The pilot reported that it was snowing during his preflight activities and takeoff roll. A snowplow operator stated that he had cleared approximately four passes on either side of the runway centerline when the accident airplane taxied onto the runway. The pilot back-taxied on the departure runway to determine how much snow covered the runway. During the subsequent takeoff roll, at approximately 80 knots, the left main landing gear encountered some deeper snow that caused the airplane to swerve left off of the runway centerline. The pilot attempted to correct the left swerve with right rudder input, but the airplane continued off the left side of the runway. The airplane was substantially damaged when its nose landing gear impacted a snowbank.