066 FXCA62 TJSJ 021911 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 311 PM AST Wed Jul 2 2025 .KEY MESSAGES... * Passing showers and gusty winds will continue this afternoon and tonight as patches of moisture continue to move into the region. * A weak tropical wave is anticipated to arrive on Friday, followed by the presence of Saharan dust resulting in hazy skies and deteriorating air quality conditions. * Anticipate seasonably hot temperatures each day, with afternoon heat indices over 100 degrees. && .SHORT TERM...Tonight through Friday... A trade wind perturbation resulted in an increased frequency of showers moving over eastern portions of Puerto Rico and smaller islands during the morning hours. These showers moved fairly quickly; however, they still left close to an inch of rain in those southeastern municipalities of Puerto Rico. By late morning to early afternoon, the trade wind perturbation continued to promote shower development, mostly over the northern half of Puerto Rico, particularly over the northwestern quadrant. These showers left about an inch of rain in very localized areas, such as northern Bayamon. Expect a continuation of these showers and possible isolated thunderstorms during the afternoon hours as surface heating and local effects aid in convective development. Additionally, breezy wind conditions were also reported. By noon, gusty wind conditions had already been observed, with several coastal weather stations recording sustained winds in the upper 20s and low 30s mph range. The La Puntilla tide weather station even reported wind gusts reaching 33 mph. The mid-level ridge that has been influencing us continues to erode due to a mid-to-upper level low approaching from the northeast. Meanwhile, high pressure over the central Atlantic will maintain a breezy east-southeast steering flow for most of the period. However, a slight dip in wind speeds is likely tomorrow before conditions return to breezy. While drier air moves in on Thursday, by late Thursday into early Friday, moisture from a tropical wave will start to increase PWAT values once more. The wave itself will cross our area later on Friday, bringing PWAT values up to around 2 inches. However, a wind surge behind the wave and moderate to high amounts of Saharan Dust are weakening the tropical wave, which will potentially limit its impacts. Despite these features, the increased moisture should trigger showers across the islands under the east-southeast flow, with stronger convection developing over western and northwestern Puerto Rico and downwind of the islands and El Yunque in the afternoon. Be aware of a limited heat threat that will persist across urban and coastal areas during the late morning to afternoon hours. Drink plenty of fluids, limit strenuous outdoor activities, and take frequent breaks in the shade. .LONG TERM...Saturday through Wednesday... /From Prev Discussion issued at 436 AM AST Wed Jul 2 2025/ Surface high pressure over the central Atlantic will maintain fresh trade winds across the region. At the lower levels, a dense Saharan Air Layer will move into the islands, resulting in hazy skies on Saturday and Sunday. Some leftover moisture will also be available, so some passing showers will continue as well. For the workweek, not many changes are anticipated, with a trade wind cap inversion around 850 mb, and all the available moisture trapped near the surface. A couple of weak tropical wave will move across the region, but also some patches of light to moderate amounts of Saharan dust as well. The weather pattern will be variable, with passing showers over the Virgin Islands and eastern Puerto Rico, and afternoon convection in western Puerto Rico. No significant or widespread flooding is expected during the forecast period. However, it will be hot, with the guidance forecasting heat indices above 102 degrees for all coastal and urban areas of the islands each afternoon. && .AVIATION... 18Z TAFS) Mostly VFR conditions expected to continue. SHRA/TSRA will continue across northwestern PR through 21Z, with brief periods of low ceilings and reduced VIS possible at TJBQ. Showers will taper off after that. Winds will slow down, below 10-12 knots after 22Z, but will speed up after 03/14Z, out of the ESE at 10-15 kts, with stronger gusts. && .MARINE... Choppy seas are expected to continue across the local Atlantic and Caribbean waters due persistent moderate to fresh easterly winds. A weak tropical wave is forecast to move over the local waters on Friday, increasing shower and thunderstorm chances. Saharan dust will follow the tropical wave, with hazy skies returning on Saturday and Sunday. && .BEACH FORECAST... Wind-driven seas will maintain a moderate risk of rip currents along most exposed beaches of the islands through much of the forecast period, although will diminish somewhat by the end of the week. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ CVB/MMC
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