AFDSJU Area Forecast Discussion National Weather Service San Juan PR 442 AM AST Fri Jan 9 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 418 AM AST Fri Jan 9 2026 * Showers and localized flooding risk this afternoon: Afternoon showers are expected across western Puerto Rico, with brief, heavy rainfall that may cause ponding in poorly drained and urban areas. * Pleasant overnight temperatures: Below-normal to seasonably cool minimum temperatures are expected across Puerto Rico and the US Virgin Islands overnight and early morning. * Moderate rip current risk: Rip currents are possible along the Atlantic-facing beaches of Puerto Rico, Culebra, St Thomas, St John, and the north and east-facing beaches in St Croix. Hazardous swimming conditions are possible at exposed beaches. && .Short Term(Today through Sunday)... Issued at 418 AM AST Fri Jan 9 2026 Overnight, Puerto Rico and the U.S. Virgin Islands experienced calm weather under clear to partly cloudy skies. While passing showers were observed across the region, most remained over the Atlantic and Caribbean waters. A few reached portions of St. Croix, resulting in minimal rainfall accumulation. Overnight lows ranged from the upper 60s to low 70s across lower elevations, while higher elevations in Puerto Rico observed temperatures in the upper 50s and low 60s. Winds remained light and variable throughout the night. A weak surface trough lingering northeast of the region will continue to bring trade wind showers into the islands. Recent precipitable water (PWAT) suggests moisture levels remaining near or slightly below seasonal levels (1.20 to 1.45 inches) through early next week. Today, passing trade wind showers will continue to affect windward sections of the islands. During the afternoon, limited moisture combined with daytime heating and sea breeze convergence will likely trigger showers across the interior and western to southwestern Puerto Rico. This weather pattern is expected to persist through Saturday. By Sunday, a mid-to-upper-level ridge will build over the southwestern Atlantic, while a Tropical Upper Tropospheric Trough (TUTT) begins to develop over the central Atlantic, northeast of the Lesser Antilles. Consequently, patches of low-level moisture will continue to drift over the islands, bringing morning showers and potential afternoon convection over interior and southwestern Puerto Rico. As temperatures at the 500 mb level drop to approximately - 10C, isolated thunderstorms cannot be ruled out during the afternoon hours. Temperatures at the 925 mb level are expected to remain near climatological normals. Daytime highs will reach the low to mid-80s across lower elevations and the mid to upper 70s across the higher elevations of Puerto Rico. && .Long Term(Monday through Friday)... Issued at 418 AM AST Fri Jan 9 2026 Looking ahead into early next week, a deep-layer mid-to-upper- level trough is forecast to amplify over the Atlantic Ocean east of the northeast Caribbean on Monday. This feature will migrate further into the Central Atlantic by Tuesday or Wednesday. As it moves, it will generate surface disturbances that the prevailing trade winds will advect into Puerto Rico and the US Virgin Islands, resulting in periods of shower activity. Simultaneously, a mid-to-upper-level ridge will build over the Northeast Caribbean. This feature is expected to limit the vertical development of showers and promote subsidence aloft (sinking air) due to the presence of a dry air mass. Model discrepancies exist around Thursday, January 15, regarding the strength of the ridge versus the influence of a secondary trough. ECMWF 09/00z suggests a mid-to-upper-level ridge holding firm over the region, maintaining suppressed convective activity. GFS 09/00z proposes a mid-to-upper-level trough swinging by the area, which would displace the ridge and provide more favorable upper-level dynamics for precipitation. However, the GFS also indicates an increase in mid-to-upper-level cloud cover, which may inhibit widespread vertical development despite the favorable dynamics. Given the aforementioned weather pattern, residents and visitors in PR and the USVI can anticipate brief periods of passing showers, especially in the evening and early morning hours in windward locations and in the afternoon in leeward locations (western and interior PR). && .AVIATION... (06Z TAFS) Issued at 418 AM AST Fri Jan 9 2026 Mainly VFR conds are expected to prevail across all terminals during the forecast period. Brief VCSH/SHRA are expected this morning at TJSJ/TIST/TISX aft 09/13Z-14Z. Locally induced SHRA over central and southwestern PR, may cause brief tempo MVFR cigs at TJPS btw 09/17Z- 21Z. E-ENE winds btw 08 to 14 kt with sea breeze variations and higher gusts expected aft 09/13z. && .MARINE... Issued at 418 AM AST Fri Jan 9 2026 A long-period northeasterly swell continues to spread across the Atlantic waters and local Caribbean passages, gradually subsiding today. A surface high pressure over the western Atlantic, along with weak induced surface troughs northeast of the region, will promote moderate east to northeast trade winds today through the the rest of the week. && .BEACH FORECAST... Issued at 418 AM AST Fri Jan 9 2026 A moderate risk of rip currents is in place along the Atlantic- facing beaches of Puerto Rico, St. Thomas, and St. John, as well as the north- and east-facing beaches of St. Croix. Under these conditions, rip currents are possible, particularly at exposed beaches, and can pose a hazard to swimmers. Beachgoers are urged to exercise caution, remain near lifeguarded areas when available, and avoid entering the water if conditions appear unsafe. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$