textproduct: San Juan

KEY MESSAGES

Updated at 157 PM AST Sat Apr 11 2026

* A Flood Watch was issued for Puerto Rico and the US Virgin Islands and will be in effect from 10 AM Monday throught8 AM Wednesday as an increase in rainfall and flooding risk is anticipated due to the approaching mid to upper level trough.

* A High Risk of Rip Currents remains in effect for the western, northern, and eastern coast of Puerto Rico and Culebra through early next workweek due to a long-period NNW swell.

Short Term(This evening through Monday)

Issued at 157 PM AST Sat Apr 11 2026

The short-term forecast remains on track for this afternoon and Sunday, with a more unsettled and wetter pattern expected to develop from Sunday night onward. For the rest of this afternoon, available moisture will remain near to slightly above normal, while east to east-southeast steering flow will support convective development across the interior and western to northwestern portions of Puerto Rico due to diurnal heating, local orographic effects, and sea breeze convergence. A limited to locally elevated flooding risk will persist where stronger showers develop, mainly in urban areas, roads, and poor drainage locations. Warm to hot conditions will continue across coastal and urban areas.

Tonight into Sunday, conditions will gradually become more favorable for shower and thunderstorm development as a mid to upper-level trough approaches from the northwest and columnar moisture increases. Overnight and morning showers will continue across eastern Puerto Rico and the local islands, followed by more active afternoon convection over the interior and western sections of Puerto Rico. Although Sunday is not expected to be the most active day of the event, broader shower coverage and isolated thunderstorms should result in an increasing flooding risk by late in the day, particularly where repeated rainfall activity occurs.

Further deteriorating weather conditions are then expected Sunday night through Monday as the trough interacts with above-normal tropical moisture over the area. Recent model guidance now places the bulk of rainfall activity somewhat farther east than previous cycles, favoring the U.S. Virgin Islands, Vieques, Culebra, and eastern to northern Puerto Rico. However, uncertainty remains in place, as the exact positioning and evolution of the upper-level trough will determine where the heaviest and most persistent rainfall ultimately develops.

Given wet antecedent conditions in portions of the area and the potential for repeated heavy rainfall, the likelihood of urban and small stream flooding, isolated flash flooding, landslides, and rapid river rises will increase early this week. Therefore, a Flood Watch is now in effect for the entire forecast area from Monday 14Z through Wednesday. The highest impacts during the short-term period are still expected late Monday into Monday night, with hazardous conditions likely to continue beyond this forecast period.

Long Term(Tuesday through next Friday)

Issued at 459 AM AST Sat Apr 11 2026

A wetter and unstable pattern will continue from Monday night into Tuesday as a deep-layered trough and upper-level low remain northwest of the region, supporting favorable conditions aloft. Deep tropical moisture will remain in place through midweek, with precipitable water values at times exceeding climatological maxima. Although some drying is possible late Wednesday into early Thursday, moisture is expected to increase again late week, maintaining a very moist pattern through at least Saturday.

The primary concern is an elevated to locally significant flooding risk, with the highest impacts expected Monday evening through Tuesday. Periods of heavy and repeated rainfall may result in urban and small stream flooding, isolated flash flooding, and localized landslides. A Hydrologic Outlook (ESFSJU) is currently in effect to highlight this potential. Rainfall amounts will be refined in later forecasts as confidence increases. While it is still too early for more specific flood headlines, a Flood Watch may be needed if conditions warrant.

Although activity may become somewhat less organized at times late week, sufficient moisture and instability will persist to support continued showers and thunderstorms with localized flooding impacts, especially over areas that become saturated earlier in the period. Confidence is moderate overall.

AVIATION

(18Z TAFS) Issued at 157 PM AST Sat Apr 11 2026

Mainly VFR conds expected through the pd. E to ESE winds 10-15 kt with sea breeze variations and higher gusts, becoming lighter/vrb aft 11/22Z. Winds will remain ESE Sun and increase to 15-20 kt with higher gusts by aftn. VCSH to continue at times across TJSJ/TIST/TISX and other windward terminals. Best potential for tempo MVFR/brief IFR conds due to SHRA/TSRA and lower cigs/vsbys will be this afternoon and aft 12/16Z.

MARINE

Issued at 157 PM AST Sat Apr 11 2026

Moderate trades will prevail through the weekend as a broad surface high pressure builds from the Central Atlantic. A 4 to 5 feet northwest to north swell will continue to spread across the Atlantic waters and passages, building seas up to 6 feet for the next few days. Therefore, small craft should continue to exercise caution, mainly across the Atlantic waters. Another pulse of the northerly swell is expected on Sunday. By early next week, a frontal boundary and a pre-frontal trough will increase showers and thunderstorms across the regional waters. Increasing winds and seas building up to 7 feet are also expected, and Small Craft Advisories could be issued for the Atlantic waters during this period.

BEACH FORECAST

Issued at 157 PM AST Sat Apr 11 2026

Another pulse will arrive on Sunday, maintaining the High Rip Current Risk in effect for the northwest to northeast beaches of Puerto Rico and Culebra through at least Monday. Across the USVI and Vieques, a moderate risk of rip currents is expected to persist over the next several days, while a low risk will continue along the southern and more protected beaches of Puerto Rico. More information is available at weather.gov/beach.sju.

HYDROLOGY

Issued at 459 AM AST Sat Apr 11 2026

As a mid to upper level trough approaches from the northwest, the likelihood of flooding is increasing for late Sunday into the next workweek. An elevated flooding risk is forecast through at least midweek. The first round of showers are expected to reach the region Sunday night into early Monday. Showers and thunderstorms will then increase in frequency on Monday, but the heaviest activity is anticipated for Monday night into Tuesday. Although a level of uncertainty is still present, the days with the highest potential for flooding are Monday and Tuesday. However, above normal moisture will persist through late in the week. The likelihood of urban and small stream flooding, isolated flash flooding, landslides and rapid river rises is increasing. Residents and visitors are urged to remain alert to changing weather conditions and to avoid flooded roadways. A Hydrologic Outlook (ESFSJU) is currently in effect to highlight this potential. A Flood Watch (FFASJU) will also likely be issued later today.

SJU WATCHES/WARNINGS/ADVISORIES

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

Flood Watch from Monday morning through Wednesday morning for PRZ001>013.

VI...Flood Watch from Monday morning through Wednesday morning for VIZ001-002.

AM...None.