206 FXCA62 TJSJ 290842 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 442 AM AST Tue Oct 29 2024 .SYNOPSIS... A gradual transition into a wetter and more unstable weather pattern is expected over the next few days, particularly between late Wednesday into Thursday. Several features will combine to maintain this weather pattern over the next 4-7 days, including the proximity of a tropical disturbance by early next week. Extremely hazardous marine and coastal conditions are also anticipated from Thursday through the weekend. Please continue to monitor the forecast as this event unfolds. && .SHORT TERM...Today through Thursday... A broad surface high-pressure building over the western Atlantic is promoting moderate to fresh east-to-northeast winds across the northeastern Caribbean. Under these northeasterly steering winds, a meandering frontal boundary to our north will move over the islands today through early Wednesday. As shower and cloud coverage increases over the islands, daytime temperatures will decrease by a few degrees across Puerto Rico and the U.S. Virgin Islands. Furthermore, another front will arrive across the area on Thursday as the surface high centers near Bermuda. Therefore, a wetter pattern is expected to unfold across the area, with showers and thunderstorms increasing in areal coverage. In addition, a polar trough is forecast to move over the region by Thursday, providing more instability and favorable conditions for thunderstorm development. Meanwhile, over the southwestern Caribbean Sea, a broad area of low pressure is forecast to develop, and this will continue to promote the pooling of tropical moisture under southerly winds across the Caribbean. Urban and small stream flooding is expected each day across the islands, with localized flash flooding and mudslides in areas of steep terrain. Tightening of the local pressure gradient and a shearline associated with the front on Thursday will increase winds between 20 and 25 knots or higher across the Atlantic waters. Therefore, breezy to windy conditions are possible along the Atlantic coastal municipalities of Puerto Rico and across the northern U.S. Virgin Islands. && .LONG TERM...Friday through Tuesday... The most recent guidance continues to suggest a deep mid-to upper-level trough across the forecast area by the end of the workweek. This weather feature will create favorable conditions for thunderstorm development. A broad area of low pressure at the surface is expected to develop under the influence of the trough, and a southerly wind flow is expected to prevail from Friday onwards. This pattern usually favors the pooling of tropical moisture over the islands. A wet and unstable period could unfold during the end of the month/beginning of November as the National Hurricane Center is monitoring an area of low pressure that is likely to develop over the southwestern Caribbean Sea. They anticipate a gradual development late this week or over the weekend as the system begins to drift northward or northeastward and potentially approach the forecast area. This area of low pressure continues to have a 40 percent chance of development in the next 7 days. However, it is far in the forecast, and we encourage people to stay informed with each update. In the long term, we anticipate temperatures below 90 degrees across most areas as the cloudiness increases over the region. && .AVIATION... (06Z TAFS) Mainly VFR conds expected early in the forecast cycle. SHRA/TSRA are expected to increase aft 29/12z across the northern and eastern terminals of the islands as a frontal system over the Atlantic waters approach the area. Tempo MVFR to brief IFR conds and mtn tops obscd are possible from around 29/16z onwards. Winds will prevail from the ENE at 12-17 kt with sea breeze variations across the southern coast of PR. Stronger gusts and lower CIGS due to FROPA aft 29/20z. && .MARINE... Moderate to fresh easterly winds will prevail through Wednesday. A broad surface high pressure building over the western Atlantic will yield moderate to locally strong, northeasterly winds today, pushing the remnants of a front across the local area through midweek. An increase in shower and thunderstorm activity is also expected across the regional waters and passages through the rest of the workweek into the weekend. && .BEACH FORECAST... A northerly swell will continue across the Atlantic waters and passages today. There is a high risk of rip currents for northwestern to eastern beaches of Puerto Rico. Thunderstorms with occasional lightning strikes are expected this afternoon. Across the USVI and Culebra, a moderate risk of rip currents continues. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through this afternoon for Prz005-002-005- 008-012. VI...None. AM...None. && $$ SHORT TERM/AVIATION...DSR LONG TERM/MARINE/BEACH FORECAST...MMC
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