625 FXCA62 TJSJ 290705 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 305 AM AST Mon Jun 29 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 257 AM AST Mon Jun 29 2026 * A passing tropical wave will result in shower and thunderstorm activity today, resulting in ponding of water over roadways and poorly drained areas, including urban and small stream flooding, across the islands. * Warmer to hot conditions are expected for the next few days, with heat indices exceeding 100 degrees Fahrenheit across urban and low- lying areas of Puerto Rico and the U.S. Virgin Islands. Stay hydrated. * Moderate to high concentrations of Saharan Dust will likely return by Tuesday morning, resulting in hazy skies, reduced visibility, and poor air quality. Sensitive groups must follow medical recommendations. && .Short Term(Today through Wednesday)... Issued at 257 AM AST Mon Jun 29 2026 Abundant moisture associated with a tropical wave moving over the region resulted in moderate to heavy rainfall across portions of eastern and northeastern Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands during the overnight hours. Doppler radar estimated rainfall accumulations of up to 1.0 inch over the municipalities of Humacao, Juncos, and Las Piedras. The strongest thunderstorms with frequent lightning remained mostly over the Anegada Passage, particularly between St. Croix and Vieques. Overnight lows across the region ranged from the upper 70s to low 80s in urban and coastal areas, and from the upper 60s to low 70s in the mountains. Showers and isolated thunderstorms will continue to move across the local waters, the U.S. Virgin Islands, and eastern Puerto Rico during the morning hours. This will likely result in the ponding of water in low-drainage areas. As the wave continues to move across the region, it will maintain an influx of abundant moisture over the islands. This moisture, combined with daytime heating and local effects, will trigger afternoon convective activity across northwestern Puerto Rico. Heavy rainfall and isolated thunderstorms are expected across these areas, resulting in an elevated risk of flooding. Potential impacts include ponding of water on roadways, urban and small-stream flooding, and localized flash flooding. Gusty winds will also be possible within the heavier shower activity. Later tonight, the wave axis will continue to move westward toward the Dominican Republic. Following the passage of the wave, drier air will begin to filter back into the region along with moderate to high concentrations of Saharan dust. This will result in hazy skies, reduced visibilities, and poor air quality through the end of the workweek. Sensitive groups, including individuals with respiratory conditions, are urged to limit prolonged outdoor exposure and take necessary precautions. Simultaneously, a broad surface high-pressure system centered over the central Atlantic and a mid-level ridge settling over the northeastern Caribbean will promote drier, stable conditions aloft, limiting widespread shower formation through the rest of the period. However, occasional patches of moisture embedded in the trade winds will still bring brief showers to the area, though no significant accumulations are expected as stable conditions prevail. Under this weather scenario, temperatures will rise into the upper 80s to low 90s across coastal and urban areas, and into the low to mid-80s in the mountains. Heat indices across the region are forecast to reach or surpass 100°F, particularly during the peak heating hours of the day. Residents and visitors are urged to practice heat safety by staying hydrated, limiting strenuous outdoor activities, and taking frequent breaks in shaded or air-conditioned areas. && .Long Term(Thursday through Monday)... Issued at 257 AM AST Mon Jun 29 2026 For the long-term forecast period, the region will experience a transition from a marginally unstable environment to a drier, hazier pattern before moisture returns early next week on Monday. At the surface, a dominant high-pressure system will maintain a generally easterly low-level wind flow, which is expected to veer to the southeast by Thursday morning. Aloft, a 250 mb cut-off low will linger near the local area from Thursday into Friday, providing modest upper-level support and atmospheric instability, with 500 mb temperatures forecast to hover between -8 °C and -7 °C during this time. On the other hand, precipitable water values are expected to range between 1.4 and 1.6 inches. Given the expected conditions, passing showers are anticipated across eastern sections of Puerto Rico during the morning hours, followed by the development of afternoon showers over the western interior and northwestern quadrants of the island, fueled by local effects and daytime heating. From Friday through Sunday, a slightly drier weather pattern will establish across the forecast area. Available moisture will become relatively shallow, generally trapped between the 1000 and 850 mb levels. Furthermore, recent NASA Goddard aerosol model guidance indicates the arrival of another mass of Saharan particulates. This dust will result in hazy skies, leading to mostly dry and variable conditions with very limited rainfall accumulations throughout the weekend. By Monday, a more uniform area of low-level moisture is forecast to filter into the region. This will aid in diminishing the hazy conditions as dust concentrations decrease, promoting a return to a more typical, scattered shower pattern across the islands. Regardless of the fluctuations in moisture and Saharan dust, persistently warm to hot conditions will dominate the entirety of the long-term period. An elevated heat threat is expected each day, particularly across urban and coastal areas. Maximum heat index values will consistently peak between 100 and 108 °F across portions of the north-central coastal plain and southern sectors of Puerto Rico during the peak daytime heating hours. && .AVIATION... (06Z TAFS) Issued at 257 AM AST Mon Jun 29 2026 Mainly VFR conds are expected to prevail across most terminals today. However, a tropical wave will continue to move across the region today, promoting the development of SHRA and iso TSTMs, this will result in VCSH/VCTS across most terminals thru 29/23z. Mtn tops obscd and BKN cigs near FL030 are expected with the wave passage. SE winds between 12-16 kt are expected with higher gusts and sea breeze variations. Winds will become light and variable at 5-10 kt aft 29/23z. && .MARINE... Issued at 257 AM AST Mon Jun 29 2026 A tropical wave will move across the US Virgin Islands and Puerto Rico, bringing gusty winds and lightning, creating localized hazardous conditions for small craft through at least this evening. Trailing the tropical wave, a dense Saharan Air Layer will deteriorate air quality on Tuesday and Wednesday. The surface high pressure across the Central Atlantic will promote the return of moderate to locally fresh east to east-southeasterly winds causing moderate chops or even choppy seas. && .BEACH FORECAST... Issued at 257 AM AST Mon Jun 29 2026 Most beaches along the east, south, and west coasts of Puerto Rico, as well as those in Culebra, Vieques, St. John, and St. Thomas, have a low risk of rip currents. However, beaches in St. Croix and northern Puerto Rico face a moderate risk of rip currents, which can be life-threatening. It's important to note that even at low-risk beaches, isolated, life-threatening rip currents can still occur, particularly near jetties, groins, reefs, and piers. This will prevail through at least the middle of the week. In addition, a tropical wave will bring thunderstorms across Puerto Rico and the US Virgin Islands today. If you are at the beach or participating in outdoor activities, remain alert for lightning. Remember: If you can hear thunder, you are close enough to be struck by lightning. Move to a substantial building or a hard-top vehicle immediately and remain there until 30 minutes after the last rumble of thunder. From Tuesday onward, expect hot, humid conditions that may produce dangerous heat levels at the beaches. Stay hydrated, seek shade frequently, wear lightweight clothing, and limit prolonged sun exposure during the hottest part of the day. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM...GRS LONG TERM....LIS MARINE & BEACH FORECAST...CAM