The second one occurred about two weeks before the accident and lasted 2.0 hours. In this case, onsite weather was available, and the clues that the field was about to go IFR were there but subtle. Weather reported at the time of the accident was measured ceiling 300 feet overcast and four miles visibility with mist. Winds were from 060 degrees at 10 kt. The temperature was 50 degrees Fahrenheit, and the dewpoint was 48 degrees.
Local geography plays a significant role in understanding how microclimates behave.
The airport has a 10,000-foot concrete runway that is 150 feet wide and oriented 080 to 260 degrees magnetic. It is located on a peninsula bordered by a large body of water immediately to the east and a river to the south and west. With that amount of moisture nearby, fog banks would tend to form quickly or blow in off the water. Most airports in close proximity to water experience similar conditions. Note that in this case the wind was coming off the water, and the air was saturated.