textproduct: San Juan

KEY MESSAGES

Issued at 1245 PM AST Mon Nov 2 2026

- A seasonal weather pattern will continue through midweek, with passing showers across eastern Puerto Rico and the U.S. Virgin Islands, followed by afternoon showers and thunderstorms mainly over western and northwestern Puerto Rico.

- Afternoon thunderstorms may produce locally heavy rainfall, frequent lightning, ponding of water on roads, and minor rises along small streams. Most activity should diminish during the evening hours.

- Warmer conditions are expected through midweek as winds become more southerly. Heat indices could reach Heat Advisory criteria across urban, coastal, and lower-elevation areas, so continue to follow heat safety recommendations.

- A wetter pattern is expected from Thursday through Saturday. Increasing moisture and slow-moving showers and thunderstorms could raise the flooding threat, including urban and small- stream flooding, with isolated flash flooding possible.

- Choppy marine conditions will gradually improve through midweek as winds and seas diminish. The risk of rip currents will also decrease across many beaches. However, another swell arriving late in the week could bring hazardous surf and rip current conditions during the weekend, particularly along the northern coast of Puerto Rico and the northern U.S. Virgin Islands. Refer to the Beach Forecast section for additional details.

Short Term(This evening through Wednesday)

Issued at 1245 PM AST Mon Nov 2 2026

Latest upper-air soundings and recent satellite-derived moisture imagery indicate a seasonal trade wind pattern across the local area, with precipitable water values lingering near 2.00 inches. A persistent east-to-southeast steering flow will continue to transport patches of shallow moisture, along with pockets of dry air and minor accumulations of Saharan dust across the U.S. Virgin Islands and Puerto Rico through midweek. While large-scale dynamic forcing remains largely absent due to an upper-level ridge, sufficient low-level moisture and daytime heating will combine with the sea breeze convergence and orographic lift to support daily convection, mainly over northwestern PR and from streamers developing downwind of the islands.

The primary threat from these afternoon thunderstorms will be localized heavy rainfall, capable of producing rapid accumulations that may lead to ponding on roadways and minor rises in small streams. Activity is expected to diminish rapidly as daytime heating wanes each evening, leaving most overnight and early morning hours relatively quiet aside from brief passing trade wind showers across windward areas. Meanwhile, winds are expected to gradually shift more southerly through midweek, in response to a developing surface low pressure from a frontal boundary well north of the region and weakening of the surface high over the western Atlantic. This light to moderate deep-layer southerly flow, combined with seasonal moisture and daytime heating, could drive afternoon heat indices into heat advisory criteria, particularly along urban and lower- elevation areas. Residents and visitors are encouraged to follow heat safety recommendations, particularly those working or spending extended periods outdoors.

Long Term(Thursday through Monday)

Issued at 310 AM AST Mon Nov 2 2026

A more unstable pattern could unfold or continue during the long term period, particularly from Thursday through Saturday. A moist environment will be present, with precipitable water around 2.0 to 2.3 inches, which is considered above normal values based on November climatology (75th percentile). The 850 to 700 mb relative humidity remains high, generally between 75 to 90%, while the 700 to 500 mb layer also shows an increase in moisture, reaching around 70 to 80% by Friday into Saturday. Overall, the moisture profile suggests a deep and relatively moist atmospheric column through this period, supporting favorable conditions for precipitation.

At the synoptic level, an upper-level low, along with its associated surface low and frontal boundary, will move northward across the Atlantic waters during the period (the most unstable part will remain north of the eastern Caribbean). However, this evolution will favor southerly to southwesterly low-level winds, allowing tropical moisture to be transported to our region, as the features move farther north. Light winds will generally prevail across the local area, contributing to weak steering flow and potentially slow moving showers, allowing showers to move slowly and increasing rainfall accumulations, mainly across southern, interior, and northern portions of Puerto Rico, as well as the U.S. Virgin Islands. As a result, flooding will remain one of the main concerns (Level 2 of 4), indicating the potential for flooding in urban areas, along roads, and near small streams and washes. Additionally, isolated flash flooding cannot be ruled out. Other factors to consider are the NCICS forecasts, including the 200-hPa Velocity Potential and Outgoing Longwave Radiation (OLR), which suggest upper-level divergence. There are also signals of equatorial Rossby and Kelvin waves across the Caribbean during this period, which could enhance rainfall activity. Continue to monitor the forecast as confidence increases and updated model guidance becomes available.

By Sunday and Monday, global models agree that a mid to upper level ridge will build bringing a more stable pattern. In terms of moisture content, model differences become more apparent. The GFS maintains higher moisture, particularly in precipitable water and the 850 to 700 mb relative humidity, suggesting that a greater amount of moisture remains available in the atmospheric column. In contrast, the ECMWF indicates more reduction in moisture, with lower precipitable water values and a drier low to mid-level profile. This disagreement introduces some uncertainty regarding the extent of moisture available during this period. Isolated to scattered afternoon showers may still develop across portions of the islands due to daytime heating and local effects, but rainfall coverage and intensity should decrease those days, reducing the flood concerns.

AVIATION

(18Z TAFS) Issued at 1245 PM AST Mon Nov 2 2026

Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. However, SHRA/TSRA development over the interior of PR may cause tempo MVFR conds at TJSJ and TJBQ through 02/21Z. Mostly VCSH expected across the rest of the PR and USVI terminals til around 02/22z. The 02/12z TJSJ sounding indicated SE winds up to 22 kt blo FL100. Weak sea breeze variations developing along the northern coast of PR should diminish by 02/21z. Light winds with a southeast component will prevail overnight.

MARINE

Issued at 1245 PM AST Mon Nov 2 2026

Moderate to locally fresh easterly winds will maintain choppy marine conditions across the regional waters through Tuesday, with seas generally between 3 and 5 feet, occasionally up to 6 feet. However, a gradual improvement in wind-driven marine conditions is expected by midweek as a broad area of low pressure develops north of the region, weakening the local pressure gradient. As a result, winds will gradually diminish and shift from the east to southeast, becoming more southerly by midweek. Although winds and seas should gradually subside during the latter part of the week, increasing moisture and instability will favor more frequent showers and thunderstorms, particularly from Thursday into the weekend. Locally higher winds and seas will remain possible near thunderstorms.

BEACH FORECAST

Issued at 1245 PM AST Mon Nov 2 2026

A moderate risk of rip currents will persist along the northern and eastern-exposed beaches of Puerto Rico, including Culebra and Vieques, and the U.S. Virgin Islands through at least tonight, while a low risk will prevail elsewhere. However, as wind-driven seas gradually diminish, the areas under a moderate risk are expected to become more limited through Thursday, with improving beach conditions across much of the region. Nevertheless, even where a low risk prevails, life-threatening rip currents can still occur near jetties, groins, piers, and reefs.

By the end of the workweek and into the weekend, a north- northwesterly swell is expected to reach the northern exposed waters. Although current model guidance suggests that this swell may not be strong enough to increase the rip current risk beyond moderate, uncertainty remains regarding its intensity. A stronger swell than currently forecast could result in more hazardous surf and rip current conditions during the weekend. Therefore, beachgoers should continue to monitor the forecast for potential changes. Additionally, showers and isolated thunderstorms will remain possible near coastal areas, with increasing activity expected from Thursday into the weekend as a wetter and more unstable weather pattern develops.

SJU WATCHES/WARNINGS/ADVISORIES

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