textproduct: San Juan

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.