Hurricane Season runs from June 1-November 30
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Area Forecast Discussion (AFD)
851 FXCA62 TJSJ 110528 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 128 AM AST Thu Jun 11 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 115 AM AST Thu Jun 11 2026 * A wetter and more unstable weather pattern is expected today, as a tropical wave interacts with an approaching upper-level trough, increasing the coverage of showers and thunderstorms across the region and posing the greatest risk of flooding this afternoon. * Hot heat indices will prevail from Friday onwards. Heat indices may exceed 100F, especially across urban, coastal, and lower- elevation areas of Puerto Rico and the U.S. Virgin Islands. Heat Advisories may be needed at times. * Another dry air mass with Saharan dust will filter producing somewhat hazy skies and reduced air quality, especially early Friday morning into early Saturday. * The potential for life-threatening rip currents will turn moderate from Friday onward, first across St Croix, then spreading to the rest of the east and north-facing beaches in the USVI and PR. && .Short Term(Today through Saturday)... Issued at 115 AM AST Thu Jun 11 2026 Like previous nights, conditions remained tranquil across the region, with mostly clear skies, light and variable winds, as well as pleasant temperatures. Coastal and urban areas observed lows in the low to mid 70s, while cooler readings in the mid to low 60s were seen across the higher terrains. Overall, stable weather conditions prevailed across Puerto Rico and the U.S. Virgin Islands overnight. Today is expected to be the most active weather day of the short-term forecast period as a tropical wave interacts with a polar trough near the region. The latest model guidance continues to indicate precipitable water values and surface to mid level relative humidity values within the 75th percentile or above normal values for this time of year. In addition, 500 mb temperatures around -8 degrees Celsius will support an unstable atmospheric pattern favorable for thunderstorm development. As a result, periods of heavy rainfall and thunderstorms are expected, especially during the afternoon hours. The greatest rainfall accumulations are forecast across the interior and north to northwestern portions of Puerto Rico, where the risk of urban and small-stream flooding remains elevated. Isolated flash flooding will also be possible in more vulnerable and flood-prone areas. Despite the elevated flooding risk, the forecast continues to favor active afternoon convection rather than continuous rainfall throughout the day. Increased cloud cover associated with the upper-level trough is also expected to limit daytime heating, reducing the likelihood of dangerous heat indices today. Residents and visitors are encouraged to remain alert and monitor forecast updates, as weather conditions may change rapidly. A drier air mass moving in behind the tropical wave will bring slightly higher concentrations of suspended Saharan dust particles, leading to somewhat hazy skies from early Friday into the weekend. Although moisture levels will gradually decrease, patches of trade wind moisture will continue to support passing showers across windward areas during the morning hours, followed by isolated afternoon convection across interior and western Puerto Rico. By Saturday, a more typical trade wind weather pattern is expected to establish across the region. As clearer skies become more dominant and temperatures remain above normal, heat indices are expected to rise once again, particularly across coastal and urban areas. As a result, heat advisory conditions may become possible from Friday into the weekend. && .Long Term(Sunday through Thursday)... Issued at 115 AM AST Thu Jun 11 2026 Confidence is increasing in global models for the long-term forecast, with mainly a typical and stable weather pattern. Wind pattern should be dominated by a surface high pressure, lingering in the western Atlantic, producing E-ESE winds that will likely result in breezy conditions across the islands. The model guidance suggests patches of moisture moving from time to time, as PWAT values may fluctuate between 1.3 and 1.6 inches, though the 700 - 500 mb moisture content may plummet, ranging between 10 and 30%. In terms of instability, a ridge should approach the local area and linger nearby through most of the forecast period, warming 500 mb temperatures (between -6 and -7 degrees Celsius), allowing sinking air and stability aloft. Additionally, the Galvez-Davison Index (GDI) suggests at most shallow convection in the afternoon over western portions of Puerto Rico, with thunderstorms, if any, becoming isolated and brief. Each day, windward sections may receive isolated showers in the morning, while the combination of local effects, daytime heating, and available moisture should bring shallow convection across western Puerto Rico. Additionally, with the winds keeping up, island streamers will likely develop, moving into portions of eastern Puerto Rico, including the San Juan Metropolitan Area. Due to the current soil conditions, low streamflows, and QPF remaining below one inch, the flooding threat will remain low throughout the forecast period. Although the latest model guidance suggests 925 mb temperatures typical for this time of the year, this, combined with the available moisture will increase the chance of heat indices reaching and exceeding 100 degrees Fahrenheit. Hence, the heat threat will remain limited through most of the long-term, increasing on Tuesday due to a slight increase in moisture content in the 1000-850 mb layer. && .AVIATION... (06Z TAFS) Issued at 115 AM AST Thu Jun 11 2026 VFR conditions across all TAF sites. However, brief MVFR condt possible over TJBQ and TJPS after 11/16Z, as a tropical wave will increase the chance of TSRA/SHRA near terminals. VCSH/-ra possible over IST/ISX/JSJ around 11/12-15z. Winds will continue from the E-ESE at 10 to 15 knots with sea breeze variations, particularly near TS through 11/23z. After that, we expect calm to light and VRB winds with land breeze variations. && .MARINE... Issued at 115 AM AST Thu Jun 11 2026 Mariners can expect moderate east to east-southeast winds, resulting in moderate chop across the surrounding waters. An induced surface trough near the region interacting with a weak tropical wave will provide a better chance for thunderstorm formation across the PR and the USVI regional waters today. As the Azores high builds across the central Atlantic, moderate to fresh east- southeast winds will return. && .BEACH FORECAST... Issued at 115 AM AST Thu Jun 11 2026 There is a low risk of rip currents today for the local beaches. However, life-threatening rip currents may still occur, especially near groins, jetties, reefs, and piers. Showers and isolated t- storms are possible, as a tropical wave moves near the islands today. Saharan dust concentrations will also move over the region. From tomorrow, Friday, onward, there will be up to a moderate risk of rip currents (life-threatening rip currents are possible) across St Croix, Culebra and northern PR. This moderate risk will then spread Saturday onwards to the rest of the east and north-facing beaches in the USVI and PR as winds increase. Always swim near a lifeguard and remember to heed the advice of the local beach patrol and flag warning systems. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM/AVIATION...MMC LONG TERM...MNG MARINE/BEACH FORECAST...MRR
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