On February 22, 2021, about 1145 eastern standard time, a Cessna 421C, N84HA, was substantially damaged when it was involved in an accident at St. Marys Municipal Airport (OYM), St. Marys, Pennsylvania. The airline transport pilot sustained minor injuries, and the two passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 corporate flight. The pilot recalled that, while the airplane was inbound to OYM, the automated weather observing system reported the cloud conditions as 600 ft broken and 1,000 ft overcast and the visibility as 1.5 miles in snow. Before being cleared for the GPS approach to runway 28, air traffic control provided notices to air mission (NOTAM) regarding an inoperative remote communications outlet and several lighted obstructions (towers) near the airport. The pilot also recalled these NOTAMs were the same as the ones that he had reviewed before departure. As the pilot began the approach, he was able to “pick up ground contact,” and, just before the airplane reached the minimum descent altitude, he saw the approach lights. As the airplane flew over the approach lights, the pilot could see the “outline of the runway.” After touchdown, the airplane struck a snow berm on the left side of the runway. Examination of the accident site revealed ground scars in the snow to the left of the runway edge, beginning about 1,000 ft from the approach end of runway 28. The marks were about 250 ft long and tracked along and through a snow berm on the left side of the runway. The airplane came to rest at the end of the snow marks and was oriented on a magnetic heading of about 130° (rotated about 210° from the runway 28 heading). At the time of the accident, the runway was covered in snow estimated to be about 3-4 inches deep. The runway edge lights, and runway end identifier lights were beneath the snow. Examination of the airplane revealed bending/displacement of the forward pressure bulkhead, buckling of the floor just forward of the pressure bulkhead, and a slight displacement of the left wing from the fuselage at the wing root. The pilot reported that the day before the accident, he contacted officials at the airport, advising of his planned arrival. It was the pilot’s understanding that airport personnel would plow the runway prior to his arrival. After the accident, the pilot learned that the airport snowplow had become stuck while plowing a side road adjacent to the airport prior to his arrival. A review of Federal Aviation Administration records revealed no NOTAMs regarding the snow on the runway, the obscuration of the runway lights, or any other field condition before the accident. According to the Federal Aviation Administration, the airport manager reported that he was relatively new in his position and that he had not been placed on the list of personnel who were authorized to issue NOTAMs. After the accident, the airport manager coordinated with the Federal Aviation Administration to be placed on that list. The 1135 weather conditions reported at OYM included clouds broken at 700 ft and overcast at 1,100 ft and visibility 0.5 mile in light snow. The visibility was reported as 0.5 mile in snow or light snow during the three previous observations (recorded at 1035, 1055, and 1115).