textproduct: San Juan

KEY MESSAGES

Issued at 130 PM AST Wed Nov 12 2025

* A long-period north-northwesterly swell will worsen marine conditions, creating life-threatening rip currents along north- and east-facing beaches in Puerto Rico and the US Virgin Islands from late this evening to Friday.

* The US Virgin Islands and Puerto Rico are expected to have mainly clear skies, with winds bringing patches of moisture and clouds, as well as occasional showers, throughout the forecast period.

* There is a moderate chance that the weather will become wetter and more unstable due to a frontal boundary approaching from the western Atlantic, near the northeast Caribbean, around the weekend.

Short Term(This evening through Friday)

Issued at 130 PM AST Wed Nov 12 2025

The US Virgin Islands and Puerto Rico experienced pleasant weather conditions during the morning hours, characterized by a mixture of sunshine and clouds. After mid-morning, the easterlies brought a patch of moisture, increasing the passing showers, mainly over PR's northeast quadrant and across the waters surrounding the US Virgin Islands. This moisture, combined with the local effects and sea breezes, results in shallow afternoon convection along and west of the Cordillera Central. Maximum temperatures reached the mid-80s, with some coastal areas seeing highs in the upper 80s. Winds were predominantly from the east to east-northeast, with speeds ranging from 10 to 20 mph, and higher gusts and variations in the sea breeze.

The mid-to-upper-level ridge will slowly weaken as an upper-level trough approaches from the northwest to the Northeast Caribbean, increasing the probability (40 percent to 50 percent) of observing afternoon activity with one or two thunderstorms. However, still a dry air mass above 700 mb will promote subsidence aloft, making it challenging to form thunderstorms. At the surface, a frontal boundary moving eastward will interact with the high pressure across the Central Atlantic, weakening the steering winds, especially around Friday.

Under the weather pattern expressed above, we can expect a seasonable weather pattern, consisting of good periods of mostly clear skies, with occasional clouds and showers arriving each day, especially overnight. On Thursday and Friday, there is a better chance (40 to 50 percent) of observing afternoon rain activity across the interior and western PR, as well as moving across the USVI, due to the weakening of the mid-level high pressure. However, 500 mb temperatures are still near normal values, and the lapse rates at low levels are still below or near normal, which suggests a challenging situation for the development of deep convection.

Long Term(Saturday through next Tuesday)

Issued at 130 PM AST Wed Nov 12 2025

The islands will be dominated mainly by a pre-frontal trough at the surface and a trough at the mid-to-upper levels. At the surface, the surface trough will weaken the pressure gradient, resulting in variable and light winds from Saturday into Sunday along the islands. According to the global model guidance, the frontal boundary will dissipate just north of the region as a surface high pressure builds just across the western Atlantic, extending into the Central Atlantic. Although the frontal boundary will remain to our north, enough deep enough moisture will reach the islands. The available moisture trapped in the first 300 MB [1000-700 MB] with precipitable water values from 1.5 to 1.7 inches, which are normal values for this time, will allow the development of afternoon convection. Isolated thunderstorms are expected, with the heaviest activity forecasted due to some instability caused by the presence of the mid-level trough, which enhances colder temperatures at 500 MB, ranging between -6 and -7 degrees Celsius. Since winds will be variable, the focus of the showers and the translation movement can contribute to some isolated urban flooding, with the heaviest showers occurring during the afternoon hours.

From Monday onwards, as the surface high pressure migrates further into the Central Atlantic, veering winds from the east-southeast will again change the weather pattern across the islands. Therefore, residents can expect a more typical weather pattern, with an increase in heat indices in some coastal areas and afternoon convection primarily across eastern sections of Puerto Rico, specifically in the vicinity of El Yunque, extending to some metropolitan areas and northwestern Puerto Rico. Rainfall accumulation is not forecast to be significant; however, some isolated urban and minor flooding cannot be ruled out in low- lying areas.

AVIATION

(18Z TAFS) Issued at 130 PM AST Wed Nov 12 2025

Expect VFR conds through the forecast period. Occasional SHRA/+SHRA will affect local terminals and surrounding waters, leaving none to minimal impacts to operations. SW-PR afternoon convection will affect the region thru 12/23z. Winds will remain mainly from the E to ENE at 10-15 kt, with occasional higher gusts and sea breeze variations, mainly during the morning and afternoon hours. Overnight, we expect calm to light and VRB winds.

MARINE

Issued at 130 PM AST Wed Nov 12 2025

A frontal boundary moving eastward across the western Atlantic will linger off to the northwest of the northeast Caribbean through the rest of the workweek. Therefore, expect moderate to locally fresh winds through at least Thursday, becoming light to gentle from Friday into the weekend, as a pre-frontal trough forms near the islands. Additionally, a long-period north-northwesterly swell, spreading across the Atlantic Ocean, will reach the local waters and passages, deteriorating marine conditions. Thus, a Small Craft Advisory is in effect from late tonight into early Friday morning.

BEACH FORECAST

Issued at 130 PM AST Wed Nov 12 2025

An approaching north-northwesterly swell will spread across the local Atlantic Waters and Caribbean Passages later this evening, deteriorating the coastal conditions overnight into Thursday. Thus, life-threatening rip currents are expected to form from Rincon to Fajardo and Culebra late tonight or early Thursday morning, creating a High Risk of rip currents. Meanwhile, the risk will moderate for the north-facing beaches along St. Thomas, St. John, and the Adjacent Islands.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...Small Craft Advisory from 6 PM this evening to midnight AST Thursday night for AMZ711.