textproduct: San Juan

KEY MESSAGES

Issued at 128 PM AST Fri Mar 27 2026

* A wet and unstable weather pattern will continue this afternoon and tonight over Puerto Rico, increasing the risk of flooding in urban areas, small streams, and places with repeated rainfall. Rapid rises in rivers may occur, along with potential landslides and rockfalls in steep terrain.

* Across the U.S. Virgin Islands, passing showers and isolated thunderstorms may cause ponding of water on roads and in low- lying areas.

* Our region is likely to experience afternoon thunderstorms daily throughout the forecast period.

* Marine and coastal conditions are expected to deteriorate from late Monday night through at least Thursday as a long-period northerly swell arrives. Hazardous surf conditions are possible, along with an increased risk of rip currents and potential Small Craft Advisories.

Short Term(This evening through Sunday)

Issued at 128 PM AST Fri Mar 27 2026

During the morning hours, most of the activity remains over the Atlantic Offshore waters. Meanwhile, the US Virgin Islands and Puerto Rico observed variable skies, with mostly sunny in some locations, especially along the west and southern PR and St Croix, and partly cloudy across the windward locations. Rain activity began to increase around noon, with some streamers developing downwind of the USVI, Vieques, Culebra, and El Yunque over the local waters and portions of the islands. Maximum temperatures were in the mid- to upper 80s across urban and coastal locations, to the upper 70s or low 80s. Winds were mainly from the east- southeast at 5 to 15 mph, with sea-breeze variations and higher gusts.

By tonight, convection will gradually diminish, though showers and isolated thunderstorms will persist overnight, with a risk of flooding present especially along the west or north coast of PR. As winds shift from east-southeast to east-northeast, low-level convergence could enhance the potential for flooding along the northern sections of PR and the northern USVI.

A wet and unstable pattern will persist through at least Saturday as a mid- to upper-level trough deepens into a cutoff low over the region. Strong upper-level divergence associated with a subtropical jet streak (near 90100 kt) and colder temperatures aloft (around -8 to -10C at 500 mb) will maintain favorable conditions for shower and thunderstorm development.

Abundant moisture combined with diurnal heating and local effects will support another round of active weather each afternoon, particularly across interior and western to northwestern Puerto Rico. Soils remain saturated in these areas due to recent rainfall, increasing the risk of flooding impacts. Urban and small stream flooding, rapid river rises, and hazardous travel conditionsespecially at nightare possible. Landslides and rockfalls remain a concern in steep terrain. Some thunderstorms may become strong, producing frequent lightning, gusty winds, and small hail, mainly across higher elevations.

Saturday will be a transitional day as slightly drier air begins to filter into the region late in the afternoon and overnight. Shower and thunderstorm activity will continue during the afternoon, with the focus shifting toward interior and southwestern Puerto Rico. By Sunday, drier air aloft and improving conditions will support a gradual decrease in widespread rainfall activity and a lower, though not zero, flooding risk. However, lingering moisture and local effects may still result in isolated showers and thunderstorms.

Long Term(Monday through next Thursday)

Issued at 129 AM AST Fri Mar 27 2026

A persistent subtropical jet will remain over the region, supporting period of favorable conditions as embedded disturbances pass nearby. At the surface, a strengthening high over the western-central North Atlantic will promote breeze to windy northeast flow early in the week, briefly shifting more east to east-northeast before a surface trough develops to the northeast. Moisture will increase rapidly after early Monday, with precipitable water values rising to well above normal and remaining elevated through the period. Despite some lingering mid-level dryness early on, conditions will support daily shower and thunderstorm development, along with increasing trade wind shower activity.

Hazard risks will increase through the period as a wetter and more unstable pattern becomes established. Flooding impacts will become more likely from Monday onward, particularly in urban and poorly- drained areas, and may be exacerbated over saturated soils. Breezy to windy conditions will persist, and thunderstorms may produce lightning and locally erratic winds. Confidence is medium in an active pattern, and uncertainty remains in the timing and intensity of embedded features that may enhance rainfall.

AVIATION

(18Z TAFS) Issued at 128 PM AST Fri Mar 27 2026

VRB conds will persists across most terminals. Aft convection will bring -TSRA/+TSRA across PR, with TEMPOs over JBQ and JSJ btwn 27/17- 27/21z, reducing CIGs/VIS and leading to MVFR conds. TSRA is expected to continue tonight for JBQ, improving by 28/06z, with PROB30s for JSJ and IST may experience MVFR conds btwn 28/03-28/06z. Winds will weaken and become light and VRB aft 27/22z, strengthening from the E-NE btwn 10-14 kt, btwn 28/12-28/13z.

MARINE

Issued at 128 PM AST Fri Mar 27 2026

A mid- to upper-level trough will continue to promote unstable weather across the region tonight and Saturday, supporting scattered showers and thunderstorms. A shearline north of the area will maintain light to moderate east-southeast winds this afternoon, increasing to moderate to fresh out from the east- northeast from tonight through the weekend and resulting in choppy seas. A cold front will approach from the western Atlantic Sunday into Monday, followed by stronger winds early next week. In addition, a long- period northerly swell will build across the local waters beginning late Monday night, leading to hazardous marine conditions through at least Thursday. These conditions will be dangerous for small craft operators.

BEACH FORECAST

Issued at 128 PM AST Fri Mar 27 2026

A moderate risk of rip currents is expected along north- and east-facing beaches of Puerto Rico and the U.S. Virgin Islands, while a low risk will persist along south-facing beaches.

Conditions are expected to deteriorate early next week. A long- period northerly swell combined with increasing winds from Tuesday through Thursday will likely result in a high risk of rip currents along exposed coastlines. Hazardous surf conditions and life-threatening rip currents are expected, particularly along north-facing beaches.

Beachgoers should exercise caution and remain aware of changing marine conditions. Always swim near a lifeguard and follow local safety guidance.

SJU WATCHES/WARNINGS/ADVISORIES

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