By Eric M. Johnson and Nia Williams CALGARY (Reuters) - Firefighters battling a massive blaze in Canada's energy heartland could see a second day of rainfall and winds on Friday, expected to beat flames back from key oil sands facilities, as a producer announced a restart in operations. The wildfire in northern Alberta has charred some 505,000 hectares (1,950 square miles) of land, more than six times the size of New York City, since it hit Fort McMurray in early May. It has forced widespread evacuations and triggered a prolonged energy shutdown that has cut Canadian oil output by a million barrels a day. The fire's footprint now exceeds the total area burned during Alberta's entire 2015 fire season, and flames spread by Thursday into the neighboring province of Saskatchewan.
