The pilot diverted to the planned alternate airport due to fog. The alternate airport was located on top of a ridge line about 2,700 feet higher than the planned destination airport. The runway was 2,200 feet long and had no services. According to witnesses, the pilot landed 'hot' about midfield, and the aircraft left skid marks on the runway that measured between 330 to 350 feet long. The aircraft departed the end of the runway, and went down an embankment and into trees. The pilot reported no mechanical malfunction.