textproduct: San Juan

KEY MESSAGES

Issued at 215 PM AST Thu Nov 20 2025 * There is a High Risk of Rip Currents for the north-facing beaches in Puerto Rico, Culebra, and eastern half St. Croix until 6 PM AST this evening.

* Residents and visitors in the USVI and PR can expect pleasant temperatures as a cooling trend will prevail, especially from Friday into next week.

* Afternoon showers and possible t-storms are forecast mainly over interior to SW Puerto Rico tomorrow.

Short Term(This evening through Saturday)

Issued at 215 PM AST Thu Nov 20 2025

Weather conditions during the morning hours remained relatively calm with mostly clear skies across Puerto Rico and the U.S. Virgin Islands. By the afternoon, shower and thunderstorm activity developed over the southwestern quadrant of Puerto Rico. Winds were generally from the northeast, keeping coastal temperatures in the 80s, with a few isolated coastal and urban areas reaching the low 90s, while temperatures across higher terrain remained in the 70s.

A generally quiet night is expected as daytime heating diminishes and convection fades. However, brief, shallow trade wind showers will still reach portions of eastern Puerto Rico and the U.S. Virgin Islands. Light to moderate northeast winds will persist, and temperatures will cool into the mid-70s along the coasts and the 60s across the interior and higher elevations.

As mentioned in previous discussions, a second, deeper shortwave is forecast to drop farther south on Friday, introducing another brief period of cooling aloft before quickly shifting east of the region. Subsidence and significant drying will take over the region after the end of the workweek, with PWAT values falling below typical levels for this time of year. At the surface, a trough and a strengthening high over the western Atlantic will reinforce northeast trade wind flow, pushing increasingly drier air across the region. The latest model guidance suggests that a gradual mid- level ridge will strengthen the trade-wind cap inversion, resulting in increasingly unfavorable conditions for deep convection. Although isolated overnight trades may still occur, the rainfall risk remains limited for tomorrow. Regardless, we anticipated a significant reduction in afternoon convection compared to recent days. As a heads up, temperatures will begin to trend slightly cooler, moderated by persistent northeast winds.

Conditions will turn more stable on Saturday as drier air deepens and the mid-level inversion strengthens further. The latest model guidance suggests that values will remain well below normal, supporting a notably drier and more stable pattern. Only isolated, brief trade wind showers are expected overnight and early morning, with little to no afternoon convection. Temperatures will remain slightly cooler, especially overnight under clearer skies. Overall, hazard risks will decrease significantly, with only a limited chance of thunderstorms or localized flooding on Friday, and little to no risk by the weekend.

Long Term(Sunday through next Wednesday)

Issued at 458 AM AST Thu Nov 20 2025

Forecast confidence remains low to moderate due to notable discrepancies between the GFS and ECMWF regarding the evolution of mid- to upper-level features early next week. These differences directly affect expectations for instability and convective coverage across Puerto Rico and the U.S. Virgin Islands.

The GFS suggests a short-wave trough replacing the zonal flow aloft Sunday into Monday, followed by additional amplification on Tuesday. This scenario would shift a mid-level ridge westward over the Bahamas/Cuba, placing PR/USVI between the ridge to the west and a deepening trough to the east, favoring increased upper-level divergence and a more unstable environment. Under this configuration, the probability of scattered afternoon convection and isolated thunderstorms would be moderate (20-40%), peaking Tuesday through the middle of the week.

In contrast, the ECMWF maintains a more stable pattern, with zonal flow on Sunday and only weak short-wave perturbations on MondayTuesday. Notably, the model retains the mid-level ridge, supporting dry air intrusions and subsidence that would limit convective development. Under this solution, afternoon showers would be more isolated (2030%), primarily driven by local sea- breeze and orographic effects. Given these differences, the forecast leans on a climatological trade- wind pattern. Therefore, expect periodic patches of moisture embedded in the trades producing passing showers across the local waters, USVI, and windward/eastern Puerto Rico. Each afternoon, isolated to scattered convection (mainly interior and western PR) remains possible, but the probability of thunderstorms stays low to moderate (1030%), highest if the GFS scenario materializes.

Overall, no strong signal is emerging for widespread rainfall or a significant instability event at this time, and uncertainty remains elevated until better model consensus develops.

Local temperatures will continue to cool, remaining slightly below normal, around the 25th percentile compared to November climatology.

AVIATION

(18Z TAFS) Issued at 215 PM AST Thu Nov 20 2025

Mainly VFR conditions for the terminals with brief MVFR conditions possible mainly over TJPS due to TSRA through 20/21Z. SHRA or possible TSRA at or in the VCTY of TIST/TISX/TJSJ during the afternoon hours followed by overnight with passing SHRA over northern terminals. Steering flow from the northeast up to 15 kts with higher gusts and sea breeze variations through 20/22Z, bcmng light and VRB through 21/13Z.

MARINE

Issued at 215 PM AST Thu Nov 20 2025

A long period north-northeasterly swell will continue to move across the local waters through this evening. An upper-level short-wave trough will help to promote afternoon thunderstorms across the Mona Passage and Caribbean waters. The remnants of the frontal boundary will slowly dissipate across the western Atlantic through Friday, when a surface high is expected to build over the region. This high pressure will promote moderate trade winds from the upcoming weekend into early next week.

BEACH FORECAST

Issued at 215 PM AST Thu Nov 20 2025

A High Risk of Rip Currents will be in effect through 6 PM AST this evening for the northern exposed beaches of Puerto Rico and Culebra, as well as eastern St. Croix, due to lingering energy from a fading north- northeasterly swell. A moderate risk of rip currents is forecast for the rest of the workweek and into the weekend. However, another north-easterly swell is likely to increase the rip current risk to high again by Tuesday.

Rip currents are powerful channels of water flowing quickly away from shore, which occur most often at low spots or breaks in the sandbar and in the vicinity of structures such as groins, jetties and piers. Heed the advice of lifeguards, beach patrol flags and signs.

If you become caught in a rip current, yell for help. Remain calm, do not exhaust yourself and stay afloat while waiting for help. If you have to swim out of a rip current, swim parallel to shore and back toward the beach when possible. Do not attempt to swim directly against a rip current as you will tire quickly.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk until 6 PM AST this evening for PRZ001-002- 005-008-012.

VI...High Rip Current Risk until 6 PM AST this evening for VIZ002.

AM...None.