textproduct: San Juan

KEY MESSAGES

Issued at 220 PM AST Tue Nov 18 2025 * Life-threatening rip currents are expected along the north- facing beaches in Puerto Rico, Culebra, and the eastern half of St. Croix through Wednesday afternoon.

* Showers and isolated thunderstorms this afternoon due to a surface trough, then a showery pattern will stretch into Wednesday morning across windward areas.

* Passing showers will bring periods of moderate to locally heavy rain across the US Virgin Islands during the overnight period.

* Drier air and cooler temperatures are anticipated by Thursday into the weekend.

Short Term(This evening through Thursday)

Issued at 220 PM AST Tue Nov 18 2025

The most recent satellite imagery shows an area of enhanced moisture, associated with a surface trough, reaching the Virgin Islands and eastern Puerto Rico. The high resolution and global models, as well as current observations, suggest that shower activity will keep streaming across the Virgin Islands, and eastern Puerto Rico this afternoon, with a low chance of experiencing urban flooding and lightning strikes. Across the interior and western Puerto Rico, while convection is expected to be heavy at times, showers will taper off by sunset, giving way to mostly clear to partly cloudy skies in the night hours.

The surface trough will depart the northeastern Caribbean islands by early tomorrow, so the showery pattern will stretch into Wednesday morning. Then, as a high pressure build at the mid levels over the western Caribbean, a much drier and cooler air mass will filter in. However, there should be enough energy to generate locally strong convection along western Puerto Rico on Wednesday afternoon, but conditions will gradually improve afterward. At the surface, the trade winds will stay from the northeast while weakening. Under this pattern, it is usual that showers pop up over the Atlantic waters in the late night and early morning hours. These showers will then reach the northeast coast of Puerto Rico and the Virgin Islands at times, but without posing a flooding risk.

Long Term(Friday through Tuesday)

Issued at 348 AM AST Tue Nov 18 2025

The long-term forecast remains on track, with mostly fair conditions for the upcoming weekend, becoming variable early next week. A surface high pressure is still expected to build over the Western Atlantic by Friday, promoting northeasterly winds through most of the period. As a drier air mass should filter into the region, the latest deterministic guidance from the GFS and ECMWF continues to suggest PWAT values mostly below climatological normal (1.2 - 1.4 inches), with a few members opting for more seasonal values (1.4 - 1.6 inches). A mid-level ridge should also establish, warming 500 mb temperatures (around -5.5 degrees Celsius), and promoting stability aloft and limiting deep convection activity. Additionally, the Galvez-Davison Index (GDI) suggests a low potential of thunderstorm development across the CWA. As mentioned in the previous discussion, the most likely scenario would be passing showers over windward sections in the late night and morning, with limited afternoon convection over the mountain ranges and southwestern portions of Puerto Rico. Although rainfall accumulations should not present a flooding threat, expect ponding of water over roadways, urban, and poorly drained areas. On Monday and Tuesday, PWAT values are expected to increase to more seasonal levels due to patches of moisture moving across the CWA, resulting in an increased frequency of showers. Nevertheless, no significant flooding or lightning risk is expected across the region.

Once again, cooler temperatures are likely across the CWA during the forecast period, as the latest guidance keeps suggesting a fall in 925 mb temperatures, well below normal. Under a northeast wind flow, the heat threat will remain low throughout the long-term period.

AVIATION

(18Z TAFS) Issued at 220 PM AST Tue Nov 18 2025

VFR with intermittent MVFR conds possible over the next hours. VCTS or TSRA will result in reduced vis and lower cigs, then will decrease aft 18/22-23Z but may linger near TJSJ and USVI terminals overnight. Winds will remain from the E with gusts at around 18 to 21 kts. Typical sea breeze variations and locally gusty winds near t-storms. Lighter winds overnight, increasing near 10 kts aft 19/13-14Z.

MARINE

Issued at 220 PM AST Tue Nov 18 2025

A surface trough will continue to bring showers and isolated thunderstorms across the local waters and passages tonight into Wednesday morning, likely generating localized hazardous conditions for small craft. Moderate easterly winds will persist through Wednesday night before shifting to the northeast as a surface trough moves east of the Leeward Islands. Pulses of a north- northeasterly swell will continue to spread across the Atlantic waters and local passages through Wednesday.

BEACH FORECAST

Issued at 220 PM AST Tue Nov 18 2025

Pulses of north-northeasterly swells continue to spread across the local Atlantic waters. Current observations from the San Juan buoy are variable, with wave heights around 3 feet at periods pulsing up to 10 to 14 seconds. Based on calculations, this is producing breaking waves of around 6 feet, maintaining a high risk of rip currents along the northern and eastern beaches of Puerto Rico, as well as Culebra and St. Croix, through this evening and potentially through at least Wednesday afternoon. For location- specific information, 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.