textproduct: San Juan

KEY MESSAGES

Issued at 219 PM AST Mon Nov 17 2025 * Life-threatening rip currents are expected to form along the north-facing beaches in Puerto Rico, Culebra, and the eastern half of St. Croix.

* We have a moderate/high risk (40-60%) chance of observing showers and thunderstorms across the interior/west of PR this afternoon.

* A surface trough will increase the frequency of passing showers, producing periods of moderate to locally heavy rain across the US Virgin Islands and eastern PR overnight into tomorrow.

Short Term(This evening through Wednesday)

Issued at 219 PM AST Mon Nov 17 2025

The skies across the US Virgin Islands and Puerto Rico remained mainly sunny throughout the morning, with some clouds developing across the interior of PR, downwind from La Sierra de Luquillo, and over the interior of St. Croix around noon. The Doppler Radar observed near El Yunque and isolated areas in the interior of PR. The winds had an east-southeast component, with speeds ranging from 5 to 15 mph, and exhibited sea breeze variations. Some showers developed downwind from St Croix. Maximum temperatures ranged from the mid-80s to the upper 80s along the coastal locations, and from the mid- to upper 70s along the mountains.

The surface high pressure across the Central Atlantic will continue to promote an east-to-east-southeast wind flow today, resulting in afternoon convection along and northwest of the Cordillera Central. TJSJ 12z RAOB observed moisture values near or below climatology, with 1.30 inches of Precipitable Water (PW). Another observation is that we noted some warming at 500 mb, accompanied by modest instability at low and mid-levels. Furthermore, we are experiencing some dry air intrusion, which will limit afternoon and evening convection unless local sea breeze convergence and diurnal heating enhance rainfall. Therefore, we expect isolated to scattered showers and thunderstorms, enhanced by local topography and sea breeze fluctuations, over the interior and west PR, downwind from El Yunque and the US Virgin Islands.

A surface trough will promote moisture increment overnight, with more frequent passing showers across the USVI and PR's windward locations. This activity will increase the chance of observing periods of moderate to locally heavy rainfall. Although dry air aloft will persist tomorrow, moisture levels will rise all the way up to 600 MB, promoting a better chance for thunderstorms to develop during the afternoon. Thus, the risk of observing flooding rains tomorrow will range from limited to relatively elevated, mainly over Puerto Rico. Most of the activity near the USVI will remain over the surrounding waters, but there is a slight chance that this activity moves occasionally inland.

By Wednesday, there will be a greater chance of favorable conditions for convection as a deepening polar trough moves east across the western Atlantic into the northeastern Caribbean. In the afternoon and evening, the region will likely experience increased instability, with 500 mb temperatures dropping to -8 to -9 C and steepening lapse rates between 700 and 500 mb. This suggests a higher likelihood of widespread showers and isolated thunderstorms.

Although northeasterly winds may limit heating in some areas, stronger upper-level forcing is expected to support convective development, resulting in showers and thunderstorms that may linger overnight over Atlantic waters and occasionally move inland. Consequently, the flood risk will increase, particularly in areas with repeated showers.

Regarding local temperatures, they will continue to be slightly above normal, but heat impacts remain unlikely, and a cooling trend is likely on the horizon.

Long Term(Thursday through next Sunday)

Issued at 219 PM AST Mon Nov 17 2025

A gradual improvement in the weather conditions is still anticipated by the end of the workweek into the upcoming weekend. Thursday may be the wettest day of the period due to lingering moisture across the region and the influence of the polar trough. From the deterministic guidance of the GFS and ECMWF, seasonal Precipitable Water values (1.5 - 1.6 inches) and colder 500 mb temperatures (around -8.5 degrees Celsius) are likely. Combined with local effects and daytime heating , afternoon convection may develop over the mountain ranges and southwestern Puerto Rico. Although rainfall accumulations may not reach significant flooding criteria, ponding of water over roadways, urban areas, and poorly drained areas may lead to isolated urban and small stream flooding over the aforementioned areas. By Friday, a surface high pressure system should build over the western Atlantic, promoting mostly NE winds. Weather conditions should improve over the weekend as drier air filters into the region with a mid level ridge dominating the weather pattern. From the latest model guidance, PWAT values are likely to decrease and remain below climatological normal (between 1.2 - 1.4 inches), while 500 mb temperatures will get warmer than normal by the end of the period. Patches of moisture will move occasionally across the CWA, bringing light to moderate passing showers over windward sections of the islands in the late night into the morning hours. Although afternoon convection is expected, shower activity will likely be limited under this weather pattern. Therefore, the flooding and lightning threat is not expected for the rest of the forecast period.

Model guidance continues to suggest a fall in 925 mb temperatures, being Thursday cooler than normal. Although the latest GFS solution is tending to warmer temperatures for Saturday, temperatures should remain seasonal, presenting no heat threat. Hence, the heat risk should remain low for the rest of the period.

AVIATION

(18Z TAFS) Issued at 219 PM AST Mon Nov 17 2025

VFR conds are present across all TAF sites. The is still a slight to moderate chance to observe a few short-lived thunderstorms over the interior and W PR may bring VCSH/VCTS to TJSJ and TJBQ, with brief MVFR and mtn obscurations possible. During the overnight period and Tuesday morning, an increase in VCSH is forecast across USVI TAF sites and TJSJ. E-SE below 10 kts, becoming calm overnight.

MARINE

Issued at 219 PM AST Mon Nov 17 2025

A surface high pressure system will begin to dominate across the central Atlantic, promoting moderate easterly winds from tonight onward. Pulses of a north northeasterly swell will spread across the Atlantic waters and local passages through Wednesday. Another frontal boundary will approach north of the region around midweek, promoting moderate winds to shift more from the northeast at the end of the forecast period. Daily showers and isolated thunderstorms could generate locally hazardous conditions for small craft.

BEACH FORECAST

Pulses of north-northeasterly swells continue to spread across the local waters. The San Juan buoy current observations show wave heights around 4 feet at a period ranging between 10 to 14 seconds. Based on calculations, that is resulting in breaking waves around 6 to 7 feet. As a result, the high risk of rip currents remains in effect for the northern and eastern beaches of Puerto Rico, Culebra, and St. Croix in the U.S. Virgin Islands this evening and will continue through at least Wednesday afternoon. Residents and visitors are urged to exercise caution, as life-threatening rip currents are present along the surf zones. Heed the advice of the flag warning system and swim near a lifeguard. Also, afternoon convection may produce gusty winds and lightning, beachgoers should remain weather alert and seek shelter whenever they hear thunder. For more information specific to your location, visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

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

VI...High Rip Current Risk through Wednesday afternoon for VIZ002.

AM...None.