AFDSJU Area Forecast Discussion National Weather Service San Juan PR 507 AM AST Tue Jan 20 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 507 AM AST Tue Jan 20 2026 * Several small craft advisories remain in effect at least until Thursday night, mostly due to an increase in the surface winds. * Hazardous coastal conditions persist today, with a high risk of rip currents across all north-exposed beaches in Puerto Rico, including Culebra, Vieques, and the U.S. Virgin Islands. * Variable weather conditions will persist today, with periods of sun and passing showers across eastern sections of Puerto Rico and the U.S. Virgin Islands. * A surface disturbance moving westward across the area from Wednesday into Friday will result in deteriorating weather conditions, increasing the potential for showers and isolated thunderstorms. && .Short Term(Today through Thursday)... Issued at 507 AM AST Tue Jan 20 2026 Variable to showery weather persists over the waters and windward areas as breezy easterly winds continue to steer showers into the region. Since midnight, radar estimated rainfall accumulations indicate that at least minimal accumulations fell over northern PR (up to 0.20 in), eastern (up to 0.60 in) PR, Vieques (up to 0.42 in), St. Thomas (0.01 in), St. John (0.01 in) and St. Croix (0.01 in). Similar to yesterday, stations over interior PR reported minimum temperatures in the low to mid 60s. Stations over western and eastern PR have reported lows in the upper 60s while other lower elevation and coastal stations over the islands reported minimum temperatures in the 70s. Patchy fog was also detected over some areas of PR. A surface high over the central to eastern Atlantic, interacting with a frontal boundary over the western Atlantic, will promote breezy to windy easterly flow for most of the period, with more ENE winds by Wednesday and ENE to ESE winds on Thursday. 925 mb winds are expected to remain above normal through at least Wednesday, supporting windy and gusty surface flow. Wednesday is forecast to be the windiest day, with sustained winds in the low to mid 20s possible with higher gusts and sea breeze variations, particularly over windward coastal areas of the islands. Unsecured outdoor items could blow around or be damaged. As a surface trough veers and backs surface flow on Thursday, conditions should be more breezy with 925 mb wind speeds at high end normal values. Unsecured items could still blow around. Current satellite derived precipitable water (PWAT) values indicate a plume with high end normal values (around 1.45 in) moving over the region. With ridging over the area already eroding, instability aloft will gradually increase during the period, evidenced by cooler 500 mb temperatures and steeper lapse rates. The frequency of showers will also gradually increase as an upper-level trough (TUTT) is east of the region. Current model guidance indicates PWAT possibly at around 1.7 in over western Puerto Rico this afternoon due to convective showers and then more seasonal PWAT values on Wednesday, with Wednesday afternoon convection over W-SW PR under the more ENE winds. The fast moving nature of these showers will serve to limit rainfall accumulations, these showers can still promote localized ponding of water over roadways, urban, and poorly drained areas. PWAT values however sharply increase to above normal values late Wednesday and Thursday with model guidance suggesting up to 1.9 inches as a surface trough/disturbance moves over the region, with available moisture reaching the mid levels resulting in above normal 850 to 500 mb relative humidity. This will all further increase shower frequency, aid in afternoon convective formation and sustain a limited flooding risk. Isolated t-storms are possible late Wednesday to Thursday, particularly over the waters during the overnight to morning hours and with stronger afternoon convection over interior to western PR. 925 mb temperatures will be normal to slightly above normal values for this time of the year. && .Long Term(Friday through Tuesday)... Issued at 507 AM AST Tue Jan 20 2026 Some changes were introduced to the long-term forecast. For Friday, surface conditions will remain unsettled as a surface disturbance moves across the area, inducing instability and plenty of moisture. Therefore, the forecast calls for a pattern with an increase in the frequency of isolated to scattered showers, especially in the morning and evening hours across eastern sections of Puerto Rico, followed by afternoon showers along the western interior. Model guidance suggests precipitable water values fluctuating between 1.6 and 1.9 inches, slightly above climatological normals. When combined with colder temperatures at 500 mb, these conditions may support the development of one or two isolated thunderstorms with the strongest shower activity. Although showers might result in some hazardous conditions, no rainfall threat is forecast due to the breezy conditions resulting in fast-moving showers across the area. Some moisture will remain across the area from early Saturday and spread during the day; therefore, in contrast to yesterday, Saturday looks more showery with isolated to scattered showers. Weather conditions will improve by late Saturday into Sunday as the disturbance moves out of the region and a drier air mass filters into the local islands. At the surface, a broad high- pressure system extending across the Atlantic basin will promote mostly easterly winds across the area. At the mid to upper levels, subsidence will inhibit widespread shower development; however, local effects may still support brief isolated to moderate showers, with no flooding threat expected each day. On late Monday into Tuesday, surface conditions will change as winds begin to veer in response to a pre-frontal trough moving southward near northern Hispaniola. Winds will turn more northeasterly, resulting in a more advective pattern and slightly cooler temperatures, particularly during the morning and nighttime hours. && .AVIATION... (06Z TAFS) Issued at 507 AM AST Tue Jan 20 2026 Mainly VFR conditions will prevail. Winds at the terminals will continue to 12 knots with higher gusts through 20/13Z. After 20/13Z E winds at up to 15 to 20 knots with gusts up to around 23 to 30 kts, as well as sea breeze variations and local effects. Winds decreasing to up to around 13 kts with higher gusts after 20/23Z. SHRA/VCSH will continue at the terminals, briefly reducing VIS and CIGS. && .MARINE... Issued at 507 AM AST Tue Jan 20 2026 A broad surface high pressure extending from the Central Atlantic into the Caribbean will continue to maintain a tight pressure gradient, producing moderate to locally fresh east winds. Therefore, wind-driven seas are forecast for the rest of the workweek, resulting in choppy to hazardous marine conditions for small craft operators. Therefore, several Small Craft Advisories remain in effect for most of the local exposed and offshore waters for the Atlantic and Caribbean, including the local passages. Improving marine conditions are forecast for the upcoming weekend. Mariners should exercise caution, particularly across the Atlantic waters and passages. && .BEACH FORECAST... Issued at 507 AM AST Tue Jan 20 2026 A high risk of rip currents remains in effect across the northern, exposed coastal areas of Puerto Rico, including Culebra, Vieques, and the U.S. Virgin Islands, due to hazardous conditions with breaking waves up to 7 feet. On Wednesday and into the rest of the week, coastal conditions might improve in some areas; however, an increase in surface winds from the east will induce choppy seas, resulting in localized hazards. Residents and visitors are urged to continue following the warning flag system and to favor beaches with lower rip current risk, such as those along Puerto Rico`s western and southern coasts. For the western and southern coastal areas, where the risk remains moderate, beachgoers can expect breezy to locally windy conditions to continue, which may still result in unsecured objects being blown around, particularly in the most exposed locations. Beachgoers should remain cautious both in and near the water until conditions improve further. For localized, up-to-date risk levels, visit weather.gov/beach/sju. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through late tonight for PRZ001-002-005- 008-012. VI...High Rip Current Risk through late tonight for VIZ001-002. AM...Small Craft Advisory until midnight AST Wednesday night for AMZ711-712-716-723-726-733. Small Craft Advisory from 6 PM this evening to midnight AST Wednesday night for AMZ741. && $$