textproduct: San Juan

KEY MESSAGES

Issued at 237 PM AST Sun Dec 14 2025

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

* Up to a moderate risk of rip currents tonight, with a northwesterly swell forecast to arrive by midweek and deteriorate conditions.

* A dry and stable air mass will continue to move over Puerto Rico and the U.S. Virgin Islands this afternoon and early tonight, limiting shower activity.

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

Short Term(This evening through Tuesday)

Issued at 237 PM AST Sun Dec 14 2025

Fair weather prevailed today, as a dry and stable air mass remained over the islands. Current satellite derived precipitable water (PWAT) values indicate between 1 to 1.3 inches, below seasonal values. ESE steering flow helped promote normal to slightly above normal 925 mb temperatures. Highs reached the mid to upper 80s, with some stations reporting highs in the low 90s, across coastal and urban areas. Higher elevations of Puerto Rico saw maximum temperatures from the 70s to around 80. Several coastal official and unofficial stations reported sustained winds up to 13 to 18 mph with higher gusts around 19 to 28 mph.

Only limited shower development is possible this afternoon and early tonight over the islands. Patchy fog will once again return over areas of the interior. The surface high over the central to western Atlantic, promoting the above mentioned steering flow, will continue gradually moving eastward as a frontal low exits the eastern U.S. Another high will then enter the western Atlantic tomorrow, leaving the islands between the two highs. This will continue to result in ESE steering flow, resulting in patches of moisture and weak surface troughs heading towards the islands tomorrow and Tuesday.

PWAT values are forecast at seasonal to above seasonal levels early in the workweek as moisture continues to be steered towards the islands, a cold front and related trough are north of the region, and an induced pre-frontal trough is near the area. Current model guidance has PWAT increasing late tonight into tomorrow, helping promote a wetter pattern and shower activity over the eastern region mainly during the morning and overnight hours and, during the afternoons, western PR with a slight chance of t-storm development. 925 mb wind speeds will continue decreasing later today and tonight before gradually increasing tomorrow onwards, in general they are forecast to be lighter and at more seasonal speeds to start the workweek. 925 mb temperatures are forecast at seasonal to above seasonal values due to the ESE steering flow.

Long Term(Wednesday through next Saturday)

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

(18Z TAFS) Issued at 237 PM AST Sun Dec 14 2025

VFR conditions are expected for the rest of today across all TAF sites. Winds from the E to SE around 10 to 15 kts thru 14/22Z, then below 7 kts thru 15/14Z across PR TAF sites. VCSH and periods of -RA across TIST and TISX during the overnight period into the morning hours, then into TJSJ, TJPS and TJBQ around 15/15-17Z onward. Expect intermittent periods of MVFR conditions due to cigs and reduced vis at times. E-SE winds form 15/14Z at around 8 to 12 kts.

MARINE

Issued at 237 PM AST Sun Dec 14 2025

A surface high-pressure system across the eastern into central Atlantic will continue to promote moderate to locally fresh east to southeast winds across the local waters tonight. Wind-driven seas are promoting hazardous marine conditions for small craft operators across the offshore Atlantic waters, where a Small Craft Advisory remain in effect at least through Monday morning. A cold front and another surface high-pressure system will move from the western Atlantic into the central Atlantic over the next few days, weakening the pressure gradient and allowing for gentle to moderate winds Monday and Tuesday. By midweek, increasing winds and a northwesterly swell will likely deteriorate marine conditions once again.

BEACH FORECAST

Issued at 237 PM AST Sun Dec 14 2025

Tonight, there is a moderate risk of rip currents along most beaches of the islands. This means that life-threatening rip currents are possible in the surf zone, and beachgoers are encouraged to exercise caution. Early this week, a moderate risk of rip currents is expected to prevail across north-facing beaches of Puerto Rico, Culebra, and the U.S. Virgin Islands, with a low risk elsewhere. Remember that even when the risk is low, life-threatening rip currents can still occur, especially near groins, jetties, reefs, and piers.

By midweek, beach conditions are anticipated to deteriorate again due to increasing winds and a northwesterly swell spreading across the local Atlantic waters. Stay tuned to the forecast! For specific location information, please visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

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