textproduct: San Juan

KEY MESSAGES

Updated at 245 PM AST Thu Apr 16 2026

* Unsettled weather will persist through Friday, with showers and isolated thunderstorms, especially in the afternoon. Localized urban and small stream flooding will remain possible.

* A moderate risk of rip currents will continue across the beaches in PR and the USVI, particularly along northern and eastern exposures. Beachgoers should exercise caution.

* Conditions will gradually improve by Saturday, leading to a more typical seasonal pattern with strong afternoon convection across western PR.

* The USVI will be affected by night and morning passing showers, which could result in brief moderate to locally heavy rain across portions of the islands.

Short Term(This evening through Saturday)

Issued at 245 PM AST Thu Apr 16 2026

The surrounding waters of St. Croix and areas downwind of St. Thomas experienced an active morning, with thunderstorms moving across the local waters. Across eastern Puerto Rico, heavy rainfall led to urban and small stream flooding, particularly near Yabucoa, San Lorenzo, Las Piedras, Patillas, and Maunabo, where rainfall totals ranged from 2 to 6 inches. The Guayanes River also exceeded bankfull, as indicated by USGS observations. In the afternoon, a second round of thunderstorms further aggravated flooding, prompting a Flash Flood Warning for Juncos, Las Piedras, and San Lorenzo. Winds remained from the east-southeast at 10 to 20 mph.

A mid- to upper-level trough, combined with above-normal moisture, will maintain an unstable, wet pattern from tonight through at least late Friday night. Soils are already saturated, and rivers are elevated; therefore, any additional periods of heavy rainfall will quickly lead to urban flooding, small stream flooding, river flooding, and flash flooding.

Periods of showers and thunderstorms will occur in pulses rather than continuously. For example, activity is expected this afternoon across much of Puerto Rico, while the USVI may see variable cloudiness with limited rainfall. Another round of showers and thunderstorms is possible this evening, particularly across eastern Puerto Rico and possibly the USVI, followed by additional activity early Friday morning. By Friday afternoon, convection is expected to redevelop across the interior and western Puerto Rico.

Although the USVI will remain under the influence of high moisture and the upper-level trough, confidence remains low regarding rainfall coverage and intensity.

A more typical pattern is expected on Saturday; however, another round of strong afternoon thunderstorms will be possible across the interior, western Puerto Rico, and the San Juan metro area. Passing showers will also remain possible across windward areas of Puerto Rico and the USVI.

Residents and visitors are urged to remain alert and monitor official forecasts, advisories, and warnings as conditions evolve.

LONG TERM(Sunday through Thursday)

Issued at 250 AM AST Thu Apr 16 2026

The latest model guidance continues to suggest an influx of relatively drier air as a surface high pressure system dominates the central Atlantic and a mid-level ridge establishes west of the region. During the first half of the period, precipitable water (PWAT) values will drop to seasonal normals of 1.25 to 1.50 inches. Under the influence of the surface high, light to moderate easterly winds will prevail through mid-week, shifting from the southeast late Wednesday as another building high pressure located over the western Atlantic begins to migrate toward the central Atlantic.

Overall weather conditions are expected to remain seasonal. Passing showers are likely over the windward portions of Puerto Rico and the U.S. Virgin Islands, followed by afternoon convective activity across the central mountain range and western Puerto Rico, driven by daytime heating and local effects. Due to this anticipated activity, showers and isolated thunderstorms will likely persist from the early afternoon into the evening.

Because of previous rainfall, soil saturation, and elevated river levels, the potential for flooding remains an active concern. Additionally, temperatures at the 500 mb level are projected to drop to -8C, increasing instability aloft and enhancing the potential for afternoon thunderstorms. Surface temperatures are expected to trend within seasonal values throughout the forecast period.

AVIATION

(18Z TAFS) Issued at 245 PM AST Thu Apr 16 2026

Generally VFR conds across most sites, however periods of MVFR/IFR conditions are possible across TJBQ/TJSJ from 16/18-23Z with TSRA, reduced vis, and low cigs. Additional periods of VCSH during the overnight across USVI TAF sites and TJSJ. Winds from the E to SE around 10 to 15 kts with higher gusts through 16/23Z. Variable winds afterward and increasing again around 17/13Z.

MARINE

Issued at 245 PM AST Thu Apr 16 2026

A mid- to upper-level trough will maintain an unstable weather pattern across the regional waters, supporting periods of strong thunderstorms through at least Friday night. These storms may produce locally higher winds, frequent lightning, and reduced visibility. At the surface, high pressure over the western to central Atlantic will promote moderate to locally fresh east to southeast winds, resulting in moderate to choppy seas through at least early next week. In addition, a small northeasterly swell will continue to propagate across the Atlantic waters and Caribbean passages through early next week, contributing to hazardous marine conditions at times.

BEACH FORECAST

Issued at 245 PM AST Thu Apr 16 2026

Beachgoers can expect a moderate risk of rip currents through much of the forecast period, especially along north- and east- facing beaches of Puerto Rico and the U.S. Virgin Islands. Looking ahead, another long-period northerly swell may arrive by early next week, potentially worsening beach conditions. In addition, beachgoers should remain alert for afternoon showers and isolated thunderstorms, particularly across western and northern Puerto Rico. These storms may produce gusty winds and frequent lightning.

SJU WATCHES/WARNINGS/ADVISORIES

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