AFDSJU Area Forecast Discussion National Weather Service San Juan PR 300 PM AST Mon Apr 6 2026 ...New SHORT TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Updated at 300 PM AST Mon Apr 6 2026 * Flooding risk will remain elevated through midweek. Afternoon and nighttime showers and isolated thunderstorms may lead to urban and small stream flooding, with isolated flash flooding possible across Puerto Rico and the US Virgin Islands. * Hazardous marine and coastal conditions will continue this evening, resulting in choppy to rough seas and life-threatening rip currents. The Rip Current Statement remains in effect through this evening, while the Small Craft Advisory was extended through late tonight. * Breezy to locally windy conditions will persist through midweek, unsecured items may blow around. * Warmer conditions are expected from Tuesday through Thursday, increasing heat risk and resulting in heat-related impacts, especially for sensitive individuals outdoors without adequate hydration or cooling.&& .Short Term(This evening through Wednesday)... Issued at 300 PM AST Mon Apr 6 2026 A strong surface high over the central Atlantic will gradually move westward during the period as lows move enter the western Atlantic and another strong high moves over the western Atlantic by around midweek. This will result in breezy ESE flow throughout most of the period as 925 mb wind speeds stays at mainly high end normal values. Precipitable water (PWAT) values will be at high- end normal to above normal (above 1.75 in) values for this time of the year throughout most of the period as moisture from the Caribbean continues to be steered over the region. The mid-level relative humidity is forecast to persist at normal to above-normal levels. Atmospheric instability will be present due to mid- to upper-level short wave troughs and a jet streak near the region. Galvez-Davison Index (GDI) values are forecast at 30 to 40 tomorrow and Wednesday, also suggesting the potential for t-storm development. Despite expectations of periods with minimal or no rainfall, portions of the islands will experience daily rounds of moderate to locally heavy showers due to available moisture, diurnal heating, local sea breeze convergence, and orographic effects all playing a role. These heavier showers are most likely during the overnight and morning hours across windward sectors and, shifting to the western and northern portions of PR, as well as downwind of El Yunque, the USVI, Vieques, and Culebra each afternoon along with possible isolated t-storms. This will result in a limited to elevated risk of flooding each day. Forecast impacts include reduced visibility, ponding of water on roads and in poorly drained areas, and flooding in urban areas, roads, small streams, and washes. Tonight, afternoon convection will gradually dissipate or move offshore, while high res model guidance suggests that trade wind showers will be steered toward windward sectors (east/south) of the islands. Showers and t-storms can also linger over the offshore waters as isolated systems or as MCSs. Under the ESE flow, 925 mb temperatures are forecast to be near to above normal. This pattern suggests a limited heat risk is possible, Tuesday and Wednesday. && .Long Term(Thursday through next Sunday)... Issued at 300 AM AST Mon Apr 6 2026 A gradual transition toward a slightly more stable pattern is now expected to begin earlier than indicated in previous model cycles, particularly starting Thursday. Mid-level moisture is forecast to decrease, with 700500 mb relative humidity values dropping closer to near-normal levels. While the overall pattern will remain somewhat moist, this trend suggests a modest reduction in the depth of available moisture compared to earlier in the week. Despite this drying trend, a generally unsettled pattern will persist. Residual troughing aloft and lingering moisture will continue to support periods of cloudiness and shower activity, especially during the afternoon hours due to diurnal heating and local effects. However, coverage and intensity of convection should be somewhat lower than in previous days. Winds will remain from the east-southeast, continuing to advect moisture into the region, although not as efficiently as earlier in the week. Saturated soils and elevated streamflows from rainfall earlier in the week will continue to support an elevated flooding risk, although more localized in nature, particularly across interior and western Puerto Rico during the afternoon hours. By Friday into Saturday, conditions are expected to become relatively more stable, with mid-level drying limiting vertical development of convection. This should result in more isolated to scattered shower activity, primarily over western and interior Puerto Rico during the afternoon, with more limited impacts elsewhere. By the end of the forecast period and beyond, model guidance suggests a return to a wetter and more unstable pattern as another deep-layered trough approaches the region and combines with well- above-normal moisture. However, this portion of the forecast remains in the longer range and carries higher uncertainty. Stay tuned for further updates as confidence improves. && .AVIATION... (18Z TAFS) Issued at 300 PM AST Mon Apr 6 2026 Mainly VFR conditions with brief MVFR conditions possible. ESE winds at 10 to 20 kts will continue with higher gusts and sea breeze variations, especially near SHRA. -SHRA/VCTS can continue to develop over the interior and over the waters and steered northward. Winds decreasing after 06/23Z, with land breeze variations and locally higher near -SHRA/possible VCTS that will be steered towards E and S sites. Winds increasing again from the ESE at 10 to 20 kts with higher gusts after 07/13Z. && .MARINE... Issued at 300 PM AST Mon Apr 6 2026 Hazardous marine conditions will persist through at least early tomorrow as a strong high-pressure system over the Atlantic maintains moderate to fresh southeasterly winds. The latest altimeter scans show seas between 6 and 8 feet across local Atlantic waters, while scatterometers show winds between 15 and 20 knots and localized areas between 20 and 25 knots. Therefore, expect confused seas, particularly across Atlantic waters and local passages throughout the day. Small Craft Advisories were extended for the Atlantic offshore waters and the Anegada Passage through midnight and late tonight, respectively. Conditions are expected to gradually improve tomorrow, Tuesday , with seas subsiding to around 5 feet in the Atlantic and up to 4 feet in the Caribbean. While trade wind showers continue to move across the region, isolated to scattered thunderstorms are likely this afternoon, especially over coastal waters near western, northern, and northwestern Puerto Rico. Shower and thunderstorm coverage may increase later this week due to a series of troughs approaching the region. Based on the latest guidance, marine conditions will deteriorate by Friday as a series of swells spread across the local Atlantic waters and passages, bringing back choppy to rough seas that may persist over the next weekend. Small craft operators are encouraged to stay informed of the latest updates regarding the marine forecast. && .BEACH FORECAST... Issued at 300 PM AST Mon Apr 6 2026 The beach forecast remains on track. The latest nearshore buoys reported seas between 3 and 5 feet, with the Arecibo buoy detecting a swell period of around 10 seconds. Adding the bathymetry component, breaking waves should range between 7 and 9 feet. Therefore, theres a high chance of life-threatening rip currents still present along the northern and eastern beaches of Puerto Rico, Culebra, and St. Croix in the U.S. Virgin Islands. Hence, the Rip Current Statement continues over the aforementioned beaches through this evening. Beachgoers are urged to avoid going into the water, walking over rocks or jetties, as life-threatening rip currents are very likely. Heed the advice of lifeguards, beach patrol flags, and signs. For the rest of the beaches, the risk should remain low to moderate, but beachgoers should exercise caution when visiting a beach under moderate risk, as life-threatening rip currents are possible. Although conditions should gradually improve tonight, they may deteriorate by the end of the week due to a series of swells arriving and spreading across local Atlantic waters and passages. Residents and visitors are encouraged to check the latest beach conditions before heading to the beach at weather.gov/sju and https://www.weather.gov/beach/forecast?site=sju&action=. In addition to the life-threatening rip currents, beachgoers visiting beaches over western and northwestern Puerto Rico in the afternoons should remain weather alert due to the development of isolated thunderstorms. Hazards include gusty winds, reduced visibility due to heavy rainfall, and lightning. Seek shelter inside a building whenever you hear lightning. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk until 6 PM AST this evening for PRZ001-002- 005-008-012. VI...High Rip Current Risk until 6 PM AST this evening for VIZ002. AM...Small Craft Advisory until 6 AM AST Tuesday for AMZ711. Small Craft Advisory until midnight AST tonight for AMZ723. && $$