Hurricane Season runs from June 1-November 30
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Area Forecast Discussion (AFD)
064 FXCA62 TJSJ 051700 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 100 PM AST Mon Oct 5 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 100 PM AST Mon Oct 5 2026 - Locally heavy rainfall and flooding will remain the main concern through Thursday, with frequent lightning possible each day. - Heat will remain a concern through the week, particularly Tuesday and again Thursday into the weekend. - A tropical wave will bring a wetter pattern late Tuesday night into Thursday. - A moderate risk of rip currents is expected Tuesday through Thursday along portions of the north- and east-facing beaches, with a lower risk returning Friday into the weekend. && .Short Term(This afternoon through Wednesday)... Issued at 100 PM AST Mon Oct 5 2026 Lingering showers and isolated thunderstorms from this afternoon may continue into the early evening, mainly across the northwestern quadrant of Puerto Rico, before gradually diminishing. Even as rainfall coverage decreases, excessive runoff, ponding, elevated streams or rivers, and lingering flooding concerns may persist for several hours in areas that received heavier rainfall. Thereafter, conditions should transition back toward a more typical trade-wind pattern overnight, with passing showers favoring the U.S. Virgin Islands and eastern Puerto Rico. Winds will become light and variable, becoming calm at times. Minimum temperatures will range from around 80 degrees across the islands and coastal areas to the lower 60s across the higher elevations of Puerto Rico. Tuesday will remain strongly influenced by daytime heating and local effects. Above-normal 925 mb temperatures will support another period of elevated heat risk, while above-normal 500 mb temperatures and a departing upper-level trough should still allow deep convective development where sufficient heating and local convergence occur. Weak steering flow will favor slow-moving showers and thunderstorms across the interior and western to northwestern portions of Puerto Rico during the afternoon. A relative lull is expected Tuesday evening into early Wednesday, likely associated with subsidence ahead of the approaching tropical wave. By late Tuesday night, the wave`s moisture field, with precipitable water values near 1.90 inches or higher, will begin reaching the U.S. Virgin Islands, then eastern Puerto Rico by Wednesday evening, before spreading farther west through Wednesday night and supporting a wetter pattern across the region. The main hazards through the period will be locally heavy rainfall and flooding, excessive heat, and lightning. Flooding concerns may linger into this evening where heavier rainfall occurred, with additional localized flooding possible Tuesday afternoon and a broader increase in rainfall coverage expected by Wednesday as tropical moisture spreads across the region. Heat will remain a concern during the late morning and early afternoon hours, while thunderstorms may produce frequent lightning and locally heavy downpours. Overall, the pattern will favor a daily transition from heat to locally heavy showers and thunderstorms, with wetter conditions becoming more established by midweek. && .Long Term(Thursday through next Monday)... Issued at 100 PM AST Mon Oct 5 2026 Moisture associated with a departing tropical wave will linger across the local region on Thursday. Another active afternoon is forecast, with scattered to numerous showers and isolated thunderstorms across the interior, western, and northwestern sections of Puerto Rico. Steering flow will remain predominantly southeasterly before turning easterly. An elevated flood threat will persist across interior and western Puerto Rico, while a limited flood threat continues for eastern Puerto Rico and the U.S. Virgin Islands as passing showers continue to affect those areas Thursday into Thursday night. Some of the activity may be accompanied by gusty winds. A transition to drier conditions is forecast on Friday as a mid-level ridge builds just north of the region. This will support mid-level warming, decreased lapse rates, and drier air aloft, making conditions less favorable for widespread convection. The 500 mb temperatures are forecast to be around -4 degrees Celsius, which is near two standard deviations above normal for this time. Nevertheless, diurnal convection driven by daytime heating and local effects will still support afternoon showers across interior to western Puerto Rico. On Saturday, similar conditions aloft will generally persist, though a slight increase in moisture will bring typical seasonal passing showers over windward areas during the overnight and morning hours, followed by afternoon convection across interior to western portions of Puerto Rico. By Sunday, the mid-level ridge retreats as a mid- to upper-level trough approaches the region from the east. Cooling in the mid-troposphere and increasing convective potential will support more active afternoon convection across the islands. Rain streamers remain possible downwind from El Yunque, Vieques, Culebra, and the U.S. Virgin Islands throughout the period. Additionally, an elevated heat threat will persist each day, and heat advisories could be issued. Continue to monitor for any updates on the forecast. && .AVIATION... (12Z TAFS) Issued at 100 PM AST Mon Oct 5 2026 SHRA/TSRA will continue across interior and W-NW PR thru 05/22-23Z, with brief MVFR/IFR CIG/VSBY possible at TJBQ and in the VC of TJPS/TJSJ. Aftn convection may also produce BKN-OVC CIGs around FL015-025, along with locally reduced VSBY, mtn obsc, LTG, and gusty/VRB winds nr stronger cells. Activity will diminish this eve, followed by mainly VCSH overnight at TJSJ/USVI. ESE winds 10-15 kt with locally higher gusts thru late aftn, becoming light/VRB overnight. Winds increase again aft 06/13Z, with another round of SHRA/TSRA expected over interior and W-NW PR aft 06/17Z. && .MARINE... Issued at 100 PM AST Mon Oct 5 2026 As a frontal low advances across the western Atlantic, surface high pressure will shift eastward, relaxing the local pressure gradient and resulting in light to moderate east to east-southeast winds. Winds are expected to strengthen slightly Tuesday into Wednesday as another surface high builds over the western Atlantic. Seas will range from 3 to 4 feet, occasionally higher. A tropical wave will move mainly across the Caribbean waters late Wednesday into Thursday, increasing shower and thunderstorm activity. && .BEACH FORECAST... Issued at 100 PM AST Mon Oct 5 2026 For this afternoon and tonight, a low risk of rip currents will dominate the local beaches. Even with a low risk, life-threatening rip currents can still occur near groins, jetties, reefs, and piers. A moderate risk of rip currents will return Tuesday and persist at least through late Thursday afternoon along the north- and east-facing beaches of Puerto Rico, as well as beaches of the U.S. Virgin Islands, Vieques, and Culebra. A low risk is expected to return Thursday night and continue through the weekend. A daily afternoon lightning risk will also affect local beaches, primarily across northern and western Puerto Rico, as well as eastern Puerto Rico where streamers develop downwind from the U.S. Virgin Islands, Vieques, and Culebra. A tropical wave will increase shower and thunderstorm activity as it moves mainly across the Caribbean waters late Wednesday into Thursday. High heat indices will persist during the late morning and afternoon, especially along exposed coastal areas. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...Heat Advisory until 3 PM AST this afternoon for PRZ001>013. VI...Heat Advisory until 3 PM AST this afternoon for VIZ001-002. AM...None. && $$ .EVE...MMC/KML .MID...YZR/RVM .DAY...ICP/MRR/JCP
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