textproduct: San Juan

KEY MESSAGES

Issued at 148 PM AST Sat May 23 2026

* Morning showers across windward areas of Puerto Rico and the U.S. Virgin Islands will be followed by afternoon showers and isolated thunderstorms, particularly across central and western Puerto Rico.

* Across the U.S. Virgin Islands, isolated to scattered showers are expected mainly during the overnight and morning hours. * Breezy to locally windy conditions will continue through the weekend, increasing further on Monday. Secure loose objects, especially along coastal areas.

* Moderate to fresh winds will result in choppy seas and a moderate risk of rip currents across most local beaches, likely increasing to a high risk by Monday. Small craft operators should exercise caution, and the issuance of a Small Craft Advisory cannot be ruled out early next week.

Short Term(This evening through Monday)

Issued at 148 PM AST Sat May 23 2026

An active weather pattern is unfolding across the forecast area due to a combination of strong deep-layer moisture and favorable large- scale dynamics. The 23/12Z TJSJ upper-air sounding indicated a moist, moderately unstable atmospheric profile with Precipitable Water (PWAT) near 1.80 inches and a CAPE of 1164 J/kg. Both satellite imagery and CIMSS Total Precipitable Water product highlights a broad plume of moisture across the eastern Caribbean. At the upper levels, a WSW jet of 60 kts will support divergence aloft. Model guidance forecasts a mid-level moistening trend through the rest of the Holiday weekend. The 700-500 mb relative humidity is expected to peak near 80%, while PWAT values push upwards towards 2.00 inches, both variables are in the 75th percentile of climatology for late May. Given this environment, scattered to widespread showers and isolated thunderstorms are expected.

For the rest of today, high-res ensemble guidance shows strong consensus that daytime heating and orographic lifting with trades around 15-20 knots will favor heavy rainfall over the interior and western portions of Puerto Rico, with rainfall accumulations of 1.50 to 2.50 inches. This will pose a threat of ponding on roads and localized urban flooding, as well as rapid rises along small streams. Similar conditions are expected on Sunday, with somewhat less moisture content available on Monday, as PWAT drops slightly to near 1.75 inches. However, showers and isolated thunderstorms are still expected to develop over the same areas as in previous days.

Meanwhile, the U.S. Virgin Islands will sit upstream of the primary orographic forcing, keeping shower activity more scattered. While brief heavy downpours cannot be ruled out within passing trade showers, overall accumulations through Monday across the USVI are expected to remain between 0.50 and 1.00 inches. Breezy conditions are expected, particularly on Monday.

Long Term(Tuesday through Saturday)

Issued at 326 AM AST Sat May 23 2026

Variable conditions are likely in the long term, with wet and slightly unstable conditions near the next midweek, transitioning to seasonal conditions by the upcoming weekend. As mentioned in previous discussions, a surface high pressure is expected to extend into the central Atlantic, promoting east-southeasterly winds, remaining breezy across coastal areas. In the mid to upper levels, theres a lingering upper-level trough extending into the region while a ridge tries to build over the western Atlantic. From the latest deterministic guidance, PWAT values are still anticipated to increase (most likely between 1.8 and 2.0 inches) from early Tuesday to Wednesday as tropical moisture pools into the region and the influence of the trough. Additionally, the latest ensemble member agrees to above normal moisture content across the CWA, with 25th and 75th percentiles close (mean around 1.9 inches). The influence of the trough should maintain cool mid-level temperatures (500 mb temperatures between -7 and -8 degrees Celsius), with divergence aloft that should allow cloud growth. Additionally, the latest model solutions keep suggesting areas of enhanced vorticity, near eastern areas of the CWA, that should increase instability as well. Given the expected conditions and considering local effects and diurnal heating, the most likely scenario could be isolated to scattered showers moving over the U.S. Virgin Islands and eastern portions of Puerto Rico, including Vieques and Culebra, with afternoon convection over interior and northwestern Puerto Rico. In addition, island streamers could also develop and likely move over the waters into portions of eastern Puerto Rico. Rainfall accumulations could lead to urban and small stream flooding, with localized flash flooding over the aforementioned areas. In addition to flooding, some other hazards may include gusty winds and lightning. From Wednesday onwards, uncertainty increases as concentrations of SAL may approach and gradually filter into the region. Nevertheless, considering that the latest model guidance is now suggesting warmer- than-normal temperatures, daytime heating, and available moisture may break and result in shallow convection over interior and northwestern Puerto Rico. Although showers are expected, the flooding threat should remain low.

As temperatures may increase and remain warmer than normal, with the available moisture, the heat threat will likely remain limited, affecting mostly individuals sensitive to heat, who must take necessary precautions. Additionally, with concentrations of SAL that may filter into the region, people sensitive to these particles should exercise caution as well and stay up to further updates.

AVIATION

(18Z TAFS) Issued at 148 PM AST Sat May 23 2026

Tempo MVFR conds are possible thru 23/18z at TISX/TIST/TJSJ, and once again btw 24/08-12z due to passing SHRA. At TJBQ/TJPS, MVFR to brief IFR conds are possible thru 23/21z due to locally induced SHRA/TSRA. SCT-BKN cigs btw FL030-050 and mtn tops obscd expected across all the islands. The latest 23/12z TJSJ sounding indicated ENE winds up to 24 kt blo FL040.

MARINE

Issued at 148 PM AST Sat May 23 2026

Moderate to fresh easterly winds will persist across the regional waters through the rest of the weekend and are expected to strengthen from fresh to locally strong on Monday due to strong high pressure over the central Atlantic. Choppy seas up to 6 feet will continue across the offshore waters and local passages, where small craft should exercise caution. Marine conditions are likely to deteriorate from Monday into Tuesday as winds strengthen and seas build up to 7 feet across portions of the offshore Atlantic waters, likely prompting the issuance of Small Craft Advisories. Isolated thunderstorms are expected to develop during the afternoon and early evening across the western waters of Puerto Rico.

BEACH FORECAST

Issued at 148 PM AST Sat May 23 2026

A moderate risk of rip currents will persist through the rest of the weekend for most beaches in Puerto Rico and the U.S. Virgin Islands. Breezy to locally windy conditions will continue, with winds and seas expected to increase further early next week. This will likely lead to a high risk of rip currents across many exposed beaches from Monday into Tuesday.

Afternoon thunderstorms are also possible each day across western Puerto Rico. Residents and visitors should seek shelter immediately if thunder is heard. For additional information and location-specific rip current details, visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

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