AFDSJU Area Forecast Discussion National Weather Service San Juan PR 305 AM AST Sun Mar 22 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 300 AM AST Sun Mar 22 2026 * A more unsettled weather pattern is forecast for today into Monday with the arrival of a frontal boundary and an induced surface trough. There is an elevated flood risk today across the eastern interior, where urban and low-lying areas are expected to flood, along with rapid rises in small streams. * There is a limited lightning threat across the area as the trough and the frontal boundary pass across the CWA. * There is a high risk of rip current across the northern coastal areas from Mayagez to Fajardo, and a small craft advisory across the offshore Atlantic waters. * A more variable weather pattern is forecast from Tuesday onwards when surface winds return from the east-northeast. * A low to moderate risk of rip currents exists across the coastal waters of Puerto Rico and the U.S. Virgin Islands. && .Short Term(Today through Tuesday)... Issued at 300 AM AST Sun Mar 22 2026 Deteriorated weather conditions persist across Puerto Rico during the night and into the early hours on Sunday with the arrival of the frontal boundary and the associated pre-frontal trough. Satellite imagery showed a significant increase in cloud coverage from west to east. Shower activity, on the other hand, remained mostly over the local waters as shown by the Doppler Radar. The peak of the showers affected the exposed Atlantic offshore waters and, at 2 AM, moved near the coastal Atlantic waters, reaching the west, north-central, and southeastern coastal areas. Overnight temperatures were in the low 60s across the mountains and in the mid 70s across the coastal areas. Conditions will continue to deteriorate as the day evolves, mainly due to the arrival of the deep moisture field from the frontal system, with precipitable water values up to 2 inches, as shown in satellite-derived imagery. This cloudiness and moisture will continue to spread into the forecast area, enhancing the potential for showers and isolated thunderstorms. Although the more unstable areas of the upper-level trough remain moving well to the north, influence from the deep system reflected at the surface will enhance unstable weather pattern with +2 standard deviation in RH % values between 850 to 500 MB and colder air temperatures at 500 MB from -7 to -8 degrees This pattern will enhance well- structured convection all day, especially across the local waters in the morning and along land areas during the day. An interesting wind pattern will also be present. At the surface, calm to light winds will mostly come from the north-northeast, but at 700 MB, more westerly winds will prevail. Given the expected 0 to 3 km wind pattern, the slow-moving showers will focus in the interior, then drift to the eastern interior and the northeastern quadrant. Therefore, the eastern interior will be the most affected area, with a moderate risk of flooding, including urban flooding in low- lying areas and rapid rises along small streams. Rainfall accumulations will depend entirely on the movement of the showers, and they could range from 1 to 2 inches, with higher amounts in some areas. On Monday, as the upper-level trough and the surface frontal boundary move farther eastward, a transition to a more localized, showery pattern is forecast. At the surface, patches of deep moisture will hold along the eastern part of the CWA, between the Culebra and Vieques municipalities and the U.S. Virgin Islands. This moisture, along with local effects, will allow some pesky passing showers to move in and out of the coastal areas of the aforementioned locations. Additionally, surface winds will remain from the north-northeast at 850 MB and from the west at 700 MB, drifting the showers mostly across eastern PR and the coastal waters. On Tuesday, surface winds veer from the east in response to a surface high-pressure system establishing across the central Atlantic and extending into the Caribbean. Moisture trapped in the local region will continue to lead to cloudy skies and variable weather. && .Long Term(Wednesday through Sunday)... Issued at 300 AM AST Sun Mar 22 2026 Moisture is expected to increase by mid-week as model guidance indicates precipitable water (PW) values rising to between 1.50 and 2.00 inches, near the 75th percentile for this time of year and therefore above normal. A weak mid- to upper-level trough moving through the region, along with a weak surface perturbation, will promote increasing cloud cover and frequent periods of showers. Temperatures at 500 mb are forecast to be near 7 degrees C, suggesting a moderate potential for instability. This could support occasional heavier showers, although widespread organized convection is not anticipated. The enhanced cloud cover will limit daytime heating, keeping high temperatures near typical seasonal values for March. Winds should remain generally light to moderate, with locally higher speeds possible in and near shower activity. These unsettled conditions are expected to persist through the end of the work week. By the weekend, a gradual transition toward a drier airmass is anticipated to filter across the islands, leading to decreasing shower coverage and clear to partly cloudy skies. Despite the drying trend, temperatures should remain relatively comfortable and consistent with March. && .AVIATION... (06Z TAFS) Issued at 300 AM AST Sun Mar 22 2026 Some MVFR to IFR conditions are expected across the PR TAF sites due to the arrival of a frontal boundary. Winds will remain VRB until 22/14Z, then peaking up to 10 knots from the N-NE and at 3 KM from the W. SHRA to TSRA will enhance BKN to OVC ceiling affecting the FL020, FL030 & FL050, and with a reduction of VIS with the strongest showers expected from 22/15Z to 22/21Z. Higher gusts through the day are expected, mostly near the strongest TSRA and SHRA. && .MARINE... Issued at 300 AM AST Sun Mar 22 2026 A frontal boundary approaching the region will bring unsettled marine conditions today, with showers and the potential of thunderstorms increasing across the local waters. A long-period northerly swell will build hazardous seas across the Atlantic waters. Behind the boundary, moderate to locally fresh northerly winds will result in choppy seas, particularly across the Mona Passage and offshore Atlantic waters. A surface high pressure building from the western to central Atlantic will promote northeasterly winds early this week, with increasing wind speeds and seas by midweek. && .BEACH FORECAST... Issued at 300 AM AST Sun Mar 22 2026 Life-threatening rip currents will likely form along the north- facing beaches of PR (from Rincon to Fajardo), with a moderate risk of rip currents across Culebra and the US Virgin Islands. Beachgoers should remain cautious, stay near lifeguards, and avoid entering the water if unsure of conditions.Lower risk conditions are expected along the more protected southern beaches, though caution is still advised. In addition, increasing moisture and instability associated with an approaching frontal boundary will promote showers throughout the day and possibly extend to Monday. Localized impacts, such as reduced visibility and brief gusty winds, may occur near showers, creating sudden hazardous conditions for beachgoers. There is a limited thunderstorm risk, but any storms that develop could produce lightning, posing a danger to those in or near the water. If thunderstorms approach, seek shelter immediately.For additional information and location-specific rip current details, please visit: weather.gov/beach/sju && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk from 6 AM AST this morning through late tonight for PRZ001-002-005-008-010. VI...None. AM...Small Craft Advisory from 6 AM this morning to 6 AM AST Monday for AMZ711. && $$