Puerto Rico and US Virgin Islands from 10NM to 19.5N Marine Forecast
| Rest Of Today...West Winds 5 To 10 Knots. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 10 Seconds. Isolated Showers. |
| Tonight...Northwest Winds 10 To 15 Knots, Becoming West After Midnight. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 10 Seconds. Isolated Showers. |
| Thursday...Northwest Winds 10 To 15 Knots. Gusts Up To 25 Knots In The Afternoon. Seas 4 To 6 Feet With Occasional Seas Up To 8 Feet, Building To 6 To 8 Feet With Occasional Seas Up To 10 Feet. Dominant Period 11 Seconds. Numerous Showers. |
| Thursday Night...North Winds 10 To 15 Knots. Gusts Up To 25 Knots In The Evening. Seas 8 To 10 Feet With Occasional Seas Up To 11 Feet. Dominant Period 11 Seconds. Isolated Showers. |
| Friday...North Winds 10 To 15 Knots, Becoming Northeast. Seas 6 To 8 Feet With Occasional Seas Up To 10 Feet. Dominant Period 11 Seconds. Isolated Showers. |
| Saturday...East Winds 5 To 10 Knots, Becoming South. Seas 8 To 10 Feet With Occasional Seas Up To 11 Feet. Dominant Period 12 Seconds. Isolated Showers. |
| Sunday...Southwest Winds 5 To 10 Knots, Becoming East. Seas 6 To 8 Feet With Occasional Seas Up To 10 Feet. Dominant Period 14 Seconds. |
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Area Forecast Discussion National Weather Service San Juan PR 519am AST Sat April 26 2025 Synopsis A wet and unstable weather pattern is expected to continue through at least the end of the workweek, bringing periods of heavy showers and thunderstorms. Winds are forecast to remain light today, promoting the development of slow-moving showers and thunderstorms. Given the expected conditions, the potential for urban and small- stream flooding remains elevated today. Additionally, a high rip current risk is likely to return this evening and persist through at least late Sunday night due to the arrival of a long-period northerly swell. .SHORT TERM...Today through Monday... During the past night and early morning hours, radar data showed showers across parts of southeastern, eastern, and northeastern Puerto Rico, as well as surrounding waters and nearby islands. The heaviest rainfall initially fell in municipalities like Luquillo and Fajardo, where about 2 to 3 inches were recorded, prompting urban and small stream flood advisories. Later, showers tracked along the coast, dropping up to 1 inch of rain, particularly in the Old San Juan area. Since midnight, the highest radar estimated rainfall totals have ranged from 0.30 to 1.00 inch. Overnight temperatures ranged from the lower 60s in the mountains to the mid 70s across urban and coastal areas of Puerto Rico and the U.S. Virgin Islands, with light to moderate east northeast winds. For the short-term period, model guidance continues to suggest a persistently wet and unstable pattern. A mid to upper level trough and an associated jet streak will enhance lift and divergence aloft, creating favorable conditions for the development of showers and thunderstorms, mainly today. According to the 00Z Tropical Analysis and Forecast Branch (TAFB) surface analysis, the axis of the surface trough is located just northwest of the region. Moisture content is expected to increase from now onward, with model guidance suggesting precipitable water (PWAT) values rising from around 1.5 inches (average) to approximately 1.9 to 2.1 inches, which is above climatological levels for this time of year, and will remain elevated throughout the forecast period. Additionally, mid-level relative humidity is expected to increase significantly, peaking at about two standard deviations above average. Furthermore, 500 mb temperatures will remain near minus 8 degrees Celsius, maintaining upper level instability and supporting continued thunderstorm development. The overall pattern suggests that showers will mainly affect local waters and the U.S. Virgin Islands during the overnight hours, reaching the northern and eastern sectors of Puerto Rico in the mornings. As the days progress, showers and potentially thunderstorms will become more concentrated across the interior and northwestern sectors of Puerto Rico. The primary concern today and likely over the next few days is the increased risk of flooding, which is expected to remain elevated. This means flooding in urban areas, roads, small streams, and washes is likely, along with the potential for landslides in areas of steep terrain. Isolated flash floods cannot be ruled out. Although the wet pattern is expected to persist in the coming days, current model trends indicate that the highest potential for moderate to heavy rainfall will occur today, particularly during the afternoon hours. Residents and visitors are encouraged to stay weather aware and monitor official forecast updates. Long Term Tuesday through Saturday... For the rest of the week, a wet and unstable weather pattern will persist. A series of shortwave troughs will move across the local islands, maintaining favorable dynamical conditions aloft for the development of showers and deep convective activity. As a result, 500 mb temperatures will remain between -8 and -9 degrees Celsius, with relatively steep 850-700 mb and 700-500 mb lapse rates expected through most of the long-term forecast period. Meanwhile, elevated moisture levels will be present at all atmospheric levels, with columnar moisture remaining well above normal for this time of year. Most indicators, including precipitable water and the GFS (Global Forecast System) Galvez- Davidson Index (GDI), suggest that Wednesday will have the highest chance of thunderstorms and heavier showers. This is when low-level moisture convergence and steep lapse rates are expected to peak. Wednesday also presents the greatest potential for widespread urban and small stream flooding, as well as localized flash flooding, particularly in areas that may have observed excessive rainfall in previous days. However, similar risks will also exist on earlier days, though with less areal coverage. It is important to note that the timing of the most active day may shift as we approach the week, depending on the simultaneous combination of favorable dynamics and above-normal moisture levels. River streamflows will remain elevated, especially across the interior of Puerto Rico. Therefore, any additional rainfall could lead to rapid river rises in these areas. Furthermore, saturated soils will enhance runoff, increasing the risk of landslides in steep terrain. Weather conditions will gradually improve by the weekend. However, lingering moisture, combined with diurnal heating and local effects, will continue to support afternoon convection across the interior of Puerto Rico and downwind of the smaller islands. Marine Light easterly winds will prevail through today increasing to moderate tonight through early Sunday. Overall conditions should remain favorable for small craft, but localized hazardous marine conditions may develop near showers and thunderstorms through at least midweek. A long-period northeasterly swell is expected to spread across the Atlantic waters tonight into Sunday, which could result in hazardous conditions for small craft, mostly across the Atlantic waters. Beach Forecast A moderate rip current risk will prevail across northern exposed beaches for most of the day today. However, a long-period northerly swell is expected to reach the northern coast and persist through early Monday. Offshore buoy 41044 is already detecting this swell, and according to these readings, the swell is expected to arrive by this evening. As a result, a Rip Current Statement has been issued for the northern beaches of Puerto Rico, from Aguadilla to Fajardo, as well as the beaches of Culebra. For more information, please refer to the latest Coastal Hazard Message (CFWSJU) and Surf Zone Forecast (SRFSJU). Residents and visitors in affected regions should heed warnings, avoid swimming in these waters, and stay informed about updates from local authorities. .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk from this evening through late Sunday night for PRZ001-002-005-008-012. VI...None. AM...None. |
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