FXCA62 TJSJ 150729 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 329 AM AST Wed Apr 15 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Updated at 327 AM AST Wed Apr 15 2026 * A high risk of rip currents will persist along the northern coast of Puerto Rico due to ongoing northerly swell activity, resulting in hazardous marine and coastal conditions. * Variable weather conditions are expected today, characterized by periods of sunshine and passing morning showers, followed by the development of afternoon convection across portions of the islands driven by local and diurnal effects. * Increasing instability from Thursday into Friday, associated with an amplifying upper-level trough and enhanced moisture availability, will promote a more active weather pattern with widespread afternoon convective development across Puerto Rico. * Southeasterly low-level winds will promote slightly above- normal temperatures, particularly across coastal and urban areas. && .Short Term(Today through Friday)... Issued at 327 AM AST Wed Apr 15 2026 A relatively tranquil weather pattern prevailed during the overnight hours, with mostly clear skies as earlier upper-level cloudiness and showers shifted eastward and remained over the surrounding waters or moved out of the forecast area. As a result, the islands experienced clear to partly cloudy conditions. Some showers and isolated thunderstorms lingered across the southeastern quadrant of the CWA, mainly affecting the Caribbean waters, with the strongest activity observed around midnight. Overnight temperatures ranged from the low to mid 70s across coastal areas, with slightly cooler and more refreshing conditions across the higher elevations. Winds remained light and variable at around 5 mph or less. An unstable and moist weather pattern is expected today across Puerto Rico and the U.S. Virgin Islands. Atmospheric conditions will support the development of showers and a few thunderstorms, aided by abundant low-level moisture and the presence of a surface trough across the region. In addition, a cut-off low aloft is enhancing upper-level westerly winds (zonal flow), which may help some storms become more organized and produce locally strong wind gusts. At the low to mid levels (1000–700 mb), winds will range from the southeast to the south due to the surface trough, with its axis over Hispaniola, and a mid-level low positioned just west of the forecast area. This wind pattern is favorable for the development of showers across northeastern Puerto Rico, extending into north-central areas. Given the mostly clear conditions early in the day, local and diurnal effects are expected to develop early, potentially leading to convection by mid-morning across northeastern Puerto Rico, including areas near El Yunque. Showers will mainly affect northeastern areas during the morning, followed by activity developing over the northwestern portions and drifting into northwestern to north-central areas, as suggested by high-resolution models. Therefore, there is a moderate to high confidence that the bulk of the showers will be between 12 PM to 6 PM across northwestern sections, where the heaviest showers can result in flooding problems in urban areas especially. For late tonight into Thursday, conditions will become slightly more favorable for instability as an upper-level trough amplifies just west of the region, placing the divergent side of the system over much of the eastern portion of the CWA. This setup will enhance upper-level diffluence and support increased upward motion, leading to a more favorable environment for convective development. This pattern is expected to persist through the rest of the period, as another cut-off low establishes over Hispaniola and stalls, maintaining a diffluent pattern across the area. Considering this overall setup, a wetter pattern is likely from Thursday into Friday. Global model guidance and high-resolution models suggest active afternoons driven by local and diurnal effects, supported by limited early cloud cover. For Thursday, an increase in low-level winds is forecast, as indicated by 925 mb wind speeds, resulting in faster-moving showers that may limit rainfall accumulations. Additionally, precipitable water values are expected to remain around the 75th percentile on both days, supporting periods of rainfall. && .Long Term(Saturday through Wednesday)... Issued at 327 AM AST Wed Apr 15 2026 Variable conditions may persist through the weekend, with a gradual improvement over the first part of the next workweek. Wind pattern will mostly be dominated by a surface high pressure lingering over the Central Atlantic, promoting winds from the E-SE. Another feature that may influence the weather pattern in the deep-layered trough that, according to the latest model guidance, is expected to linger over Hispaniola. From the deterministic guidance of the GFS and ECMWF, it seems that Saturday and Sunday will most likely be the wettest days of the period, with PWAT values lingering between 1.8 and 2.0 inches, wet for this time of the year. Additionally, low to mid level moisture content will remain high (above 60%), while model sounding suggests skinny profiles. Conditions look favorable for convection, as the influence of the trough will maintain slightly cooler than normal mid level temperatures (around -8 degrees Celsius) and a nearby jet with strong winds aloft (around 60 knots), allowing cloud growth and ventilation. With the favorable side of the trough over the CWA, divergence aloft will also increase the chance of deeper convection, particularly over western Puerto Rico and the U.S. Virgin Islands. Hence, for the U.S. Virgin Islands, showers and isolated thunderstorms will likely move occasionally throughout the day, while interior and western Puerto Rico can expect showers and thunderstorms in the afternoon that may persist into the evening. Due to previous rainfall activity, soil saturation, and high river levels, the potential for flooding may increase. Hence, the flooding threat will remain limited to elevated for the aforementioned areas. Besides flooding, expect gusty winds and lightning across these areas. For the rest of the areas, passing showers may move from time to time, though a significant flooding threat is not expected. Weather conditions will gradually improve Monday onwards, as moisture content may decrease and the subsident side of the trough moves over the CWA. Nevertheless, there’s uncertainty between global solutions as GFS continues with a wet pattern (above normal PWAT) while the ECMWF on the side is moving toward a more seasonal to drier pattern. From the latest grand ensemble, there’s variability between them (PWAT difference of half an inch), particularly in the mid to high level moisture content. At the moment, expect a seasonal weather pattern, with isolated showers moving over windward sections in the morning hours, with afternoon convection over interior and western Puerto Rico. Due to the uncertainty, the flood threat will remain limited. && .AVIATION... (06Z TAFS) Issued at 327 AM AST Wed Apr 15 2026 SHRA with VCTS will persist near TISX, while VFR conditions prevail across the remaining TAF sites during the morning hours. Winds will remain light and variable at less than 5 kt, increasing around 15/15Z from the S-SE at 10–15 kt. SHRA and isolated TSRA are expected to impact TJBQ and TJSJ from 15/18Z onward, resulting in reduced CIGS and VIS, with ceilings lowering to FL020–FL050. && .MARINE... Issued at 327 AM AST Wed Apr 15 2026 A surface high pressure system over the eastern to central Atlantic, interacting with a stationary frontal boundary north of the region, will promote light to gentle winds tonight. Pulses of northerly swell spreading across the Atlantic waters will continue to maintain seas up to 6 feet across exposed areas, where small craft should exercise caution over the next several days. Showers and strong thunderstorms will continue across the local waters due to the presence of a frontal system and a trough, creating locally hazardous marine conditions through this afternoon. Winds are expected to become gentle to moderate from the east to east- southeast today through the weekend. && .BEACH FORECAST... Issued at 327 AM AST Wed Apr 15 2026 A High Rip Current Risk is in effect for the northern exposed beaches of Puerto Rico and Culebra through this afternoon due to the arrival of pulses of a weak northerly swell. Beachgoers are urged to heed the advice of lifeguards, as well as beach patrol flags and posted signs. Elsewhere, a low to moderate risk of rip currents will persists. Increasing winds from midweek onward could lead to a moderate risk of rip currents persisting along north-exposed beaches through at least next Saturday. Residents and visitors are encouraged to exercise caution, especially along exposed coasts. For more specific area details, refer to weather.gov/beach/sju. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through this afternoon for PRZ001-002-005- 008-010-012. VI...None. AM...None. && $$ SHORT TERM...LIS LONG TERM....ICP AVIATION...LIS