Marine Weather and Tide Forecast for Guayama, PR

.Short Term(Today through Saturday)...
Issued at 250 AM AST Thu Apr 16 2026

A variable weather pattern prevailed during the night into the early morning hours. Over the local waters, periods of showers with strong thunderstorms affected the Caribbean and Atlantic waters. Therefore, several marine weather statements and a Special Marine Warning were issued during the night. Over land areas, some showers developed across the southern coastal sections of Puerto Rico, leaving between 1 and 1.5 inches of rainfall across municipalities around Arroyo and Patillas. Around 2 AM, showers diminished in that area and developed over the El Yunque region, leaving around one inch of rainfall as well. Overnight temperatures, as of 3 AM, were in the mid to upper 70s across coastal areas and cooler across the mountains. Winds remained light and from the southeast.

Today, the cut-off low clearly visible in satellite imagery will remain northeast of the forecast area, while a deepening upper-level trough persists, keeping the region under its divergent side to the southeast. This setup, combined with a weak mid-level ridge, will support cooler temperatures at 500 mb and promote some instability across the area. From 0 to 3 km, winds will remain similar to those observed yesterday, with a southeasterly component at the surface (1000–850 mb) and a more southerly flow at 700 mb, steering shower activity once again toward the northwestern and northern sections of Puerto Rico. Therefore, although widespread rainfall is not expected across the entire island, afternoon convection will support periods of locally strong showers with isolated thunderstorms, and gusty winds, which may lead to urban and low-lying flooding where the heaviest activity occurs. Temperatures will slightly increase during the day due to the wind pattern and periods of reduced cloud cover, with heat indices reaching around 100°F, especially across north- central sections.

On Friday, as the upper-level trough amplifies further across the western Atlantic, the forecast area will remain under its divergent side to the southeast, allowing similar conditions to persist with cooler temperatures at 500 mb and sufficiently favorable relative humidity values between 850–500 mb to support shower development.
Model guidance suggests an increase in precipitable water, with values ranging between 1.75 and 2.0 inches (around the 75th percentile). Additionally, the Gálvez-Davison Index (GDI)
indicates the potential for isolated to scattered showers, especially during the afternoon hours, along with a slight chance of isolated thunderstorms over the surrounding waters. At the surface, conditions will gradually shift as winds become more easterly, with the induced surface trough moving farther west away from the CWA and a surface high pressure system over the central Atlantic dominating the local flow. Given these conditions, Friday is expected to remain on the typical seasonal pattern, with relatively quiet morning hours followed by a more active afternoon characterized by showers across the Cordillera Central and the western interior. As a result, an elevated flooding risk will persist in these areas, as rainfall accumulations could enhance the potential for urban and low-lying flooding.

Conditions will improve by Saturday, with the driest and most stable day of the period. At the surface, precipitable water values will decrease from around the 75th percentile to near the 50th percentile, remaining within a more typical seasonal pattern.
Additionally, at upper levels, the influence of the trough will shift farther east, resulting in more stable and warmer conditions at 500 mb. These factors will support mostly limited shower activity during the morning hours, followed by localized afternoon showers across the western sections of the islands. For the San Juan metro area, afternoon conditions indicate around a 40% chance of rain, which should still be generally suitable for the Hurricane Hunter visit at Fernando Luis Ribas Dominicci Airport in San Juan from 9 AM to 3 PM AST.

.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 -8°C, increasing instability aloft and enhancing the potential for afternoon thunderstorms. Surface temperatures are expected to trend within seasonal values throughout the forecast period.

AVIATION
(06Z TAFS)
Issued at 250 AM AST Thu Apr 16 2026

VFR conditions will prevail across all TAF sites during the period, with brief MVFR conditions possible at TJBQ from 16/18Z to 16/22Z. Winds will remain from the southeast at around 5 knots, increasing after 16/15Z to near 15 knots across the area, with sea breeze variations. Afternoon showers and isolated thunderstorms will lower ceilings and reduce visibility, particularly across the Cordillera Central and northern sections due to SHRA and TS activity. Winds will decrease again after 17/00Z, becoming more easterly at less that 10 knots.

MARINE
Issued at 250 AM AST Thu Apr 16 2026

A surface high pressure system over the eastern to central Atlantic, interacting with surface trough north of the region, will promote east-southeast light to moderate winds. A subsiding northerly swell will continue to spread across the Atlantic waters, maintaining seas from 5 to 6 feet across exposed areas, small craft should exercise caution. Showers and thunderstorms associated to the trough will continue across the local waters, creating locally hazardous marine conditions through the weekend. Model guidance suggests another long- period northerly swell that may arrive and spread across local waters and passages by next week, resulting in choppy to rough seas and becoming hazardous for small craft.

BEACH FORECAST
Issued at 250 AM AST Thu Apr 16 2026

No changes were introduced to the beach forecast. Beach conditions have been improving as the northerly swell continues to diminish across the local waters and passages. Nevertheless, straitening winds will result in breaking waves between 4 and 5 feet across northern beaches of Puerto Rico, including Vieques and Culebra, and the U.S. Virgin Islands. Hence, a moderate risk will continue for the next several days across the aforementioned areas. Although there's no high risk, beachgoers should exercise caution, as life- threatening rip currents remain possible along beaches under moderate risk. A low risk risk will remain elsewhere. Another long- period northerly swell may arrive and spread across local waters and passages by next week.

Besides rip currents, beachgoers should remain weather alert as showers and isolated thunderstorms are expected each day in the afternoons, particularly over western and northern beaches of Puerto Rico, and hazards may include gusty winds and lightning. For more specific area details, refer to weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES
PR...None.
VI...None.
AM...None.