Hurricane Season runs from June 1-November 30
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494 FXCA62 TJSJ 090855 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 455 AM AST Fri May 9 2025 .KEY MESSAGES... * Showers will continue to filter across eastern Puerto Rico and the U.S. Virging Islands through the morning hours today. * Like previous days, afternoon showers and isolated thunderstorms are expected each day and could generate localized flooding impacts, including landslides in areas of steep terrain, particularly in vulnerable areas with saturated soils. * Strengthening winds over the weekend into early next week will elevate the risk of life-threatening rip currents for beachgoers and create rough seas for small craft. && .SHORT TERM...Today through Sunday... A variable weather pattern prevailed during the night hours, where shower activity was observed throughout northeastern Puerto Rici. Most of the showers were observed first along Dorado and the vicinity around Rio Grande and Loiza. Rainfall accumulations were one to two inches in some areas. Overnight temperatures remained in the lower 80s around the coastal areas and even more fresh across the interior sections. A stable and generally dry weather pattern will persist across Puerto Rico and the U.S. Virgin Islands through at least today, primarily due to the presence of a mid-to upper-level ridge extending over the northeastern Caribbean. This ridge promotes atmospheric subsidence, suppressing vertical motion and deep convective development. Model guidance indicates that lapse rates in the mid-levels, between 700 and 500 millibars, range from 5.0 to 5.5 degrees Celsius per kilometer,allowing a more stable pattern. Additionally, temperatures at 500 millibars remain cool, near minus 7 degrees Celsius, but not cold enough to generate significant widespread thunderstorms activity. Moisture content remains limited, with PWAT values fluctuating between 1.70 and 1.75 inches, which aligns closely with climatological normals. These conditions will continue to support mostly stable weather, with only isolated to scattered afternoon showers developing across interior and western Puerto Rico due to local sea breeze convergence and orographic effects. Thunderstorm activity is expected to remain limited because of the weak instability and capping aloft. Across the U.S. Virgin Islands, stable and dry conditions will dominate, with only a few brief and shallow showers possible in the early morning hours. By Saturday into Sunday, conditions turn more stable, as shown by the 250 MB with the presence of a mid to upper-level ridge. This feature will provide stable and drier conditions aloft and warmer temperatures at 500 MB, rounding from -7 to -6 Celsius degrees. Although upper-level conditions will significantly improve, PWAT water values will rise slightly from 1.70 to 1.90 inches. The available moisture will support more favorable conditions for afternoon shower development. Although this increase in moisture may lead to more frequent afternoon showers, particularly across the northwestern and interior portions of Puerto Rico, the lack of significant instability aloft will limit the intensity and vertical growth of any convection. Rainfall accumulations are expected to be light to moderate at most. The U.S. Virgin Islands may experience a slight increase in early morning or overnight showers, but no major rainfall or thunderstorm activity is anticipated. Overall, conditions will trend toward slightly wetter afternoons while still being influenced by stable upper-level conditions. .LONG TERM...Monday through Friday... The long-term period begins with a strengthening surface high over the central Atlantic, which will tighten the local pressure gradient and lead to increasing trade winds from Monday through at least Wednesday. At the same time, precipitable water values are expected to remain near seasonal normals (around 1.6 to 1.8 inches), supporting typical afternoon shower and thunderstorm development across the interior and western sections of Puerto Rico. Eastern Puerto Rico and the US Virgin Islands will likely experience brief, trade wind-driven showers during the late night and early morning hours. During the second half of the workweek, a developing low-pressure system over the western Atlantic will introduce changes to the overall pattern. As it deepens and moves eastward, it will increase moisture transport into the region while weakening the trade wind inversion and enhancing upper-level support. PWAT values could rise above 1.8 inches, allowing a more humid and unstable environment. This evolving setup will favor more widespread and intense convection Thursday and Friday, with showers becoming deeper and more persistent. We encourage people to stay informed with the latest updates. && .AVIATION... (06Z) VCSH to SHRA will persist along TJSJ, TIST until 09/15Z. Winds will continue VRB peaking up at 09/15Z from the E at 15 knots with gusty winds near the showers. SHRA/TSRA will start at around 09/18Z across mountains, inducing lower ceilings and a reduction in VIS. VCSH/SRHA will affect TJBQ at 09/18Z. && .MARINE... A broad surface high pressure extending into the Central Atlantic, in combination with an induced surface trough northeast of the region, will result in light to gentle flow through the end of the workweek. Winds will increase by the end of the weekend as the surface high pressure builds across the Atlantic. Mariners can expect seas between 2 to 4 feet, occasionally 5 feet, for the next several days. Occasional thunderstorms are likely across the regional waters, especially in the afternoon, resulting in dangerous conditions for mariners. && .BEACH FORECAST... Beachgoers can expect a moderate risk of rip currents along the northwestern coastal areas of Puerto Rico, while the rest of the local beaches should experience a low risk throughout the workweek. However, life- threatening rip currents often occur near groins, jetties, reefs, and piers. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ MIDNIGHT CREW...MMC
