textproduct: San Juan

KEY MESSAGES

Issued at 417 AM AST Sat Mar 28 2026

* A wet and unsettled weather pattern will persist across the region today, with the most active period expected during the afternoon hours. Scattered to numerous showers and thunderstorms are likely, particularly across interior and western/southwestern Puerto Rico.

* This may lead to urban and small stream flooding, along with quick river rises, especially in areas that have received recent rainfall. The strongest thunderstorms may also produce gusty winds and locally heavy rainfall.

* For the U.S. Virgin Islands, passing showers and isolated thunderstorms are expected, with periods of ponding of water on roads and in low-lying areas.

* Marine and coastal conditions are expected to deteriorate early next week as a northerly swell arrives. This will likely result in Small Craft Advisories and Rip Current Statements, with hazardous breaking waves and dangerous surf conditions possible. High Surf Advisories cannot be ruled out.

Short Term(Today through Monday)

Issued at 417 AM AST Sat Mar 28 2026

A fairly active afternoon and evening was observed across Puerto Rico on Friday, with several Flood Advisories, Flash Flood Warnings, and Flood Warnings issued. Heavy rainfall resulted in flooding reports, mostly over portions of Puerto Rico, including reports of the Rio Culebrinas out of its banks. By early in the night, thunderstorm activity gradually diminished, transitioning into more stratified rainfall as the most active convection shifted away from the region.

The overall pattern has not changed much, with a wet and unsettled weather pattern expected to persist. For today, winds will gradually shift from east-southeast to east-northeast to northeast, promoting a more focused area of convection across interior and southwestern Puerto Rico during the afternoon hours. Although slight warming aloft will result in somewhat reduced instability compared to previous days, conditions will remain favorable for shower and thunderstorm development. In addition, the 90-100 kt subtropical jet will remain better positioned aloft, enhancing upper-level ventilation and potentially adding intensity to thunderstorm activity this afternoon. Given recent rainfall, soils remain saturated, and streamflows are elevated. Therefore, any additional rainfall will increase the risk of urban and small stream flooding, as well as rapid river rises. Flooding impacts could develop quickly, particularly across interior and western/southwestern Puerto Rico. Landslides and rockfalls will also remain possible in areas of steep terrain.

By Sunday, conditions are expected to improve as drier air filters into the region. Model guidance indicates 700-500 mb relative humidity values decreasing from well above normal levels, previously exceeding two standard deviations above climatology, to below normal levels. This will result in a reduction in shower and thunderstorm activity, making Sunday the driest day of the period. However, isolated afternoon convection cannot be ruled out, particularly across western/southwestern Puerto Rico.

On Monday, moisture will increase once again, with precipitable water values rising to near or above normal levels and mid-level moisture rebounding to around 40-60 percent. Under a northeasterly wind flow and continued troughiness aloft, another round of afternoon convection is expected. Activity is expected to be less widespread compared to previous days, but localized heavy rainfall will still be possible. Overall, despite a brief improvement on Sunday, the combination of saturated soils, elevated rivers, and additional rounds of convection will continue to pose a flooding risk through the period.

Long Term(Tuesday through Saturday)

Issued at 417 AM AST Sat Mar 28 2026

Strong low to mid level high pressure will maintain a strong northeasterly wind flow through much of the workweek. The steering flow is expected to be at 15 to 25 kts. At the upper level, the jet stream will maintain speeds of nearly 80 knots. Under the low level winds, weak disturbances will stream at times across the islands. This will maintain the probability of precipitation on the medium and high side. In general, showery weather will persist for most of the Virgin Islands and eastern Puerto Rico. Then, in the afternoon, diurnal heating will trigger showers and thunderstorm along the interior and western Puerto Rico. Because the winds are expected to be strong, the risk of flooding will be mostly limited. Impacts may include hazardous driving conditions due to low visibility and ponding of water. In the west, urban and small stream flooding could still occur, although not widespread.

AVIATION

(06Z TAFS) Issued at 417 AM AST Sat Mar 28 2026

Mainly VFR conds will prevail across most terminals. Sct SHRA ovr lcl waters and btw terminals may cause brief MVFR/IFR CIGs/VIS. Aft 28/16z, SHRA/TSRA incr across PR, mainly affecting interior/W & S terminals (TJBQ/TJPS) with TEMPO MVFR/IFR conds. VCTS exp at TJSJ/TJPS/TJBQ, with PROB30 TSRA at TJBQ/TJPS. USVI (TIST/TISX), VFR prevails with VCSH and brief MVFR psbl. Winds lgt/VRB bcmg E-NE 8-14 kt aft 14z, with higher gusts near TSRA and sea breeze variations.

MARINE

Issued at 417 AM AST Sat Mar 28 2026

A mid to upper-level trough will continue to promote unstable weather across the region today, supporting scattered showers and thunderstorms. A surface inverted trough northeast of the area will maintain light to moderate east-northeast winds this afternoon, increasing to moderate to fresh on Sunday and resulting in choppy seas. A cold front will approach from the western Atlantic early next week, followed by stronger winds for the rest of the 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 417 AM AST Sat Mar 28 2026

Today, a moderate risk of rip currents persists along the north- facing beaches of Puerto Rico, Culebra, and the U.S. Virgin Islands, while south-facing beaches and Vieques will experience a low risk. Beachgoers should continue to exercise caution as a moderate risk means that life-threatening rip currents are possible in the surf zones.

Beach conditions are expected to worsen early next week. The arrival of a long-period northerly swell, combined with strengthening winds from late Monday night through the rest of the week, will likely lead to a high risk of rip currents along exposed coastlines. Hazardous surf and life-threatening rip currents are anticipated, especially along north-facing beaches.

Beachgoers are urged to use caution and continue to monitor the forecast for any updates. Always swim near a lifeguard and follow local safety guidance. For additional information and location- specific rip current details, please visit: weather.gov/beach/sju

SJU WATCHES/WARNINGS/ADVISORIES

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