Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
928 FXCA62 TJSJ 080938 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 538 AM AST Wed Oct 8 2025 .KEY MESSAGES... * Another active day is expected across the islands with periods of heavy rainfall and thunderstorm activity. There is a limited to elevated flooding risk, particularly over the northwestern quadrant of Puerto Rico. * Frequent lightning, gusty wind conditions, and urban or small- stream flooding are possible, with isolated flash flooding cannot be ruled out. * A Heat Advisory is in effect for the coastal and urban areas of Puerto Rico from 10 AM to 4 PM AST. Vulnerable groups and outdoor workers should stay aware of these conditions. Remember to drink plenty of fluids, stay in an air-conditioned room and out of the sun during the peak heat hours. * For the US Virgin Islands, minor flooding and lightning possible today due to showers and thunderstorms across the area. * The National Hurricane Center (NHC) continues monitoring Tropical Storm Jerry, located over the central Atlantic. This system is expected to approach the northeast Caribbean by Friday. Residents and visitors should remain informed and monitor official updates from the National Hurricane Center and our local office as Jerry approaches the Lesser Antilles. && .SHORT TERM...Today through Friday... Current satellite derived precipitable water (PWAT) values show generally above 2 inches over the islands with isolated sectors at around 1.8 in. A tropical wave over the region and a weakening upper level low WNW of PR continue to contribute to this plume of moisture over the region. Since midnight, most showers and t-storms remained over the local waters, with some leaving low radar estimated accumulations over eastern PR, Vieques, and Culebra. The highest radar estimated accumulations as of 445 PM were observed over central St. Croix, at 0.30 in. Lows were in the mid 70s to low 80s over coastal and urban areas of Puerto Rico and in the mid 60s over interior Puerto Rico. Lows were in the upper 70s to low 80s over the USVI, Culebra and Vieques. As the wave continues to move west-northwestward, southeasterly steering flow will persist, bringing moisture into the islands. PWAT will remain near or above 2.0 inches through the short-term period, with current model guidance not being as aggressive with drier air intrusion as before, for today, leaving PWAT values at around 1.88 inches over south and western Puerto Rico. In general high end normal to above normal values will continue during the period as moisture continues to be steered over the islands. The upper level low will continue moving northward today, as an upper level ridge starts to dominate. 500 mb temperatures are forecast to remain at normal values at around -7 to -5 degrees Celsius, gradually decreasing during the period. 925 mb temperatures will be normal to above normal during the period, this and available moisture will maintain above-normal temperatures and elevated heat indices, over coastal and urban areas under periods of reduced cloud coverage. A limited to elevated heat risk will be in effect today. A limited to elevated flooding risk will persist with convective showers and thunderstorms forecast for interior to western, northern and northwestern Puerto Rico today, with lines of convection also possible downwind of the local islands and El Yunque. Advective shower and isolated t-storm activity is also forecast to affect windward sectors of the islands during the morning and overnight hours as the nearby above mentioned features provide enough instability and moisture and as Tropical Storm Jerry continues to approach the Caribbean. Hazards include lightning, gusty winds, ponding of water and localized flooding associated with afternoon t- storms. Minor to isolated flash flooding will be possible, especially in areas with poor drainage or with more persistent rain. On Thursday and Friday, the weather pattern will be influenced by Tropical Storm Jerry, which is currently around 975 mi SE of St. Croix, at coordinates 13.3N, 50.7W. The latest advisory has Jerry as a hurricane with its closest approach being 196 miles NE of St. John on Friday morning. However, uncertainty remains regarding its track and intensity forecast. Under the latest guidance showers and afternoon convection are still forecast to be under southeasterly flow on Thursday and more southwesterly flow on Friday. Residents and visitors should remain informed and monitor official updates from the National Hurricane Center and our local office. .LONG TERM...Saturday through Wednesday... The forecast remains on track, with the arrival of trailing moisture associated with Tropical Storm Jerry. Latest precipitable water (PWAT) guidance indicates values above the normal climatological range (2.25 to 2.50 inches) across the region. This suggests a wet and moist pattern is likely from Saturday through at least Monday across Puerto Rico and the U.S. Virgin Islands. As Tropical Storm Jerry tracks north of the region, prevailing winds will initially be southeasterly, then will shift from the southeast starting Sunday. Showers and thunderstorms are expected this weekend, a result of the high moisture environment combined with daytime heating and local effects. While most of the area will experience some activity associated with the system, the U.S. Virgin Islands are expected to observe most of the activity due to their closer proximity to the storm`s path. Portions of eastern Puerto Rico, Culebra, and Vieques will also observe frequent showers. On Saturday, with winds prevailing from the south, activity will be focused over central and northern Puerto Rico, including the San Juan metro area, mainly during the afternoon hours. From Sunday onward, as winds shift from the southeast, the activity will primarily focus over central Puerto Rico toward the northwestern quadrant of the island. Under this persistent moist pattern, the risk of flooding remains elevated through the beginning of the workweek. Additional hazards include: urban and small stream flooding, minor flooding in low- lying areas, quick river rises, the potential for landslides, and frequent lightning. Conditions are expected to improve quickly starting Tuesday as a surface high-pressure system and a mid-level ridge settle over the central Atlantic. This pattern will promote drier and more stable atmospheric conditions through the end of the forecast period. Residents and visitors are urged to continue monitoring the progress of Tropical Storm Jerry and updates from the National Hurricane Center and our local office as the system approaches the Lesser Antilles. && .AVIATION... (06Z TAFs) Mainly VFR conditions to prevail. Due to a tropical wave, SHRA and TSRA over the waters can reach or move close to TJSJ/TIST/TISX/TJPS, under ESE steering flow, during the period. After around 17Z, SHRA/TSRA over the Cordillera will spread mainly to western/north/northwestern affecting PRs terminals or their VCTY, mainly TJSJ/TJBQ. These can produce brief periods of reduced visibilities and lower ceilings. Winds up to around 12 kts with sea breeze variations and higher gusts, decreasing after 8/23Z. && .MARINE... Moisture associated with a tropical wave will influence the region today, increasing the frequency of showers and thunderstorms over the regional waters, especially during the morning and afternoon hours. Tropical Storm Jerry is expected to move northeast of the region by Friday. Tropical storm conditions are possible by Thursday night, mostly across the eastern half of the regional waters including Atlantic and Caribbean waters, and the Anegada Passage. && .BEACH FORECAST... A moderate risk of rip currents will continue to persist across the exposed Atlantic beaches of Puerto Rico, Culebra, and the U.S. Virgin Islands through at least Friday. The risk is expected to become high for Saint Croix by the end of the workweek as Tropical Storm Jerry approaches the region. We encourage people to stay updated for any changes in the forecast from the National Hurricane Center. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ MRR/GRS