The Shadow Lake Fire more than doubled in size over the weekend. The Central Oregon heat and low humidity allowed the Shadow Lake Fire, northwest of Sisters, to grow over the weekend. Fire officials sensed the danger and took action to protect people in the area.   Close to 500 campers and hikers were evacuated Saturday from the area of the Big Lake Youth Camp and surrounding campsites.   A portion of the Pacific Crest Trail between Highways 20 and 242 was also closed due to the fire danger.   The fire doubled in size overnight, pushing it to over 1400 acres by Sunday morning. Then, on Sunday afternoon, the wind shifted, and drove the flames to the north with an estimated 800 more acres going up in smoke.   Despite all of the growth, fire officials say there still is no danger to any structure or to the public.    Because the fire is in a wilderness area, firefighters continue to use indirect tactics, including bulldozers and water drops from helicopters.