has traveled almost 5,000 miles (8,000 kilometers) to Britain and other parts of northern Europe, scientists said Wednesday.The current weather system, which favors a westerly wind across the higher levels of the atmosphere, is to blame for the reach of the smoke, experts explained. “We always seem, at times, to get the right combination of enough smoke and the upper level jet stream to line up to bring that across the country, so we’re just seeing this again,” said Matt Solum with the National Weather Service’s regional operations center in Salt Lake City, Utah.