At 11:16 Allegheny Flight 561 departed Clarksburg for a flight to Morgantown, WV but the pilot decided not to make an approach at Morgantown because the ILS glide slope was out of service, and the visibility was 1/2 mile. The flight returned to Clarksburg and landed at 11:46. The aircraft was refueled and prepared for a rescheduled flight 561 to Washington-National Airport. The Nord 262 was de-iced between 12:20 and 12:35. When the crew taxied out at about 12:57 there was again some wet snow on all its horizontal surfaces. Shortly after lift-off from runway 21 the aircraft rolled 45deg to the right, 45deg to the left and back to the right again until the wing struck the ground. The aircraft crashed and came to rest inverted. PROBABLE CAUSE: “The captain’s decision to take off with snow on the aircraft’s wing and empennage surfaces which resulted in a loss of lateral control and a loss of lift as the aircraft ascended out of ground effect.”