textproduct: San Juan

KEY MESSAGES

Issued at 231 AM AST Mon Nov 9 2026

* The urban and small-stream flooding threat will remain elevated across the interior of Puerto Rico this afternoon. Isolated flash flooding and mudslides in steep terrain cannot be ruled out due to saturated soils.

* Mostly sunny to partly cloudy skies with occasional passing showers are expected across the U.S. Virgin Islands.

* Northeast swells will maintain a high risk of life-threatening rip currents along northern beaches of Puerto Rico and Culebra through Tuesday afternoon. * Southeast winds and hot temperatures along urban and coastal areas will return from midweek onward. Afternoon thunderstorms will shift towards the west/northwest quadrant of PR.

Short Term(Today through Wednesday)

Issued at 231 AM AST Mon Nov 9 2026

A deep tropical moisture pool with precipitable water values above 2.00 inches remains pooled across the northeastern Caribbean under a very weak low-level pressure gradient. Intense daytime heating, combined with local sea breeze convergence and terrain effects, will produce strong, slow-moving showers and thunderstorms across interior, northern, and western Puerto Rico each afternoon through Tuesday. Rainfall accumulations of 1.50 to 2.50 inches across these sectors will create hazardous driving conditions, urban and small-stream flooding, localized flash flooding, and mudslides in steep terrain. The U.S. Virgin Islands will remain on the periphery of this activity, with shower impacts limited to mostly light passing showers.

The combination of high moisture content, 925 mb temperatures around 22C, and surface winds under 10 knots will create muggy conditions before the onset of afternoon showers each day. Heat indices are projected to range between 98 and 106 degrees Fahrenheit across the northern, western, and southern coastal municipalities, raising heat exhaustion concerns for outdoor activities and vulnerable populations.

A pronounced shift to much drier, more stable conditions is expected on Wednesday as high pressure builds across the western Atlantic and the moisture plume pulls away from the region. Mid- level relative humidity will drop sharply below 50 percent, and precipitable water content will fall below 1.80 inches, as a strong trade wind inversion establishes and suppresses convective development across PR. A seasonal trade wind shower pattern will return as east to southeast trade winds strengthen to 10 to 15 knots, primarily impacting windward coastal areas and the USVI during the night and early morning hours.

Long Term(Thursday through Monday)

Issued at 231 AM AST Mon Nov 9 2026

The long-term forecast remains on track, with weather conditions becoming more stable by late this weekend. A surface high pressure building over the Central Atlantic should increase local pressure gradient, with strengthening winds from the S-SE. The latest model guidance suggests abundant tropical moisture moving into the region early Thursday and Friday, with PWAT values up to 1.75 inches, typical for this time of the year. However, moisture content should gradually diminish as a drier air mass filters in the mid-levels on Saturday and Sunday, limiting deep convection. In the mid and upper levels, the nearby short-wave troughs should introduce troughiness across the area on Thursday and Friday, with slightly cool mid-level temperatures (around -6 C), allowing cloud growth. However, a building ridge northeast of the CWA should dominate the weather pattern in the weekend, warming mid- level temperatures (up to -4 and -5 C), leading to subsidence and stability aloft. Additionally, the Galvez-Davison Index suggest the potential for thunderstorms across the local area mainly on Thursday and Friday, while Saturday and Sunday should become more shallow in the afternoons. The latest model solutions suggest a frontal boundary approaching the northern Caribbean by Sunday, though the best area of deep convection should remain outside the CWA. Overall, showers are likely to move during the night and morning hours, particularly across windward sections of the islands, followed by afternoon convection, particularly across interior and northwestern/northern Puerto Rico. As mentioned above, the best opportunity for deeper convection is Thursday and Friday, with mainly ponding of water over roadways and poorly drained areas, along with isolated urban and small stream flooding.

Under a S-SE wind flow, the latest model guidance suggest warmer than normal 925 mb temperatures across the CWA. With the available moisture, heat indices could easily exceed 100 F, particularly across urban and low-lying areas of the islands during the peak hours of the day. Therefore, the heat threat will remain limited to elevated.

AVIATION

(06Z TAFS) Issued at 231 AM AST Mon Nov 9 2026

Mainly VFR conditions expected to prevail across all terminals during the next 24 hours. However, locally induced afternoon SHRA/TSRA over the interior of PR will drift towards coastal areas, producing VCTS across the PR terminals, and may cause tempo MVFR to brief IFR conds at TJSJ btw 09/18-21z. Light and variable winds early through the morning hours, turning more ESE aft 09/14z with weak sea breeze variations.

MARINE

Issued at 231 AM AST Mon Nov 9 2026

The northeasterly swell will maintain offshore Atlantic seas at 4 to 5 feet today. As the low pressure northeast of the region moves eastward, surface high pressure will begin to build across the western Atlantic. This pattern will result in light to gentle winds across the eastern Caribbean that will gradually become easterly today and Tuesday, then increase to moderate by Wednesday onward. Seas across the Atlantic waters will generally range from 3 to 5 feet, while seas in the Caribbean remain at 1 to 3 feet. Showers and isolated thunderstorms may produce locally higher winds and seas.

BEACH FORECAST

Issued at 231 AM AST Mon Nov 9 2026

Energy from a northeasterly swell will continue to impact the Atlantic waters and local passages, producing breaking waves of 5 to 8 feet along the western to eastern beaches of Puerto Rico and Culebra. This means life-threatening rip currents are likely in the surf zones. Additional pulses of northeasterly swell will likely arrive Tuesday afternoon. As a result, the high risk of rip currents was extended through at least Tuesday afternoon. Continue to monitor the forecast for updates. A moderate risk of rip currents also remains along the beaches of Vieques and the U.S. Virgin Islands. Remain cautious, as rip currents are possible.

Another beach hazard will be thunderstorms, particularly during the afternoon hours. If thunder is heard, seek shelter immediately.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through Tuesday afternoon for PRZ001-002- 005-008-010-012.

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