textproduct: San Juan

KEY MESSAGES

Issued at 335 AM AST Sat Oct 24 2026

* Life-threatening rip currents will affect exposed beaches of northern, western, and eastern Puerto Rico, Culebra, and St. Thomas through late Sunday evening. Another northerly swell arriving Monday will renew hazardous surf and rip currents into the workweek.

* Hazardous seas up to 7 feet will affect portions of the Atlantic waters and Mona Passage today. A Small Craft Advisory remains in effect through noon AST. Brief improvement Sunday will precede another increase in seas Monday.

* Afternoon showers and thunderstorms will bring localized flooding, lightning, and gusty winds, particularly across interior and western Puerto Rico through Monday. Differences in moisture guidance limit confidence in rainfall coverage Sunday and Monday.

* Additional showers and thunderstorms Tuesday will maintain the threat of urban and small stream flooding and rapid river rises. Drier air from Wednesday onward should reduce rainfall coverage and flooding potential, although isolated afternoon thunderstorms will continue.

* Warm, humid conditions will primarily affect people sensitive to heat and those outdoors without adequate hydration or effective cooling.

Short Term(Today through Monday)

Issued at 335 AM AST Sat Oct 24 2026

Subsidence limited rainfall coverage through much of the night. Nevertheless, sufficient moisture supported passing showers over the local waters, the U.S. Virgin Islands, and windward Puerto Rico, with some moving farther inland. East to southeast winds remained at 10 mph or less, with occasional higher gusts across the U.S. Virgin Islands. Overnight temperatures remained above normal across much of the region.

Moisture and instability will support afternoon showers and thunderstorms today, particularly across interior, northern, and western Puerto Rico. The evening San Juan sounding measured precipitable water near 2.15 inches, close to the climatological reference shown in the supplied analysis. Both GFS and ECMWF guidance maintain sufficient moisture through today, although a stable layer and extensive cloud cover could limit daytime heating and convective coverage. If heavier showers persist or repeatedly develop, localized urban and small-stream flooding will remain a concern. Isolated thunderstorms will also bring lightning and brief gusty winds.

Guidance diverges on moisture availability Sunday and Monday. The GFS maintains precipitable water near 2.0 to 2.2 inches into Sunday, while the ECMWF introduces drier air, with values falling to around 1.6 to 1.8 inches before partially recovering Monday. Both models indicate rising upper-level heights, warming near 500 mb, and weaker lapse rates than today, suggesting a less favorable environment for deep convection. However, lingering moisture, daytime heating, sea breeze convergence, and terrain effects will continue to support afternoon showers and isolated thunderstorms, mainly across interior and western Puerto Rico. The wetter GFS solution would increase the threat of localized heavy rainfall, while the drier ECMWF solution would favor reduced coverage and shorter rainfall duration. Passing showers will continue to affect windward areas overnight and in the morning.

Both models maintain above-normal temperatures near 925 mb through Monday, supporting continued warm and humid conditions. Heat impacts will primarily affect sensitive individuals and those spending extended periods outdoors without adequate hydration or effective cooling.

Long Term(Tuesday through Saturday)

Issued at 335 AM AST Sat Oct 24 2026

Wetter conditions may persist Tuesday, then transition to a seasonal pattern Wednesday onward. A surface high pressure building over the Central Atlantic should maintain a SE-S steering flow, though it will likely remain weak through most of the period as the local pressure gradient weakens due to the interaction of the high with a deep-layered trough. The trough should also interact with a mid to upper-level ridge northeast of the region. The latest model guidance suggests abundant moisture content across the region, with PWAT values reaching well above climatological normal (up to 2.25 inches). Although low to mid levels RH remains high (above 60%), the latest solutions suggest that a portion of the PWAT is also associated with high clouds across the CWA. If cloud cover dominates during Tuesday morning, this may inhibit deeper convection, with mainly an advective pattern over windward areas. Otherwise, showers and thunderstorms over the mountain ranges of Puerto Rico may lead to urban and small stream flooding, without ruling out rapid river rises.

Wednesday onwards, PWAT values should drop to seasonal and below normal (between 1.5 and 1.75 inches), as a drier slot filters in the mid levels on Wednesday, followed by another slot in the 850- 700 mb layer. Although the ridge may linger near the area and bring subsidence aloft, the combination of daytime heating, local effects, sea-breeze convergence, and available moisture will be the main driver of convection each afternoon, particularly across the mountain ranges of Puerto Rico into northern/northwestern portions. Additionally, during that period, the vicinity of the Madden-Julian oscillation (MJO) and Kelvin waves may boost upward motion, aiding deep convection. Although the flooding risk should be lower from Wednesday onwards due to the drier air, during the afternoons, isolated thunderstorms could still produce gusty winds and lightning.

AVIATION

(06Z TAFS) Issued at 335 AM AST Sat Oct 24 2026

Mainly VFR conditions will prevail across the terminals. Passing SHRA will affect eastern PR and USVI terminals this morning. Afternoon SHRA/isolated TSRA over interior and western PR may affect TJBQ/TJSJ. Brief MVFR conditions, mountain obscuration, and gusty winds are expected near convection. Activity will diminish this evening, with passing SHRA overnight. ESE winds around 10 kt, with daytime sea breeze variations and higher gusts near SHRA/isold TSRA.

MARINE

Issued at 335 AM AST Sat Oct 24 2026

A surface high-pressure over the central Atlantic continues to promote moderate to locally fresh southeasterly winds across the region. A northerly swell continues to spread across the local waters, combining with wind-driven seas and resulting in seas up to 7 feet, particularly across the Atlantic waters and Mona Passage. These conditions will continue to produce choppy and hazardous seas, especially across the offshore Atlantic waters and exposed passages. As a result, a Small Craft Advisory remains in effect through 12 PM AST Saturday. Marine conditions are expected to briefly improve on Sunday as the northerly swell gradually subsides. However, another northerly swell is expected to arrive across the local waters by Monday, increasing seas once again and maintaining hazardous marine conditions across the Atlantic waters and passages into the upcoming workweek. Small craft operators should continue to exercise caution, as deteriorating marine conditions may persist through much of the workweek.

BEACH FORECAST

Issued at 335 AM AST Sat Oct 24 2026

A northerly swell continues to spread across the local Atlantic waters and passages, maintaining hazardous coastal conditions across the region. As a result, a high risk of life-threatening rip currents remains in effect through late Sunday evening for the northern, western, and eastern coastal areas of Puerto Rico, including Culebra and St. Thomas. Breaking waves along exposed beaches will continue to produce dangerous swimming conditions, particularly along north-facing beaches.

Coastal conditions are expected to slightly improve by Sunday as the northerly swell gradually subsides. However, another long-period northerly swell is expected to arrive across the Atlantic waters by Monday, spreading toward the local islands and resulting in deteriorating coastal conditions once again. This additional swell will likely increase breaking wave heights and maintain a high risk of life-threatening rip currents along exposed beaches into the upcoming workweek. Beachgoers are strongly urged to avoid entering the water at beaches experiencing hazardous surf and life- threatening rip currents, as these conditions can be dangerous even for experienced swimmers. Always follow local authorities and lifeguards guidance.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through late Sunday night for PRZ001-002- 005-008-010-012.

VI...High Rip Current Risk through this afternoon for VIZ001.

AM...Small Craft Advisory until noon AST today for AMZ711-712-741.