The airplane impacted in an open field about 1/2 mile southeast of the airport in a left wing low, nose low attitude. A ground witness, who was a pilot, stated that he heard the airplane's engine accelerate and enter a left turn just prior to impact. The witness lived about 200 yards from where impact occurred. The airport where the accident occurred was about ten miles south of the pilot's intended destination. The weather and light conditions at the time were thick fog with about 1/8 mile visibility and dark night. During the weather briefing the non-instrument rated private pilot was advised that VFR flight was not recommended and that she should call back prior to departure. The pilot did not call back. The pilot had a total of 14 hours night time and 3 hours simulated instrument time. It was not determined if the pilot had landed at the accident airport or if she had just made a low pass. Total ETE for the flight would have been about 47 minutes. Total elapsed time from takeoff to the accident was 1 hour and 42 minutes.