414 FXCA62 TJSJ 111844 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 244 PM AST Fri Jul 11 2025 .KEY MESSAGES... * A dense Saharan Air Layer will persist through at least early Sunday, maintaining hazy skies, reduced visibility, and unhealthy air quality levels across Puerto Rico and the US Virgin Islands. * Limited overnight cooling due to the Saharan dust will lead to warmer- than-normal mornings and dangerously hot daytime temperatures, especially in coastal and urban areas. Heat advisories remain likely. * Moderate to fresh winds will prevail, with isolated trade wind showers mainly across eastern areas at night and early morning. Afternoon shower activity will shift farther south due to changing wind patterns. * A tropical wave will arrive for the middle of next week. * A moderate risk of rip currents continues along north- and east-facing beaches of Puerto Rico and parts of the U.S. Virgin Islands. && .SHORT TERM...Tonight through Sunday... Mostly sunny and hazy skies persisted across Puerto Rico and the US Virgin Islands due to a dense Saharan Air Layer (SAL) with moderate to high concentrations of suspended dust particles. Warm to hot heat indices were recorded around the coastal locations, where a Heat Advisory was still in effect. Winds were from the east-southeast at 10 to 20 mph with higher wind gusts and sea breeze variations. A few afternoon showers will develop across the western locations, while the rest of the region will observe mainly hazy skies and uncomfortable heat indices the rest of the afternoon. This evening, isolated trade wind showers may drift across the islands, producing light rainfall mainly over eastern Puerto Rico and the USVI. Minimum temperatures will remain warm, staying in the low 80s across coastal and lower elevations, and ranging from the mid-60s to low 70s in the interior highlands. Winds will shift from east-northeast to northeast between 612 mph, with occasional gusts up to 20 mph. A high-pressure system extending from the surface to the low-mid levels will maintain breezy conditions today and Saturday, with east to east-southeast winds around 1520 mph. By Saturday night into Sunday, the weakening of this high and the influence of a new high from the central Atlantic will shift winds more northeasterly. This change will result in afternoon showers focusing farther south than in previous days, and slightly lower heat indicesespecially by Sunday. Despite these subtle changes, expect hazy and hot conditions to continue through the weekend, with limited overnight cooling due to the SAL. As a result, mornings will start warmer than usual, and daytime highs across coastal and urban areas will remain above normal. Heat advisory conditions are likely to persist. Residents and visitors should stay hydrated, avoid prolonged sun exposure, and limit outdoor activityparticularly those sensitive to heat and poor air quality. A surface high pressure across the central Atlantic will continue to result in moderate southeasterly winds across the region. Therefore, mariners can expect moderate to fresh easterly winds and choppy seas across the islands through the weekend. An extensive Saharan Air Layer will move across the Northeastern Caribbean lingering through the weekend, and leaving hazy skies, reduced visibilities a deteriorated air quality. .LONG TERM...Monday through Friday...from previous discussion... A enhancement in moisture levels is expected by the beginning of the workweek with the arrival of several trade wind perturbations into the islands. The latest precipitable water content shows values between 1.60 to 2.00 inches from early Monday through late Tuesday. Therefore, there is an increase in the potential for shower activity across the area, in particular over eastern Puerto Rico and the U.S. Virgin Islands during the morning hours. As the week progresses, a tropical wave is expected to approach the islands from the east by early evening on Wednesday and lasting through at least Friday. The latest model guidances has the bulk of the wave arriving into the area by Thursday morning, increasing the chance for showers and thunderstorms across the region with PWAT values up to 2.20 inches. Despite of the wave passage, moderate to heavy showers and thunderstorms are anticipated each afternoon, particularly across the central and western municipalities of Puerto Rico. We will continue to monitor the weather conditions closely for any significant changes in the forecast. Saharan dust concentrations will begin to decrease on Monday. Nonetheless, minor concetrations of these particles will continue to linger across the region through Thursday. Another pulse of Saharan dust will arrive by late Thursday/ early Friday following the wave passage. This event will promote, once again, hazy skies, reduced visibilities and deteriorated air quality throughout the area until the weekend. && .AVIATION... (18Z TAFs) Mainly VFR conditions are expected to prevail across all TAF sites during the forecast period. Some passing VCSH cannot be ruled out across TJBQ through around 11/22Z. Main aviation concerns remain to be the Saharan Air Layer resulting in reduced visibilities and the E- ESE breezy winds through around 11/23Z. Then , lighter winds are expected overnight, increasing again Saturday morning (after 12z- 13Z) to around 14 to 18 knots with gusts up to 25 to 28 knots. && .MARINE... A surface high pressure across the central Atlantic will continue to result in moderate southeasterly winds across the region. Therefore, mariners can expect moderate to fresh easterly winds and choppy seas across the islands through the weekend. An extensive Saharan Air Layer will move across the Northeastern Caribbean lingering through the weekend, and leaving hazy skies, reduced visibilities a deteriorated air quality. && .BEACH FORECAST... Expect a moderate risk of rip currents along the north- and east- facing beaches of Puerto Rico and parts of the U.S. Virgin Islands. Precautions: Swim only near lifeguards, heed posted warnings. Conditions may quickly become dangerous, especially for less experienced swimmers. Hot, hazy conditions are expected to persist through the weekend with heat index values likely exceeding the 108F in urban and coastal zones. Safety Tips: Stay well hydrated. Seek shade frequently. Avoid outdoor activity during peak sun hours (typically 11AM2PM). && .SJU WATCHES/WARNINGS/ADVISORIES... PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007- 008-010-011. VI...None. AM...None. && $$ SHORT TERM...CAM LONG TERM....YZR AVIATION...YZR
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