textproduct: San Juan

KEY MESSAGES

Issued at 227 PM AST Sat Nov 7 2026

* Slow-moving thunderstorms will keep the potential for urban and small-stream flooding risk this afternoon, especially across interior and northeastern Puerto Rico, including the San Juan metro area.

* Saturated soils increase the potential for rapid river rises and isolated mudslides. Shower coverage should decrease Sunday into Monday, but localized flooding will remain possible with afternoon thunderstorms across interior and northern Puerto Rico.

* A northerly swell will maintain a high risk of life- threatening rip currents along exposed northern and northeastern beaches of Puerto Rico and portions of Culebra through Sunday. * Atlantic seas will build to 5 to 6 feet tonight through Sunday before gradually subsiding early next week. Thunderstorms may produce locally higher winds and seas.

* By mid-week next week a stable weather pattern is expected to prevail across the region.

Short Term(This evening through Monday)

Issued at 227 PM AST Sat Nov 7 2026

Relaxed pressure gradient will continue as surface low, positioned well north across the western Atlantic, will maintain a relatively weak west-southwest steering regime over the northeastern Caribbean. The 07/12Z TJSJ sounding sampled this environment well, observing 8 to 12 knot west-southwesterlies within the lowest 3 km. Aloft, the main trough axis has pushed east of the local islands, displacing the strongest dynamic support, while low vertical wind shear prevails. Despite the lack of upper-level forcing, above normal tropical moisture continues advecting from the southwest. Precipitable water (PWAT) values will hold between 2.0 and 2.2 inches through early Sunday (surpassing the 75th climatological percentile), combining with rich low-level moisture (850700 mb RH around 80%).

Daytime heating, local sea breeze convergence, and orographic lifting is initiating another round of showers and thunderstorms across the interior into northeastern Puerto Rico, including the San Juan metropolitan area. Although activity should be somewhat less widespread than Friday due to the departing trough, slow storm motions over increasingly saturated soils sustain an elevated flood threat across the northeast. Urban and small-stream flooding, rapid rises along smaller rivers, ponding of water in poorly drained roadways, and isolated mudslides along areas of steep terrain remain the primary concerns. Downwind streamers originating off the U.S. Virgin Islands could brush the eastern and northern half of all the USVI themself based on the orientation of the streamer, aligned with the islands. Tonight through Sunday morning, the atypical southwest flow will continue to carry occasional passing showers across southern and western Puerto Rico, as well as the USVI.

On Sunday, an approaching col area will cause steering winds to weaken further. As mid-level dry air filters in and upper-level ridging draws closer, afternoon shower coverage should become more isolated. Nevertheless, afternoon convection will remain centered over the interior and northeastern sections with an ongoing elevated flood risk, though light, erratic winds could drift some cells into nearby coastal sectors. By Monday, steering winds will remain very weak at 2 to 5 knots and become generally southerly. The deepest moisture axis will move eastward, dropping PWAT values to seasonal levels between 1.70 and 1.90 inches and relatively dry mid-level RH (700500 mb) between 50-60 percent. Even with this drying trend, the light southerly wind regime and localized sea-breeze boundaries will focus afternoon thunderstorms and localized elevated flood threat across interior to northern Puerto Rico, while USVI activity trends more isolated.

The heat threat is not expected to be a major concern during the period. However, limited heat impacts are still anticipated, primarily affecting individuals who are extremely sensitive to heat, especially those spending extended time outdoors without effective cooling and adequate hydration.

Long Term(Tuesday through Saturday)

Issued at 331 AM AST Sat Nov 7 2026

As the low pressure north of the region moves further into the central Atlantic and the surface high pressure builds to the NW of the region, winds should become more S-SSE across the Islands throughout the long-term period. Calm winds will prevail into mid- week with conditions becoming locally breezy by Friday. The beginning of the week will be characterized by variable conditions as with average precipitable water (PWAT) and abundant moisture in the low and mid levels. Low steering winds combined with local effects, daytime heating, and sea breeze convergence will lead to rainfall activity with a focus on the interior and northern portions of Puerto Rico each afternoon. Shower activity from streamers and advective showers will should also move during the morning and over night hours across the US Virgin Islands, SE Puerto Rico and the San Juan metro area each day as well. During the second part of the next workweek, a mid-level ridge will move into the vicinity of the region to the east of the islands, warming the mid-temperatures, leading to sinking air, and stability aloft. This will act as a limiting factor for the development of deep convective cells by the end of the workweek. Another limiting factor for the development of widespread convection will be the lack of available moisture in the mid-levels.

Thus, the potential for excessive rainfall and lighting associated risks will decrease as the week progresses. The focus of the activity will be predominantly the interior and northern portions of Puerto Rico during the afternoons. This level of risk may lead to ponding of water over roadways and poorly drained areas, without ruling out isolated urban flooding. The available moisture, above average low tropospheric temperatures, and low surface winds will lead to a level of heat that may affect those individuals sensitive to heat especially when outdoors without effective cooling and/or adequate hydration. Individuals are invited to continue monitoring the weather conditions as they evolve.

AVIATION

(18Z TAFS) Issued at 227 PM AST Sat Nov 7 2026

Mainly VFR conds expected across terminals thru the forecast prd. SHRA/TSRA developing over interior/NE-PR, and the USVI this afternoon may produce brief MVFR/IFR conditions at TJSJ/TIST/TISX with mtn obsc. VCSH possible at TJBQ/TJPS terminals. Activity should diminish this evening, although passing SHRA/VCTS may persist overnight across southern and western PR and the USVI. Light W-SW winds and sea breeze variations will become light and variable overnight. Brief gusty winds are possible near TSRA.

MARINE

Issued at 227 PM AST Sat Nov 7 2026

A low-pressure system northeast of the region will move eastward over the next few days, while a surface ridge builds across the western Atlantic. This pattern will favor light to moderate westerly to southwesterly northerly winds, gradually becoming northeasterly to easterly early next week.

A northerly swell will raise Atlantic seas from 4 to 5 feet today to 5 to 6 feet tonight through Sunday, with occasional waves up to 8 feet and dominant periods around 11 seconds. Seas will subside to 4 to 5 feet on Monday. In the offshore Caribbean waters, including Saint Croix, seas will remain at 2 to 3 feet through Tuesday and increase to 3 to 4 feet by Wednesday night as easterly winds strengthen.

Although forecast wave heights remain below Small Craft Advisory criteria, the longer-period swell may produce locally rough conditions near exposed Atlantic coastal entrances.

BEACH FORECAST

Issued at 227 PM AST Sat Nov 7 2026

A northerly swell will maintain a high risk of life-threatening rip currents along exposed northern and northeastern beaches of Puerto Rico and portions of Culebra through Sunday. A moderate risk will persist along other exposed beaches, including portions of Vieques and the U.S. Virgin Islands. Conditions should gradually improve early next week as the swell subsides, although a moderate rip current risk will linger.

Thunderstorms will pose an additional hazard, especially this afternoon, with isolated thunderstorms possible Sunday through Wednesday. Avoid swimming at beaches under a high rip current risk. If thunder is heard, leave the beach and seek shelter in a substantial building or enclosed vehicle.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through Sunday afternoon for PRZ001-002- 005-008-012.

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