Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
770 FXCA62 TJSJ 302138 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 538 PM AST Tue Apr 30 2024 .SYNOPSIS... A broad surface high pressure over the western Atlantic will weaken in the next few days. Expect breezy northeasterly winds through at least midweek. From mid-week onwards, instability and moisture levels increase once again as a mid to upper level trough lingers over the western Atlantic and lighter east to southeast winds return. Marine conditions will remain hazardous through at least tomorrow night. A High Risk of Rip Currents will continue across northern and eastern coastline of Puerto Rico and Culebra through at least Thursday afternoon. && .SHORT TERM...Tonight through Thursday... During the morning, a similar pattern continued with showers moving across northern, eastern, and interior portions of PR and the US Virgin Islands. Doppler radar estimates registered around one inch or less in those areas. By the afternoon, rain focused over west central municipalities. At the moment, around 2 to 4 inches of rain has fallen. A Flood Advisory continues in effect until 6 PM AST this evening. In addition, activity of thunderstorms has persisted over the Caribbean waters, with winds at around 30 knots. Tonight, like the past few nights, expect additional showers developing across portions of the USVI, northern, and eastern sectors of Puerto Rico, and the Caribbean waters, along with some breezy and gusty periods.Minimum temperatures will range from the mid and upper 70s across coastal areas to the mid-60s in the higher elevations. The latest model`s guidance continues in agreement that the surface high pressure; now located over the western Atlantic, will weaken during the next few days as it moves into the Central Atlantic changing the wind flow across the forecast area. Winds should gradually turn from the east tomorrow and become lighter tomorrow evening through the rest of the short term. Not a lot of improvement is expected for the next several days, on the contrary, a wetter and more unstable pattern should evolve on Wednesday and Thursday as an upper-level trough approaches the area from the west, and an induced surface trough develops north of the region. Consequently, above-normal moisture levels for this time of the year will prevail over the local region enhancing shower and thunderstorm development across much of Puerto Rico and USVI. For that reason, the risk of flooding will likely remain elevated across most islands every day for the rest of the period and the main impacts remain to be: urban and small stream flooding, localized flash flooding, and mudslides in areas of steep terrain. It is crucial to be cautious and aware of these potential risks, as well as monitor the forecast for future updates. && .LONG TERM...Friday through Monday... .PREV DISCUSSION... /issued 423 AM AST Tue Apr 30 2024/ The latest model guidance continues to suggest wet and unstable weather conditions even through the end of the workweek, notonly for the island of Puerto Rico but also for the U.S. Virgin Islands. This pattern should prevail as an upper-level trough approaches the area from the west, and an induced surface trough develops north of the region enhancing additional rainfall activity and allowing it to be the dominant feature throughout the long-term period. On Friday, a mid to upper level, yet maxima, should move across the area with winds around 70 knots. This yet maxima will allow the trough to deepen, enhancing the unstable conditions. By the weekend, expect the Precipitable Water (PW) values to range above normal climatological levels for this of the year to above two standard deviations. We foresee active afternoons each day with the potential increase in the frequency of showers and isolated thunderstorms. As a side note, heat indices across the lower elevations of the islands could likely range between 102 and 106 degrees on Friday and Saturday before the onset of afternoon convection. Overall, the main hazards from Friday into the beginning of the workweek are the increased risk of flooding across the islands and the risk of mudslides, particularly in areas of steep terrain in Puerto Rico. Therefore, we encourage citizens and visitors to be aware of any additional updates in the forecast. && .AVIATION... (18z) TAFS Expect showery weather with breezy trade winds through the forecast period. TSRA/SHRA will affect mainland PR and downwind from St Croix, some SHRA/+SHRA may impact JBQ/JPS/ISX this afternoon. Mountain obsc will prevail along the Cordillera Central and near the Luquillo Mountain Range thru 30/23z. The unstable and wet pattern will continue tomorrow. We expect 10-20 kt easterly winds with gusts btwn 20 and 30 kt, aft 30/23z winds will range between 5-15 kt and will return from the E-ESE aft 01/13z at 15-20 kt. && .MARINE... A surface high pressure across the western to central Atlantic will tighten the local pressure gradient, promoting moderate to locally fresh trade winds across the Northeast Caribbean through at least tomorrow. As a result, expect hazardous seas for small craft operators due to confused seas associated with the increasing winds and a northeasterly swell spreading across the local waters. An induced surface trough, north of the islands, will weaken the pressure gradient and winds will shift from the east to east-southeast by the latter part of the week. && .BEACH FORECAST... A northerly swell and stronger winds are resulting in High Risk of Rip Currents across local area beaches. The High Risk will continue in St. Croix until this afternoon, across western beaches of Puerto Rico, St. Thomas, and St. John through at least late Wednesday, and across the northern and eastern coastline of Puerto Rico and Culebra through at least Thursday afternoon. For more information and details about the latest forecast please refer to the Surf Zone Forecast (SRFSJU) and the Coastal Hazard Message product (CFWSJU). && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through Thursday afternoon for PRZ001-002- 005-008-012. High Rip Current Risk through late Wednesday night for PRZ010. VI...High Rip Current Risk through late Wednesday night for VIZ001. High Rip Current Risk until 6 PM AST this evening for VIZ002. AM...Small Craft Advisory until midnight AST Wednesday night for AMZ711-712-716. Small Craft Advisory until noon AST Wednesday for AMZ723-741-742. Small Craft Advisory until 6 PM AST this evening for AMZ726. && $$ SHORT TERM/MARINE/BEACH FORECAST...YZR LONG TERM....MMC AVIATION...CAM/CVB PUBLIC...ERG