AFDSJU Area Forecast Discussion...CORRECTED National Weather Service San Juan PR 644 AM AST Mon Dec 22 2025 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 530 AM AST Mon Dec 22 2025 * Cloudiness with passing showers, followed by a 50-70 percent chance of afternoon showers across western and southwestern Puerto Rico. Overnight, passing showers (40-50 percent) are expected across the U.S. Virgin Islands and windward Puerto Rico, with little to none flooding impacts. * A break in significant hazardous marine and coastal conditions is expected through Tuesday morning. However, conditions are forecast to become hazardous again by midweek with the arrival of another swell. * Increasing moisture and an upper-level trough will raise the potential for more widespread and heavier rainfall beginning Tuesday afternoon into midweek. There is moderate to high confidence in periods of locally heavy rain that could lead to localized flooding and brief gusty winds. && .Short Term(Today through Wednesday)... Issued at 530 AM AST Mon Dec 22 2025 Overnight, partly cloudy skies prevailed across the region, with periods of frequent showers affecting the U.S. Virgin Islands, as well as northern and eastern Puerto Rico, as a weak induced surface trough moved through the area. Despite these showers, rainfall accumulations generally remained below 0.55 inches over land as the heaviest activity stayed over the waters, limiting flooding impacts. Overnight temperatures fell into the 60s across higher elevations and the 70s in urban and coastal areas. Winds were mainly from the northeast at 6-10 knots, briefly increasing near areas of heavier shower activity. Today through Tuesday, there is a moderate to high probability of partly cloudy conditions during the morning and early afternoon hours. As daytime heating increases, there is a 50-70 percent chance of shower development across western and southwestern Puerto Rico, which could result in brief periods of moderate rainfall and localized ponding of water. During the overnight hours, passing showers are likely (40-50 percent) across the U.S. Virgin Islands and windward sections of Puerto Rico, with generally minor flooding impacts. Moisture levels are expected to temporarily increase to near or slightly above normal on Tuesday afternoon as a frontal boundary approaches from the Atlantic waters. At the same time, an upper- level trough will introduce colder-than-normal temperatures near the 500 mb level through midweek. This pattern increases the potential for deep and unstable rainfall activity particularly heading into midweek. There is a moderate to high confidence. The primary impacts during this period would include localized flooding and brief gusty winds. && .Long Term(Thursday through Monday)... Issued at 530 AM AST Mon Dec 22 2025 Current model guidance suggest precipitable water (PWAT) values of around 1.4 inches to start the period. A series of mid to upper level troughs will move north of the region through the Friday, while a cold front approaches and likely moves over the region on Thursday (Christmas Day). Although they start an upward trend, instability is evident as 500 mb temperatures will still be below normal on Thursday at -10 to -8 degrees Celsius. A limited flooding risk will be present for most of the region, as the frontal boundary moves over the region, resulting in showers and possible isolated t-storms under north-northeast steering flow. Model guidance has been fairly consistent with each run regarding the approach of these features. With uncertainty remaining in the exact impacts across Puerto Rico and the U.S. Virgin Islands. As drier air behind the front will promote improved weather conditions with a cooling trend continuing Friday through Monday, 925 mb temperatures are forecast to be below normal for this period. Lows are forecast in the 50s to low 60s across higher elevations of PR, in the upper 60s to mid 70s across lower elevations of PR, and in the low to mid 70s across the USVI. Highs are forecast in the around the mid 80s across lower elevations of the islands, with isolated/urban areas a bit higher. Although PWAT values are forecast at around to below an inch, isolated patches of moisture will reach the area and promote passing showers from time to time. && .AVIATION... (06Z TAFS) Issued at 530 AM AST Mon Dec 22 2025 VFR conditions are expected to prevail across most terminals through the period. However, SHRA may intermittently affect TJSJ, TIST, and TISX, especially during the overnight and early morning hours. TJPS could experience VCSH after 1217Z. Winds will remain from the NE at 6-10 knots, with occasional higher gusts near passing showers. && .MARINE... Issued at 530 AM AST Mon Dec 22 2025 A building surface high over the western Atlantic and a frontal low over the north-central Atlantic, will promote east to northeast winds to start the period. A series of surface highs and frontal lows will continue moving into the Atlantic during the period, resulting in moderate to locally fresh east to northeast winds through at least Wednesday, when they back to become more north-northeasterly. A fading northeasterly swell will promote seas up to 6 feet for the offshore Atlantic Waters today. Marine conditions will continue briefly improving tonight into early Tuesday. A northerly long-period swell, from one of the above mentioned frontal lows, will once again result in hazardous marine conditions for small craft at the offshore Atlantic Waters by Tuesday afternoon. Hazardous conditions will continue through the workweek as seas build to 6 to 9 feet and spread to the nearshore Atlantic Waters and local Passages. && .BEACH FORECAST... Issued at 530 AM AST Mon Dec 22 2025 A fading northeasterly swell will result in mostly a moderate risk of rip currents to start the workweek, across the northern and eastern coastline of Puerto Rico, Culebra and Vieques, as well as for beaches of the USVI. Coastal conditions will continue gradually improving through Tuesday night; however, another northerly long-period swell will increase the risk up to high again by Wednesday through probably the rest of the week. Please continue to monitor the forecast for updates as conditions evolve. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...Small Craft Advisory from noon Tuesday to midnight AST Thursday night for AMZ711. && $$