textproduct: San Juan

KEY MESSAGES

Issued at 449 AM AST Sun Dec 7 2025

* Mostly fair and stable conditions will continue through the period, with brief overnight and morning showers on windward sides and isolated afternoon showers across the interior and west. No flooding impacts are expected.

* Winds will increase late in the week, leading to breezy to windy conditions across coastal and elevated areas by Thursday and Friday. Lightweight outdoor items may be blown around in exposed locations.

* For the U.S. Virgin Islands, fair weather will prevail, with a few quick passing showers mainly during the night and early morning. Winds will become noticeably stronger late in the week.

* Marine and beach conditions will deteriorate mid- to late week as increasing winds and an incoming long-period northerly swell raise seas and rip current risks. Hazardous surf and Small Craft Advisories are likely.

Short Term(Today through Tuesday)

Issued at 449 AM AST Sun Dec 7 2025

A variable weather pattern prevailed during the night into the early morning hours, with abundant cloud cover and isolated to scattered showers across the eastern section of Puerto Rico and the U.S. Virgin Islands. Rainfall activity was frequent, diminishing at 2 AM, and rainfall accumulations were less than 0.5 inches. The rest of the morning, cloudiness prevailed across the area as the surface disturbance moved more westward into the Mona Passage. Overnight temperatures remained in the mid to upper 70s across the coastal and urban areas and in the 60s across the mountains.

For today, a similar weather pattern is expected, mostly due to a mid- to upper-level broad ridge anchored in the central Atlantic. This main weather feature will maintain very stable conditions aloft, resulting in drier conditions, warmer temperatures at 500 MB, and a drastically stable 850-700 MB lapse rate. At the surface, a moderate easterly wind flow will remain in place as the broad surface high pressure extending from the eastern Atlantic into the Caribbean continues to result in a tight pressure gradient. Therefore, today residents can expect breezy conditions across coastal areas and local waters. Under the easterly wind flow, a drier airmass will filter in, with precipitable water values of 1.1 in, as indicated by GOES-derived satellite imagery.

From Monday into Tuesday, a more east-southeasterly wind flow is expected as the surface high pressure establishes across the central Atlantic. Similar to previous days, precipitable water values will remain quite low relative to the seasonal average, enhancing mostly stable weather conditions with little rainfall activity. Although excellent weather conditions will persist, diurnal heating at the local level may enhance short-lived afternoon showers across the western interior and northwestern sections. This shower activity is not expected to pose a flooding threat across the affected areas. Also, the wind component can help keep temperatures within seasonal climatological normals and even slightly warmer in some coastal areas.

Long Term(Wednesday through Sunday)

Issued at 449 AM AST Sun Dec 7 2025

A persistent and increasingly dominant mid-level ridge will govern the period, maintaining well-below-normal mid-level moisture. Recent model cycles show 700-500 mb relative humidity frequently dipping below 20 percent and at times near 10 percent, supporting a strong and persistent inversion based near 850 mb through most of the forecast period. This pattern will continue to favor stable conditions and suppress deep convection for the most part. However, occasional shallow moisture surges embedded in the trade winds will periodically lift the inversion height above the 700 mb layer, allowing for an uptick in passing showers. These events will favor the overnight and morning hours across windward coastal areas. During the afternoons, isolated to scattered showers remain possible across the interior and western Puerto Rico, but any thunderstorms that develop will be short-lived and very isolated. No significant flooding threat is expected.

Toward the latter part of the period, surface high pressure over the central Atlantic is forecast to strengthen while a frontal boundary approaches from the northwest. This will tighten the pressure gradient across the northeastern Caribbean and result in breezy to windy conditions, especially across coastal and elevated areas from late week into the weekend. These winds may cause unsecured or lightweight outdoor items to blow around and could produce localized minor impacts in areas exposed to stronger gusts.

Overall, conditions will remain largely stable with shallow convection, limited rainfall amounts, and a notable increase in winds late in the workweek into the weekend.

AVIATION

(06Z TAFS) Issued at 449 AM AST Sun Dec 7 2025

VFR conditions will persist throughout the period at all TAF sites. Winds will remain from the east at 10 knots or less, increasing at 07/14Z up to 15 knots with gusty winds. Some brief RA to SHRA until 07/15z might continue to result in lower ceilings and a slight reduction in VIS across TJSJ, TIST & TISX.

MARINE

Issued at 449 AM AST Sun Dec 7 2025

Marine conditions will remain moderate through early in the week, with moderate easterly trades maintaining choppy seas across the offshore waters and local passages. By midweek, strengthening high pressure north of the region will tighten the pressure gradient and increase easterly winds, allowing seas to build across the Atlantic waters and exposed passages. At the same time, a long-period northerly swell arriving midweek will further worsen conditions. Hazardous seas and moderate to fresh winds are expected Thursday into Friday, with Small Craft Advisories likely. A gradual improvement remains possible over the weekend as winds and swell ease.

BEACH FORECAST

Issued at 449 AM AST Sun Dec 7 2025

A low to moderate rip current risk will persist across the region through the start of the week, primarily affecting the northern and eastern exposed beaches of the islands, where weak northeasterly swells and local winds are keeping the nearshore waters slightly rougher. Conditions will start to change by midweek as a long-period northerly swell moves into the area, which is expected to increase wave energy and significantly raise the rip current risk along north- facing beaches of Puerto Rico and the U.S. Virgin Islands. Some uncertainty remains regarding the exact timing and strength of this swell, but the overall trend suggests a more hazardous setup from Wednesday onward. Beachgoers should stay updated, since conditions could deteriorate quickly once the swell arrives.

For localized and updated risk levels, visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...None.