Hurricane Season runs from June 1-November 30
[10/10]
956 FXCA62 TJSJ 131913 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 313 PM AST Sat Sep 13 2025 .KEY MESSAGES... * Afternoon showers and thunderstorms will persist this afternoon, with a tropical wave bringing increased shower activity late tonight into early Sunday across eastern Puerto Rico. Local impacts include ponding of water on roadways, quick river rises, landslides in vulnerable areas, and frequent lightning. * Cloud coverage from the tropical wave may limit the usual afternoon activity on Sunday, but periods of heavy showers are still possible. * Heat risk continues each day, with heat index values above 100F across coastal areas, though Sundays clouds may slightly hinder the highest values. * A wetter and more unstable pattern is expected mid to late week as above-normal moisture combines with a deep-layer trough, heightening the threat for flooding rains, frequent lightning, river rises, and landslides. * In the U.S. Virgin Islands, expect increased showers late tonight into Sunday, continued dangerous heat risk each day, and unsettled weather mid to late week with potential for heavy rains and frequent lightning. && .SHORT TERM...Tonight through Monday... Diurnal heating, local orographic effects, available moisture and troughiness over the region (an upper trough is to our northeast) helped develop convection by late morning. Lines of showers and started to develop from the USVI, Vieques and Culebra by around 10 AM, before developing into t-storms. Convective t-storms then developed by 1030 AM over Canovanas and Carolina and over Salinas and Coamo. As the day progressed, shower and t-storm activity spread to interior, northern, north-central, northwestern and western Puerto Rico where strong t-storms are currently affecting those areas. As of 230 PM, radar estimated accumulations indicated that Canovanas, Carolina, Salinas, Aibonito, Ciales, Florida, Manati, Barceloneta, Utuado, Lares and Isabela, saw at to above 2 inches of rain. By 230 PM, Florida, Arecibo and Canovanas saw the highest radar estimated accumulations with 4.16 in, 3.44 in and 3.20 in, respectively. Heat indices reached Heat Advisory Criteria but quickly decreased over most areas as the late morning to afternoon convection developed. Under east-southeast steering flow this convective activity will gradually dissipate and/or move offshore we head towards the evening. However, a tropical wave, currently over the Lesser Antilles and eastern Caribbean Sea, will continue to move eastward and approach the region later tonight. It`s moisture field, with precipitable water values above 2 inches and reaching 2.25 inches, will cross the Anegada Passage and reach the USVI late tonight and into the overnight hours. Late in the overnight hours and to start tomorrow morning, the moisture field from this tropical wave will reach eastern Puerto Rico. As this wave approaches the aforementioned regions will see an increase in showers and isolated t-storms during the overnight to morning hours. Afternoon showers and t-storms are forecast to develop once again across central PR to W-NW PR, as well as downwind of El Yunque and the USVI. A limited to elevated flooding risk remains for tomorrow, although limiting factors to rainfall accumulations could be extended cloud cover during the morning and increased winds (faster moving showers and t-storms). Diurnal heating, instability from the wave, local effects, and nearby troughiness will serve to support this afternoon activity and redevelopment of its outflows. The wave`s moisture field will gradually leave the region during the overnight hours Sunday to Monday. A dry slot will then move over the area, but it will be short lived as another patch of moisture approaches followed by a patch of moisture. This patch of moisture has PWAT values of around 2 inches and will serve to enhance rain and t-storm potentials during the day, particularly during afternoon convection. A tropical wave will also approach the area to end the period and reach the islands to start the long term period. 925 mb temperatures are expected to be at normal values during the short term period, Limited to elevated heat risks are expected at more prone sectors but afternoon convection will still serve as relief. .LONG TERM...Tuesday through Saturday... ./FROM PREV DISCUSSION...Issued at 347 AM AST Sat Sep 13 2025/ Unsettled weather conditions are expected during the workweek as a couple of tropical waves moves into the region. The first wave moves in Tuesday and Wednesday, bringing an increase in showers across the Virgin Islands, and then this cluster of moisture will reach Puerto Rico. As a result, the frequency of showers and thunderstorms will increase. Areas that receive heavy rain will experience flooding, and rapid river rises. Lightning strikes will remain a concern for those in the exterior at the times of thunderstorms. Instability will increase further on Thursday as an upper level low moves just north of the islands. By the end of the period, yet another tropical wave moves close to the islands, bringing intermittent periods of showers into the region. Areas that do not experience rain or cloudiness, however, will continue to observe elevated heat indices, much above normal values. As it has been consistently hot for the past couple of week, those without effective cooling or adequate hydration will could be affected. && .AVIATION... (18Z TAFS) Mainly VFR to brief MVFR conditions over the terminals or their VCTY. Persisting through 13/22Z for TJBQ and possibly TJSJ. SHRA/TSRA over the vicinity of TJPS/TIST/TISX will move away from them during the afternoon. Sfc winds from the ESE up to 16 mph, with higher gusts and sea breeze variations, decreasing after 23Z and picking up again after 14/13Z. A tropical wave will approach the area late tonight and promote VCSH/VCTS over TISX/TIST beginning at around 14/02Z and possibly over TJSJ by 14/12Z. && .MARINE... A surface high pressure over the central Atlantic and a front over the western Atlantic will promote light to moderate east to southeast winds through this afternoon, increasing to moderate to fresh tonight through early next week as a tropical wave crosses the region. Afternoon showers and thunderstorms are likely each day, particularly over the western waters of Puerto Rico and the Mona Passage. The tropical wave will bring additional showers and thunderstorms across the local waters on Sunday. && .BEACH FORECAST... The risk of life-threatening rip currents will increase to moderate beginning Sunday and persist through most of the workweek, particularly for northern and eastern exposed beaches of Puerto Rico and U.S. Virgin Islands. Even with a low risk, life-threatening rip currents can still occur near groins, jetties, reefs, and piers, so beachgoers are advised to exercise caution at all times. Additionally, thunderstorms are likely during the afternoon hours, producing dangerous lightning strikes; be prepared to seek shelter if thunder is heard. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM/AVIATION...MRR LONG TERM...ERG MARINE/BEACH FORECAST...CVB
