About 50 Girl Scouts camped out on the White House lawn Tuesday evening, at least until rain and thunder storms forced a move inside to a nearby conference room. The event was to promote outdoor activities and national parks. While the weather held out, President Barack Obama and first lady Michelle Obama joined the girls on the lawn for knot-tying and songs. “What are you guys doing in my yard?” the president joked when he arrived. “When did you guys show up?”