Marine Weather and Tide Forecast for Isabela, PR

.Short Term(Today through Thursday)...
Issued at 232 AM AST Tue Apr 14 2026

Overnight conditions were mostly cloudy to overcast across the entire forecast area, with skies remaining largely covered through the night. Shower activity over land was limited, with only a few brief and isolated showers observed; however, more persistent shower activity prevailed across the Caribbean and Atlantic waters, occasionally moving near the coastal areas. These cloudier conditions helped keep temperatures relatively mild along the coasts, generally in the mid-70s, while cooler temperatures were observed across the higher elevations due to elevation and cloud cover. Overall, it was a calm but cloudy night with most of the rainfall remaining offshore.

A mid-level cut-off low will remain positioned north of the region today, promoting a strong upper-level jet streak of over 90 knots across the local area and supporting enhanced divergence aloft, which will favor convective development. At 500 mb, a low will induce a southwesterly flow around 25 knots, while at the surface, an induced trough will promote variable to east- southeasterly winds across eastern Puerto Rico and surrounding waters, introducing some uncertainty in the focus of showers throughout the day. Moisture will remain abundant, with precipitable water values around the 75th percentile, well above climatological normals, while mid-level relative humidity values between 750–500 mb will exceed two standard deviations above normal early in the day before gradually decreasing. Cold temperatures aloft, ranging between -9 to -10°C at 500 mb, will enhance instability and support the development of isolated to scattered thunderstorms embedded within the broader shower activity. Based on the latest analysis and model guidance, shower activity is expected to start around mid to late morning and then become more widespread across the interior and western sections of Puerto Rico during the afternoon hours, with some showers becoming locally heavy and resulting in urban and small stream flooding. Therefore, a Flood Watch remains in effect for today, with an elevated to significant flooding risk across portions of the islands, although some uncertainty persists regarding the exact placement and movement of the heaviest rainfall due to the variable low-level wind flow associated with the surface trough.

For Wednesday, surface conditions will evolve as winds within the 0–3 km layer remain from the southeast while a surface perturbation moves across the forecast area. According to model guidance, the induced surface trough is expected to move east of the CWA earlier in the day; however, the GFS places a more defined low center just northwest of the area, and these discrepancies may introduce some uncertainty in the overall conditions. Nonetheless, sufficient deep moisture, with precipitable water values near 1.8 inches, above-normal relative humidity between 850–700 mb, and slightly colder temperatures at 500 mb will support a convective pattern with better-organized convection, especially during the afternoon as cloudiness interacts with local effects. Given these conditions, an elevated flooding risk is expected, particularly across northwestern sections of the islands, including the San Juan metro area, due to the prevailing wind direction as the induced surface trough moves across the region.

For Thursday, conditions become slightly more interesting at 250 mb as the previous cut-off low shifts eastward out of the area, while a deep-layered trough continues to deepen with its axis positioned over Hispaniola, leaving Puerto Rico and the U.S.
Virgin Islands under its influence. As a result, a more unstable and dynamic weather pattern is expected, with abundant moisture and increasing instability combining with favorable upper-level support to promote the development of scattered to numerous showers and thunderstorms across the region. Activity will likely begin by late morning and become more widespread through the afternoon, especially across interior and western Puerto Rico, where locally heavy rainfall is expected, supporting efficient rainfall processes and some storm organization, which will increase the risk of urban and small stream flooding along with isolated gusty winds.

.Long Term(Friday through Tuesday)...
Issued at 232 AM AST Tue Apr 14 2026

An unsettled weather pattern is expected Friday through the weekend into early next week as a short wave trough sinks into the Caribbean. At the surface, high pressure over the western to central Atlantic will promote moderate to fresh ESE to easterly winds Friday and Saturday, becoming easterly Sunday and slightly ENE by Monday.
The pressure gradient will remain uneven, with stronger winds across eastern areas and weaker flow farther west, supporting faster moving showers in the east and slower storm motion in the west. Moisture will increase Friday into the weekend, with PWAT values above normal and at times exceeding climatological maxima, before slightly drier air filters in late Sunday into Monday. Aloft, a jet streak will lift over the area by Monday, while mid level temperatures remain modestly cool. This pattern will support periods of convection and isolated to locally scattered thunderstorm development across the region. Confidence is medium, as details depend on the timing and placement of the trough and deeper moisture.

Flooding will be the primary hazard, followed by lightning and breezy conditions. Showers and isolated to locally scattered thunderstorms are expected daily, generally favoring eastern Puerto Rico and the U.S. Virgin Islands overnight into the morning, then shifting westward each afternoon based on the latest model guidance.
The greatest risk will focus over northwestern Puerto Rico Friday and Saturday, western Puerto Rico on Sunday, and southwestern Puerto Rico by Monday. Faster storm motion over eastern areas may limit rainfall totals, but slower moving convection in western sectors could enhance flooding impacts. Breezy conditions will persist due to the general wind flow and may be locally enhanced by thunderstorm downdrafts. Soils may remain saturated, which could further increase the risk of flooding, landslides, and rapid river rises. This pattern will likely disrupt outdoor plans at times. Conditions should gradually improve late Sunday into Monday, though some uncertainty remains.

AVIATION
(06Z TAFS)
Issued at 232 AM AST Tue Apr 14 2026

Mainly VFR conditions are expected across the local terminals early in the period, deteriorating to MVFR at times due to increasing SHRA and isolated TSRA, particularly across TJSJ, TJBQ, and TJPS between 14/17Z and 14/23Z. Periods of lower ceilings and reduced visibility are likely with the heaviest activity. Winds will remain light and variable through around 14/15Z, then increase from the E-SE at around 10 knots, with higher gusts possible near showers and thunderstorms.

MARINE
Issued at 232 AM AST Tue Apr 14 2026

A broad surface high pressure across the central Atlantic and a frontal boundary over the western Atlantic will promote light to moderate trades through the rest of the weekend. Pulses of northerly swell will continue to move through the Atlantic waters and passages, where small craft should continue to exercise caution over the next several days. The combination of the front and associated pre-frontal trough will increase showers and thunderstorms across the local waters, creating locally hazardous marine conditions through at least mid-week.

BEACH FORECAST
Issued at 232 AM AST Tue Apr 14 2026

A moderate risk of rip currents will continue for most north-and east-facing beaches of Puerto Rico, including Vieques and Culebra, and the U.S. Virgin Islands, where rip currents are possible and can be life-threatening. A low risk will likely persist across western and southern Puerto Rico. Increasing winds early to midweek could lead to a return of more hazardous marine and coastal conditions.
Residents and visitors are encourage to exercise caution at the beach, especially along the exposed coasts.

SJU WATCHES/WARNINGS/ADVISORIES
PR...Flood Watch through Wednesday morning for PRZ001>013.

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

AM...None.