Northwestern Puerto Rico out 10nm Marine Forecast
| Rest Of Tonight...Northeast Winds 10 To 15 Knots With Gusts Up To 20 Knots. Seas 2 To 3 Feet, Occasionally To 4 Feet. Wave Detail: Northeast 3 Feet At 4 Seconds And North 1 Foot At 9 Seconds. Scattered Showers Early This Evening, Then Isolated Showers. |
| Saturday...Northeast Winds 10 To 15 Knots, Increasing To 15 To 20 Knots In The Afternoon. Seas 2 To 4 Feet, Occasionally To 5 Feet. Wave Detail: North 3 Feet At 5 Seconds. Scattered Showers In The Afternoon. |
| Saturday Night...Northeast Winds 15 To 20 Knots With Gusts Up To 25 Knots. Seas 3 To 5 Feet, Occasionally To 6 Feet. Wave Detail: Northeast 5 Feet At 7 Seconds. |
| Sunday...Northeast Winds 15 To 20 Knots With Gusts Up To 30 Knots. Seas 4 To 6 Feet, Occasionally To 8 Feet. Wave Detail: Northeast 6 Feet At 9 Seconds. |
| Sunday Night...Northeast Winds 15 To 20 Knots With Gusts Up To 30 Knots. Seas 5 To 7 Feet, Occasionally To 9 Feet. Wave Detail: North 7 Feet At 9 Seconds. |
| Monday...North Winds 15 To 20 Knots With Gusts Up To 25 Knots. Seas 5 To 7 Feet, Occasionally To 9 Feet. Wave Detail: North 7 Feet At 9 Seconds. |
| Monday Night...North Winds 15 To 20 Knots, Becoming Northeast 10 To 15 Knots After Midnight. Seas 4 To 6 Feet, Occasionally To 8 Feet. |
| Tuesday...Northeast Winds 10 To 15 Knots. Seas 4 To 6 Feet, Occasionally To 8 Feet. |
| Tuesday Night...Northeast Winds 10 To 15 Knots, Becoming East 5 To 10 Knots After Midnight. Seas 4 To 6 Feet, Occasionally To 8 Feet. |
| Wednesday...Northeast Winds 5 To 10 Knots. Seas 3 To 5 Feet, Occasionally To 6 Feet. Numerous Showers In The Afternoon. |
| Wednesday Night...East Winds 5 To 10 Knots. Seas 2 To 4 Feet, Occasionally To 5 Feet. Scattered Showers. |
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Area Forecast Discussion National Weather Service San Juan PR 420pm AST Fri April 18 2025 Synopsis An induced surface trough and plenty of moisture will continue to generate a wet and unstable weather pattern through this weekend. Therefore, periods of strong showers with thunderstorms will increase the potential for urban flooding and minor small- stream flooding. The heaviest activity will be lightning, with the threat of lightning present as well. Tranquil marine conditions will persist and deteriorate for the upcoming workweek. .SHORT TERM...Tonight through Sunday... During the morning hours, showers continued to move across the U.S. Virgin Islands, the eastern half of Puerto Rico, and the municipal island of Culebra. Radar estimates indicated rainfall amounts between 1.0 and 1.5 inches in those areas. Later, a line of showers accompanied by isolated thunderstorms developed over southern Puerto Rico, prompting flood advisories for Mayagüez, Hormigueros, and Cabo Rojo. As of 3pm AST, those areas received between 1 to 2.5 inches of rainfall. Winds remained light, generally from the east to northeast. Daytime temperatures stayed in the low to mid-80s across coastal areas and ranged from the upper 70s to low 70s in the mountainous regions. The short-term forecast remains on track. Weather conditions will continue to be influenced by a mid-to-upper-level trough approaching from the west, which is expected to linger through the weekend. At the surface, an induced trough is moving across the area, enhancing low-level convergence across the northeastern Caribbean. According to the latest model guidance, precipitable water values are forecast to range from 1.8 to 2.10 inches through early Sunday—above the climatological average for this time of year. This afternoon, additional showers and thunderstorms are expected to develop across Puerto Rico’s interior and spread outward, fueled by daytime heating and sea breeze convergence. The risk of flooding remains elevated today and into Saturday. Expect ponding of water on roadways and in poorly drained areas, with the potential for more significant urban and small stream flooding. Saturday is expected to be another variable day, with cloudy skies and periods of scattered to numerous showers. Isolated to scattered thunderstorms are also likely to continue, particularly over the interior and western half of Puerto Rico, and across surrounding waters overnight. By Sunday, expect showers mainly over the surrounding waters, the U.S. Virgin Islands, and eastern Puerto Rico, with a limited flood risk early in the day. Afternoon convection may develop, supported by available moisture and local effects. A gradual improvement in rainfall conditions is expected later in the day. Long Term Monday through Friday... An unsettled and moist weather pattern will prevail at the beginning of the workweek. On Monday, upper-air analysis indicates a pronounced trough evolving into a cut-off low just north of the forecast area. This synoptic feature will induce significant instability, as reflected in model-derived 500 MB temperatures dropping between -8°C and -10°C, which is supported by the latest TJSJ RAOB (Radiosonde Observation or Upper-Air Observation) and GFS (Global Forecast System) analysis. This colder air aloft will promote robust convective development and increase the potential for thunderstorm activity across the region, particularly over interior and western Puerto Rico during the afternoon hours. At the surface, a strengthening Atlantic high will enhance the local pressure gradient, with 925 MB wind speeds peaking between 15 to 25 knots and occasional gusts above that range, according to GFS guidance. Winds will shift from the northeast, resulting in breezy to windy conditions and advecting fast-moving showers across the northern and eastern municipalities of Puerto Rico, as well as the U.S. Virgin Islands. However, given the enhanced steering flow, rainfall totals are expected to be limited from late Sunday into Monday despite periods of active weather. Additionally, both 700–500 MB and 850–700 MB relative humidity values exceed the 75th percentile, suggesting a deeply saturated column and increased potential for vertically developed convection during this period. From Tuesday through Friday, weather conditions are expected to gradually improve. The upper-level divergence zone tied to the cut-off low will migrate eastward, allowing for the development of a mid-level ridge that will introduce drier and more stable air masses over the region. The global model shows a notable drop in PWAT (Precipitable Water) values, reaching below 1.0 inch by Sunday, indicative of a more suppressed convective environment. Despite this drying trend, residual cloudiness and embedded moisture from the proximity of the lingering surface low may still bring passing showers, especially across eastern Puerto Rico and the U.S. Virgin Islands under continued northeasterly trade winds. Marine An induced surface trough and a broad surface high pressure over the central Atlantic will promote light southeasterly winds across the region through tomorrow. By Sunday, increasing surface winds due to another surface high pressure over the western Atlantic will result in wind-driven seas between 6 to 7 feet, enhancing choppy marine conditions along the area. Thunderstorm activity will be present across the local waters today into Sunday due to strong showers and thunderstorms, resulting in localized hazardous marine conditions. Beach Forecast A low risk of rip currents is expected across all coastal areas through Saturday. However, the risk will increase to moderate on Sunday and become high by Sunday afternoon and into the upcoming workweek due to strengthening winds. Moderate easterly winds will raise the rip current threat along most north- and east-facing beaches of Puerto Rico and St. Croix. Additionally, deteriorating marine conditions over the weekend will further elevate the hazard. Beachgoers should also remain vigilant for afternoon thunderstorms, especially along the western and southwestern coasts of Puerto Rico, where dangerous lightning may occur. .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. |
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