textproduct: San Juan

KEY MESSAGES

Issued at 404 PM AST Fri Nov 6 2026

- A west-southwest to southwesterly steering flow and abundant moisture will continue to move shower and thunderstorm activity to the eastern half of Puerto Rico and the US Virgin Islands later this evening into tonight.

- The unstable and moist weather pattern will maintain elevated risks for urban and small-stream flooding, quick river rises, localized flash flooding until Sunday. Mudslides can not be ruled out due to saturated soils.

- A moderate-to-high risk for life threatening rip currents will persist through the weekend with a peak on Sunday.

- By mid-next week a stable weather pattern will prevail across the region.

Short Term(This evening through Sunday)

Issued at 404 PM AST Fri Nov 6 2026

For the rest of the day and into the weekend, a broad mid-to-upper- level trough now over the local area and a surface low north of the region will continue to dominate the local weather pattern. The interaction between these systems is driving a 7-10 knot west- southwesterly steering flow, pulling tropical moisture up from the Caribbean. Consequently, precipitable water (PWAT) values will reach well above normal values up to 2.00-2.40 inches. This deep moisture content, combined with forcing from the mid-to-upper level trough, will produce showers moving from the south-southwest to north- northwest across Puerto Rico and the U.S. Virgin Islands. While activity began earlier today, coverage will increase this afternoon as daytime heating, sea breeze convergence, and terrain interaction enhance showers and thunderstorm development. As the trough axis shifts eastward tonight, scattered showers and strong thunderstorms will persist, but shifting focus over eastern Puerto Rico, San Juan metro area and the U.S. Virgin Islands.

This unsettled pattern will linger through Sunday. As the surface low and mid-to-upper level trough move toward the central Atlantic, activity will shift focus to northern and eastern Puerto Rico and the US Virgin Islands. Slow-moving showers will bring a threat of urban, road, stream, and wash flooding. The flooding risk peaks today, but will persist through the weekend into early next week, especially across the central and eastern interior, as well as the San Juan metro area. Saturated soils will also increase the risk of mudslides. The strongest activity could be accompanied by lightning and gusty winds, while the strongest thunderstorms over water could produce waterspouts across coastal waters. Because of the cloud cover expected due to the unsettled pattern during most of the short term period, the heat risk will be limited for Saturday onwards, affecting those sensitive individuals to heat, thus they should avoid outdoor activities during peak daytime heating hours and stay hydrated.

Long Term(Monday through Friday)

Issued at 404 AM AST Fri Nov 6 2026

To start the next workweek, a plume of tropical moisture will linger near the region under a light southwesterly steering flow as a frontal low continues to move away from the region. Both the GFS and the ECMWF are in general agreement with regards to available moisture towards midweek. Precipitable water (PWAT) values should stay generally above normal values (2.0 inches) through midweek. 850- 870 mb relative humidity (RH) is forecast to range between high-end normal values to above normal values through Tuesday, before trending towards more normal values. 700-500 mb should stay above normal through most of the period. 925 mb wind speeds will be on a decreasing trend through Tuesday (being light and variable) before gradually increasing once again towards Wednesday and through the end of the forecast period.

A surface high and then another frontal low will move over the western Atlantic towards the end of the period. The steering flow is forecast to be southwesterly on Monday before becoming more southerly Tuesday onwards, with more moderate E to SE surface flow to end the period. Diurnal heating and local effects are forecast to result in afternoon showers and t-storms, guided by the above mentioned flow. This will sustain a flooding risk, especially each afternoon. Overnight and morning showers will also affect windward sectors. Although the moisture plume will linger towards early Thursday, the southerly steering flow will quickly result in additional moisture over the islands towards the end of the period as the above mentioned frontal low moves northward towards the Western Atlantic, possibly sustaining the flooding risk. The model guidance diverges more through this period, with the GFS trending towards above normal PWAT and 700-500 mb RH while the ECMWF trends towards more normal values. Above normal 925 mb temperatures are forecast for most of the period, prompting at least a limited heat risk and possibly reaching two standard deviations by the second half of the workweek.

AVIATION

(18Z TAFS) Issued at 404 PM AST Fri Nov 6 2026

SHRA/TSRA will develop across the local flying area. This activity will impact TJSJ/TJPS/TIST/TISX thru this evening. Thus, MVFR to brief IFR conds are possible at TJSJ/TJPS/TIST/TISX due to TSRA/SHRA with mtn tops obscd along the Cordillera and eastern mountain ranges. Mostly VCSH expected across the rest of the PR and USVI terminals. Expect surface winds out from the SSW to WSW at 5 to 15 knots, accompanied by local sea breeze variations and higher gusts. Another round of SHRA/TSRA is possible btwn 07/02-13z.

MARINE

Issued at 404 PM AST Fri Nov 6 2026

Light to gentle southwesterly winds will gradually shift to a more westerly flow through Saturday as a low pressure strengthens north of the region. Increasing showers and thunderstorms this evening into the weekend will result in deteriorating weather conditions over most regional waters and local passages particularly across the Atlantic waters.

Gusty winds, reduced visibility, and frequent lightning are possible with the strongest thunderstorms. A northerly swell will continue to spread across the Atlantic waters this afternoon onwards, with most of the swell energy expected by Saturday evening into Sunday and persisting through early next week. This may result in hazardous marine conditions, particularly across the Atlantic waters and northern passages.

BEACH FORECAST

Issued at 404 PM AST Fri Nov 6 2026

A moderate risk for rip currents will persist until Saturday, predominantly affecting north, west, and east facing beaches of Puerto Rico and the US Virgin Islands. Conditions will deteriorate from Saturday night into Sunday as a northerly swell begins to reach the local waters, builds seas and increases the likelihood of life- threatening rip currents along the northern and eastern facing beaches of Puerto Rico. While a moderate threat for rip currents will remain for the rest of the region with the exception of southern Puerto Rico. Beachgoers should closely monitor forecast updates and follow the advice of local beach patrols and flag warning systems.

In addition, there is a chance for isolated thunderstorms and showers along with gusty wind conditions throughout the forecast period that may affect beachgoers, especially in the afternoons, especially across the CWA on Saturday and northern to northeastern Puerto Rico for the remainder of the forecast period. Seek shelter immediately if you hear thunder even in the thunderstorms are offshore. The heat risk remains limited for the US Virgin Islands and Puerto Rico. The associated heat stress may affect individuals that are extremely sensitive to heat particularly during the late morning and early afternoon hours. As you head into the weekend, remain weather alert with the latest forecasts as they become available.

SJU WATCHES/WARNINGS/ADVISORIES

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