MKC84LA043

During takeoff on a snow covered rwy at night the aircraft ran off the left side of the runway & was damaged. At that time, the rwy was covered with a thin layer of dry snow over the top of hard packed snow. A 50 ft strip had previously been plowed along the 150 ft wide rwy. However, the tower was closed & no snow removal was permitted after 2400 CST. The plt reported that he was concerned about the oil pressure after starting in cold wx. As he applied takeoff power, he glanced at the eng instruments, oil pressure & temp in particular. He stated that he 'had just gone visually outside' when the copilot said 'watch yourself.' At that point, the acft was angling to the left. The plt kept the nose wheel steering engaged & applied right rudder, but was unable to maintain rwy alignment. He reported the left main gear was in 3 inches of snow while the right gear was in 1 inch of snow and this increased drag to the left. The plt believed that improper snow removal was the 'sole reason.' Other acft landed & departed without major difficulty.