textproduct: San Juan

KEY MESSAGES

Issued at 200 PM AST Sat Dec 20 2025

* Frequent light to moderate showers will persist across the local islands for the rest of the day, with a limited flood threat across eastern and southwestern sections of Puerto Rico and some coastal areas of the U.S. Virgin Islands.

* A small craft advisory is in effect until 6 PM on Sunday, due to increasing winds and a northeasterly swell producing hazardous seas. Life-threatening rip currents are expected along the north and east facing beaches of the islands.

* For the Christmas week, a wet and unstable weather pattern is forecast with a high chance of widespread showers and thunderstorms. Residents and visitors are urged to stay tuned for further updates.

Short Term(This afternoon through Monday)

Issued at 200 PM AST Sat Dec 20 2025

Sunny to partly cloudy skies prevailed across the islands today. A band of showers moved over the islands early this morning, crossing from east to west, leaving measurable rainfall amounts across most areas. The Doppler radar estimated between 0.10-0.30 inches in general with this activity. By noon, this surge in moisture combined with the sea breeze convergence to produce heavier showers over the southwest quadrant of PR, and up to 1 inch was observed from Penuelas to Yauco. For the rest of this afternoon, showers will continue to develop mainly over western PR. In general, maximum temperatures were from the mid to upper 80s across the lower elevations of the islands. The wind was from the northeast between 10 and 20 mph with higher gusts at times.

For the rest of the short-term period, patches of moisture embedded in the trade winds will continue to bring passing showers at times across the USVI and PR. A mid-to upper-level ridge will continue to inhibit the vertical development of showers, maintaining a low probability of thunderstorms. The overall drier air layer aloft and warmer than normal 500mb temperatures, suggest that fair weather conditions should prevail in general, with the exception of the occasional trade wind shower moving over windward areas. However, across western PR, and due to the enhancement of the sea breeze convergence and daytime heating, heavier showers are expected to develop each afternoon.

Minimum temperatures will range from the low 60s across the higher elevations of PR, to the upper 60s and low 70s across the lower elevations of the islands. Daytime highs will continue from the mid to upper 80s across the southern and western lower elevations of PR.

Long Term(Tuesday through next Saturday)

Issued at 531 AM AST Sat Dec 20 2025

By the beginning of the long term, an upper-level trough tied to the subtropical jet stream will bring cooler mid-level temperatures as the mid-level ridge weakens and moves westward. Patches of low level moisture will continue to move across the area, resulting in isolated to scattered showers over windward sections of Puerto Rico and the U.S. Virgin Islands, mainly during the night and morning hours. By late morning into the afternoon, a moderate chance of scattered showers, around 50 percent, is expected across interior and western Puerto Rico with low chances of flooding concerns.

For Wednesday and Thursday, Christmas Eve and Christmas Day, atmospheric instability will increase somewhat as 500 mb temperatures continue to cool further to below normal values between -8 and -10 degrees Celsius. A polar trough will extend southward into the Caribbean, while an additional upper-level trough will interact with a surface frontal boundary north of the region. The frontal boundary will move close to the area or cross the region, allowing a slight increase in moisture, while enhanced upper-level divergence. However, the global models have been somewhat unstable from run to run, but the latest guidance is now indicating less available moisture compared to yesterday. Precipitable water (PWAT) values are trending closer to seasonal levels, generally around 1.5 to 1.6 inches. Although some uncertainty remains, the reduction in moisture has led to a slight downward adjustment in rain chances. A moderate chance (around 50%) is expected for scattered showers with isolated thunderstorms. Galvez-Davison Index values have also lowered, suggesting reduced instability and supporting only a few isolated thunderstorms, with convection remaining mostly shallow.

Friday and Saturday, models are suggesting drier-than-normal air, leading to stable weather. Cooler temperatures are expected during the holiday period, as indicated by a trend toward below normal 925 mb temperatures.

AVIATION

(18Z TAFS) Issued at 200 PM AST Sat Dec 20 2025

Mainly VFR conditions expected across all terminals during the next 24 hours. However, quick passing -SHRA could move at times across TJSJ/TJBQ and the USVI terminals. Tempo MVFR conds are possible at TISX btw 21/04-10z. NE winds up to 19 kt blo FL100.

MARINE

Issued at 200 PM AST Sat Dec 20 2025

No changes to previous forecasts. Deteriorating marine conditions are forecast from later today into the evening hours due to a north- northeast swell filtering into the region. As a result, seas will build up to 7-8 feet, especially across the offshore Atlantic waters and local passages. As a result, there is a small craft advisory in effect for the offshore Atlantic waters and the Anegada passage until 6 AM AST on Sunday. For the rest of the local waters and seas, waves will remain up to 5 feet. Improving marine conditions are forecast for Tuesday into early Wednesday, when another northerly swell moves into the area, deteriorating marine conditions again for small craft operators.

BEACH FORECAST

Issued at 200 PM AST Sat Dec 20 2025

For the rest of the day, a moderate risk of rip currents will persist as coastal marine conditions deteriorate with the arrival of the north-northeasterly swell. Therefore, from 6 PM AST onward, there is a high risk of rip currents across all northern coastal areas, including Culebra and St. Croix, until Monday evening. Coastal conditions will improve by Tuesday; however, another northerly swell will increase the risk up to high again by late Wednesday into Thursday.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk from 6 PM AST this evening through late Sunday night for PRZ001-002-005-008-012.

VI...High Rip Current Risk from 6 PM AST this evening through late Sunday night for VIZ002.

AM...Small Craft Advisory until 6 PM AST Sunday for AMZ711.

Small Craft Advisory from 6 PM this evening to 6 PM AST Sunday for AMZ723.