textproduct: San Juan

KEY MESSAGES

Issued at 435 AM AST Tue Oct 27 2026

* Heat: Hot and humid conditions will persist today. A Heat Advisory is in effect for Puerto Rico and the U.S. Virgin Islands, with the greatest heat impacts expected across coastal and urban areas.

* Flooding: Showers and isolated thunderstorms may produce locally heavy rainfall today and tonight. The greatest flooding risk is across southern and southeastern Puerto Rico, where repeated heavy rainfall could cause urban and small stream flooding. Flash flooding remains possible.

* Wednesday: Afternoon showers may produce ponding on roads and in poorly drained areas, particularly across interior and western Puerto Rico. Drier conditions are expected to limit rainfall coverage on Thursday.

* Beach and coastal hazards: Dangerous surf and life-threatening rip currents continue along exposed northern beaches. Higher- than- normal tides, combined with wave runup, may cause localized coastal flooding in vulnerable areas around high tide today.

Short Term(Today through Thursday)

Issued at 435 AM AST Tue Oct 27 2026

Mostly clear to partly cloudy skies prevailed overnight across eastern Puerto Rico and the U.S. Virgin Islands. Farther west, clouds and thunderstorms moved from the Caribbean waters into southwestern Puerto Rico, producing periods of moderate to locally heavy rain. Winds were mainly from the southeast, with local land breeze variations. Temperatures remained above typical October minimum values across much of the region. Minimum readings since midnight ranged from the mid-70s to the lower 80s across many coastal areas, the lower to mid-80s across the U.S. Virgin Islands, and the mid-60s to 70s in Puerto Ricos interior.

High surf continued overnight along north-facing beaches, with breaking waves of 8 to 12 feet reported. Early this morning, the Rincon, Arecibo, and San Juan buoys reported significant wave heights of about 7, 5, and 6 feet, respectively, with a northerly swell with periods of about 12 to 13 seconds.

Warm and humid conditions will persist today, with temperatures rising quickly across coastal and urban areas of Puerto Rico and the U.S. Virgin Islands. A Heat Advisory is in effect for the region. Southeasterly winds will occasionally carry showers into windward areas, with additional showers expected this afternoon and overnight. The greatest flooding risk is across southern and southeastern Puerto Rico, where repeated or persistent heavy rainfall could cause urban and small stream flooding. Flash flooding remains possible. Elsewhere, heavier showers may result in ponding on roads and in poorly drained areas.

The ridge aloft may limit convection coverage and depth. Nevertheless, available moisture, daytime heating, sea breeze convergence, and terrain effects may support isolated thunderstorms. Any developing thunderstorms could produce lightning and locally heavy rainfall.

Additionally, higher-than-normal spring tides combined with high surf may cause localized coastal flooding in vulnerable, low- lying areas around high tide today, particularly along exposed northern beaches and adjacent coastal areas. Wave runup may worsen flooding along exposed shorelines.

Model guidance places Puerto Rico and the U.S. Virgin Islands between a trough over the western Caribbean and a ridge over the eastern Caribbean through Wednesday. Above-normal sea surface temperatures and a moist southerly flow will keep conditions warm and humid. Although moisture is expected to decrease gradually, passing showers and afternoon convection will remain possible, supported by daytime heating, sea breeze convergence, and terrain effects. The NWS ensemble favors the highest rainfall accumulations across interior and western Puerto Rico on Wednesday, where heavier showers could cause ponding on roads and in poorly drained areas.

By Thursday, an upper-level low moving northwestward near the region may weaken the ridge. However, the GFS and ECMWF indicate lower precipitable water and mid-level moisture than on Wednesday, which may limit shower coverage despite the potential reduction in subsidence. Ensemble guidance also favors lower rainfall accumulations on Thursday. Warm conditions will continue, particularly across coastal and urban areas.

Long Term(Friday through Tuesday)

Issued at 435 AM AST Tue Oct 27 2026

Some changes were introduced to the long-term forecast, as the wetter and unstable conditions may persist early next week. As mentioned in the previous discussions, a surface high lingering over the central Atlantic should maintain southeasterly winds on Friday and Saturday, but the steering flow may weaken and turn more easterly as an induced trough moves across the region, shifting back from the southeast by early Monday.

The weather conditions on Friday may be marginally unstable, though the latest model guidance suggest lingering dry air in the mid levels that may limit deep convection. Although showers and thunderstorms are expected Friday afternoon, flood potential will likely remain limited. Saturday onwards, trough deepening into the tropics should strengthen, weakening the mid-level ridge, and dominating the weather pattern across the CWA. Based on the latest model guidance, low and mid-level moisture should gradually increase across the area, reaching above-normal levels (> 60%) by Sunday and Monday.

In terms of instability, the trough should maintain cool mid- level temperatures (between -6 and - 8 C), with steep lapse rates and divergence aloft, allowing cloud growth and enhancing deeper convection across the area. Additionally, NCICS CFS continues to forecast the approach of the MJO over the local area, with a transition to a more convective environment across the Caribbean. Therefore, showers and thunderstorms can be expected during the night and morning hours Saturday onward, becoming more frequent on Sunday and Monday, particularly across the U.S. Virgin Islands and eastern/southeastern Puerto Rico. Afternoon convection should mainly concentrate across interior and western/northwestern Puerto Rico, including the San Juan Metro Area. Rainfall accumulations will likely lead to urban and small stream flooding, without ruling out localized flash flood, and rapid river rises. In addition, thunderstorms could lead to frequent lightning and gusty winds.

AVIATION

(06Z TAFS) Issued at 435 AM AST Tue Oct 27 2026

Mainly VFR conditions will prevail. Passing SHRA may cause brief MVFR conditions at windward terminals. SHRA and isolated TSRA may develop over PR throughout the day, especially in the afternoon, particularly across the interior and southern slopes, potentially causing MVFR conditions and mountain obscurations near JPS and JBQ. Light SE winds will continue thru around 27/13z, then between 10 and 15 kt with sea breeze variations after 27/13Z. Passing SHRA remain possible tonight.

MARINE

Issued at 435 AM AST Tue Oct 27 2026

A long-period northerly swell will continue spreading across the Atlantic waters and local passages today, building seas to 6 to 7 feet through at least this evening. Surface high pressure over the central Atlantic will promote moderate to locally fresh east- to- southeasterly winds across the region through midweek. Small Craft Advisories remain in effect for the Atlantic offshore waters, the northern nearshore waters, the northwestern nearshore waters and the Mona Passage through 6 PM AST. Strong showers and isolated t-storms are forecast to develop mainly over the Caribbean waters, the Mona Passage, and offshore Atlantic waters over the next few days.

BEACH FORECAST

Issued at 435 AM AST Tue Oct 27 2026

A long-period northerly swell will continue to deteriorate coastal conditions along mainly the north-facing beaches of Puerto Rico, Culebra, St. Thomas and St. John. A High Surf Advisory will continue in effect for the northern coastline of Puerto Rico (from Rincon to Fajardo) through 6 PM AST, as breaking waves can reach 7 to 12 feet, especially during the morning to early afternoon. High waves that can wash over jetties and sweep people and pets onto jagged rocks. Rough surf may also knock you down. Large breaking waves will result in localized beach/dune structure erosion and dangerous swimming conditions. Minor Coastal Flooding Possible, especially with the spring tides tomorrow morning.

A High Risk of Rip Currents will be in effect for the north- facing beaches of Puerto Rico, Culebra, St. Thomas and St. John through at least 6 AM AST Wednesday. Rip currents can sweep even the best swimmers away from shore into deeper water, where it becomes difficult to return to safety. Beachgoers are strongly urged to stay out of the water at beaches under these advisories and to heed all warning flags, posted signs, and instructions from lifeguards and local officials.

Please refer to the latest Coastal Hazard Message (CFWSJU) for updates, the most vulnerable areas and for more information.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through late tonight for PRZ001-002-005- 008-010-012.

High Surf Advisory until 6 PM AST this evening for PRZ001-002- 005-008-010.

Heat Advisory from 9 AM this morning to 5 PM AST this afternoon for PRZ001>013.

VI...Heat Advisory from 9 AM this morning to 5 PM AST this afternoon for VIZ001-002.

High Rip Current Risk through late tonight for VIZ001.

AM...Small Craft Advisory until 6 PM AST this evening for AMZ711-712- 741-742.