The private, non-instrument-rated pilot reported departing on a local personal flight. About 45 minutes after departure he encountered reduced visibility and elected to perform an off-field landing on a road. During the landing roll the airplane encountered a snow bank and nosed over. The airplane sustained substantial damage to the vertical stabilizer, rudder, and left wing during the accident sequence. The closest weather reporting station to the departure airport reported a visibility of 3/4 miles, mist with a few clouds at 400 feet above ground level, and a broken layer at 1,200 feet about the time of departure. The same station reported visibilities of 1/4 mile, fog, with a broken cloud layer of 200 feet, and overcast 700 feet at the time of the accident. The pilot did not obtain a weather briefing prior to departure; he additionally reported no preexisting mechanical malfunctions or failures with the airplane.