrees Celsius),
indicating unfavorable conditions for deeper convection.
Nevertheless, HIRES models continue to suggest the development of
shower activity across western portions of Puerto Rico, though
rainfall accumulations should remain minimal.

The short-term forecast remains on track. The surface high pressure
over the Central Atlantic continues to dominate the wind pattern,
mainly from the E-ESE, becoming briefly from the E-ENE late
Saturday. As the local pressure gradient continues to increase,
breezy to locally windy conditions will likely continue,
particularly across coastal areas and higher elevations of the
islands. In the mid to high levels, a ridge will establish north of
the region, warming mid-level temperatures (between -4 and -5
degrees Celsius), leading to subsidence and stability aloft. A drier
air mass should gradually filter in tomorrow, Saturday, limiting
shower activity, though afternoon convection can be expected over
western Puerto Rico due to local effects and daytime heating. The
latest satellite-derived product shows an area of higher tropical
moisture associated with a tropical wave located along 43.5 W, south
of 18 N. From the latest model guidance, the tropical wave is
expected to approach the Caribbean Basin by Sunday, but it may
weaken while interacting with drier air and Saharan Dust surrounding
it. Although an increase in shower activity can be expected over
windward sections of the islands in the morning and western Puerto
Rico in the afternoon, the dry slot in the mid levels, along with
the presence of the ridge, may not favor deep convection, with at
most localized ponding of water over roadways and poorly drained
areas. By Sunday evening, a dense plume of Saharan Dust is expected
to move and spread across the islands, leading to hazy skies,
reduced visibility, and poor air quality. Sensitive groups must
follow medical recommendations.

Although moisture content should remain below normal for most of the
period, combined with slightly warmer than normal temperatures may
lead to heat indices exceeding 100 degrees Fahrenheit, which may
impact individuals sensitive to heat  without effective cooling
and/or adequate hydration. Hence, the heat risk will remain limited
throughout the weekend.

&&

.Long Term(Monday through next Thursday)...
Issued at 207 PM AST Fri Jul 17 2026

Current model guidance continues to indicate that the workweek will
start with moderate to high concentrations of Saharan Dust,
promoting hazy skies and deteriorated air quality. Concentrations
should decrease to low before once again spiking to at least
moderate on Thursday. Warm to hot conditions will continue, with 925
temperatures being at seasonal values Monday, above normal Tuesday
and Wednesday, and more seasonal once again on Thursday. Combined
with sufficient moisture, these conditions will continue to result
in limited to elevated heat risks. By Tuesday and Wednesday,
environmental conditions can transition to support more convective
activity. A series of upper-level lows, troughs may cause cooling
aloft (500 mb temps cooling to more seasonal levels), weakening of
the trade wind cap and more seasonal relative humidities and
precipitable water.

A limited flooding risk has been added on these days, mainly due
to afternoon convection over western PR due to diurnal heating,
sea breeze convergence and local effects. Drier air will then
filter in on Thursday, alongside the aforementioned Saharan Dust,
leaving more limited shower activity. Wind speeds are forecast to
decrease gradually toward midweek, followed by an increase later
in the week. Steering flow will continue to result in passing
showers over windward sectors at times, and will back from
easterly to northeasterly to start the workweek and veering once
again to east to southeast by midweek onwards.

&&

.AVIATION...
(18Z TAFS)
Issued at 207 PM AST Fri Jul 17 2026

VFR conds will persist across all TAF sites throughout the fcst prd.
Aftn -SHRA can be expected over W PR, which may reduce CIGs and lead
to VCSH over JBQ. Winds from the E-ESE will continue, btwn 15 - 20
kt, gusty winds up to 30 kt, and weakening btwn 6 - 12 kt and
becoming VRB aft 17/23z. By 18/12-13, winds should pick up once
again and remain btwn 15 - 20 kt, with gusts up to 30 kt. VCSH from
time to time can also be expctd across most terminals aft 18/13z.

&&

.MARINE...
Issued at 207 PM AST Fri Jul 17 2026

A surface high over the central Atlantic continues to interact with
the Panama-Colombia low, maintaining moderate to locally fresh east
to east-southeast winds and choppy to locally rough seas through the
weekend. Traces to low to moderate concentrations of Saharan dust
will linger through the weekend, with another plume of moderate
concentrations expected to reach the local area by late Sunday into
early next week, resulting in hazy skies and locally reduced
visibility.

&&

.BEACH FORECAST...
Issued at 207 PM AST Fri Jul 17 2026

A low risk of rip currents remains across the local breaches today.
However, increasing winds will result in a moderate risk from
tonight onward across most beaches of Puerto Rico and the U.S.
Virgin Islands, increasing the potential for life-threatening rip
currents. These conditions should persist through the weekend and
into Monday before returning to low on Tuesday as winds decrease.

Beachgoers along the western coast of Puerto Rico should also remain
weather aware, as showers and isolated thunderstorms may affect
coastal areas, particularly this afternoon. Saharan Dust
concentrations will linger for the rest of the week, though another
plume may reach the local area by Sunday into early next week,
resulting once again in hazy skies and locally reduced visibility.

&&

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

$$

DAY SHIFT...GRS/MNG
EVE SHIFT...ICP/YZR

NWS SJU Office Area Forecast Discussion