A Gulfstream II corporate jet, N74RQ, was substantially damaged when it departed the runway and impacted a snow bank during landing roll at Logan-Cache Airport (LGU), Utah. Night instrument meteorological conditions prevailed at the time of the accident. There were no injuries. The cross-country flight originated at Kansas City (MKC), Missouri, approximately 17:30. According to a written statement submitted by the captain, they had flown the GPS approach to runway 35. When they did not see the runway or runway environment they initiated a missed approach. During the missed approach procedure, they were able to see the first 4 to 5 thousand feet on the approach end of runway 17. They “elected to circle to the north west to set up for a visual approach to runway 17.” The captain stated that the approach was “slightly high and as a result, the flare was a bit higher than normal.” The airplane entered the fog layer just prior to touchdown. The captain stated that during the landing flare the airplane drifted to the left and “the aircraft settled onto the runway to the left of centerline and shortly thereafter the left main gear impacted a snow berm.” The airplane turned hard to the left and departed the runway. The nose gear separated, the radome was crushed and the cockpit pressure bulkhead was compromised. An examination of the airplane’s systems, conducted by the FAA, revealed no anomalies. PROBABLE CAUSE: “The pilot’s improper IFR operation by which he failed to comply to the missed approach procedure, and his improper evaluation of the weather resulting in an encounter with fog and his loss of visual contact with the runway during the landing.”