Mona Passage Southward to 17N Marine Forecast
| Today...East Winds 15 To 20 Knots With Gusts Up To 25 Knots. Seas 4 To 6 Feet. Wave Detail: East 6 Feet At 7 Seconds And North 2 Feet At 10 Seconds. Isolated Showers Early This Morning. Isolated Showers This Afternoon. |
| Tonight...East Winds 15 To 20 Knots With Gusts Up To 25 Knots. Seas 4 To 6 Feet. Wave Detail: East 5 Feet At 7 Seconds And North 1 Foot At 10 Seconds. |
| Tuesday...East Winds 15 To 20 Knots With Gusts Up To 25 Knots. Seas 4 To 6 Feet. Wave Detail: East 5 Feet At 7 Seconds And North 1 Foot At 9 Seconds. |
| Tuesday Night...East Winds 15 To 20 Knots, Increasing To 20 To 25 Knots After Midnight. Seas 5 To 7 Feet. Wave Detail: East 6 Feet At 7 Seconds And North 1 Foot At 8 Seconds. Scattered Showers. |
| Wednesday...East Winds 15 To 20 Knots With Gusts Up To 30 Knots. Seas 5 To 7 Feet. Wave Detail: East 6 Feet At 7 Seconds. Scattered Showers In The Afternoon. |
| Wednesday Night...East Winds 20 To 25 Knots, Diminishing To 15 To 20 Knots After Midnight. Seas 5 To 7 Feet. Wave Detail: East 7 Feet At 7 Seconds. Scattered Showers. |
| Thursday...East Winds 15 To 20 Knots. Seas 5 To 7 Feet. Scattered Showers. |
| Thursday Night...East Winds 15 To 20 Knots. Seas 5 To 6 Feet. |
| Friday...East Winds 10 To 15 Knots, Increasing To 15 To 20 Knots In The Afternoon. Seas 4 To 6 Feet. Scattered Showers In The Morning. |
| Friday Night...East Winds 15 To 20 Knots. Seas 4 To 6 Feet. Scattered Showers. |
| Area Forecast Discussion National Weather Service San Juan PR 231pm AST Sunday Jan 18 2026 .Short Term(This evening through Tuesday)... Issued at 226pm AST Sunday Jan 18 2026 Mostly fair conditions prevailed during the morning hours. Passing showers moved mainly across the waters, a few moving over portions of St. Croix in the U.S. Virgin Islands and eastern portions of Puerto Rico. Breezy to windy conditions continue across the islands, as CWOP/ASOS stations reported maximum wind gusts between 30 and 33 mph over coastal areas (31 mph at the Henry E. Rohlsen International Airport in St. Croix, VI, and 33 mph at Camp Santiago in Salinas, PR) and higher elevations. Today’s 12z RAOB (Radiosonde Observation or Upper-Air Observation) showed slightly lower PWAT (Precipitable Water) values compared to the 00z (from 1.36 to 1.18 inches), due to a drier airmass that filtered into the region early today. Considering that HIRES models do not suggest significant rainfall accumulation for this afternoon, shallow convection is the most likely scenario, with passing showers moving through the western portions of Puerto Rico. No major changes were introduced to the short-term forecast, as variable and breezy to windy (winds between 15 - 25 mph) conditions are expected to continue across the CWA. The wind pattern will continue from the east to east-southeast due to a broad surface high pressure over the Central Atlantic. Based on the latest model guidance, the moisture content is expected to increase late tonight due to a patch of moisture. According to the deterministic guidance of the GFS (Global Forecast System) and ECMWF, PWAT (Precipitable Water) values are expected to increase (between 1.2 and 1.4 inches), typical for the season. An increase in frequency of showers can be expected, particularly affecting portions of the U.S. Virgin Islands and windward sections of Puerto Rico. Due to strengthening winds, short-lived showers should not leave significant rainfall accumulations. The presence of a mid- level ridge will dominate most of the weather pattern across the local area, as warmer-than-normal 500 mb temperatures (around -4 degrees Celsius), low 700 - 500 mb lapse rates (between 5 and 5 degrees Celsius per kilometer), and lower RH content in the 700 - 500 mb levels indicate unfavorable conditions for deep convection. Hence, from Monday onwards, the variable conditions will continue due to abundant low level moisture content across the CWA, with passing showers across windward sections during the morning hours and shallow afternoon convection over western Puerto Rico, along with the U.S. Virgin Islands streamers. The highest accumulations may be expected over western PR, with mainly localized ponding of water over roadways, urban, and poorly drained areas. .Long Term(Wednesday through next Saturday)... Issued at 413am AST Sunday Jan 18 2026 As noted in previous discussions, model guidance continues to indicate a humid and unsettled pattern throughout the long-term period across Puerto Rico and the U.S. Virgin Islands. The most unstable conditions are expected on Thursday, with unsettled weather persisting through Saturday. Precipitable water values rising above 1.75 inches after Wednesday reflect above-normal moisture associated with a deep tropical plume, enhancing overall shower coverage. This pattern will support thunderstorms and periods of moderate to locally heavy rainfall, increasing the potential for localized flooding, particularly in urban, poor drainage, and low-lying areas. Repeated showers over the same locations could worsen runoff issues, while frequent lightning may pose hazards to outdoor activities. Although east to northeast winds of 17 to 20 mph should help limit widespread flooding, locally enhanced rainfall will remain possible, especially in terrain-favored areas. Temperatures are expected to trend back toward seasonal norms by Thursday, but persistent high moisture and cloud cover will maintain humid conditions through the remainder of the period. Marine Issued at 226pm AST Sunday Jan 18 2026 Broad surface high pressure over the central Atlantic will continue to influence the regional waters through at least tonight. Fresh to locally strong east winds will persist, maintaining choppy to rough seas, although conditions are expected to gradually subside later today. Small Craft Advisories remain in effect at least through this afternoon, as hazardous marine conditions will continue, especially across the offshore Atlantic waters and passages. Mariners should continue to exercise caution until seas and winds further diminish. Beach Forecast Issued at 226pm AST Sunday Jan 18 2026 A High Rip Current Statement remains in effect for the north and east-facing beaches of Puerto Rico, including Culebra, and the U.S. Virgin Islands through 6am AST on Monday. While marine and surf conditions are slowly subsiding, hazardous rip current conditions persist, and the risk remains high along exposed beaches. Residents and visitors are urged to continue following the warning flag system and to favor beaches with lower rip current risk, such as those along the western and southern coasts of Puerto Rico. In addition, breezy to locally windy conditions continue along coastal areas, which may still result in unsecured objects being blown around, particularly in the most exposed locations. Beachgoers should remain cautious both in and near the water until conditions improve further. For localized and updated risk levels, visit weather.gov/beach/sju. .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through late tonight for PRZ001-002-005- 008-012. VI...High Rip Current Risk through late tonight for VIZ001-002. AM...Small Craft Advisory until midnight AST Monday night for AMZ711- 723. Small Craft Advisory until 6pm AST this evening for AMZ712-716- 726-733-741. |
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