Northern US Virgin Islands and Culebra Marine Forecast
| Rest Of Today...West Winds 5 To 10 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 11 Seconds. Isolated Showers. |
| Tonight...West Winds 10 To 15 Knots. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 10 Seconds. |
| Thursday...Northwest Winds 10 To 15 Knots. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 11 Seconds. Numerous Showers. |
| Thursday Night...North Winds 10 To 15 Knots. Seas 6 To 8 Feet With Occasional Seas Up To 10 Feet. Dominant Period 12 Seconds. Scattered Showers. |
| Friday...North Winds 10 To 15 Knots. Seas 6 To 8 Feet With Occasional Seas Up To 10 Feet. Dominant Period 11 Seconds. Isolated Showers. |
| Saturday...Southeast Winds 5 To 10 Knots. Seas 6 To 8 Feet With Occasional Seas Up To 10 Feet. Dominant Period 12 Seconds. Isolated Showers. |
| Sunday...South 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 527am AST Monday May 12 2025 .KEY MESSAGES... * Afternoon showers and thunderstorms will affect western PR and downwind of the local islands. * More unstable and wet weather conditions are forecast by Friday and into the upcoming weekend. * Breezy conditions will persist for the next few days. * Increasing winds will lead to choppy to rough seas and a moderate risk of rip currents. .SHORT TERM...Today through Wednesday... Variable weather conditions persisted across the local islands during the night and early morning hours. Brief showers were detected by Doppler radar over portions of the eastern region, leaving minimal rainfall accumulations. Across the western half of Puerto Rico, mostly clear skies prevailed. Overnight temperatures remained in the lower 80s along coastal areas and were noticeably cooler in the mountainous regions. From today into early Wednesday, the weather pattern is expected to become more favorable across the CWA (County Warning Area) as a mid-to-upper-level ridge establishes itself over the western Atlantic. This feature will promote drier conditions aloft and a pronounced trade wind cap inversion, which will limit the vertical development of stronger showers. At the surface, a broad high-pressure system over the central Atlantic extending into the Caribbean will slightly tighten the pressure gradient, resulting in breezier conditions across the CWA. These conditions will support a stable but variable weather pattern during the morning, with extended periods of sunshine and some brief showers over eastern Puerto Rico and the U.S. Virgin Islands. Although the potential for significant rainfall is reduced, afternoon convection due to diurnal heating is forecast across the western interior and nearby municipalities. Rainfall totals are expected to range between 1 and 2 inches in areas affected by the bulk of the activity, though fast-moving showers driven by the prevailing trade winds will likely result in only localized impacts. A similar pattern is expected on Tuesday; however, GFS (Global Forecast System) model guidance suggests a slight decrease in precipitable water values from 0–3 km, down to around 1.1 inches. These drier conditions indicate that Tuesday may be the most stable day across the region. By Wednesday, the surface high over the western Atlantic is forecast to sink southward and interact with an induced surface trough, resulting in veering winds across the region. This southeasterly wind flow will lead to an increase in atmospheric moisture, raising the potential for shower development and contributing to higher heat index values, marking the beginning of a warming trend. Long Term Thursday through Monday... Increasingly wet and unstable condtions are forecast during most of the long term forecast period. After mid-week, current model guidance has precipitable water (PWAT) values close to around 2 inches, above normal values for this time of the week. A decrease in PWAT (Precipitable Water) values is forecast by late Sunday and Monday, decreasing to around 1.8 inches. A mid to upper-level ridge present on Thursday will gradually weaken as a mid to upper level trough moves eastward from the western Atlantic towards the local islands, this will promote more favorable conditions for shower and thunderstorm development late Thursday onwards. A surface trough will also develop, also providing instability and promoting, along with a surface high over the central Atlantic, more east-southeast to southeast steering flow over the region. Deep tropical moisture will start to move into the region, with current model guidance showing a completely moist atmospheric profile, possibly being somewhat confined once again to below 650mb by late Saturday and into early next week. With the prevailing wind flow, increased temperatures are also forecast in areas without significant cloudiness, particularly during the late morning hours. Ultimately this diurnal heating, along with sea breeze convergence and local orographic effects, can also help promote shower and thunderstorm development, adding to the already unstable atmospheric conditions. By Friday and into the weekend, conditions will be conducive to increased convective activity. Widespread showers and thunderstorms are forecast, particularly across the Cordillera Central and western Puerto Rico, with lines of convection possibly also developing from the local islands and El Yunque. With already saturated soils and these moist and unstable conditions, a limited to elevated flooding risk is forecast during these days, meaning that urban, small stream and flash flooding is possible. Stay tuned for any updates. Marine A broad surface high pressure over the Central Atlantic will sink southward over the next few days, resulting in increasing winds and choppy conditions across the offshore waters. A Small Craft Advisory is now in effect for the Atlantic offshore waters and the Anegada Passage due to seas building up to 7 feet by this afternoon. Small Craft Should Exercise Caution over most of the other waters. Thunderstorm activity is likely across the regional waters, especially in the afternoons and evenings, resulting in locally higher winds and seas. Beach Forecast There is currently a moderate risk of rip currents for the northern to eastern beaches of Puerto Rico, from Aguadilla to Ceiba, as well as for southwestern Puerto Rico, and most of Culebra, Vieques, St. Croix, St. John and St. Thomas. The moderate risk of rip currents will extend tonight to areas of southern and northwestern Puerto Rico tonight. In general, a low to moderate risk of rip currents will persist through the workweek. Life- threatening rip currents often occur in the vicinity of groins, jetties, reefs, and piers. If you become caught in a rip current, yell for help. Remain calm, do not exhaust yourself and stay afloat while waiting for help. If you have to swim out of a rip current, swim parallel to shore and back toward the beach when possible. Do not attempt to swim directly against a rip current as you will tire quickly. .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...Small Craft Advisory from noon today to 6am AST Tuesday for AMZ711-723. |
San Juan Radar
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