textproduct: San Juan

KEY MESSAGES

Issued at 115 PM AST Mon Dec 29 2025

* Life-threatening rip currents will continue to prevail across the north-facing beaches of Puerto Rico, Culebra, and the northern U.S. Virgin Islands through Tuesday. The rip current risk is expected to decrease to moderate by midweek as the swell action subsides.

* The risk of lightning and localized flooding will increase from New Years Eve through the end of the week.

Short Term(This afternoon through Wednesday)

Issued at 115 PM AST Mon Dec 29 2025

Mostly sunny skies prevailed across the forecast area today, with minimal rainfall activity observed. Maximum temperatures ranged from the upper 70s to the mid 80s under light northeast winds.

Heights are forecast to fall toward the end of the period as a mid to upper level trough moves across the western tropical Atlantic into the central Caribbean. At lower levels, northeast winds will persist through tonight, shifting to the east southeast by Tuesday afternoon into Wednesday as the aforementioned trough and its associated frontal boundary approach from the west. This evolving pattern will promote moisture pooling across the region, with precipitable water values exceeding climatological values on Wednesday.

Meanwhile, tonight and Tuesday, limited shower activity is expected to continue, supported by precipitable water values below 1.0 inch and the absence of significant upper level forcing. As a result, isolated to locally scattered passing showers are expected overnight into Tuesday morning across the north and east coastal areas of Puerto Rico, as well as the northern U.S. Virgin Islands, followed by limited convection over the western interior of Puerto Rico on Tuesday afternoon. Shower and thunderstorm coverage is expected to increase on Wednesday, potentially elevating the risk of lightning and localized flooding.

LONG TERM...(Thursday through Monday)

Issued at 420 AM AST Mon Dec 29 2025

A shortwave trough is expected to swing across the Northeast Caribbean by Thursday (New Year's Day), followed by an amplifying mid- to upper-level trough over the region through Friday. This pattern will promote increased instability and a more unsettled weather regime, especially as a frontal boundary and associated pre- frontal trough approach the area late Thursday night into Friday. At the surface, a high-pressure system over the central Atlantic will maintain an east to east-southeast low-level wind flow through early next week.

The most favorable window for widespread rainfall appears to be between Thursday afternoon and Friday evening. However, model guidance continues to show timing discrepancies regarding both the onset and departure of the most active period. Rainfall could begin as early as early Thursday morning and linger into early Saturday morning. At this time, the highest confidence for widespread shower activity is from Thursday afternoon into Friday, when periods of moderate to heavy rain and thunderstorms are most likely. Another negative factor for the formation of widespread activity could be the available moisture over the region, where we observed another discrepancy in the model guidance.

By Saturday, the region will transition to the subsident side of the mid- to upper-level trough as it lifts eastward, with subsidence gradually increasing. This will result in a decreasing trend in shower and thunderstorm coverage and intensity through the weekend. Although passing showers will remain possible Saturday into Sunday, vertical development will be limited as a mid- to upper-level ridge builds over the area.

Late Sunday night into Monday, another shortwave trough is forecast to approach the region, increasing mid- to upper-level instability. This may lead to a gradual uptick in shower activity, with the trough aloft expected to further amplify by Monday night into Tuesday, potentially signaling a return to more unsettled conditions early next week.

AVIATION

(18Z TAFS)

Mainly VFR conds across all TAF sites, with VCSH for IST for the rest of the aftn, then for JSJ later tonight, reducing CIGs. Winds from the NE will become light and VRB after 29/22z, increasing from the E btwn 6 - 11 kt by 30/13-14z.

MARINE

Issued at 115 PM AST Mon Dec 29 2025

A northeast wind flow will continue to prevail across the local waters through midweek, gradually veering to the east and east- southeast as a frontal boundary approaches from the west, increasing the potential for showers and thunderstorms. Pulses of long-period northerly swell will persist across the Atlantic waters and Caribbean passages through the middle of the week.

BEACH FORECAST

Issued at 115 PM AST Mon Dec 29 2025

A long period northerly swell will continue to prevail across the local waters, maintaining a high risk of life threatening rip currents along the north-facing beaches of Puerto Rico, Culebra, and the northern U.S. Virgin Islands through at least Tuesday afternoon. The rip current risk is expected to decrease to moderate on Wednesday as swell action gradually subsides. Nevertheless, beachgoers are urged to exercise caution at all times.

FIRE WEATHER

Issued at 420 AM AST Mon Dec 29 2025

Drying conditions continue, especially across southern Puerto Rico, where minimum relative humidity has fallen below 40% for a second consecutive day, with some locations dropping into the 20s to 30s. Winds remain light, limiting fire spread at this time. KBDI values continue to increase, with Cabo Rojo exceeding fire danger thresholds (above 550) and Camp Santiago approaching similar levels, indicating increasingly dry fuels. While no significant fire weather threat is expected today, continued drying through mid to late week warrants close monitoring, particularly as stronger winds are possible Friday into Saturday, which could elevate fire spread potential if dry conditions persist.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through Tuesday afternoon for PRZ001-002- 005-008-010-012.

VI...High Rip Current Risk through Tuesday afternoon for VIZ001.

AM...None.