textproduct: San Juan

KEY MESSAGES

Issued at 215 PM AST Sat Nov 15 2025

* An unstable wet pattern is expected to persist across Puerto Rico and the US Virgin Islands throughout the weekend.

* There is a high chance of observing strong afternoon thunderstorms across Puerto Rico the rest of this afternoon and tomorrow.

* There is a moderate chance of observing heavy rain and isolated thunderstorms across the U.S. Virgin Islands this evening and tomorrow.

* The exposed north-facing beaches in Puerto Rico and the northern U.S. Virgin Islands will have a moderate risk of rip currents, especially by Sunday.

Short Term (This evening through Monday)

Issued at 215 PM AST Sat Nov 15 2025

The TJSJ RAOB 12z sounding data indicated a weak southeasterly wind flow at the surface, which prevailed during the morning hours. They allowed much of this morning's rain to remain almost stationary across portions of the regional waters. The skies were mostly sunny, but southerly winds pushed patches of clouds across the U.S. Virgin Islands. Some clouds were also noted over the southern plains of Puerto Rico. From mid-morning onward, cloudiness began to increase over Puerto Rico, especially in the mountainous areas, resulting in the development of showers. Additional slow moving shower activity and thunderstorms are forecast to continue through the afternoon hours. Maximum temperatures ranged from the upper 80s across the coastal sections to the low 80s in the mountain areas.

A prefrontal trough lingering north of the region will promote low-level moisture to pool over the islands throughout the weekend, till it dissipates. Additionally, a mid-to-upper-level trough amplifying near the Northeast Caribbean will slowly increase instability across the region the rest of today and Sunday. Thus, the 500 mb temperatures indicated a cooling trend, with values below normal, which could enhance the formation of thunderstorms when combined with orographic effects, sea breeze, and diurnal heating. Additionally, the weak steering wind flow will allow the activity that develops to remain longer than usual, increasing the potential for flooding. Therefore, we have a moderate risk of flooding rains in the mountain areas of PR, with a slight to moderate risk of spreading to the surrounding coastal locations, from which they originate. Some showers will impact the US Virgin Islands, but there is currently a non-to-slight risk of flooding at this time.

Overnight, the proximity of the prefrontal trough interacting with the amplifying trough, combined with above-average, warmer- than- normal sea surface temperatures, will allow the formation of showers and thunderstorms across the Atlantic Waters and Caribbean Passages. There is a slight to moderate chance of observing this activity slowly drift into the coastal locations, especially along the northern coastline of PR. A mixture of sunshine and clouds will prevail on Sunday morning, followed by the formation of afternoon convection, once again over the mountain areas. However, there is a better potential for the activity to spread into the north and northwest coast of PR. The US Virgin Islands will experience a few showers crossing the islands, resulting in occasional periods of moderate to locally heavy rainfall.

A seasonal weather pattern is expected to return on Monday, as the upper-level flow becomes more zonal and the frontal boundary finally dissipates, leaving high pressure across the Central Atlantic to be the dominant surface feature. Thus, a mixture of sunshine and clouds with occasional passing showers will be the predominant weather pattern.

Long Term (Tuesday through Saturday)

Issued at 425 AM AST Sat Nov 15 2025

During early Tuesday into early Wednesday, the islands will be mainly influenced by a surface high pressure over the central Atlantic, resulting in mostly east-southeasterly winds. Embedded within this wind flow are patches of trapped tropical moisture with precipitable water values between 1.4 and 1.6 inches. Although this moisture will be present and concentrated near 850 MB, drier conditions are expected from 500 to 250 MB due to a stable weather pattern. Global models suggest this setup will bring some showers across the U.S. Virgin Islands and eastern Puerto Rico at times, followed by afternoon convection over western Puerto Rico. Since the available moisture is expected to remain shallow, rainfall should be only locally heavy, with a low probability of urban or small-stream flooding.

A more stable and drier weather pattern is forecast from late Thursday into Friday. A broad and strengthening surface high pressure system exiting the eastern coast of the United States and extending into the central Atlantic will establish a northeasterly wind flow across the region. This shift in the wind pattern will transport a drier and cooler air mass over the islands, limiting shower development and improving overall weather conditions. This shift will also support a cold-advection pattern mainly across the local northern waters. According to the 925 MB temperature fields, temperatures are expected to decrease across the islands.

AVIATION

(18Z TAFS) Issued at 215 PM AST Sat Nov 15 2025

Unstable weather pattern will prevail across the local flying area tonight. Occasional periods of MVFR conds are possible due to VCTS or TSRA across TJSJ, TJPS and TJBQ resulting in lower ceilings, brief higher winds, and reduced vis. After 15/23Z, VFR conds will prevail, but prds of VCSH/VCTS cannot be ruled out, especially near JBQ/JSJ overnight. There is a moderate chance to observe an active afternoon on Sunday. Expect S-SE winds btwn 5-10 kt with higher gusts and sea breezes, becoming calm to light and VRB overnight.

MARINE

Issued at 215 PM AST Sat Nov 15 2025

A pre-frontal trough to the north will continue to promote a light south to southeasterly wind flow through Monday. Strong showers and isolated thunderstorms could lead to locally hazardous conditions for small craft, particularly during the weekend. A surface high-pressure system will build across the central Atlantic by Monday, bringing moderate easterly winds by Monday or Tuesday. Additionally, a north to northeasterly swell will spread across the local waters starting Sunday, with a second pulse expected by Tuesday.

BEACH FORECAST

Issued at 215 PM AST Sat Nov 15 2025

Beachgoers can expect coastal conditions to continue improving today, with a low risk along the west and southern coasts of PR and the USVI. However, another north-northeasterly swell will increase the risk of rip currents to moderate on Sunday, turning high on Monday. A second pulse will maintain the risk high on Tuesday.

Afternoon thunderstorms will promote lightning activity. We encourage our locals and visitors to remain vigilant in case they hear thunder, as lightning can strike remote locations from where it forms.

SJU WATCHES/WARNINGS/ADVISORIES

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