Hurricane Season runs from June 1-November 30
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Area Forecast Discussion (AFD)
405 FXCA62 TJSJ 220600 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 200 AM AST Thu Oct 22 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 200 AM AST Thu Oct 22 2026 * A wetter pattern today through Saturday will bring more frequent showers and thunderstorms, including nighttime activity. Heavy downpours may cause urban and small-stream flooding, rapid river rises, and isolated flash flooding. Repeated rainfall will also increase the potential for landslides along vulnerable slopes. * A moderate risk of rip currents will persist along exposed northern beaches today. Another northerly swell arriving early Friday will bring a renewed high risk along northern Puerto Rico, with dangerous rip currents potentially continuing through the weekend and into early next week. * Warm and humid conditions will continue, particularly during periods of sunshine. Heat impacts may become more pronounced Sunday and Monday, especially across coastal and urban areas and among individuals sensitive to heat. && .Short Term(Today through Saturday)... Issued at 200 AM AST Thu Oct 22 2026 A transition toward wetter conditions is expected across Puerto Rico and the U.S. Virgin Islands as deeper tropical moisture spreads northward into the northeastern Caribbean. Surface high pressure over the central Atlantic and broad troughing northwest of the region will maintain a generally southeasterly flow, favoring passing showers and isolated thunderstorms over the surrounding waters, the U.S. Virgin Islands, and eastern and southern Puerto Rico during the overnight and morning hours. The latest GFS guidance indicates precipitable water values increasing to around 2.1 to 2.2 inches today, accompanied by a substantial increase in mid-level moisture. During the afternoon, daytime heating, sea-breeze convergence, and local terrain effects will favor scattered to numerous showers and isolated to scattered thunderstorms across interior, northern, and northwestern Puerto Rico. Increasing cloud cover may limit daytime heating in some areas, but sufficient moisture and instability should remain available for locally heavy rainfall. Some activity may persist into the evening. A moist and unsettled pattern will continue Friday and Saturday, with precipitable water values generally remaining near 2.1 to 2.2 inches. Support from the upper-level trough should gradually weaken as heights rise and temperatures aloft warm. Nevertheless, abundant moisture through the lower and middle levels will continue to support showers and thunderstorms. At the surface, a tightening pressure gradient between the Atlantic ridge and low pressure developing northwest of the region will promote a more east-southeasterly flow, with winds increasing Friday. Passing showers will continue to favor windward sectors during the overnight and morning hours, followed by afternoon convection across interior, northern, and western Puerto Rico. Increasing steering winds should help showers move more readily, although repeated rounds of rainfall may still affect the same areas. Additional showers and thunderstorms over the surrounding waters may reach coastal areas during the evening and overnight hours. The primary concern through the short-term period will be locally heavy rainfall capable of producing urban and small-stream flooding, rapid river rises, and isolated flash flooding, particularly where showers move slowly or repeatedly affect the same locations. As rainfall accumulates over several days, landslides will become a greater concern along steep and vulnerable slopes. The strongest thunderstorms may also produce frequent lightning and gusty winds. These hazards will not be confined to the afternoon, as showers and thunderstorms may continue or redevelop during the evening and overnight hours. Confidence remains high in the wetter pattern, while the timing and placement of the heaviest rainfall will depend on cloud cover, local convergence, and the evolution of individual showers and thunderstorms. Warm and humid conditions will persist between periods of rainfall, with some heat impacts possible during prolonged breaks in cloud cover. && .Long Term(Sunday through Thursday)... Issued at 200 AM AST Thu Oct 22 2026 Wet and unsettled conditions will continue into Sunday before gradually improving early next week as drier and more stable air spreads across the region. Surface high pressure over the central Atlantic and lower pressure to the northwest will maintain a southeasterly flow, keeping tropical moisture over Puerto Rico and the U.S. Virgin Islands. Precipitable water values near 2.0 to 2.2 inches and sufficient mid-level moisture will support passing showers and isolated thunderstorms across windward sectors during the overnight and morning hours. During the afternoon, daytime heating, sea-breeze convergence, and local terrain effects will favor additional showers and thunderstorms across interior, northern, and western Puerto Rico. Although the overall rainfall threat should be lower than during the preceding days, locally heavy downpours may still cause urban and small-stream flooding where showers repeatedly affect the same areas. Rainfall accumulated during the short-term period may also leave vulnerable slopes more susceptible to landslides. A more noticeable drying trend is expected Monday as drier air filters into the midlevels and available moisture becomes increasingly confined to the lower portion of the atmosphere. Precipitable water values should decrease toward seasonal levels, although residual moisture and local effects will continue to support afternoon showers and isolated thunderstorms, mainly across interior and western Puerto Rico. Lighter steering winds could allow localized rainfall accumulations, maintaining some flooding potential despite decreasing overall shower coverage. Warm and humid conditions will also remain a concern, particularly Sunday and Monday, when periods of sunshine may increase heat impacts across coastal and urban areas and among heat-sensitive individuals. From Tuesday through Thursday, a building mid-level ridge and increasingly limited moisture should favor a drier and more stable weather pattern. Subsidence and warming aloft will suppress widespread convective development as precipitable water values trend below normal. Brief passing showers and isolated afternoon convection will remain possible, but the potential for widespread heavy rainfall and flooding should diminish as the week progresses. && .AVIATION... (06Z TAFS) Issued at 200 AM AST Thu Oct 22 2026 Mainly VFR conds expected, with VCSH at TJPS/TIST/TISX overnight into the morning as moisture increases from the S. SHRA/TSRA developing over interior and northern PR aft 22/17Z may produce periods of MVFR and brief IFR cigs/vsbys with direct +RA/TSRA passage at TJBQ and possibly TJSJ, with TJBQ impacts favored later in the 22/17-23Z period. Brief MVFR vsbys also psbl with passing SHRA at USVI terminals. Sfc winds L/V overnight, bcmg ESE-SE at 8-10 kt aft 22/13Z, with sea-breeze variations and locally gusty winds near TSRA. && .MARINE... Issued at 200 AM AST Thu Oct 22 2026 Light to gentle southeasterly winds will become east to southeast and increase to moderate to locally fresh speeds Friday into the weekend as the pressure gradient tightens. The current northerly swell will continue to subside today before another north- northwesterly swell arrives early Friday, followed by additional pulses through the weekend. Seas will build to 5 to 6 feet across portions of the Atlantic waters and Mona Passage, generally remaining below Small Craft Advisory criteria, although small craft should exercise caution. More frequent showers and thunderstorms, including nighttime activity, will bring lightning, gusty winds, reduced visibility, and locally higher seas. && .BEACH FORECAST... Issued at 200 AM AST Thu Oct 22 2026 Subsiding northerly swell will allow a moderate risk of rip currents today along exposed beaches of northern and northwestern Puerto Rico, Culebra, St. Thomas, and St. John. Another north- northwesterly swell arriving early Friday will bring a renewed high risk along northern Puerto Rico, where breaking waves around 6 feet are forecast Friday and Saturday. Additional swell pulses may maintain dangerous rip currents through the weekend and into early next week. Increasing shower and thunderstorm activity will also bring lightning and gusty winds to coastal areas. Beachgoers should avoid swimming where the rip current risk is high and seek shelter indoors when thunderstorms approach. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ EVE...MRR/MMC MID...ICP
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