Leeward Islands Offshore Forecast
| Today...E Winds 10 To 15 Kt. Seas 4 To 6 Ft. Isolated Showers. |
| Tonight...Ne To E Winds 15 To 20 Kt. Seas 4 To 6 Ft. Isolated Showers. |
| Fri...Ne To E Winds 15 To 20 Kt. Seas 4 To 6 Ft. Isolated Showers. |
| Fri Night...Ne To E Winds 20 Kt. Seas 6 To 8 Ft. Scattered Showers. |
| Sat...Ne To E Winds 15 To 20 Kt. Seas 6 To 8 Ft. |
| Sat Night...Ne To E Winds 15 To 20 Kt. Seas 6 To 9 Ft In Ne Swell. |
| Sun...E Winds 15 To 20 Kt. Seas 6 To 9 Ft In Ne Swell. |
| Sun Night...E Winds 15 To 20 Kt. Seas 6 To 9 Ft In N To Ne Swell. |
| Mon...E Winds 15 Kt. Seas 6 To 9 Ft In N To Ne Swell. |
| Mon Night...Ne To E Winds 15 To 20 Kt. Seas 4 To 6 Ft In The Caribbean, And 6 To 8 Ft In The Atlc. |
| Area Forecast Discussion National Weather Service San Juan PR 435am AST Thu Mar 30 2023 Synopsis Rounds of passing scattered showers will affect the region today as shallow moisture filters in. This activity will likely spread mainly over interior and northwestern Puerto Rico in the afternoon. Less shower activity, stronger winds and drier air are expected tomorrow and into the weekend. There is a High Rip Current Risk today for the north- and east-facing beaches of Puerto Rico, as well as for Culebra and St Croix. .SHORT TERM...Today through Saturday... High pressure exiting the Eastern U.S. will move slowly eastward across the Western Atlantic over the next few days. This surface high pressure promotes east to northeast winds across the local region. Winds become stronger at around 20 knots from Friday into the weekend. These fresh trade winds will push fragments of low- level clouds and scattered showers across the U.S. Virgin Islands and Puerto Rico from time to time. For today, satellite-derived precipitable water analysis suggests that moisture will increase by around 1.25 inches. However, these showers will be shallow as the 700 mb - 500 mb high pressure will keep dry and relatively stable conditions aloft. High-resolution models suggest that the first round of scattered showers will affect portions of the U.S. Virgin Islands, Culebra, Vieques, and eastern Puerto Rico around mid- morning. Then, scattered showers will likely spread over the interior and northwestern Puerto Rico early in the afternoon. Rain accumulations will range between a few tenths of an inch in eastern PR and half an inch to an inch over the interior and northwest Puerto Rico. A strong trade wind cap will trap the moisture below 850 mb Friday and Saturday. Also, a dry and stable air mass will move over the local islands under a fresh northeast flow. Rainfall probabilities are very low for Friday and Saturday as precipitable water values plunge below 0.8 inches, way below normal for this time of the year. Although an upper-level trough develops over Puerto Rico early in the weekend, the high pressure at the mid-level will dominate the weather conditions keeping the local area under fair weather. Long Term Sunday through Thursday... By Sunday and into the next workweek intervals of patches of moisture and dry air will filter into the region, promoting passing shower activity across windward sectors of the islands. Overall moisture will continue to be a limiting factor in shower activity at this time. Model guidance has varied in the timing of the patches of moisture but shows an overall increase by Wednesday and Thursday, with precipitable water (PWAT) values at to slightly above normal values. In the upper levels, the long term period is forecast to start with an upper level trough gradually exiting the region, promoting gradually increasing stability. Current model guidance seems aggressive in developing an upper-level trough over the region by early Wednesday, this feature would continue to affect the islands through the end of the short term forecast period. To start next week, moisture will be limited to the lower levels with mid level ridging persisting, but current model guidance indicates that available moisture will reach the mid to upper levels by Wednesday and Thursday. At surface level, a high pressure system will be over the central Atlantic to start the week and another high pressure will move into the western Atlantic to end the forecast period. Winds start off next week being generally easterly, before becoming more northeasterly by midweek. For early next week shower activity will be mostly dependent on those patches of shallow moisture, reaching near normal PWAT (Precipitable Water) values, embedded in the trade wind flow and reaching windward sectors during the evening and morning hours. Limited afternoon convection, due to diurnal and local effects, is possible mainly over western/southwestern Puerto Rico. As moisture and instability will possibly increase by midweek, shower activity could increase, with stronger showers and afternoon convection. This possible development will continue to be monitored. Marine A surface high pressure stretched across the Atlantic Basin will continue to promote moderate to locally fresh trade winds across the regional waters, resulting in choppy seas up to 5 ft, mainly over Atlantic waters and the local passages. A subsiding northeasterly swell will continue to affect the local Atlantic waters and passages. Winds will up to around 15 knots, locally higher, particularly across nearshore northern waters of Puerto Rico where Small Craft Should Exercise Caution. Marine conditions will deteriorate by Friday night into the weekend due to strong winds. There is a High Rip Current Risk for the north and east- facing beaches of Puerto Rico, as well as for Culebra, St Thomas, St John and St Croix. St. Thomas and St. John, however will have only up to a moderate risk of rip currents by 6am AST. .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through late Friday night for PRZ001-002- 005-008-012. VI...High Rip Current Risk until 6am AST early this morning for VIZ001. High Rip Current Risk through this afternoon for VIZ002. AM...None. |