textproduct: San Juan

KEY MESSAGES

Issued at 350 AM AST Fri Oct 23 2026

* Showers and thunderstorms will continue through the weekend, with locally heavy rainfall that could cause urban and small- stream flooding, rapid river rises, and isolated flash flooding. Saturated, steep slopes may also be susceptible to landslides.

* Afternoon convection will favor interior, northern, and western Puerto Rico, with passing showers affecting windward areas overnight and during the morning. Some improvement is possible Sunday, though uncertainty remains about how much drying will occur.

* Dangerous breaking waves and life-threatening rip currents will affect exposed northern beaches today and Saturday. A High Surf Advisory is in effect today for north- central Puerto Rico, with breaking waves around 10 feet. Additional swell pulses may keep swimming conditions hazardous into early next week.

* Seas of 5 to 6 feet across portions of the Atlantic waters and Mona Passage warrant caution for small craft. Thunderstorms may produce locally gusty winds, lightning, and reduced visibility.

* Warm and humid conditions will persist, with heat impacts potentially increasing this weekend into early next week, particularly in coastal, low-lying, and urban areas.

Short Term(Today through Sunday)

Issued at 350 AM AST Fri Oct 23 2026

Cloudy skies prevailed across most of Puerto Rico overnight, while the U.S. Virgin Islands remained mostly clear to partly cloudy. Showers and thunderstorms were concentrated over the Caribbean waters and Mona Passage, with little or no rainfall over land aside from isolated windward showers. Temperatures ranged from the lower to mid-70s across portions of northern Puerto Rico to the lower 80s along the southern coast and across the U.S. Virgin Islands. Mountain temperatures fell into the upper 60s.

A moist pattern will support showers and thunderstorms through the weekend, though model differences create uncertainty in rainfall coverage, especially on Sunday. The latest 00Z GFS maintains precipitable water values near 1.9-2.2 inches, generally near or above normal. The earlier GFS-ECMWF comparison shows a drier ECMWF solution by Sunday. Today, a shortwave trough and available moisture will favor morning showers and isolated thunderstorms over the Caribbean waters and southern Puerto Rico, followed by afternoon convection across interior, northern, and western Puerto Rico. Cloud cover may limit daytime heating and make afternoon development more localized.

A surface high over the central Atlantic and a low to the northwest will maintain an east-southeast to southeast flow through Saturday. Passing showers will affect eastern Puerto Rico and the U.S. Virgin Islands overnight and during the morning, with additional convection developing over Puerto Rico each afternoon. GFS 925 mb winds increase to around 15-17 kt, suggesting faster- moving showers; however, repeated development along local convergence boundaries could still produce locally heavy rainfall. Urban and small stream flooding, rapid river rises, and localized flash flooding remain possible where heavier rainfall persists. Additional rainfall could also increase landslide susceptibility on saturated, steep slopes.

By Sunday, rising upper-level heights, warming 500 mb temperatures, and weaker mid-level lapse rates suggest increasing stability and less favorable conditions for deep convection. Nevertheless, lingering moisture and local effects will support passing showers and localized afternoon thunderstorms. The extent of improvement remains uncertain because moisture forecasts differ. Warm and humid conditions will continue, with localized heat impacts primarily affecting heat-sensitive individuals without adequate cooling or hydration.

Long Term(Monday through Friday)

Issued at 350 AM AST Fri Oct 23 2026

A gradual drying trend is expected across Puerto Rico and the U.S. Virgin Islands during the long term period, although periods of unsettled weather may persist through Wednesday before more favorable conditions develop Thursday and Friday. The latest model guidance suggests precipitable water values decreasing from around 1.8 to 2.0 inches early in the period to 1.2 to 1.5 inches, potentially near or below the 25th percentile of the late-October values. Despite the decrease in moisture, daytime heating, sea- breeze convergence, and local terrain effects will continue to support afternoon showers and isolated thunderstorms, particularly across interior and western Puerto Rico.

On Monday, periods of sunshine should prevail across many areas, although locally heavy afternoon showers could still produce ponding of water on roads and isolated urban or small-stream flooding. Tuesday and Wednesday may remain somewhat unsettled as cooling temperatures aloft and slightly steeper mid-level lapse rates maintain sufficient instability for convective development despite increasing mid-level dryness. This could result in afternoon showers and thunderstorms across interior Puerto Rico, with some activity potentially affecting northern sections with the prevailing southeasterly wind flow. Brief passing showers may also reach windward areas and the U.S. Virgin Islands. While widespread rainfall is not anticipated, localized downpours and lightning could affect outdoor activities. Meanwhile, periods of sunshine combined with lingering low-level humidity may contribute to locally elevated heat indices, particularly across coastal and urban areas.

By Thursday and Friday, generally fair weather with longer periods with clear skies and reduced shower coverage across the islands. Although isolated afternoon convection remains possible over interior and western Puerto Rico, the potential for widespread heavy rainfall and flooding should remain low. These days currently offer the most favorable conditions for outdoor activities, especially during daylight hours. However, people doing prolongated outdoor work should remain mindful of potential heat stress.

AVIATION

(06Z TAFS) Issued at 350 AM AST Fri Oct 23 2026

Mainly VFR conds expected today. SHRA/TSRA over the Caribbean waters and Mona Passage may bring brief MVFR conditions to TJPS early this morning. Afternoon convection will favor interior, northern, and western PR, with potential impacts at TJBQ and TJSJ, including brief MVFR/IFR conditions, mountain obscuration, and gusty winds. Passing SHRA may affect TIST/TISX intermittently. Light SE winds will become E-ESE around 10-15 kt after 23/14Z, with sea breeze variations and higher gusts near TSRA.

MARINE

Issued at 350 AM AST Fri Oct 23 2026

Moderate to locally fresh (15-20 kt) east to southeast winds will prevail through the weekend as the surface pressure gradient tightens across the regional waters. A north-northwesterly swell will maintain seas between 5 and 7 feet across the Atlantic waters and the Mona Passage today, followed by reinforcing northerly swell pulses through early next week. Small Craft Advisories remain in effect for the Atlantic waters and the Mona Passage through at least Saturday. Isolated thunderstorms with scattered showers are expected to continue across the Caribbean and western waters of PR today, where locally higher seas and strong gusty winds are possible.

BEACH FORECAST

Issued at 350 AM AST Fri Oct 23 2026

The arrival of a long-period (12-14 seconds) north-northwest swell today will produce hazardous breaking waves of 6 to 12 feet along exposed northern and western coastlines of Puerto Rico, including Culebra and St. Thomas. Therefore, a Rip Current Statement is in effect for beaches along western to northeastern PR, Culebra, and the northern U.S. Virgin Islands through at least Saturday. A High Surf Advisory is in effect for the north-facing beaches of PR through at least 6 PM AST this afternoon.

Beachgoers and inexperienced surfers should follow lifeguard instructions and avoid swimming or walking near rock formations at exposed beaches. Additional pulses of the northerly swell are expected through early next week, keeping an elevated threat of life-threatening rip currents.

SJU WATCHES/WARNINGS/ADVISORIES

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

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

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

AM...Small Craft Advisory from noon today to noon AST Saturday for AMZ711-712.

Small Craft Advisory from 6 PM this evening to noon AST Saturday for AMZ741.