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 508am AST Tuesday Jan 14 2025 Synopsis Increased cloud coverage and some showers are expected today as a weak old frontal boundary crosses the islands. However, only minor shower activity is anticipated, with no flooding threat expected. Hazardous seas and life-threatening rip currents will persist through at least Thursday. .SHORT TERM...Today through Thursday... It was a fair evening and overnight for the local islands, with no precipitation over the islands detected by radar. Northeasterly winds did steer patches of low level clouds over several inland areas, and patchy fog was detected over areas of interior PR. Winds over land were light to calm and variable, with land breezes in coastal areas, except over several areas of Culebra, St. Thomas and St. John where northeasterly flow was around 15 mph with higher gusts. Surface observations showed overnight temperatures ranging from the mid-50s in the higher elevations of the Cordillera Central to the lower 70s in coastal areas and local islands. Lows were in the mid 50s to mid 60s across higher elevations of Puerto Rico, and in the upper 60s to mid 70s across lower elevations of the islands. During the late overnight hours, the doppler radar detected isolated showers over the offshore Atlantic Waters moving towards the local islands. These are related to a weak frontal boundary approaching the region that extends from a low pressure around 2500 mi NE of San Juan. A surface high-pressure moving eastward across the SW Atlantic will also continue to promote increasing NNE to NE flow. The mid level ridge that has been affecting our area recently will weaken. Current satelite derived precipitable water (PWAT) values indicate up to 1.35 in (at normal values) with this boundary. Model guidance has these PWAT (Precipitable Water) values and related light to moderate shower activity to reach the northern sectors in the morning and early afternoon, and finally being south of the islands by the evening. This will bring a moderate increase in shower activity, thus the potential for flooding is very limited and conditions will further improve after sunset. PWAT (Precipitable Water) values will slightly decrease early Wednesday before increasing to normal PWAT (Precipitable Water) values through Thursday. NE winds, becoming breezy, will also be present especially late tonight through the short term period due to a surface high over the western Atlantic. Passing showers will reach windward areas at times. Persistent mid-level ridging and a trade wind inversion will continue to keep most available moisture below 800 mb through the short term period. Northeasterly winds will also promote slightly below normal temperatures across the islands, with model-estimated 925 mb temperatures at below normal to normal values. Highs can reach the low to mid 80s (locally higher) across lower elevations of the islands. Lows can again reach the mid 50s to mid 60s across higher elevations of Puerto Rico, and from the upper 60s to mid 70s across lower elevations of the islands. Patchy fog can also be present during the overnight to early morning hours across interior Puerto Rico. Long Term Friday through Tuesday... The low to mid-level ridge is expected to shift east-northeast of the northern Leewards early in the cycle, allowing the trade wind cap to relax over the weekend. At the same time, the remnants of a frontal system south of the forecast area will move northwestward over the local islands, increasing moisture convergence across the northeastern Caribbean. Precipitable water values are expected to increase to near-normal levels on Friday and above-normal levels through the weekend. The combination of increased vertical mixing and enhanced moisture content will support shallow convection across the region. During the morning hours of the weekend, showery weather could affect windward coastal areas of the islands, while local effects and sea breeze convergence may promote showers across the interior and western portions of Puerto Rico in the afternoon. Warmer-than-normal temperatures are also expected during this period as an east- southeast wind flow develops, particularly on Sunday. By Monday, the 500 mb ridge is forecast to move over the islands, promoting drier air intrusion and stable conditions once again. However, model guidance suggests the development of a mid-to upper- level cut-off low on the southern edge of the ridge, which could approach the area by Tuesday. Nonetheless, forecast confidence remains low, as its location continues to vary with each model cycle. Marine Breezy conditions are expected to develop by this evening across the regional waters, with winds peaking between 15-20 knots and higher gusts. Additionally, another long-period northerly swell will spread across the Atlantic waters and portions of the local passages. This will result in hazardous seas of 7-9 feet and choppy conditions due to wind-driven seas. Consequently, a Small Craft Advisory (MWWSJU) is in effect through at least Thursday afternoon. Beach Forecast There is a high risk of rip currents across the northwestern, northern, and eastern exposed beaches of Puerto Rico, Culebra, and the northern U.S. Virgin Islands. As a result, a Rip Current Statement is in effect. Life-threatening rip currents are expected to persist through at least Thursday due to the combination of wind- driven seas and pulses of a northerly swell. A High Surf Advisory may be necessary during the peak of the northerly swell. For more information, please refer to the SRFSJU and CFWSJU text products. .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through Thursday afternoon for PRZ001-002- 005-008-010-012. VI...High Rip Current Risk through Thursday afternoon for VIZ001. AM...Small Craft Advisory from noon today to 6pm AST Thursday for AMZ711. Small Craft Advisory from midnight tonight to 6pm AST Thursday for AMZ712-716-741. |
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