textproduct: San Juan

KEY MESSAGES

Issued at 106 PM AST Sat Jun 27 2026

* Showers and isolated thunderstorms today and Monday will result in ponding of water over roadways and could enhance urban and small stream flooding across the western side of Puerto Rico. Turn around and avoid flooded areas.

* Warmer to hot conditions are expected for the next few days, with heat indices exceeding 100 degrees Fahrenheit across urban and low-lying areas of Puerto Rico and the U.S. Virgin Islands. Stay hydrated.

* The low risk of rip current will persist for the rest of the weekend and early next week across the islands.

Short Term(This evening through Monday)

Issued at 106 PM AST Sat Jun 27 2026

Showers and isolated thunderstorms were developing just before noon across portions of Puerto Rico and downwind of the U.S. Virgin Islands. This activity was triggered by enough low-level moisture from a departing surface trough interacting with daytime heating and sea breeze convergence. Additional showers and thunderstorms are expected to redevelop across the same areas, but primarily over the interior and western PR. The main hazards expected with these thunderstorms are localized urban and small- stream flooding, ponding of water on roads, strong gusty winds, and possible minor mudslides in areas of steep terrain.

Conditions are expected to dry rapidly tonight through Sunday as a weak Saharan Air Layer (SAL) with minor Saharan dust concentrations filters across the region. This overall dry, dusty air mass will cause a drop in precipitable water from around 1.80 inches today to near 1.20 inches by Sunday morning. Also, a brief but strong trade wind cap will help suppress widespread convective development. Therefore, a combination of hazy and mostly sunny skies, with minimal shower activity, is expected. Additionally, the lack of cloud cover will increase the heat risk, with max temperatures reaching the low 90s, with heat indices easily surpassing 100F across most coastal and urban areas of all the islands.

This overall dry pattern will be short-lived, as a tropical wave arrives from the east by early Monday morning. Deep tropical moisture will surge across the regional islands, sending precipitable water values well above seasonal normals to near 2.20 inches. This tropical wave will increase cloudiness, showers, and thunderstorms across the islands in general. This transition back to a wet pattern will increase the risk of urban and flash flooding, quick river rises, and mudslides across steep terrain.

Long Term(Tuesday through next Friday)

Issued at 106 PM AST Sat Jun 27 2026

During the long-term period, a surface high pressure system centered over the central Atlantic and extending into the Caribbean will maintain a southeasterly low-level wind flow (03 km) across Puerto Rico and the U.S. Virgin Islands. Aloft, nearly zonal flow at 200 mb is expected on Tuesday and Wednesday, providing little in the way of upper-level support for organized convection. Lingering moisture associated with the previous tropical wave will remain over the region on Tuesday, with precipitable water values around 1.8 inches supporting scattered showers, primarily during the afternoon across western and interior Puerto Rico. Although moisture will gradually decrease by Thursday, sufficient low-level moisture will remain to support isolated to scattered afternoon convection, but widespread rainfall activity is not anticipated. Meanwhile, a moderate concentration of Saharan dust is expected to spread across the islands Tuesday and Wednesday, resulting in hazy skies and limiting overall convective development.

Despite the presence of Saharan dust, the persistent southeasterly flow will continue to promote a warm pattern, with above-normal temperatures and elevated heat indices across urban and coastal sections. Consequently, an elevated heat threat is expected to persist through the middle of the week. By Friday into Saturday, a drier air mass will move into the region, reducing precipitable water values and limiting shower activity across the local islands. In addition, the NASA Goddard Earth Observing System (GEOS) Model V5 continues to suggest another pulse of Saharan dust arriving late Friday into Saturday, reinforcing the drier pattern while maintaining hazy skies.

AVIATION

(18Z TAFS) Issued at 106 PM AST Sat Jun 27 2026

SHRA/TSRA will continue to increase across PR through this afternoon. This may lead to tempo MVFR to brief IFR conds at TJBQ thru 27/22z. Elsewhere in PR, mostly VCTS expected, and VCSH at the USVI terminals. The 27/12z TJSJ sounding indicated E-ESE winds btw 7-20 kt blo FL060. HZ due to Saharan dust will increase from late tonight through Sunday, but VSBY should remain P6SM.

MARINE

Issued at 106 PM AST Sat Jun 27 2026

A surface trough northwest of the region will continue to produce isolated to scattered showers across regional waters this afternoon. As the trough continues to shift west-northwestward, the broad surface high pressure over the Central Atlantic should increase the local pressure gradient, with winds becoming moderate from the east- southeast. By Sunday, low concentrations of Saharan Dust will gradually filter into the region, slightly reducing visibility. A tropical wave approaching the Caribbean Basin will increase shower and thunderstorm activity across regional waters, bringing gusty winds and lightning, creating localized hazardous conditions for small craft.

BEACH FORECAST

Issued at 106 PM AST Sat Jun 27 2026

The low risk of rip currents continues across the islands for the rest of today, as winds have weakened and nearshore buoys report seas between 2 and 3 feet. Although the risk remains low, beachgoers should be aware of the possibility of life-threatening rip currents near groins, jetties, reefs, and piers. Winds should gradually strengthen later tonight, though the risk will likely remain low across the islands through early next week. Nevertheless, beachgoers should pay attention to the beach conditions and stay updated with the latest forecast. Besides rip currents, showers and isolated thunderstorms may move near coastal areas of the islands this afternoon due to a surface trough northwest of the CWA, then again on Monday due to a tropical wave approaching the Caribbean Basin and the local area. Beachgoers are encouraged to monitor weather conditions, as isolated thunderstorms may bring heavy rainfall, gusty winds, and lightning.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...None.