textproduct: San Juan

KEY MESSAGES

Issued at 403 AM AST Sun Dec 14 2025

* A drier and stable air mass will continue to move across the islands today, promoting limited showers.

* Choppy to rough seas are expected to continue across the offshore Atlantic waters through at least Monday morning.

* For the U.S. Virgin Islands, mainly fair weather conditions are expected with few passing showers moving into the area.

* The approach of a frontal system and its associated upper-level trough over the western Atlantic will promote unstable conditions during the first half of the workweek.

Short Term(Today through Tuesday)

Issued at 403 AM AST Sun Dec 14 2025

A drier and more stable air mass will continue to gradually fill over the region today. This will promote mostly fair weather conditions across the islands, with limited shower development this afternoon over land areas. On Monday and Tuesday, global model guidance continues to suggest a wet period, as an approaching cold front and associated upper level trough from the western Atlantic induces a pre-frontal trough near the local area. The precipitable water content is expected to increase near 1.75 inches, which is above normal levels. This pooling of moisture will allow for weak surface troughs to move from the east, increasing the chance of showers between 50-70% each day across the islands, with a slight chance of thunderstorm development over western PR in the afternoon hours. As the front remains north of the region, and the area sits between two areas of high pressure over the Azores and behind the front over western Atlantic, a southeasterly wind flow will prevail. This will lead to warmer than normal temperatures before the onset of afternoon showers.

Long Term(Wednesday through Sunday)

Issued at 403 AM AST Sun Dec 14 2025

The inherited forecast remains on track. Instability is expected to arrive in the area on Wednesday, driven by an upper-level trough positioned along a frontal boundary north of the region. At the surface, a building high-pressure system over the western Atlantic will begin to push moisture associated with this front into the local area, promoting wetter conditions by the latter part of the week. As this surface high strengthens, winds will shift to the northeast, pushing slightly cooler air into the area. Under this pattern, frequent passing showers are expected during the morning hours across portions of eastern Puerto Rico and the U.S. Virgin Islands, followed by afternoon showers over portions of central and western Puerto Rico. During this period, precipitable water content values are expected to range from 1.6 to 1.8 inches, suggesting normal to near-above-normal values for the season. At the 500 mb level, temperatures are expected to remain around -6C; however, isolated thunderstorms cannot be ruled out, particularly with the afternoon activity over western Puerto Rico. Furthermore, the increasing pressure gradient force driven by the strengthening high pressure will result in breezy conditions during the latter half of the week, with wind speeds sustained between 15 to 20 knots.

AVIATION

(06Z TAFS) Issued at 403 AM AST Sun Dec 14 2025

Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. Mostly VCSH expected at times across the area terminals. Winds will prevail from the east at 15-20 kt with sea breeze variations and stronger gusts aft 14/14z.

MARINE

Issued at 403 AM AST Sun Dec 14 2025

A surface high-pressure system will continue to build near the Azores, promoting moderate to fresh east to southeast winds across the local waters. Increasing winds and a fading long-period northerly swell will result in choppy to rough seas, mainly across the Atlantic waters. Small Craft Advisories remain in effect at least through Monday morning across the offshore Atlantic waters. A cold front and another surface high- pressure system will move from the western Atlantic into the central Atlantic early next week, weakening the pressure gradient and allowing for gentle to moderate winds through Tuesday. By midweek, increasing winds and a northwesterly swell will deteriorate marine conditions once again.

BEACH FORECAST

Issued at 403 AM AST Sun Dec 14 2025

A fading, long-period northerly swell will create life-threatening rip currents along the north and east facing beaches of the islands, where a Rip Current Statement remains in effect at least through early this morning. Beachgoers are urged to avoid swimming under these conditions. For the rest of the area, a low to moderate risk of rip currents is expected to dominate from today onwards, with beach conditions deteriorating again by midweek as a northwesterly swell spreads across the local Atlantic waters. For specific location information, please visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk until 6 AM AST early this morning for PRZ001-002-005-008.

VI...None. AM...Small Craft Advisory until 6 AM AST Monday for AMZ711.