textproduct: San Juan

KEY MESSAGES

Issued at 1015 AM AST Tue Mar 10 2026

* Fresh to strong winds will continue to result in choppy to rough seas across the region through Wednesday.

* Breezy to locally windy conditions will continue across Puerto Rico and the U.S. Virgin Islands through Wednesday. Unsecured and outdoor objects may blow around.

* Frequent passing trade wind showers are expected to move over the region today, maintaining a limited flood threat.

* Across the U.S. Virgin Islands, quick passing trade wind showers will move at times, with a drying trend expected by the end of the week.

Short Term(This afternoon through Thursday)

Issued at 1015 AM AST Tue Mar 10 2026

Overnight, scattered showers moved across the northern and eastern coasts of Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands, leaving minimal rainfall accumulations. Low temperatures remained in the low to mid-70s across lower elevations and reached the mid-60s in the mountains. Winds prevailed from the east at 5 to 10 mph, with gusts up to 20 mph, particularly over the U.S. Virgin Islands and Vieques.

Today, weather conditions will remain similar to previous days, with frequent passing showers across the region during the morning, followed by afternoon showers over the interior and western portions of Puerto Rico. A surface high-pressure system migrating from the central to the eastern Atlantic will gradually weaken the pressure gradient over the next few days. Consequently, a decrease in wind speed is expected from Wednesday through the end of the period. At the upper levels, a deepening trough will enhance instability aloft before gradually weakening on Thursday as it moves eastward.

Regarding moisture, a drier air patch is expected to move across the islands today, with precipitable water (PWAT) values reaching up to 1.40 inches. However, wetter conditions will return by early Wednesday as another moisture patch reaches the region, increasing PWAT values to 1.70 inches. The 500 mb temperatures will remain cool through Thursday, ranging from -9C to -11C, further supporting the potential for a few thunderstorms. Seasonal temperatures will persist as 925 mb levels remain within normal climatological values. Highs will stay in the mid-80s across lower elevations and range from the upper 70s to low 80s in the mountains.

Long Term(Friday through next Tuesday)

Issued at 1015 AM AST Tue Mar 10 2026

Unstable weather conditions will persist across the local islands for the first part of the long-term forecast. At the upper levels, a strong jet stream exceeding 100 mph will continue to generate divergence aloft, resulting in favorable conditions for vertical development of showers and thunderstorms. Combined with this upper- level feature, recent model guidance suggests decent amounts of moisture in the lower levels, with precipitable water values slightly reaching climatological normals of 1.20 to 1.50 inches. This pattern will drive the appropriate conditions for afternoon convection, especially across the interior and northeastern sections, as well as the southwest quadrant due to a wind shift more toward the east-northeast. From Saturday onward, a broad surface high pressure will shift further east into the western Atlantic, reducing the pressure gradient and allowing the islands to experience moderate easterly winds of 10 to 15 mph, with gusty conditions near the coastal areas and in the vicinity of showers. For much of Saturday, slightly drier air will dominate, limiting shower chances across the region. However, on Sunday, increased moisture from the east will filter into the region, enhancing convective chances once again. As a result, Saturday looks to be the day with the least rainfall potential, while Sunday shapes up as the wettest day of the weekend. Upper-level instability will persist through Saturday into Sunday, continuing to support shower and thunderstorm development during the afternoon hours.

For Monday into Tuesday, stable conditions will dominate at the upper levels, characterized by a mostly zonal flow and warmer temperatures at 500 mb, effectively suppressing deep convective development across the region. The lack of upper-level support, combined with a more stable atmospheric profile, will limit the vertical development of showers throughout the day. As a result, mostly sunny skies are expected across coastal and nearshore areas, with good periods of sunshine throughout the day. Although the overall pattern will remain stable, the afternoon diurnal heating peak will still be sufficient to trigger isolated convective showers across the interior sections. Rainfall amounts associated with these afternoon showers are expected to remain light to moderate, with no significant flooding concerns anticipated at this time. Temperatures will trend warmer under the influence of a stable, mostly sunny pattern, with coastal highs expected to reach the upper 80s to near 90 degrees.

AVIATION

(12Z TAFS) Issued at 1015 AM AST Tue Mar 10 2026

Mainly VFR conditions are expected to prevail across all terminals through the forecast period. However, quick trade wind SHRA will move at times across the area terminals, causing brief MVFR cigs. The 10/12z TJSJ sounding indicated east winds up to 28 knots blo FL050.

MARINE

Issued at 1015 AM AST Tue Mar 10 2026

Seas will remain up to 7 feet across the offshore waters due to steady moderate to fresh easterly winds resulting from a broad surface high pressure extending across the Central Atlantic. Therefore, Small craft advisories will remain in effect for all the exposed waters and local passages until tonight. In nearshore and coastal waters, seas will remain 5 to 6 feet, resulting in choppy marine conditions. Surface winds will remain from the east between 15-20 knots with gusty winds. Small craft operators are urged to exercise caution and check the latest marine forecasts before venturing into the local waters. Improving marine conditions are forecast from Wednesday into the second part of the workweek.

BEACH FORECAST

Issued at 1015 AM AST Tue Mar 10 2026

A broad surface high pressure will continue to result in moderate to locally fresh easterly winds across the region. As a result, wind-driven seas are forecast for most of the offshore Atlantic waters, with seas up to 7 feet. Along the coastal areas, choppy seas are expected, ranging between 5 to 6 feet and winds up to 20 knots, with gusty conditions during the day due to temperature variations. Therefore, a moderate risk of rip currents is expected to prevail across all exposed coastlines today through the rest of the week, including the northern, western, southern, and southeastern beaches of Puerto Rico, as well as Culebra and the U.S. Virgin Islands. Beachgoers are urged to exercise caution and remain alert to changing surf conditions. For more detailed information, visit: www.weather.gov/sju/marine.

FIRE WEATHER

Issued at 1015 AM AST Tue Mar 10 2026

The KBDI remains above critical fire weather thresholds in Cabo Rojo (669) and below thresholds in Guanica (519) and Camp Santiago (383). Breezy to windy easterly winds will continue between 14 to 19 mph with higher gusts up to 30 mph. Today, RH values will drop near and below critical levels at times as a patch of drier air filters into the area by mid-morning. Passing showers will continue to move across the area from time to time; however, drying soils, lower humidity later in the day and and strong winds will maintain a moderate fire danger risk today. From Wednesday onwards, winds are expected to become more light to moderate and RH are expected increase due to the arrival of a surge of moisture. At this time an RFD will not be issued. We urge partners to continue monitoring updates during the morning for a possible elevated fire danger risk if conditions warrant.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...Small Craft Advisory until noon AST Wednesday for AMZ711.

Small Craft Advisory until noon AST today for AMZ723-733-741.