Celebrate one of this country's more peculiar holidays this week at the N.C. Museum of Natural Sciences in Raleigh. The museum's Groundhog Day events will not be starring Billy Murray, but the equally lovable Sir Walter Wally, a real live woodchuck who will emerge on Friday, Feb. 2, to see or not see his shadow and determine the demise of winter. In addition to this noble appearance, Groundhog Day will feature the unveiling of a statewide Weather Watch map. Schoolchildren all over the state will be sending in descriptions their local weather that morning and the State Climate Office of North Carolina will combine their reports on the map. The event runs from 11 a.m. to 2 p.m., and all ages are welcome. Call 733-7450 for details.